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THESV Sn L: IBRARIES \\l\\\\\\\\\\l\\\\\\\\llllllll \l‘l‘ {Hill \I 3129 l This is to certify that the thesis entitled Development and Evaluation of Shipping Systems for Bedding Plants presented by Scott L. Derthick has been accepted towards fulfillment of the requirements for Master . Science (Horticulture) degree in 421%.. //. my“ Major professor Datew 0-7639 MS U is an Affirmative Action/Equal Opportunity Institution LIBRARY Michigan State University PLACE IN RETURN BOX to remove this checkout from your record. TO AVOID FINES return on or before date due. DATE DUE DATE DUE DATE DUE MSU Is An Aflirmdlve Action/Equal Opportunity Inetltution cMma-pd DEVELOPMENT AND EVALUATION OF SHIPPING SYSTEMS FOR BEDDING PLANTS By Scott L. Derthick A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of Master of Science Department of Horticulture 1991 ABSTRACT Development and Evaluation of Shipping Systems for Bedding Plants by Scott Derthick Seven new methods of shipping commercially grown bedding plants have been developed, studied and evaluated. The seven packaging systems are: 1. stackable, disposable rack constructed from honeycomb paperboard 2. column of flats held together by metal comers and stretch wrap plastic 3. rigid, stackable, plastic carrier flats 4. resin/wax treated corrugated boxes 5. collapsible plastic or metal shipping racks 6. Patented "Smitty Table" constructed of plywood and plastic center side posts 7. Stackable rack constructed of a combination of honeycomb paperboard and plywood. All these systems have been subjected to vibration testing to simulate long distance shipping, ethylene concentration evaluations, moisture retention capacity, and other measures to maintain plant quality during shipping. Selected species of bedding plants were vibrated at various frequencies and measured for changes in growth rates seven days after the treatment. Six of the packages have been structurally modified to be able to withstand the ASTM vibration testing requirements for long distance shipping. ACKNOWLEDGMENTS Michigan State University has become my second home and many of the people that I have worked with have come to be my extended family. The Department of Horticulture is filled with incredibly intelligent and helpful people. I have much heartfelt gratitude and appreciation for Dr. William Carlson, my major professor, for all of his help both educationally and personally to complete this degree. Thanks also to the other members of my committee, Dr. Julian Lee, Dr. Art Cameron, and Dr. Randy Beaudry, for their time, expertise and advice. I Would also like to acknowledge a special thank you to Sandy Allen, for all of her smiles, supportive and encouraging words, helping me with the computer, and mostly her longtime friendship. I also want to thank others in the Department of Horticulture who have gone above and beyond their call of duty to help me maximize my educational experience and grow as a person. Thank you Doug Badgero, best wishes in the future with the new gardens, Dr. Jack Kelly for taking me "under his wing" as a freshman, and Dr. Lowell Ewart I hope that someday you get that perfect orange geranium. I would also like to express my deep gratitude and thanks to Nina Silbergleit, the House Manager from Wharton Center. I wouldn’t give up the memories of one minute of my Wharton experiences. You have been a super boss, great friend and a wonderful influence. , Outside of the University I also want to thank several people. My family for all of their support, words of encouragement, friendship and love. Without your influence, support, and help, none of this would have ever been possible. Thank you Brad, Joan, Dad, Mom, Margaret, Jack, Doug, Grandma, Grandpa, and everyone else. Thank you to all of my friends who have helped me over the years, especially Nancy, Rick, JP, Tamara, Mary, and the Make-A-Wish Foundation Clan. I have learned a great deal in the classroom, but the things that I have learned from my family and friends about people and life are of equal, or more, importance. Thanks to all of you, for making me who and what I am today. Guidance Committee: The paper format was adopted for this thesis in accordance with Departmental and University regulations. The Development and Evaluation of Shipping Systems for Bedding Plants is to be submitted to Horticulture Technology. TABLE OF CONTENTS LIST OF TABLES vi LIST OF FIGURES vii LITERATURE REVIEW Introduction 1 Effects of Mechanical Stress 4 Effects of Ethylene ' 14 Effects of Chilling Temperature 17 Effects of Water Stress 17 Effects of Humidity 23 Effects of Simulated Transit 26 Literature Cited 27 DEVELOPMENT AND EVALUATION OF SHIPPING SYSTEMS FOR BEDDING PLANTS Abstract 33 Introduction 34 Materials and Methods 36 ASTM Standards for Vibration Testing 36 Ethylene Bioassay 38 Moisture Retention of the Plants and Media 40 Cost of Shipping Systems 40 Mechanical Vibration of Bedding Plants 42 Results and Discussions 57 Conclusion 80 literature Cited 83 Table LIST OF TABLES Page Literature Review Effects of Shaking on Growth Parameters of ’Wells 11’ Soybean. 12 Leaves and stipule abscised and chlorotic leaves in Philadendron scandens subsp. oxycardium exposed to ethylene and 5% carbon dioxide for 2 days at 23.5 C in light. 15 Effects of relative humidity and type of container on the growth of marigold (cv. ‘Double Eagle’) seedlings after 14 days of controlled environment treatment. 25 Development and Evaluation of Shipping Systems for Bedding Plants The average weight loss and standard deviation in grams of the different shipping systems when held in the dark for three days at 60F. 76 The per flat cost of the packaging systems for the initial shipment, shipments two through five and an average of the first five package uses. 76 The growth in cm of Impatiens wallerana cv. ‘Novette Series’, seven days after applying mechanical vibration for ten minutes at specific frequencies. 78 Duncan’s Multiple Range Test results for Impatiens wallerana cv. ‘Novette Series’. The plants were measured, applied with mechanical stress for 10 minutes at specific frequencies, and measured again after seven days. 79 Ranking of the packaging systems by factors important to the ultimate success and acceptance of the packages and the average ranking of packaging systems considering all factors. 81 The rank order of packaging systems calculated from the criteria above. 82 vi FIGURES Figure Page Literature Review 1. Time course of stem growth of ‘Bonny Best’ tomato as a function of daily gyratory shaking. Treatments included unstressed controls (C), 30 seconds of stress once daily (IX), and 30 seconds of stress twice daily (2X). 5 2. Effect of mechanical stress applied at different stages of growth and development of Chrysanthemum cv. ‘Indianapolis White’. 8 3. Cumulative height growth of greenhouse tree seedlings as affected by shading and shaking treatments. 9 Development'and Evaluation of Shipping Systems for Bedding Plants 1. The current non-collapsible metal racks. 34 2. Assembling the honeycomb pieces at Klooster’s Greenhouse 45 Kalamazoo, MI. 3. The honeycomb packaging system. 45 4. The corner ledges provide the support in the corners of the flat. 46 5. The metal corner and plastic stretch wrap system. 47 6. The durable plastic carrier flats. 49 7. The resin or wax coated corrugated boxes. 51 8. Collapsible racks are similar in appearance to non- collapsible racks. 52 9. The patented Smitty table. 53 10. The new disposable Smitty Table. 54 11. The plywood and honeycomb paper rack. 56 vii LITERATURE REVIEW INTRODUCTION As far back as 500 BC. the Romans were building forcing structures to extend the growing season and to overwinter plants. Probably around that same time gardeners started selling and trading their crops to other gardening enthusiasts. However crude, the early trading and selling of plants, also brought about the earliest forms of shipping, handling, and transportation of bedding plants as well. The earliest forms of shipping and handling were probably no more than carrying the plants home in their hands or in some type of a handmade basket (Carlson, 1985). The first commercial bedding plants were probably available from vegetable growers and garden market type operations where extra plants were started and sold along with the vegetable crops. The earliest forms of bedding plants were brought over from Europe in the form of seeds and cuttings (Carlson, 1985). Reportedly, the Dutch in 1655, were growing crops such as stocks, sweet William, fritillaria, violets, pinks, wallflowers, marigolds, and many other flowers and vegetables. Early flower breeding in the United States mostly centered around the more populated areas such as Boston, New York and Philadelphia (Ball, 1976). Peter Crouwels in Philadelphia was advertizing and selling geraniums, marigolds, sensitive plants, myrtle, and other crops in the late 1780’s. Other early gardening experts such as Richard Morris in 1825 suggested that tender plants such as ageratum, lobelia, fuchsias, begonias, alyssum, verbena, and zonal geraniums, could be started in greenhouses and then put outside as soon as favorable weather arrived. 2 During this whole period shipping and transportation were still done crudely and by hand (Ball, 1976). After the Civil War had passed, larger displays, greater quantities, and increased desire for bedding plants existed. Especially in the south, it became common for large beds of flowers using perennials and annuals. Although the desire for bedding plants grew, large quantities of bedding plants were still not sold commercially until the 1920’s. In 1923, bedding plants were in much greater demand and were starting to become a good extra source of income for vegetable growers. In Kalamazoo County, Michigan area vegetable growers had been growing celery since the Civil War. In the early 1920’s Jim Bell and John Shuring began to grow bedding plants as well (Wenke, 1990). The majority of the early Michigan bedding plants were pansies that were greenhouse sown and then field grown. Local growers would dig out bare rooted pansy plants, wrap them in newspapers and put the wrapped plants in grape or cherry lugs and sell them to local people. This was the beginning of the "modern” bedding plant and shipping industry. Consumption grew through the 1930’s with the major crops being petunias, marigolds, and pansies. In the early 1940’s the bedding plant industry was worth about 10 million dollars a year. After World War II the business and consumption boomed. By the end of the 1950’s it had reached over 32.8 million dollars a year and-by the end of the 1960’s business was up to over 61 million dollars a year. By the early 1980’s the business was earning over 300 million dollars a year, and is expected to reach over 500 million dollars by this year. 3 As the dollar values have blossomed into big business, so has the technology for breeding, sowing, growing, selling, shipping, handling, and transportation. The entire production of bedding plants has undergone complete metamorphosis from the early days of being a side job for vegetable growers. As the Kalamazoo area’s celery production declined, more and more of the celery farmers turned to bedding plants to make their livelihood. Today, the Kalamazoo Valley area is the largest seasonal bedding plant production area in the world. The method of sowing the seeds inside and transplanting them to the field has been replaced to complete production inside the greenhouse. The early greenhouse produced plants were grown in soil filled benches until they were sold. Once ready to be sold, they were cut out of the bench and put into wooden lug type flats which measured about 12" by 20". In the mid 1950’s Leonard Bettinger of Toledo Ohio set the trend of things to come by converting his entire operation from the heavy wooden flats to lighter plastic flats. Soon to follow was the development of inserts which allowed smaller numbers of plants to be planted in a flat and allowed the possibility of selling off parts of the original flat rather than the entire thing. Alma Plastics was first, followed by Fred Blackmore and Ken Diller to get involved with adopting plastic systems that were especially designed for use in growing bedding plants. Plastics began to catch on with the majority of growers by the mid 1960’s. Most growers, instead of changing to plastic all at once, first converted to a flat with wooden slats along the bottom which required eight plastic trays to fit inside of the wooden frame. By 1974, the entire bedding plant industry 'was virtually using only 4 plastic. The original inserts only had eight packs, at the time more often called baskets or pills (Carlson, 1985). By the end of the 1970’s the flats were pretty much as they are today, predominantly 12 or 15 packs, but having up to 18 to 24 break- apart packs. Despite its popularity, the future of the plastic flat system is unclear due to growing public skepticism about the use of disposable, nondegradable plastics. MECHANICAL STRESS A In the 1970’s, investigations were initiated to understand how mechanical stress effects plant growth (seismomorphogenesis). Mechanical stress (i.e., flexing or shaking) was determined to reduce the elongation of greenhouse Chrysanthemums. The frequency of the stress has an effect on the reduction of elongation. Stress applied for 30 seconds a day was less effective than tWo times a day (Hammer et al., 1974). Hammer considers "greenhouse lushness" a result of protection from the wind, higher relative humidity, less ultraviolet radiation and smaller variations in temperature. Shortly after that, studies at Purdue showed the growth of Lycopersicon esculentum and Pisum sativum was dwarfed when mechanical stimulation such as flexing, shaking, or rubbing of the plant axis occurred (Mitchell et al., 1975). Shaking of tomato plants once or twice a day reduced node and leaf number, shorten the intemodes, caused nodal swelling, epinasty of leaves and turned new leaves deeper green in color (Figure 2). NASA became interested in this phenomenon due to their curiosity of how 5 food will be grown in space stations. Further work at Purdue expanded the species known that were dwarfed by mechanical stress to include tomato, coleus, 105.0- 9.0-4 :ffn / Figure 1. Time H, course of stem gr OWth Of ’Bonny Best’ tomato as a function of daily gyratory shaking. Treatments included unstressed controls . (C), 30 seconds of 3““ . . stress once daily (IX), and 30 seconds 15.0- of stress twice daily // (2X). '. _. / . 0.0 , , 0m $.00 10.00 SIEH LENGTH (CH) e e .0 x 00::- i1{.oo ruler lHEl DRYS l Chrysanthemum, beans, soybeans and etiolated peas. It was also determined that herbaceous plants appear responsive to touch as well as shaking, and where the ‘ stimulus is applied has an effect on the response. Generally, they determined that shoot tips and rapidly expanding leaves are most sensitive to touch. Localized treatment with a stimulus does not however retard the growth on a different area of the plant (Mitchell, 1977). , The growth rate of etiolated Pisum sativum cv. Alaska seedlings was shown to be reduced by a single mechanical disturbance (Mitchell, 1977). Thigmo (contact)- 6 stress was more effective than seismo (vibrational)-stress. They also showed that manipulation of the epicotyl was less effective than manipulation of the hook region. The growth of the basal section (no auxin) was not affected by either type of stress, which indicates the stress response is specific for the auxin-dependent component of growth. Ethylene pretreatment and hook removal of the seedlings had the same effect with respect to growth as the thigmo—stress did on the hook region. Overall, this research suggested an auxin/ ethylene interaction is involved with the reduction of growth caused by the mechanical stress. Beyl and Mitchell developed a bench known as an automated, mechanical oscillatory shaking (AMOS) device (Beyl and Mitchell, 1977). The device was designed to test how height could be controlled in selected Chrysanthemum moriflorum cultivars in a commercial setting, using the AMOS device. The AMOS device automatically and uniformly applied a simultaneous shaking stress for 4 minutes at 8:00 am, which consisted of 160 to 220 gyratory cycles per minute. The fresh weight and height of all the cultivars tested were significantly reduced. The AMOS device was also used on C. monflorum cv. ’May Shoesmith’, to determine the dwarfing effect was greater on plants shaken at 8:00 am than ones that were shaken at 4:00 pm. or midnight. For significant dwarfing, thirty seconds to two minutes of stress per day is required, the effect is saturated at four to five minutes. Four-minute treatments, 2 - 4 times per day, will maximize the response (Beyl and Mitchell, 1977). Additionally, a one 4-minute stress per day had the same growth-retarding effect as four l-minute stresses. Shaking reduced fresh weight, dry weight and the number of 7 nodes. The dryeto-fresh weight ratio of the plants increased. Shaking did not cause a significant effect on flower size, floral keeping quality or flower bud initiation. Supporting studies showed that if the stress is applied during the rapid growth phase of plant growth development, it will result in the greatest reduction in height. Greatest plant height reduction occurs when the stress is applied during the macroscopic flower bud development. Stress during the early vegetative growth of the plant is least effective on overall plant height at flowering (Jerzy and Piszczek, 1979) (Figure 2). Inhibition in the growth of young tomato plants also occurs under the influence of vibrational stress. The response of the plants was stronger in winter than in the summer. The results of the mechanical stress treatment depended on the dosage: small doses of stress given repeatedly slowed down the growth of the transplant much more effectively than larger single doses given every day or every several days. The fresh weight of the shoots decreased under the influence of the stress, as did the dry weight, but to a smaller degree, thus the percentage of dry weight increased. The chlorophyll content in the leaves of plants treated with mechanical stress also increased (Piszczek and Jerzy, 1987). Mitchell also used Lycopersicon esculentum cv. ’Kokomo’ for further understanding of mechanical stress. Thigmomorphogenesis (contact stress) as well as seismomorphogenesis (vibrational stress) of the leaf surfaces increased leaf diffusion resistance and decreased transpiration on both stressed and unstressed . A 0—r—c— ‘—|__°—T—c 5 mass conraor no 513255 counter z 9 .- ( e 3 I .a II E i in ; iT IISI I 125456739ouu u i25456759oia own AND DEVELOPMENT (mks) atom AND DEVELOPMENT (mks) ,_ A—1—b—1—C A—r—B—r—C 5 no srnrss CONTROI . no sraess‘ couraor z t' -, 9 iii . = .i; .; 3 "'i . Hi 0 "i ' i I I .o I I g I, I I g In I l | ' ,- I.l I I I | Ill /IIII'III|. 5 I11 , IIIIIIIIII. :- amass IS 1 R E s s. w . III I I I I I I I I I I I I 1234561890ln '12545570960/ II 'GMNIH AND NEW (mks) N Figure 2. Effect of mechanical stress applied at different stages of growth and development of Chrysanthemum cv. ‘Indianapolis White’ . I - during vegetative growth (A) II - during microscopic flower bud development (B) 111 - during macroscopic flower bud development (C) IV - continuously during vegetative growth and reproductive growth and reproductive development (A + B + C) Open circle - flower bud visible Closed circle - florets colored 9 control plants. These responses suggest that the dry weight and growth reduction are not mused by prolonged reduction of stomatal aperture, changes in photosynthetic efficiency or respiratory rates (Mitchell et al., 1977). They did find, however, that the increase in dry weight paralleled increases in leaf area “for both stressed and unstressed plants, which suggested to them that the reduced photosynthesis was not the cause, but rather the result of retarded plant growth. Further work supports this where hardwood tree species (black walnut, sweet gum, and silver maple) were given mechanical stresses. Within a few days, daily shaking for only 30 seconds each, started to reduce growth (Ashby et al., 1979) (Figure 3). Except for black walnut, dry weight, leaf area and stem diameter were HEIGHT m ICU.) HEIGHT Om ICUJ I O - SILVER MAPLE o—(h-O UT SHADED—MT WK EN am men—swim BLACK WALNUT em MED-MT ”KEN go ... "3...... not stucco-men 10 — 335W” 9 1 1 1 1 1 1 1 1 1 1 22 2. 0 10 I. 22 a 3 9 15 21 " ‘11 “AV “E HEIGHT am tea.) a r- SWEETGUM a i— n i— 10 "’ “W‘M Ame aha-.m- n h WM W _ 1 J 1 1 1 1 1 1 1 l a a 0 10 i0 22 a a e is a: unit ’ new we Figure 3. Qimulative height growth of greenhouse tree seedlings as affected by shading and shaking treatments. , 10 not significantly reduced during a 50- to 60-day period. This led to the thought that shaking mainly affects the endogenous process rather than affecting photosynthesis. Sunflowers (Helianthus annuus) also experience reduction in stem length, shoot fresh weight, and leaf surface area when exposed to periodic shaking, rubbing, or drought stress treatments (Beyl and Mitchell, 1983). Exudate from the thigmo stress plants contained a broad band of extractable inhibitors, some of these bands co-chromatographed with abscisic acid (ABA). ABA-like substances were not detected in tall or dwarf controls. Enhanced cytokinin (CK)-like substances were found in the exudate collected from seismo stressed plants. Shoot tip extracts from thigmo stressed plants did not contain any detectable gibberellin (GA)-like substances. However, tip extracts from non-stressed plants contained multiple zones of GA—like activity. This provided them with evidence that other endogenous hormones, GA-like substances in particular, along with auxin and ethylene influence the plant’s growth when mechanical stress is present. The time of year also plays a roll in how affective these treatments are. For tomatoes, reduction of leaf area, stem length, water content and dry weight of leaves and stems is much more evident in the winter than the summer. This is apparently due to the difference in solar flux (Heuchert and Mitchell, 1983). The stems of shaken plants had greater cellulose, moduli of elasticity, rupture and ultimate shear strength than did controls (Heuchert et al., 1983). However, with peas (Pisum sativum cv. ‘Alaska’) that were tested during fall, winter, and spring, the plants grown in the winter, were least affected by thigmo-stress (Akers and Mitchell, 1983). 11 Shaking reduced growth in all seasons, and in all parameters except for the number of leaves and root dry weight after 16 days of treatment. Growth responses due to mechanical stress during the reproductive stages of growth (days 16 to 35) include a delay of anthesis, but no reduction on the number of fruit set. However, shaking also reduced the number of seeds per pod, but not their weight (Akers and Mitchell, 1983). Work done on poinsettia cultivars shows a relationship between mechanical stress and ethylene production. Mechanically bent petioles of potted Euphorbiapulchen'ima cvs. ‘Eckespoint C-l Red’, ‘V-14’, ‘Annette Hegg Diva’, ‘Annette Hegg White’, and ‘Annette Hegg Hot Pink’ produced between 3 and 70 times as much ethylene as petioles from non-stressed plants. The ‘Annette Hegg’ cultivars showed the greatest enhancement of ethylene evolution after being mechanically stressed for 24 hours and also were the most susceptible to leaf epinasty after being sleeved for 24 hours. The same pattern of epinasty as mechanically stress could be obtained by exposing the plants to 10 ppm ethylene for four hours. Spraying the plants with 250 ppm silver thiosulfate reduced the amount of epinastic behavior in the sleeved plants. ‘Eckespoint 01 Red’ and ‘V-14’ are less susceptible to ethylene, having reduced epinasty and produced less stress related ethylene (Saltveit et al., 1979). Research on soybeans (Glycine max cv. ‘Well H’) grown in greenhouses on gyratory shakers were shown to have shorter stems, less leaf area and lower leaf and plant dry weight than undisturbed greenhouse grown plants after 16 days of treatment (Pappas and Mitchell, 1985 ) (Table 1). Plants that were grown outdoors are 12 subjected to other environmental stresses such as ultraviolet radiation, wind, great fluctuations in relative humidity and temperature, were also smaller and had less dry weight than the greenhouse grown controls. Plants grown outdoors on gyratory shakers were not further inhibited than those plants not grown on the shaker (Pappas and Mitchell, 1985). Mechanical stress affects factors other than the height of the plants. In 1985, Akers and Mitchell of Purdue determined that sexual and asexual reproductive structures are also affected by periodic shaking stress. Shaking delayed anthesis in tomato but not marigold or potatoes. On marigold plants that were shaken, the Table 1. Effects of Shaking on Growth Parameters of ‘Wells 11’ Soybean. Seismic stress treatments was a five minute shake at 240 rpm administered three times daily for 15 days. Means (n=6) within rows followed by a different letter are different according to F test at 0.05 level of significance. GrowthParamctcr w . _ _ Plant dry wt (3) Leaf area (sq. cm) Stem length (cm) Specific leaf wt. ‘ Specific leaf water flower size was smaller than those of unshaken plants. Tomato plants however had a reduced number of buds and flowers, but fruit set was increased on the plants that had experienced mechanical stress. The affect of shaking on potatoes did not reduce 13 the number of tubers but did decrease their size. Overall, seismic stress seems to reduce the growth of reproductive structures and sometimes the number of reproductive structures (Akers and Mitchell, 1985). Takahashi and Suge, in 1980, studied sex expression in cucumber plants, as affected by mechanical stress. Their research involved looking at how mechanical stress affected four cultivars of cucumbers with different genetic backgrounds for sex expression. Mechanical stress given to the plants greatly reduced growth and increased the number of pistillate (female) flowers in the monoecious type, but mechanical stress had no effect on the sex expression of the gynoecious type. The effect of mechanical stress on the growth and sex expression of the monoecious type was nullified by the foliar application of GA4 and GA7. Silver nitrate had similar effects on nullifying the effect of mechanical stress on sex expression, but did not have the effect of growth retardation. Pistillate flowers were reduced on the gynoecious strain when silver nitrate was applied (Takahashi and Suge, 1980). Another study shows how eggplants and soybean seedlings were affected by being grown in greenhouses, outdoors protected from wind and outdoors with wind, and treated with mechanical stress in the forms of shaking, flexing, or undisturbed. The dry weight, leaf area and stem length were reduced by mechanical stress in the greenhouse and outdoor-windless environments. Plants grown outdoors developed increased leaf and stem weight, except for mechanical stressed outdoor plants which only enhanced the leaf weight but not the stem weight (Latimer et al., 1986). Similar is true for carrots grown indoors and mechanically stressed. Shoot height and weight 14 and fibrous root weight was reduced at all harvest intervals (25, 36, and 43 days) (Biddington and Dearman, 1987). It has also been shown that calcium ions inhibited growth when plants also received mechanical stress (Jones and Mitchell, 1989). Mechanical shaking has been shown to affect fruit from cucumber plants in adverse ways. Storage of fruit after shaking increases cell wall degrading enzymes (Miller et al., 1987). The mechanical stress induces biochemical and morphological changes in the major tissues of the fruit. However, tissue firmness and/ or ethylene production does not serve as an indicator of these changes. The effects of mechanical stress does not appear to be mediated through the action of ethylene. EFFECT OF ETHYLENE The importance of ethylene goes beyond its effects on reducing plant height or weight. In the closed environment of a semi-trailer truck, close monitoring needs to be done to control ethylene accumulation. Ethylene concentrations greater than 1 part per million (ppm) when exposed to ornamental lime plants (Citrus lattfolia cv. ‘Persian’), in airtight containers causes significant defoliation (Cunningham and Staby, 1975 ). Research done with Philodendron scandens subspecies oxycardium show interesting relationships between ethylene concentrations, temperature, carbon dioxide concentrations and light level and how leaf abscission is affected (Marousky and Harbaugh, 1979). Ethylene concentrations of 2.5 to 10 ul ethylene per liter air caused leaf and stipule abscission, chlorotic foliage, and overall, the plants grew 15 poorly. When the level and duration of exposure to the ethylene is increased, the degree of leaf abscission also increased. According to their work, plants exposed to 5 ul ethylene/liter air and held at 23.5 degrees C in light for 3 days, caused greater than 50% leaf abscission. However, plants held in the dark under the same temperature and, ethylene concentration lost only 20% of their leaves. If ethylene concentration is kept constant and temperature is decreased, the number of leaves abscised also decreases. Total leaf abscission occurred when plants were held at 27 degrees C at a concentration of 10 ul ethylene per liter air. The fewest number of leaves abscised when plants were stored in air that was enhanced to 5% carbon dioxide or when the leaves were coated with lanolin (Marousky and Harbaugh, 1979) (Table 2). Table 2. Leaves and stipules abscised and chlorotic leaves in Philodendmn scandens subsp. oxycardium exposed to ethylene and 5% carbon dioxide for 2 days at 23.5 degrees C in light. Erh‘yi Added ” Initial plLeeffiff::;11;..Lcaf': stipule)? {snpuie gycmae, level carbon number abscisfab'sCis " abscis. ‘rabscns.i '3 ,_‘;_i leaves (pl/l) dioxide Vof ‘ after after 3 ‘ after ' after 3 ' 73after 7 4 ’ (%) ‘* Wm? ' 6W L'ijdaYSit “PO“ . X14731??? :7 days o o 4.8 o o o o o o 5 4.7 o o o o o 5 o 45 05 22 25 ' 2.7 2.0 I 5 5 4.7 o 02 1.2 1.7 2.7 l6 Marousky and Harbaugh also studied flowering of Kalanchoe blossfeldiana when exposed to ethylene concentrations ranging from 0 to 1 pl ethylene per liter of air. Plants held for two days at 23.5 degrees C incurred damage at ethylene levels of 0.5 pl ethylene per liter of air or higher. Ethylene induced leaf abscission, chlorosis and sleepiness (the permanent closing of open florets). Bud florets were not as prone to injury as open florets. Bud floret opening is delayed, but they will open if ethylene is removed from the environment. Plants exposed to 2.5 pl ethylene per liter air were lightly injured at 6 degrees C for three days and were injured more severely as temperature is increased (Marousky and Harbaugh, 1979). Similar work was done in the Netherlands on over 50 species of ornamental potted plants. Plants were exposed to ethylene concentrations ranging form 0 to 15 pl ethylene per liter of air for 72 hours at 20 degrees C in the dark. After 24 hours, flowers, flower buds and / or whole inflorescence had abscised on the flowering potted plants. By 72 hours, most plants were beginning to experience leaf abscission. The species examined were found to vary in their sensitivity to ethylene (Woltering, 1986). Water stress, in addition to ethylene and temperature, plays an important role via its potentia to reduce plant quality. As with bedding plants, bare-root perennials are greatly affected by water stress. Higher temperatures and low relative humidity levels in conjunction with duration of exposure to these conditions, will accelerate moisture loss (Heiden and Cameron, 1986). Some species of plants are very susceptible and easily damaged by water stress, while other have a less critical reaction to water stress. Long term effects of water stress are not easy to detect at 17 first, the plants must first be planted and grown until all effects may manifest themselves. Other work by Cameron and Maqbool, showed a significant inverse linear relationship between water loss and regrowth quality (r2 > 0.90 in all cases) for bare-th hardy perennials. Models have also been developed which predict regrowth quality based on measured transpiration rates and these results (Cameron and Maqbool, 1986). EFFECTS OF CHILLING INJURY Cucumis sativus seedlings three days after emergence were exposed to chilling temperatures of 2 degrees C for one 24 hour period. Within six days, necrosis in the cotyledons and reduction of root and shoot growth became evident. Resistance to chilling (a reduction in necrosis to the cotyledons and less root and shoot stunting) was achieved by applying pretreatments. The most effective pretreatments to reduce the chilling injury were abscisic acid applied to the seedlings, withholding water from the seedlings, and salinization of the growing media (Rikin et al., 1976). From their data, it was concluded that ABA, whether applied to the seedlings directly or induced to increase naturally by exposing the plants to a shortage of water, leads to the development of chilling resistance in cucumber seedlings (Rikin et al., 1976). EFFECTS OF WATER STRESS ABA treatments and water stress were also studied by Cornish in 1985 on Chrysanthemum monfolium cv. ‘Puritan’. It was found that the reduced stomatal 18 aperture that followed water stress was associated with increased levels of endogenous ABA concentrations. Plants that were stressed by irrigation with 100mM NaCl before harvesting, reduced the subsequent water loss and reduced the stomatal aperture, but had no effect on the ABA content in the leaves. It was concluded from this that salt-induced stress affects the stomatal apertures directly (Cornish et al., 1985). Further work done by Cornish and Zeevaart at Michigan State University (1985) confirms the role of ABA’s involvement with water stress. Detached roots of Xanthium strumarium L. and Lycopersicon esculentum were stressed to various degrees under warm air and in the osmoticum Aquacide III. The roots of both species experienced increased levels of ABA accumulated when stronger and stronger stress was experienced. Because ABA was accumulated in detached roots and in the roots of girdled plants proved that ABA was being synthesized in the roots and not just transported there from the shoots. ABA levels in Xanthium increased by 100 times over their pre-stressed values and 15 times original values in tomato. Maximum ABA accumulation occurred after a 60 to 70% loss in fresh weight. The roots exhibit much greater relative increases than observed in the leaves, which suggested that the endogenous levels of ABA in roots could rise prior to the leaves wilting, and could possibly modify the plant’s water economy before the plant’s leaves wilt (Cornish and Zeevaart, 1985). Abscisic acid at 10“ M induced almost complete stomatal closure in isolated epidermal strips of Chrysanthemum X monfolium, and in cut shoots when taken up 19 in the transpiration stream. ABA sprayed onto intact leaves was less effective. In the greenhouse, ABA reduced the water loss of cuttings under conditions of low humidity, and stimulated root growth, although the hormone did not improve either the water content or rooting performance of cuttings under mist (Orton, 1979). A pot experiment was conducted in greenhouses to determine and compare the responses of rice (Oryza sativa L. var. IR36), maize (Zea mays L. var. DMR-Z), and soybean (Glycine max L. Merr. var. Clark 63) to soil water stress. Leaf ‘ elongation, dawn leaf water potential, transpiration rate, and nutrient uptake in stressed rice declined earlier than in maize and soybean. When compared to rice, maize and soybean maintained higher dawn leaf water potential for a longer period of water stress before leaf elongation significantly declined. Nutrient uptake under water stress conditions was influenced more by the capacity of the roots to absorb nutrients than by transpiration. I It was concluded that the ability of maize and soybean to grow better than, rice under water stress conditions maybe due to their ability to maintain turgor as a result of the slow decline in leaf water potential brought about by its lower transpiration rate (Tanguilig et al., 1987). Ekanayake and others determined that water deficits at the anthesis stage of rice (Oiyza sativa L.) were found to induce a high percentage of spikelet sterility and reduce grain yield. A well watered treatment and two water stress treatments were imposed on greenhouse grown, potted rice cultivars IRAT 13 (an upland cultivar) and IR 20 (a lowland cultivar) at the time of flowering. The IR 20 cultivar had a high level of response between control plants and drought stressed plants. The 20 deleterious effects of water deficits on spikelet opening and spikelet water loss contributed to reduced spikelet fertility (Ekanayake et al., 1989). Wudiri and Henderson in 1985 studied how drought stress affects the flowering and fruit set on tomatoes. Greenhouse and field experiments were done to study the effects of drought stress on tomato cultivars ‘Saladette’ and ‘VF145B- 7879’. ‘Saladette’ is a determinate, compact, non-branching cultivar while ‘VF145B- 7879’ is a semi-determinate cultivar with a branching habit. Water stress was much more pronounced on ‘VF145B-7879’ than in ‘Saladette’. Severe drought stress reduced the fruit set by more than 90% in ‘VF145B-7879’ while ‘Saladette’ fruit set was reduced by 40%. ‘Saladette’ was considered to perform better because it had the ability to roll-up its leaves during high evaporative demand, thereby maintaining high leaf water potential, and ‘VF145B«7879 did not have this adaptation (Wudiri and Henderson, 1985). Another study on water stress looked also at how ozone levels affect growth responses. Three-year-old Fraser fir (Abies fi-asen') seedlings were exposed to three levels of moisture stress and ozone levels of 0.02, 0.05 and 0.10 ppm three days per week for a period of four hours per day for a total of ten weeks. Water stressed caused a significant decrease in Fraser fir biomass, transpiration and needle conductance. Water stress reduced the root and shoot dry weight by. at least 20%. Even moderate water stress was significant in reducing the transpiration and needle conductance. It was also realized that the water use efficiency improved by 30% after ten weeks of exposure to severe water stress (T seng et al., 1988). 21 Leaf water potential, leaf water vapor diffusion resistance and transpiration of azalea (Rhododendron simsii cvs. ‘Hellmut Vogel’ and ‘Reinhold Ambrosius’) were measured throughout a seven day drying period. Recovery after severe water stress was found to be rapid. The two cultivars differed with regard to stomatal dimension and densities. The difference in behavior to the water stress seemed to be very dependent on the root to shoot ratio (Ceulemans et al., 1979). Besides changes in the growth response in plants, drought stress also affects the level of proline accumulated inside plants. Several varieties of Lycopersicon exculentum Mill. were exposed to seven days of drought stress followed by a 15 day rewatering period. Proline accumulation was greater in ‘Hosen’ and ‘S-S’ than in ‘LX-ll’, ‘1970’, ‘Pakmor’, ‘Faculty-16’, ‘Alcobaca’ and ‘475’. Rewatering in ‘Hosen’ and ‘S-S’ also resulted in a decrease of proline when compared to the controls, while in the other varieties proline accumulation continued long after turgor had been regained. The extent of this continued accumulation was not correlated with the degree to which the varieties were dehydrated. Once the plants were being watered again, the rate of leaf elongation increased, however, the final leaf size and the whole shoot and root fresh weight of the plants after recovery were not found to be correlated to the level of suffering the plants incurred. It was concluded from this that proline accumulation at the time of dehydration signals drought stress in tomato plants but does not correlate with the overall varieties’ sensitivity to transient dehydration in recovered plants (Aloni and Rosenshtein, 1984). Antitranspirants also play a role in the proline accumulation during dehydration 22 as well as effecting stomatal openings and relative water content in tomato. These factors were investigated when four cultivars of tomatoes were tested with three antitranspirants, phenyl mercuric acetate (PMA), 8-hydroxyquinoline sulphate (8-HQ) and koalinite. Results showed some 20 to 33% of stomata were closed in the different cultivars. There were significant differences in cultivar response, the reduction in stomatal aperture ranged from 32% to 37%. PMA was the most effective in reducing the stomatal aperture and increasing both proline concentration and the relative water content. The antitranspirants caused a significant difference in both proline accumulation and relative water content in all cultivars. The data showed that the tomato cultivars treated with antitranspirants appeared to have a better maintenance of high values of relative water content with a higher degree of stomatal control (Srinivasa Rao, 1986). Dwyer and Stewart did research on effects of water stress on growth yield and development rate of barley. It was found that water stress hastened leaf area senescence and, in general, the more severe the stress, the greater the reduction in leaf area. Most stress treatments also resulted in lower shoot/ root ratios and significant yield reductions relative to well-watered controls. Development was significantly delayed by several water stress treatments and no treatment significantly hastened development (Dwyer and Stewart, 1987). Water relations and temperature in plants not only affect the growth responses in plants but also have an effect on the net photosynthesis (Khairi and Hall, 1976). In Citrus sinensis cv. ‘Osbeck’ and Citrus paradisi the net photosynthesis was shown 23 to decrease with higher temperatures or greater water vapor pressure differences between the leaves and the air. The reduction in net photosynthesis due to higher temperatures was associated with reduction in mesophyll conductance to C02. The , effects of greater vapor pressure differences on net photosynthesis were associated with changes in total leaf conductance to water vapor. The actual level of water-use efficiency was reduced at higher temperatures and greater water vapor pressure differences. However, the internal water-use efficiency when calculated for a constant vapor pressure difference, increased with increases in vapor pressure differences, which indicated a possible adaptive mechanism for condition during high evaporative demands (Khairi and Hall, 1976). EFFECTS OF HUMIDITY The interaction of carbon dioxide and relative air humidity also have been shown to effect the growth of Chrysanthemum X monfolium cv. ‘Fiesta’. The Chrysanthemums were grown hydroponically for six weeks in grth chambers at relative humidity (RH) levels of 50 and 95% and carbon dioxide (C02) levels of 340 to 940 pl 1". The higher RH and higher CO2 concentrations resulted in an increased relative growth rate (RGR), increased dry weight of leaves, stems and roots, and increased the leaf area of the main and lateral stems during the first two weeks of growth. Between three and six weeks of growth, the interaction of RH and CO, was either lost or, as in the same case of RGR and root dry weight, reversed in such a way that a negative effect of high CO2 at high RH was found. At six weeks positive 24 growth effects from RH and CO2 were noticed, but no interaction appeared in plant height, number of leaves on lateral shoots, or number and length of lateral shoots. Data showed increases in RH resulted in an increase in shoot to root dry weight. Water consumption decreased sharply at higher RH levels and moderately with high levels of C02. Stomatal aperture was larger at high RH, but smaller at high CO2 levels. From this, it was concluded that increased plant growth resulting from increased RH might be caused by an increase in stomatal aperture and facilitates C02 absorption and utilization (Gislerod and Nelson, 1989). It has been known for a long time that humidity affects the grth of plants in particular controlled environments. In 1971, Krizek and others studied three levels of relative humidity (40%, 65%, and 90%) and two types of containers (clay and plastic) on the seedling growth of three F1 hybrid annuals (Ageratum houstonianwn cv. ‘Blue Blazer’, Petunia hybrida cv. ‘Pink Cascade’ and Tagetes erecta cv. ‘Double Eagle’). After 14 days at 40% RH the growth of all species were reduced when compared against the controls. Plants grown at 65% RH had much greater increases in fresh weight, dry weight and leaf area than those grown at 40% RH. Using clay pots instead of plastic pots also increased plant weight and size. Another difference in the plants grown at 65% RH was an increase in plant height, however, the number of nodes was only slightly increased. Further increasing the RH to 90% had no significant increase on fresh weight, dry weight, or percent dry weight for any of the species, in either container (Krizek et al., 1971). 25 Table 3. Effects of relative humidity and type of container on the growth of marigold (cv. ‘Double Eagle’) seedlings after 14 days of controlled-environment treatment. 40% RH 92 303 73 8.4 Clay Pot D C AB C 40% RH 11.0 115.0 6.7 327 Plastic Pot BC A BC A 65% RH 105 67.0 6.0 220 Clay Pot I C B C B 65% RH ' 113 1956.0 1143 6.0 38.1 Plastic Pot ABC A A C A 90% RH 105 1163.3 67.3 6.0 20.8 Clay Pot C B B C B 90% RH 122 2358.3 138.3 6.0 38.8 Plastic Pot A A A C A Means not followed by the same letter are significantly different at the 5% level applying Duncan’s Multiple Range Test. The RH effect has also been demonstrated by more recent work done in Norway in 1986 by Mortensen. In the Norway experiment, young plants of 10 greenhouse species were grown from 24 to 100 days at 5560, 70-75, or 90-95% RH in growth rooms. Six of the crops experienced a significant increase in dry weight when comparing the lowest and the highest levels of RH. The increase in dry weights ranged from; 68% in Nephrolepl's exaltata, 20% in Lycopersicon esculentum, 31% in Chrysanthemum X monfolium, 47% in Begonia X hiemalis, 31% in Euphorbia pulcherrima, and 36% in Saintpaulia ionantha. The dry weight of Campanula isophylla, Rosa, Cucumis sativa and Lactuca sativa was not affected by changes in RH, 26 and Soleirolia soleirolii was negatively. affected. The fresh weights of cucumbers and lettuce increased even though the dry weights did not. In most of the species, increasing the RH greatly increased the shoot length. Same is true for the number of leaves, in most species as the RH increased, so did the number of leaves. The number of flowers and flower buds increased in Saintpaulia as the humidity increased. It was also observed that the time to flower was reduced with increased RH in Saintpaulia, Begonia and Campanula (Mortensen, 1986). SIMULATED TRANSIT In 1984, Auer and McConnell researched the effects of simulated transit vibration on Begonia and Schefflera. Vibrations of 0.02 gravitational force (g) at 4.1 cycles per second (cps) were applied to Begonia cv. ‘Medora’ and Schefllera arboricola cv. ‘Merrill’ during six days of simulated transit. Vibration caused leaf abscission, necrotic leaf areas and severed stein tips. Silver thiosulfate (STS) increased leaf abscission of Begonia but not Scheffleras during the simulated transit. Ethylene emanation from stem tips of both species increased as STS concentration increased, Ethylene emanation from stem tips was not affected by vibration. During four weeks of simulated retail holding, STS decreased Begonia leaf abscission (Auer, 1984). LITERATURE CITED Abeles, EB. 1973. Ethylene in Plant Biology. New York, London: Acad. Akers, Stuart W., Cary A. Mitchell. 1984. Seismic stress effect on vegetative and reproductive development of ’Alaska’ pea. Canadian Journal of Botany 62:2011-2015. . Akers, Stuart W., Cary A. Mitchell. 1985. Seismic stress effects on reproductive structures of tomato, potato, and marigold. HortScience 20(4):684-686. Aloni, Beny, Gila Rosenshtein. 1984. Proline accumulation: A parameter for evaluation of sensitivity of tomato varieties to drought stress? Physiologia Plantarum 61:231-235. Ashby, W. Clark, C.A. Kolar, T.R. Hendricks, R.E. Phares. 1979. Effects of shaking and shading on growth of three hardwood species. Forest Science 25(2):212- 216. Auer, C. A., D.B. McConnell. 1984. Simulated transit vibration and silver thiosulfate applications affect ethylene production and leaf abscission of Begonia cultivar Medora and Schefi'lera arboricola. HortScience 19(4):517-519. Ball, V. 1976. Early American horticulture. Grower Talks 40(3):50-53. Beyl, Caula A., Cary A. Mitchell. 1977. Characterization of mechanical stress dwarfing in chrysanthemum. Journal of the American Society for Horticultural Science 102(5):591-594. Beyl, Caula A., Cary A. Mitchell. 1977. Automated mechanical stress application for height control of greenhouse chrysanthemum. HortScience 12(6):575-577. Beyl, Caula A., Cary A. Mitchell. 1983. Alteration of growth, exudation rate, and endogenous hormone profiles in mechanically dwarfed sunflower. Journal of the American Society for Horticultural Science 108(2):257-262. Biddington, N. L., A.S. Dearman. 1987. The effects of mechanical stress on carrot growth. Journal of Horticultural Science 62(3):359-362. Cameron, Arthur C., M. Maqbool. 1986. Postharvest storage of bare-root hardy perennials: the relation of water loss to storage survival. Acta Horticulturae 181:323-329. 27 28 Carlson, William H. 1985. The bedding plant industry- past and present. Bedding Plants III, A manual on the culture of bedding plants as a greenhouse crop. Edited by John W. Mastalerz and E. Jay Holcomb. Pennsylvania Flower Growers. pgs. 1-7. Ceulemans, R., I. Irnpens, R. Gabriels. 1979. Comparative study of leaf water potential, diffusion resistance, and transpiration of azalea cultivars subjected to water stress. HortScience 14(4):507-509. Cornish, K., A.I. King, M.S. Reid, J .1... Paul. 1985. Role of ABA in stress-induced reduction of water loss from potted chrysanthemum plants. Acta Horticulturae 167:381-385. Cornish, K., J.A.D. Zeevaart. 1985. Abscisic acid accumulation by roots of Xanthium strumarium L. and Lycopersicon esculentum Mill. in relation to water stress. Plant Physiology 79(3):653-658. - Cunningham, J .L., G.L. Staby. 1975. Ethylene and Defoliation of Ornamental Lime Plants in Transit. HortScience. 10(2):174-175. Dwyer L. M., D.W. Stewart. 1987. Influence of photoperiod and water stress on growth yield and development rate of barley measured in heat units. Canadian Journal of Plant Science 67(1):21-34. Ekanayake, I. 1., SK. DeDatta, P.L. Steponkus. 1989. Spikelet sterility and flowering response of rice to water stress at anthesis. Annals of Botany 63(2):257-264. Gislerod, Hans R., P.V. Nelson. 1989. The interaction of relative air humidity and carbon dioxide enrichment in the grth of Chrysanthemum X man'folium Ramat. Scientia Horticulturae 38:305-313. F unke, G.L., F. deCoeyer, . deDecker, J. Maton. 1938. Response time to ethylene in tomato. Biol. Jaarb. 5:335. Hammer, Allen R, C.A. Mitchell, T.C. Weller. 1974. Height control in greenhOuse chrysanthemum by mechanical stress. HortScience 9(5):474-475. Heiden, Ralph, Arthur C. Cameron. 1986. Bare-root perennials require cautious handling. American Nurseryman April 1, 1986:75-88. Heuchert, Joan C., 1.8. Marks, C.A. Mitchell. 1983. Strengthening of tomato shoots by gyratory shaking. Journal of the American Society for Horticultural Science 108(5):801-805. 29 Heuchert, Joan C., Cary A. Mitchell. 1983. Inhibition of shoot growth in greenhouse- grown tomato by periodic gyratory shaking. Journal of the American Society for Horticultural Science 108(5):795-800. J erzy M., P. Piszczek. 1979. The retardation of chrysanthemum by mechanical stress applied at different stages of grth and development. Acta Horticulturae 91:377-381. Jones, Russell 8., Cary A. Mitchell. 1989. Calcium ion involvement in growth inhibition of mechanically stressed soybean (Glycine max) seedlings. Physiologia Plantarum 76:598-602. Khairi, Mohamed M.A., Anthony E. Hall. 1976. Temperature and humidity effects on net photosynthesis and transpiration of Citrus. Physiologia Plantarum 36:29- 34. Krizek, Donald T., W.A. Bailey, H.H. Klueter. 1971. Effects of relative humidity and type of container on the growth of F1 hybrid annuals in controlled environments. American Journal of Botany 58(6):544-551. Latimer, Joyce 6., T. Pappas, C.A. Mitchell. 1986. Growth responses of eggplant and soybean seedling to mechanical stress in greenhouse and outdoor environments. Journal of the American Society for Horticultural Science 111(5):694-698. Latimer, Joyce G., Cary A. Mitchell. 1988. Effects of mechanical stress or abscisic acid on growth, water status and leaf abscisic acid content of eggplant seedling. Scientia Horticulturae 36:37-46. Marousky, F .J ., B.K. Harbaugh. 1979. Interactions of ethylene, temperature, light, and carbon dioxide on leaf and stipule abscission, and chlorosis in Philodendron scandens subsp. oxycartlium. Journal of the American Society for Horticultwul Science 104(6):876-880. Miller, Raymond A., J.P. Dalmasso, D.W. Kretchman. 1987. Mechanical stress, storage time and temperature influence cell wall-degrading enzymes, firmness, and ethylene production by cucumbers. Journal of the American Society for Horticultural Science 112(4):666-671. Mitchell, Cary A., C.J. Severson, J .A. Wott, P.A. Hammer. 1975. Seismomorphogenic regulation of plant growth. Journal of the American Society for Horticultural Science 100(2):161-165. 30 Mitchell, Cary A. 1977. Influence of mechanical stress on auxin-stimulated growth of excised pea stem sections. Physiologia Plantarum 41:129-134. Mitchell, Cary A. 1977. NASA launches a new experiment to explore how plants react to stress. Horticulture September 1977: 10-13. Mitchell, Cary A., H.C. Dostal, T.M. Seipel. 1977. Dry Weight Reduction on mechanically-dwarfed tomato plants. Journal of the American Society for Horticultural Science 102(5):605-608. Mortensen, LM. 1986. Effect of relative humidity on growth and flowering of some greenhouse plants. Scientia Horticulturae 29:301-307. Orton, P. J. 1979. The influence of water stress and abscisic acid on the root development of Chrysanthemum X monfolium cuttings during propagation. Journal of Horticultural Science 54(3):171-180. Pappas, Thalia, Cary A. Mitchell. 1985. Influence of seismic stress on photosynthetic productivity, gas exchange, and leaf diffusive resistance of Glycine max (I...) Merrill cv. Wells II. Plant Physiology 79:285-289. Pappas, Thalia, Cary A. Mitchell. 1985. Effects of seismic stress on the vegetative growth of Glycine max (1..) Merrill cv. Wells 11. Plant, Cell and Environment 8:143- 148. Piszczek, P. M., M. Jerzy. 1987. The response of Lycopersicon esculentum Mill. transplants to mechanical stress. Acta Agrobotanica 40(1-2):5-14. Rikin, Amon, A. Blumenfeld, A. Richmond. 1976. Chilling resistance as affected by stressing environments and abscisic acid. Botanical Gazette 137(4):307-312. Saltveit, M. J r., D.M. Pharr, R.A. Larson. 1979. Mechanical stress induces ethylene production and epinasty in Euphorbia pulcherrima cultivars. Journal of the American Society for Horticultural Science 104(4):452-455. Srinivasa Rao, N.K. 1986. The effects of antitranspirants on stomatal opening, and the proline and relative water contents in the tomato. Journal of Horticultural Science 61(3):369-372. Takahashi, H., H. Suge. 1980. Sex expression in cucumber plants as affected by mechanical stress. Plant and Cell Physiology 21(2):303—310. 31 Tanguilig, V . C., E.B. Yambao, J .C. O’Toole, S.K. DeDatta. 1987. Water stress effects on leaf elongation leaf water potential transpiration and nutrient uptake of rice, maize and soybean. Plant and Soil 103(2):155-168. Tseng, E. C., J .R. Seiler, B.I. Chevone. 1988. Effects of ozone and water stress on greenhouse grown Fraser fir seedlings growth and physiology. Environmental and Experimental Botany 28(1):37-42. WOltering, E. J. 1986. Sensitivity of various foliage and flowering plants to ethylene. Acta Horticulturae 181:489-492. Wenke, Chris, W.H. Carlson, G. Arent, M. Klooster, T. Stiles. June 1990. Personal interview to discuss the history of the Michigan Bedding Plant Industry. Wudiri, B. B., D.W. Henderson. 1985. Effects of water stress on flowering and fruit set in processing Lycopersicon. Scientia Horticulturae 27(3-4):189-198. DEVELOPMENT AND E VAL UA TION 0F SHIPPING SYSTEMS FOR BEDDING PLANTS Development and Evaluation of Shipping Systems for Bedding Plants Scott L. Derthick and William H. Carlson Department of Horticulture, Michigan State University, East Lansing, MI. 48824-1325 Additional index words. Shipping systems, bedding plants, natural frequency, ethylene accumulation, moisture retention, vibration simulator, resonance, packaging systems, ASTM Standards, resonance frequency. Received for publication . Michigan State University Agricultural Experimental Station Paper no. . This project was funded in part by the Kalamazoo Valley Plant Growers Cooperative. Supplies were supplied by Hexacomb, Honeycomb Corp. of Kalamazoo, MI., Sico-Boxes of the Netherlands, Gene Smith, holding patents for the Smitty Tables, Davenport IA., and the School of Packaging, Michigan State University. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked Mm solely to indicate this fact. 32 ABSTRACT Seven new methods of shipping commercially grown bedding plants have been developed, studied and evaluated. The seven packaging systems are: 1. a stackable, disposable rack constructed from honeycomb paperboard 2. a column of flats held together by metal corners and stretch wrap plastic 3. rigid, stackable, plastic carrier flats 4. resin or wax treated corrugated boxes 5. collapsible plastic or metal shipping racks 6. The patented "Smitty Table" constructed of plywood and plastic center side posts 7. A stackable rack constructed of a combination of honeycomb paperboard and plywood. All of these systems have been subjected to vibration testing to simulate long distance shipping, ethylene concentration evaluations, moisture retention capacity, and other measures to maintain the quality of the plants during shipping. Selected species of bedding plants were vibrated at various frequencies and measured for changes in growth rates seven days after the treatment. All the systems were modified after testing to withstand the experimental parameters established by ASTM Standards to meet the requirements that are essential for long distance shipping. The packaging systems have been tested on a vibration table at each resonance point for ten minutes at one half G, six of the packages have been structurally modified to be able to withstand the ASTM vibration testing. The modified honeycomb system and the corrugated box systems have been used for shipping plants from Michigan to southern United States markets. The patented "Smitty Table" is also being used in the United States. 33 INTRODUCTION The current method of packaging and shipping bedding plants in Michigan is inefficient and costly. The present method involves shipping flats on non-collapsible racks in semi-trailer trucks (Figure 1). The disadvantage of this method is the trucks must retum to Michigan without a paying backhaul. Until recently this financial luxury was tolerated, however, the southern US. growers are now becoming very competitive, which is forcing the Michigan growers to look for financially acceptable alternatives. Great strides have already taken place in Europe and other areas to efficiently ship plant material grown in flats. Figure 1. The current non-collapsible racks. 34 35 There are two strategies that can be used in designing packages, either a disposable system or a collapsible and returnable system. It is difficult when using a disposable system to design a package that is strong enough to support the massive weight of the product and inexpensive enough to justify it being used only once and then disposed of. Using returnable systems creates a situation where it is mandatory to keep track of where all of the shipping containers are, and how and when they will be returned from their drop off points. I Seven shipping systems have been selected for this project, one is used as a disposable system, three can be either disposable or reusable, and three are collapsible and returnable. The seven systems are: 1. A rack system constructed from honeycomb paper. 2. A system where the flats are assembled into columns using metal corners and stretch wrap plastic. 3. Durable plastic carrying flats with interchangeable corner pieces. 4. Disposable resin and/ or wax treated corrugated paperboard boxes. 5. Collapsible metal or plastic shipping racks. 6. The patented Smitty Table, which uses plywood shelves and plastic center side supports. 7. A rack system constructed of honeycomb paper and plywood. MATERIALS AND METHODS ASTM STANDARDS FOR VIBRATION TESTING The American Society for Testing and Materials (ASTM) has determined procedures to follow to evaluate the estimated strength of packages during transportation. Shipping containers of all types are exposed to complex dynamic stresses when subjected to the vibration present during the transportation process. Resonant responses during shipping can be severe and may lead to package or product failure. By identifying the critical frequencies, it may be possible to minimize the effect of these occurrences. Exposure to vibration can affect all aspects of the shipping container, its interior, means of closure, and the contents. The simulated vibration testing allows analysis of the interaction of these components. Design modifications can be utilized to achieve optimum interaction of all packaging components. (ASTM Standard D 999). Method "0 under ASTM Standard-D 999 details the procedures required for testing a palletized load, unitized load, or vertical stack resonance test. The procedure specifies that a full-size load either unitized or palletized should be loaded on the vibration machine to a height equal to that used in shipping. A single vertical column of shipping containers can be used if a vertical stack alignment is used in shipping. If this method is used, restraining devices should be applied to the 36 37 vibration platform to prevent the packages from horizontal movement off of the platform or to prevent the column from toppling over. To allow for free movement during vibration, the restraining devices should allow 0.4 inches clearance in all horizontal directions around the test specimens. An accelerometer should be attached to the platform near the specimens, but not so it will come in contact with the packages. The vibration simulator should be set to a force not less than, 1/2 the force of gravity (1 /2 G). The simulator should be programmed for a sweep between 2.0 and 100 Hertz, the vibrations which are normally experienced during highway travel via a semi-trailer truck. ‘ The vibration simulator starts at the low end of the frequencies and sweeps logarithmically upward at a rate of 0.5 to 1.0 octaves per minute. The sweep should proceed all the way up to the high limit and then back down, and then repeated one more time. During the sweep, all resonance responses (severe vibration or bouncing) should be noted. Once the ranges of resonance have been determined, the package should be held continuously (dwell time) at the peak resonance points for a duration of ten minutes. Multiple unit loads can exhibit several resonance responses. The resonance ranges may overlap or they may be distinctively different from one another. If they are all within a narrow range, one test-hold is sufficient at the most severe frequency. If several distinctive resonance points are determined, a ten minute dwell time should be completed on the four most severe resonance responses. If damage occurs during the dwell time, the vibration can be paused to examine the package and make a determination if the vibration testing should continue. At the conclusion of all dwell times, the package 38 should be thoroughly inspected for damages to all components of the packaging system. Further testing must be done after each change in the structural design or manufacturing practices of the package. The ASTM Standard concerning the duration of dwell time is ASTM D-4169. ETHYLENE BIOASSAY Ethylene is a hormone produced by plants that regulates many aspects of plant growth and development. Ethylene has an important role in plant physiology during seed germination, leaf senescence and fruit ripening. Ethylene production is also increased due to certain types of Stress such as, temperature extremes, chemicals, drought, irradiation, overwatering, damage from insects or diseases and mechanical damage (Abeles, 1973). Due to the tightly enclosed construction of semi-trailer trucks and possible mechanical damage due to plant vibration during shipping, close monitoring of ethylene concentration and accumulation is essential. After the packaging systems were developed and tested for vibrational stability, it was determined that how these packages affect the air circulation around the packages should be determined. Ethylene concentrations as low as 1.0 ppm have been shown to cause significant defoliation of ornamental lime plants (Cunningham and Staby, 1975). The open florets and flowers buds of Kalanchoe blossfeldiana are also prone to permanent 39 damage at very low concentrations (0.5 pl of ethylene per liter of air) of ethylene (Marousky and Harbaugh, 1979). To determine if the packages being investigated were causing an accumulation of ethylene, an ethylene bioassay was developed. Tomato plants were used for the bioassay because they. have been shown to be susceptible to ethylene damage at all stages of plant development (Funke et al., 1938). Tomato plants ranging from three weeks to eight weeks old were grown under normal greenhouse conditions. Before being assembled into the shipping packages, half were treated with vibration testing at a force of 1/2 G at frequencies ranging from 2.0 to 100 Hertz for 20 minutes. The other half of the flats of tomatoes were not subjected to vibrational stress. The plants were then randomly assigned to the seven different packaging Systems. The packages were assembled similar to the way that they were during the vibrational testing. All of the packages were then put in a dark, tightly enclosed room at 60 degrees F, for three days. At the end of the three days, the plants were removed from the packages and put back under normal greenhouse conditions. The plants were observed immediately after removal from the packages and observed daily for the next two weeks. Any noticeable signs of characteristic ethylene damage were documented. 4o MOISTURE RETENTION OF THE PLANTS AND MEDIA One method of determining the amount of air exchange between the inside and outside of the package would be to determine the amount of water loss from the plants and soil. The greater the circulation of air moving through the package, would result in a greater amount of water loss from the flats of plants and growing media. If circulation of air through the packaging systems was minimal, the result would be an increase in humidity inside the moist package environment, resulting in a lower water vapor deficit between the plants and the air, which would result in the flats loosing minimal amounts of water. Before the tomato plants were assembled into their respective packages, the flats of five week old plants were thoroughly watered and then weighed. The plants were stored for three days under the conditions mentioned above. After the three days in storage, the plants were weighed a second time to determine the weight (water) lost during the period of storage. This method would make it possible to rank the packages in order of likelihood to experience drought and ethylene related problems. COST OF SHIPPING SYSTEMS Cost is a very important factor in determining the likelihood of whether or not a shipping system can effectively be implemented into an actual business operation. 41 The cost of the systems can be influenced by the region they are being implemented in, cost of materials, quantities of materials ordered (the larger the order the cheaper the cost), availability and cost of labor in the area, useful life of the package, if parts of the packaging systems are lost during transit or at the retail market, and many other factors. It is also important to calculate the cost of the shipping systems the for the first time the packaging systems are used, as well as subsequent uses. Disposable systems would need to be remanufactured and repurchased each shipment, while returnable systems can be returned and reused cheaper than they can be remanufactured. For these returnable systems, the initial cost might be higher than the disposable systems, but when the cost is spread over several uses, they can become more competitive. For this reason, the cost/benefit relationships will be calculated for shipment one, shipments two through five, and then averaged out on a per usage basis for shipments one through five. The cost of the shipping systems is to be calculated on the premise that the returnable components are not lost and can be returned without excessive damage. In the event of lost and / or damaged components, the cost of shipments two through five would have to be increased to reflect the damages. 42 MECHANICAL VIBRATION OF BEDDING PLANTS The Literature Review section of this thesis goes into great depth concerning the work done by Mitchell and others about mechanical stress and vibrating plants. Mechanical stress to plants causes many various plant responses (see Literature Review), the most typical is, a reduction in plant height. For the work done in this project, two questions arose concerning how and/or if plants respond to the vibrational stress encountered during their shipping and handling. One question proposed was, would a one time vibrational stress at a specific frequency, rather than a daily, or several times daily, non specific frequency stress reduce plant growth? The second question was, does the vibration encountered during the shipping and handling cause any adverse side-effects to the plants. Experiments were designed to test these questions on impatiens, tomato, peppers, dahlia, geraniums, and begonias. The plants were grown in four inch pots under 65 F nights and 68 F days under natural light conditions. Once the plants had reached flowering, the 64 most homogeneous plants of each species were selected for the testing. Four plants from each species were randomly assigned to 16 different treatments. Plant height was measured and documented along with comments about the plant’s appearance of flowers and leaves. The treatments consisted of vibration in a range of specific frequencies between 2 and 90 Hertz. The plants were held for ten minutes (dwell time) at the following frequencies: 2 Hz, 6 Hz, 10 Hz, 14 Hz, 17 Hz,20Hz,25Hz,30Hz,40Hz,50Hz,70Hz,90Hz,plantsthatwereswept 43 ' through the entire range, plants that experienced every frequency for ten minutes at each one, a control (blank) with plants that were taken to the Packaging building but not vibrated, and control plants that stayed in the greenhouse the entire time. After receiving the vibration testing, the plants were returned to the same greenhouse that they had been grown in. The plants were observed daily for signs of damage. Signs of damage included; yellowing, broken or drooping leaves, flower blasting or abscission, and any other "unusual” occurrences. Seven days after receiving the treatments, the plants were measured to determine changes in height that had occurred. SHIPPING SYSTEM 1: Honeycomb Paper Rack System A relatively new product used for a packaging material is a modification of corrugated paperboard known as honeycomb paper. Honeycomb paper derives its name from its honeycomb like appearance and can be made in any thickness from one to four inches. Honeycomb boards that are over four inches thick, lose considerable amount of their strength. Inside the honeycomb boards are vertical flutes, the shorter the flutes (the closer together the horizontal support) the greater the proportional strength that can be achieved, the longer the flutes, and thus the further apart the horizontal support, results in a weaker proportional strength. For example, two pieces of two-inch honeycomb board are considerably stronger than one 44 4-inch honeycomb board, and four 1 inch honeycomb boards are much stronger than either two 2 inch boards or one 4 inch board. The original package that was designed used 48" X 48" X 3" (W X L X D) sheets of honeycomb. In the center of the honeycomb sheets, a 44" X 44" area was compressed down two inches so that eight flats would fit into the compressed area. The compression of the center area greatly reduced the structural integrity, making this concept unacceptable. The system was redesigned using 48 X 48 X 1" honeycomb with a two inch wide and one inch high border around the perimeter of the sheets to keep the flats in place, this prevents any side to side shifting and movement during transportation. The layers of flats are suspended from each other by 8" X 2" X 3" (L X W X D) L shaped corner pieces (Figure 2). Each piece of the honeycomb used in this test were three inches thick, one advantage of having the pieces relatively thin is it allows the distance between shelves to fluxuate which is beneficial for plants that might be of different heights. For example, it is possible to keep all of the very short things on one shelf that is only three inches high, the medium height plants on six inch high shelves, and the taller plant material on nine inch high shelves. During testing, it was determined that the one by two inch border was not needed, but instead, an additional 6 inch long by 2 inch wide side supports would maximize strength and still prevent all side to side shifting of the flats. The rack can be assembled as tall as the inside dimension of the truck (Figure 3). Once the column has been assembled, it is seemed by wrapping the entire rack with stretch wrap plastic film. 45 Figure 2 (left). Assembling the honeycomb pieces at Klooster’s Greenhouse, Kalamazoo, MI. Figure 3 (right). The honeycomb paper packaging system. SHIPPING SYSTEM 2: Metal Corners and Plastic Stretch Wrap This shipping method is modified from a shipping system currently being manufactured in Italy and used in several parts of Europe. Both the Italian system 46 and the newly developed modifications done at Michigan State University allow for great variations in plant height without wasting a lot of space between flats. The plant height is taken into account by a specially made rack which can hold up 10 to 12 flats one on top of another. This method involves placing the flats on a specially designed tall rack-like cart which has shelves that can be adjusted to allow for plant heights of all combinations. The shelves are adjusted to have a minimum amount of head space between the flats. Head space is the amount of air space between the top of one flat of plants and the bottom of the flat that is directly above it. Next, L shaped metal corners are placed on each of the four corners next to the column of flats. The metal corners are manufactured with small ledges sticking out at variable distances apart which correspond to the same intervals as the flats are spaced on the tall Column-like cart (Figure 4). The entire column of flats and metal corners are Figure 4. The comer ledges provide the support in the corners of the flat. 47 then tightly stretch wrapped together and palletized. The plants are held in place by the ledges of the corner pieces, the rigidity of the plastic flats supply the packages with horizontal stability. It is very important at this point to avoiding excessive wrapping without providing proper air slits through the plastic which would prohibit adequate air circulation (Figure 5). The entire pallet is banded together after eight columns of stretch wrapped plants and their corner pieces have been loaded. These pallets can then be fork-lifted into the truck for easy loading. After shipping, disassembly is very fast and easy, a cart similar to the original tall column-like cart Figure 5. The metal corner and plastic stretch wrap system. 48 that held the plants is used to punch through the plastic wrap of an individual column of plants. Once the cart has pierced through the shipping rack that was wrapped plastic, the stretch wrapped plastic film can then be cut and each flat will land and rest on a shelf that corresponds to its level in the wrapped column. After the stretch wrapped is removed the metal corners can be collected and returned for reuse. SHIPPING SYSTEM 3: Durable Plastic Carrier Flats This system uses a heavy weight, durable plastic carrying flat with interchangeable corner pieces. The comer pieces are made in several sizes so each layer can be as tall as the flats (Figure 6). This method is already being used in Europe. One such system is manufactured by Plastic Carry in the Netherlands, their product is under the trade name ’Sico Boxes’. Sico Boxes are 22 inches by 14 inches With corner pieces ranging from 4 to 12 inches. A size adaptation needs to be made from the present system so each carrier would be 22 inches by 22 inches which would allow each "carrying flat" to hold two "standard" United States size flats (22" X 11"). This would supply greater stability and prevent the narrow columns of assembled carriers from tipping over. It would also lower the cost of having each carrier flat only holding one flat of plants. After the columns of carrying flats are assembled and filled with plants they can be palletized, metal or plastic banded or stretch wrapped, fork-lift loaded into the truck and shipped. After unloading, the corner pieces are 49 disassembled and stored inside the carrying flats. The collapsed carrier flats and corners can then be stacked and returned for reusage. Figure 6. The Durable plastic carrier flats. Another adaptation from the European design would be to color code the corner pieces to easily distinguish between different heights, for example, six inch pieces could be blue, eight inch pieces could be green. This would reduce time for the 50 workers so they would not have to look so closely at each piece during column assembly to make sure they are all the same height. SHIPPING SYSTEM 4: Resin or Wax Coated Corrugated Boxes The disposable resin and/ or wax coated corrugated box was the first idea developed when the project began of investigating new packaging strategies and techniques. The development of the corrugated box originated from the fact that most other greenhouse grown floriculture crops have been shipped successfully in corrugated containers for several years. This system had limited usage by the Kalamazoo Valley Plant Growers Co-operative. The height of the plants is used to determine which of two different sized boxes will be used. The boxes are 22 X 22 inches wide and either eight or ten inches high, which allow for two flats of plants to fit side by side in the bottom of the box. The bottom of the boxes have 4 1/2 inch flaps supporting the underside perimeter of the flats and 2 1/2 inch flaps around the perimeter on the top of the boxes to supply support from the top. Four boxes comprise each layer on the square 48 inch pallet, and stacked as high as the inside measurements of the truck will allow (Figure 7). After stacking is completed, the entire pallet can be banded with metal or plastic banding straps or stretch wrapped, and then fork-lift loaded into the semi—trailers for shipping. To prevent ethylene accumulation, the corrugated boxes have port-holes on the side of the walls to allow sufficient air movement into and out of the boxes. 51 Figure 7. The resin or wax coated corrugated boxes. , SHIPPING SYSTEM 5: Collapsible Metal or Plastic Racks The current system using noncollapsible racks has many problems, the greatest being that they are not collapsible. This problem prohibits the trucks from being able to return with a paying backhaul. Collapsible metal or plastic racks have been available for many uses for several years, and have been designed for the Kalamazoo Valley Bedding Plant Growers Co-operative for use in the shipping of bedding plants. The design allows the racks to be collapsed to only 20% of their original size with the removal of as few as 20 nuts and bolts. The collapsible racks have the same 52 dimensions once assembled as the noncollapsible racks that are currently being used. The racks are assembled and loaded with plants in the greenhouse and then fork-lift loaded into the semi-trailer truck (Figure 8). The racks can be used for a display Figure 8. Collapsible racks are similar in appearance to the noncollapsible racks. and a merchandising rack by the retailer and then disassembled. The disassembled racks can be loaded into the front of the semi-trailer truck and returned to the growers. "Underbelly" carriers are also available which are designed to carry the racks under the trailer, this would allow for 100% space availability inside the trailer for carrying return cargo. Since this system is very similar to the present method it 53 is more desirable by some of the greenhouse growers and owners. SHIPPING SYSTEM 6: The Patented "Smitty Table" Greenhouse grower, owner and inventor, Gene Smith of Iowa, has developed and patented a packaging concept known as the "Smitty Table". His system uses plywood shelves that are suspended from one another by plastic center-side posts (Figure 9). This idea of having the supports in the center of the shelf as opposed to the corner Figure 9. The patented Smitty Table. 54 of the shelf is very unique compared to other rack systems. The uniqueness of this center-side post system has warranted one of his patents. The side supports are made of durable plastic and have multiple positions and heights for holding the plywood shelves. Each shelf of the multi-layer table is 33 inches wide by 44 inches long, which allows for six flats to comprise each level. The entire shipping package is held together by plastic bands and can be easily disassembled, collapsed and returned for multiple usages. The number of shelves that each table will have depends on the height of the plants that are being shipped. For most crops, it is possible to have three or four shelves per table, however, for taller crops, only two shelves might be possible. Three tables are stacked one on top of another maximize space utilization in the semi-trailer truck. This system is currently in limited commercial use. L _, r Table 10. The new disposable Smitty Table. 55 Gene Smith is currently working on perfecting a disposable packaging system similar to the Smitty Table. The new system works on the same premise of using center side supports rather than corner supports. In the disposable system, the plastic side posts are substituted with wood and the wooden shelves are substituted with heavy wax coated corrugated board (Figure 10). These tables are stacked on top of one another similarly to the original Smitty Table. SHIPPING SYSTEM 7: Plywood and Honeycomb Paper Rack System This packaging system was developed to reduce complications that were consistently causing problems with the honeycomb system. The massive weight and constant vibration of the plants and their flats sitting on the honeycomb during prolonged shipping tests were persistently causing stress cracks across the honeycomb board. It was determined that plywood would serve the same purpose as the . honeycomb paper layers, would be thinner, and would also be strong enough to prevent the stress cracking that was developing. The first plywood shelves developed were the same 48 by 48 inch dimension as the honeycomb board. The thickness of each layer could be reduced from the one inch thick honeycomb board to three- eighth of an inch with plywood. This reduction in the thickness of the layers allows the racks to have one extra layer plants per column. In the initial tests, the corner and side supports used were still made from the 8" X 2" X 3" honeycomb board (Figure 11). In later testing, the honeycomb corners and side pieces were replaced 56 Figure 11. The plywood and honeycomb paper rack. with interlocking plywood corners and side supports. This adaptation allowed the plywood sheets to be reduced to 45" X 45". This reduction in material benefits the growers by saving weight, space in the truck, money, and wasted materials. RESULTS AND DISCUSSION SHIPPING SYSTEM 1: Honeycomb Paper Rack System The package was tested on a vibration simulator according to ASTM standards, ten minutes at each resonance point at a force of 1/2 G. One of the original designs used one inch thick sheets of honeycomb board. When testing this packaging system, the resonance began at the top of the column at a frequency of 4.2 Hertz and moved shelf by shelf down the rack until resonance at the bottom of the rack stopped at 9.8 Hertz. Peak resonance occurred between 5.0 and 5.5 Hertz, the package was held at 5.2 Hertz for the ten minute test period. Eight minutes into the ASTM test, major deflection occurred to the top layer at 5.2 Hertz, by ten minutes into the test the top three layers experienced deflection. The deflections signifies failure of the long distance shipping test by ASTM standards. Similar testing was done on a new package constructed from 1 1/2" honeycomb with narrower flutes. The resonance for the thicker honeycomb package ranged from 6.8 Hertz to 17 Hertz, with the major resonance between 8.5 and 11.0 Hertz. The packaging system peaked at 9.0 Hertz, where it was held for 10 minutes. After the test was completed, the package was examined with no damage occurring. Once completing the ten minute vibration testing at 1/2 G without any problems or damages, the force was increased to 3 /4 G. This amount of force is far in excess of the ASTM requirements and not 57 58 expected to occur under normal shipping circumstances. After ten minutes at 3 /4 G, there was some minor deflection to the top two shelves, this deflection was less than ten degrees. A deflection of ten degrees would not significantly decrease the strength of the rack. In an attempt to "stiffen-up” the honeycomb package and reduce the amount of bouncing during resonance, a center cross shaped plywood support was introduced into the packaging system. The supports were constructed of 3 / 8" plywood cut in pieces; six inches high by twelve inches long. A three inch cut was made in the middle of the twelve inch length portion of the board, this allows for two boards to fit together in a cross shape. The addition of the support reduced the range of resonance to 7.6 Hertz to 14.0 Hertz with the peak resonance occurring at 9.0 Hertz. Even with the added support, some bouncing of the flats still occurred, but it was greatly reduced when compared to the packages without the center supports. The packaging system was held at 9.0 Hertz at a force of 1/2 G for 10 minutes of continuous vibration with no damage. The force was then increased to 3 /4 G for ten minutes without any visible damage or deflection. This packaging system far exceeded the ASTM standards for long distance shipping strength requirements. When the ethylene concentration bioassay was completed on these packaging systems, they were wrapped the same way that they were during the vibration testing. The packages were held in the dark at 60 degrees F for three days. After three days in storage, the plants were unwrapped and observed for two weeks. There was no time during the two weeks that any of the plants experienced any signs of ethylene 59 damage. Before the flats of plants were put into the honeycomb package, they were weighed and then after the three day storage was completed they were weighed again. The flats of plants lost an average of 268 grams of water over the three day storage period. The honeycomb paper that had been treated with resin to repel the water, had some free water standing underneath the flats. The honeycomb boards that had not been treated with resin were slightly moist under each flat. This suggests that not all of the water had been evaporated, but rather some had been absorbed by the honeycomb paper. It was not determined what portion of the water lost from the flat was absorbed by the package verses evaporated out of the packaging system. The cost considerations of this packaging system are based on the honeycomb shelves to be saved and returned for reusage. The first use costs for one 88 flat pallet-load of the honeycomb system are: a disposable pallet- $2.00, 11 sheets of honeycomb board at $4.00 a sheet- $44.00, and honeycomb corners and plywood center supports- $13.00. For a first usage pallet cost of $59.00 or $0.67 per flat. A ' honeycomb board should be able to be reused one time, which would reduce the second shipment cost to: returning honeycomb boards- $3.16, disposable pallet- $2.00, and new corner and center supports- $13.00. For a shipment two cost of $0.21 per flat. The honeycomb boards are not likely to allow a third usage, which results in an average cost per trip over the first five usages of $0.44 per flat. Advantages ‘of the honeycomb paper rack system include; great strength for one 60 time shock protection and long term vibration protection, offers good display and storage capabilities, relatively light weight, and can be reused several times if returned. Another positive feature of this packaging system is that it can be made of recycled paper and is biodegradable. Disadvantages of the honeycomb paper rack system include; not very cost effective if not returned and reused, takes time and manpower to construct the corner pieces, and the bulky nature of the packaging system reduces the amount of backhaul that can be allowed if they are returned, and if they are not returned, it creates a large amount of paper to dispose of. SHIPPING SYSTEM 2: Metal Corners and Plastic Stretch Wrap The packaging system tested consisted of the column of flats being ten flats high. This packaging system relies solely on corner support and the support of the plastic stretch wrap holding it all tightly together. The first step during package testing on the vibration table is to sweep though the frequencies that a semi-trailer truck would experience during shipping, for the general experimenting done on these packages a range of 2.0 Hertz to 100 Hertz was used. This procedure is used to determine the range of bouncing and where the resonation points are. The first column-like package tested collapsed during this initial test sweep phase at about 8.0 Hertz. It was difficult to determine the exact cause or nature of the failure, but it seemed to be due to one of the corners on the flat third from the top slipping off of the corner 61 resting position on the vertical metal comer support. After it had slipped off of the ledge that it was resting on, it fell onto the flat below it, which caused the lower flat to break in the center, due to the magnified weight of two flats and the severe vibration it was experiencing when vibrating at 8.0 Hertz. Once a couple of the flats had lost their integrity, the collapse and failure of the entire package followed quickly. Upon failure of the first package, the second package was wrapped much tighter. So tightly that the entire package was completely covered by the plastic stretch wrap. The testing of the second package proved more successful. The package was swept though the vibration range with little resonance in the corner of the flats. The range of resonance for this system was quite severe in the center of the flat between 7.5 and 14.0 Hertz, with a peak occurring at 9.8 Hertz. The packaging system was held at 9.8 Hertz for 10 minutes with some damage to the top layers of flats. The corners of the flats were held tightly by the wrap and the package maintained its integrity. The center area of the flats however experienced considerable bouncing. Bouncing was so severe in some flats, particularly near the top of the column, that a few of the individual cell packs broke apart and were bouncing so high they had turned upside- down. This package was tested with flats filled with wet growing media, but without plants. If the flats had been filled with plants, the head space for the flats would have been greatly reduced. The head space being the distance between the top of one flat and the bottom of the flat above it. When the amount of space available for bouncing to occur is greatly reduced, it would have reduced the amount of bouncing, 62 which would limit the likelihood that the cell packs would overturn. During the ethylene accumulation bioassay, the packages where wrapped with the same amount of stretch wrapped plastic that they had been wrapped with during the successful vibration test. The package was completely covered with stretch wrap plastic. To simulate normal greenhouse procedures, the flats of plants were freshly watered and then assembled into the column-like package. Within two hours of the wrapping, the surface of the plastic was heavily beaded with water vapor. After three days of sitting in a dark room at 60 degrees F, the plants were removed. The soil and plants were still very wet and there was some botrytis growth on some of the flowers and decaying leaves. These flats lost an average of only 35 grams of weight (water) during the three days of storage. Characteristics of ethylene damage such as leaf drooping followed by leaf yellowing and leaf abscision were observed on the tomato seedlings. A second package was wrapped with the same amount of plastic stretch wrap as the first but with horizontal air slits cut though the plastic wrap on all four sides of the package and at all ten plant levels. Under the same storage 5 conditions much less water vapor collected on the inside of the plastic wrap and the plants and flats were 190 grams lighter when compared with those wrapped tightly. The increase in water loss indicates that water vapor was allowed to exit the package through the ventilation slits, which signifies that gas exchange was possible. These plants did not experience any visible signs of ethylene damage. Vibration testing was redone on a column-like package with similar amounts of plastic stretch wrap and the same number and size of horizontal air slits throughout 63 the package. This package was subjected to the same 1/2 G force and ranges in Hertz as the former package. After ten minutes of vibration testing the third layer from the top had slipped off of its ledge, but did not cause the flat below it to break. The cost of this system is quite low for the first shipment and even less for subsequent uses if the components are returned for reusage. The cost the first shipment would consist of: a disposable pallet- $2.00, stretch wrap plastic- $4.00, metal corner pieces (24 pieces each 8’3” at $0.15 per foot)- $28.80. The total cost for a 88 flat pallet load would be $34.80 or $0.40 per flat. Due to its collapsible nature, the system is very economical to return. The second time usage cost would include: disposable pallet- $2.00, stretch wrap plastic- $4.00, and a component return cost of- $3.16. These figures calculate to second time usage cost of $ 0.10 per flat, and first five trip average of only $ 0.16 per flat. The costs do not include the holding carts that are required to hold the flats while being packaged and the cart to assist in unpacking the flats at the retail end. The advantages of this shipping system include, lightweight, the strength of the system is not reduced when wet, easily collapsible, very cost effective over time. Disadvantages of this system include, minimal side to side stability, somewhat unstable until the pallet is full and banded, and need to return the metal comers. This system can be somewhat awkward to keep flats stable while starting the stretch wrap procedure. Excessive stretch wrapping of the column can cause ethylene accumulation and damage, temperature gradations and other problems associated with improper air circulation. This problem can be minimized and/or corrected by 64 making horizontal slits though the plastic to allow. for proper air exchange. SHIPPING SYSTEM 3: Durable Plastic Carrier Flats The plastic carrier flats are constructed of heavy durable high density polyethylene. They satisfied the ASTM vibration testing with no difficulty. For the vibration testing, both eight and twelve inch heights of the corner elongation pieces were used. This was done to determine whether problems could be expected at any possible height combinations. The packages experienced resonance between 8.5 and 14 Hertz. Similar to the other packages, resonation began at the top of the column and progressed down the column as the number of Hertz increased. The peak resonance occurred at 9.8 Hertz. The package was held at 9.8 Hertz for ten minutes dwell time at a force of 1/2 G. No physical problems to the carrier flats resulted from this testing. The force was then increased to 3 /4 G for 10 minutes at 9.8 Hertz. The packages also experienced no difficulty in maintaining integrity throughout these tests. The ethylene bioassay for this package was performed along with the other packages. By nature of the package design, little trouble was expected from ethylene accumulating near the plants. This packaging system is very open on all sides including the top and the bottom. The columns filled with plants were put in the same dark room as the other packages, at 60 degree F for three days. No visible problems occurred upon removing the flats from storage or at any time during the 65 two week observation period which followed storage. This packaging system experienced the largest reduction in weight of any of the packages evaluated. This is not surprising considering the very open nature of the package design. The average weight loss due to evaporation of water from the plants and the media was 628 grams. This is the average amount of weight loss over the three day storage period per flat. One pallet of the durable plastic carrying racks are quite expensive. The initial shipment of using the system would include: a disposable pallet- $2.00, banding straps- $1.00, 44 plastic carriers at $6.00 each- $264.00, and 160 elongation corner pieces at $ 0.60 each- $96.00, which results in a first shipment cost of $363.00. The second through fifth trip costs would be dramatically lower, the only costs would be pallets, banding and returning the carrier flats. Which would result in a usage cost of only $0.10 per flat, and a five trip average of $0.86 per flat. Advantages of the carrier flat system are quick assembly and disassembly without equipment, various sizes of corner elongation height pieces for different plant heights, great strength, long lasting, offers unique storage and marketing possibilities. The disadvantages of this system include, carriers are too expensive to not require return, deposit, or retail purchasing, hard to keep track of the carrier flats and corner elongation ‘ pieces at the retail level. Other disadvantages include high initial investment to get plastic companies to manufacture carriers to hold two U.S. sized flats (22" X 22"). .With this shipping method, all parts of the packaging system must be returned for reuse. 66 SHIPPING SYSTEM 4: Resin or Wax Coated Corrugated Boxes Of the seven packaging systems developed and tested, the corrugated wax or resin treated boxes is the only system than did not pass the vibration simulation test. Failure to pass the test makes the package unacceptable by the ASTM Standards to be expected to survive the vibration of long distance shipping via semi-trailer truck. The packaging system failed during three different repetitions of the initial vibration simulator sweep of the 2.0 to 100 Hertz testing range. This initial sweep is required to determine the resonance points for the package, and then the package must be held and tested at the resonance point for ten minutes. On the first sweep, the vibration simulator was set at a force of 1/2 G. The sweep started out at 2.0 Hertz and upon reaching 3.5 Hertz, the corner crushed on the third corrugated box from the bottom and the column, ten boxes high, collapsed upon itself and toppled over. During the second sweep, the force was maintained at the 1/2 G level that is required by ASTM. In this trial, at 3.4 Hertz, the fourth box from the bottom in this stack of ten experienced similar corner crush out and resulted in the column of flats collapsing. In an attempt to try and determine where the range of resonation of this package was, the force was decreased to 1/3 G. This test survived until the package reached 4.9 Hertz, at which point the third box from the bottom also collapsed. This decrease in force eliminated the package from meeting the ASTM standards. However in an attempt to at least determine what the natural frequency of this 67 packaging system would be, the force was decreased to 1/4 G. The package experienced resonance in the range of 5.8 and 10.0 Hertz. The package experienced peak resonance at about 7.8 Hertz. The vibration simulator was then set for a 'ten minute dwell time at 7.8 Hertz at a force of 1/4 G. The package collapsed shortly after five minutes of the test holding at the peak resonance point. ‘ The weight loss of the plants and growing media for the corrugated box system was relatively low compared to the other packages evaluated. The average weight loss per flat over the three day storage period was only 153 grams. This small level of weight loss is probably due to the air ventilation holes in the boxes not being very large, and the stretch wrap plastic covering some of the cracks. Considerable care was taken during the wrapping of the boxes with the stretch wrap plastic to minimize the number of air holes covered by plastic. The plants in this test did not Show any signs of ethylene damage. It would be easy to conclude however that this system would be near the borderline as far as possibly experiencing ethylene damage. The reason for this presumption is that, the tightly wrapped metal corner system lost only 35 grams of weight per flat over the three day test period and this system lost only 153 grams. Hence, there should be some value between 35 and 153 grams of weight loss that would be the threshold for ethylene damage to occur. Therefore, great care must be taken when using this shipping system to prevent overly wrapping with the stretch plastic wrap and covering up the air ventilation holes or damage could result. Resin or wax treated corrugated boxes are not returnable or reusable from-a 68 production standpoint, which makes the first through five trip costs the same. The cost of this system works out to include: a disposable pallet- $2.00, banding and strapping- $1.00, 44 corrugated boxes at $0.80 each- $35.20. Which calculates to a pallet of corrugated shippers costing about $38.20, or $0.43 per flat. The advantages of using wax or resin treated corrugated boxes include; low cost, disposability, and limited watering, storing, and selling without removing the flats from the boxes. Disadvantages of the corrugated wax boxes are; eventual loss of strength due to moisture vapor and possible ethylene accumulation if wrapped to tightly during shipping. Resistance from the growers having time to assemble the boxes during busy times is a common complaint. Possible reasons for damages could be due to the age of the corrugated box packages. The boxes being tested were three years old and had been stored in conditions of fluxuating temperature and humidity. These test specimens do not fall into the required holding specifications state in ASTM Standard D-4332. SHIPPING SYSTEM 5: Collapsible Metal or Plastic Racks The Kalamazoo Valley Plant Growers Co-operative have developed this system on paper, but there are no full size models of the collapsible metal or plastic racks. Even though still in the early stages of development, the new system would be very similar to the present system, with the exception of it being collapsible by the removal of as few as 20 nuts and bolts. Due to its similarity with the present system, 69 similar conclusions might be drawn as to the success of the current system. The current system is very strong and sturdy with few problems occurring due to the package not being strong enough for the weights required. The present system also experienced no problems with ethylene accumulation due to its very open and uninhibited design. The open design of this system as with the durable plastic carrier flat system and Smitty Table, would allow the plants to loose considerably more moisture than the more enclosed systems, like the resin treated corrugated boxes or the metal corner and stretch wrap plastic shipping systems. The convenience of using this system has a draw back in it’s price. The estimated cost of each rack (which will hold 88 flats) is $1500.00 each. This would result in a per flat average of $17.19. This amount is unrealistic to imagine until you factor in the longevity of the rack’s lifetime. These racks are expected to last for twenty years each, and the only fixed costs associated with them would be cost of returning them. The average return cost would calculate out to $0.14 per flat. Even though the usage cost after the first trip is quite high, the average cost for the first five trips of using the racks is still $3.55 per flat. Advantages of collapsible metal or plastic racks include; greater acceptance by the grower because this is closest to their present system, long lasting, durable, and can double as a display and marketing device at the retail end of the chain. The disadvantages of collapsible rack are; intolerably high initial cost, significant weight, difficultly in keeping track of the racks after they are delivered at the market. Other consideration are, the racks still must to be returned, and when collapsed, the rack 70 still occupies 20% of the truck volume, along with a considerable portion of the trucks weight limit. SHIPPING SYSTEM 6: The Patented "Smitty Table" The very sturdy patented Smitty Table experienced no problems satisfying the ASTM requirements for shipping systems. Three Smitty Tables with three shelves on each table were assembled and stacked for use in testing. The initial sweep determined that the range of vibration was in resonance between 5.9 Hertz and 11.0 Hertz. The natural frequency (peak resonance) occurred at 7.6 Hertz. The vibration simulator was then set at a force of 1/2 G for the ten minute dwell time, which resulted in no signs of damage to the stack of tables. As with some of the other systems, the force was then increased to 3 /4 G and held for ten minutes. This brutal vibration test also resulted without any visual damage occurring to the stack of tables. During the ethylene bioassay, the packages did not experience any problems. The Smitty Tables were held in darkness for three days in a 60 degree F room. As with the other open designed packages, there was no sign of ethylene accumulation or damage after three days of storage in their packages. The plants were placed in ‘ the greenhouse for three weeks of observation after the storage treatment, the plants did not Show any visual signs of ethylene damage during the observation period. The open nature of the packages left the plants and soil susceptible to losing considerable moisture. Over the three day period in storage, the flats each lost an 71 average of 568 grams. This weight loss is presumably due to reduction in water from the soil and plants. The plants were not visually water stressed, and the soil still held considerable amounts of moisture. The Smitty Table also encounters a high initial price tag. The average table would hold 18 flats and the cost associated with each table includes: four side pieces at $5.00 each- $20.00, banding and strapping- $1.00, and plywood for the shelves- $5.00. These prices result in first time usage cost of $26.00 per table or $1.44 per flat. The second through fifth time usage is reduced to include: return of the side pieces- $0.50, banding and strapping- $1.00, and new wooden shelves- $5.00. This would reduce the second through fifth time usage price to $6.50 per table or $0.35 per flat, and reduces the first five time average to $0.55 per flat per usage. The Smitty Table packaging system is long lasting, has great strength and the plants can be watered while still sitting on the tables. The packages can be . assembled before they are actually needed, and are very easy to disassemble once they reach the retail market. Conveniently, the plants can be left on the tables for storage, presentation, and merchandising. Once the tables are disassembled they occupy only a fraction of their original size, which allows for a less bulky return. The disadvantages of the Smitty Tables are; they are quite expensive, which requires great care in making sure they are properly returned, and they take considerable amounts of time to assemble. The tables are also smaller than the 48 inch by 48 inch standard that the other systems occupy, which requires a larger number of tables to be in inventory. The plywood sheets to be used as shelves for the Smitty Tables also 72 require considerable time to cut into the proper shape and configurations. SHIPPING SYSTEM 7: Plywood and Honeycomb Paper Rack System The plywood and honeycomb system was conceived after the honeycomb paper system. It relies on very much the same principles and performed similarly in the tests as its original counterpart. The package without center support experienced resonation between 5.3 Hertz and 11.0 Hertz. The peak resonance occurred at 6.5 Hertz were it was held for ten minutes at a force of 1/2 G. The package did not experience any difficulty with this test. The force was then increased to 3/4 G, for ten minutes, this test also resulted in no visible damage to the package. Another package was then tested which used the same cross-shaped plywood center supports which were used with the honeycomb paper package. These supports help to reduce the 48 inch horizontal span in half, which up until then had no support. By decreasing the distance that is without support, it is possible to greatly reduce the wave action and deflection that can occur across the shelf. By adding the support the range of resonance was 5.2 Hertz to 9.5 Hertz with a peak at 7.0 Hertz. The range ‘ of resonance was still about the same, but the severity of vibration and bouncing was considerably dampened by adding the center supports. This package was held at 7.0 Hertz for ten minutes at a force of 1/2 G and at a force of 3/4 G, with no problems resulting from either treatment. To help further reduce wasted space in the truck, the honeycomb corners can be 73 completely eliminated from the package by introducing plywood corner pieces. Since the plywood is only 3 / 8 inch thick compared to inch wide corners honeycomb allows the package size to be reduced to 45 inches by 45 inches. This is enough space saved to allow two extra racks of plants per truck compared with the honeycomb paper method. This change in the package design had very little influence on the range of resonation. The all plywood packaging system was in resonance between 5.4 Hertz and 9.3 Hertz. The package’s resonance frequency was 6.9 Hertz, the package was held at 6.9 Hertz for ten minutes a force of 1/2 G, and at a force of 3/4 G. There was no damage determined when using either treatment. A package was prepared for usage in the ethylene bioassay and immediately prior to being placed in the storage room was wrapped in stretch wrapped plastic. The same amount of stretch wrap plastic was applied during the ethylene bioassay as was applied during the vibration testing. The wrapped column of package and plants was put into dark storage with the other packages at 60 degrees F for three days. After the three day storage treatment was over, the package was unwrapped and the plants were observed and weighed. The plants did not exhibit any signs of characteristic ethylene damage. The plants were observed under normal greenhouse conditions for two weeks without any signs of ethylene damage appearing on the test plants. The flats of plants and growing media in the honeycomb and plywood package lost an average of 253 grams over the course of the three .day storage period. This value is similar to the weight loss measured (268 grams per flat per three days) in the honeycomb paper packaging system. The flats from the honeycomb package might 74 have lost more moisture due to the rather absorbent nature of the honeycomb paper board. Although plywood is obviously also wood fiber, it takes a longer period of time for the water to be absorbed, possibly creating a smaller water vapor deficit, resulting in less water loss to the plywood package. This system along with having many other positive features turned out to be one of the most, economical. The cost of first time usage of a plywood rack would include: a disposable pallet- $2.00, plastic stretch wrap- $1.00, 5.5 sheets of plywood at $5.00 a sheet- $27.50, and .5 sheets of plywood for corner pieces and center support pieces- $2.50. This calculates out to $33.00 per pallet or $0.38 per flat for the first time the system is used. The next four times the system would be used the cost would be reduced to include: stretch wrap plastic- $1.00, .5 sheet of plywood for comers and center support pieces- $2.50, a disposable pallet- $2.00, and return of the original plywood shelves- $3.80. The total for these pallets would be $9.30 or $0.10 per flat. This also would reduce the average costs of the first five usages to only $0.16 per flat. The advantages of the plywood and honeycomb system include; rather inexpensive compared to some of the other methods, plywood is readily available in all areas, and the thinner shelving material allows for increased number of flats and plants per truck. This method also allows for the materials to be returned or the plywood could be sold for scrap at the retail market. This system is very easy and quick to assemble, especially when using the all plywood system. The plywood system allows the flexibility of being able to use the plywood racks as marketing and 75 sales devices for selling the plants at the retail market. The plants can easily be watered without having to remove them from the column-like racks and even allows the plants to be stored in the package for a limited time, until they are needed. This system also supplies great strength and is not weakened by moisture. The disadvantages of the plywood system include; need to find some usage for the plywood at the retail end of the chain or the plywood must be returned. If the plywood is going to be returned, it requires room and takes up considerable weight in the semi-trailer truck. It is however, less bulky than some of the other systems investigated. This method takes some time and effort to get the plywood cut originally. Care must be taken during the wrapping of the packages with the stretch wrap plastic to ensure that the package has proper air circulation to prevent ethylene accumulation. 76 MOISTURE RETENTION OF THE PLANTS AND MEDIA Table 1. The average weight loss and standard deviation in grams per flat of the different shipping systems when held in the dark for three days at 60 degrees F. Racks Metal Corners and Plastic Durable Plastic Flats Resin or Wax Treated Boxes and Racks Patented Table COST OF SHIPPING SYSTEMS Table 2. The per flat cost of the packaging systems for the initial shipment, shipments two through five and an average of the first five package uses. Shipping System Shipment 1 Shipment 2— Uses 1-20 Per Flat 5 Aver. Flat Cost Per Flat Cost Cost Honeycomb Paper Racks $ 0.67 $ 0.21 $ 0.24 Metal Corners and Plastic Wrap $ 0.40 $ 0.10 $ 0.12 Durable Plastic Carrying Flats $ 4.20 $ 0.10 $ 0.31 Resin or Wax Treated Corr. Boxes $ 0.43 $ 0.43 $ 0.43 Collapsible Metal or Plastic Racks $17.19 $ 0.14 $ 1.00 Patented Smitty Table $ 1.44 $ 0.35 $ 0.42 Plywood and Honeycomb Racks 3 0.38 $ 0.10 $ 0.12 77 MECHANICAL VIBRATION OF BEDDING PLANTS The daily observations of the plants showed that in the geraniums and impatiens, the plants vibrated at frequencies below 14 Hertz experienced more flower necrosis and premature flower blasting than the higher frequencies and controls. virtually all of the plants that received vibration for ten minutes at all 12 frequencies experienced total necrotic or blasted flowers. These observations may account for some of the flower damage currently being noticed during the shipping process. The data of the six species of bedding plants (impatiens, begonia, tomato, peppers, dahlia, and geranium) was so variable that no conclusions can be made concerning the data. However, observations on the preliminary trials of the impatiens can be drawn. The numbers presented in Table 3 and Table 4 reflect the statistical analysis using Duncan’s Multiple Range Test of the Impatiens plants that were vibrated during the testing. 78 Table 3. The growth in cm of Impatiens wallerana cv. ‘Novette Series’ seven days after applying mechanical vibration for ten minutes at specific frequencies. Treatment Impatiens in Hertz of 2.3 C 2.1 C 10 1.5 C 14 3.0 BC 17 4.8 ABC 21 3.8 ABC 25 4.8 ABC 30 7.1 AB 40 4.1 ABC 50 1.6 C 70 5.0 ABC 90 3.8 ABC 2-90 3.6 ABC Hold at all 1.4 C 3.3 BC Control no 8.1 A Means not followed by the same letter are significantly different at the 5% level applying Duncan’s Multiple Range Test. 2-90 Sweep = Plants were sweep through the entire range of frequencies between 2 and 90 Hertz. Hold at all Freq. = Plants left on the vibration simulator for entire duration of the exp., plants received 10 mins. at each freq. Control (w/ trip) = Plants went to Packaging bld., but not vibrated. Control (without trip) = Plants did not leave the greenhouse. . , 36:25on :3“ 8m 88% :03v cougar, me E: 893 2: SH 033 dogs? 05 no coon—m 203 355 n =< $568 nouns? 85o o: :5 mag—am wafiaxomm 05 9 at“ 05 55 find—a 3380 u H+U .53: co 9 N Bob wfiwfia 865.605 no @0026. 2:58 3 a 3382 353 u .Bm "mosses mangoes 2: 2 as 2: Boss 353 3:80 u Ho amok. ownam 0:532 @5885 warn—“Ea _o>o_ oSm on: 3 Schema. museum—Emma 03 3:2 088 2: .3 v03o=8 $802 .53 :38 Bad Emma @8338 ES .momoaoavob £627. on SEES 3 H8 823. Roam—~38 £5 conga 62838 203 85E 2:. ..motom 8852. .3 32333: Sagas .8“ 3:58 “mop. owned 032:2 Madonna 3. 033. CONCLUSIONS There are several factors to determine which of the packages are the most likely to be implemented by the growers. Factors such as cost, how easily it can fit into their operations and amount of water loss are of obvious importance to the grower. However, of equal importance are considerations such as vibrational strength and likelihood of the package to trap ethylene inside the package. The following chart ranks the packages that were evaluated on all of these factors and then averages all of these factors to give an approximate ranking of which packages would be considered most effective in all aspects of the shipping process (Table 5). This project offers several exciting and beneficial ideas for new ways to ship bedding plants and replace the current archaic and financially troubled methods. Without new cost effective methods of . Shipping, the Michigan bedding plant growers could lose their competitive edge to the growers of the southern US. and forfeit this valuable multi-state market. Further studies on the vibrational frequencies that are sensitive to plant growth and development might also uncover some interesting and worthwhile information. 80 vd v m H H H 8onth 88.50 3 H m N H N 38¢ H.835 N N m H H m 29d. .986 Mo. mm a m H H H 82% oEHmaaHHoO Gm m H H. m m moxom H.880 e83 v.~ v m H H H 32th 233m Wm H H w v m 96:80 H802 N m N N N N 38¢ 2:855: magnum Ho>< nH mom: H8 33 noun—:EHSSN. fiwfiEm 9656:0th 829$ H3950 H80 0353. you“? 0:235 H3235; 5380 mags—8m 580$ HHa 35288 macaw? wane—22H Ho weigh omSozw ofi HE.» $9363 23 Ho 853385 HE“ 3803. 0382: 2: S Eaton—E macaw .3 macs? mime—ea 2: Ho magnum .m oEuH. 82 Table 6. The acceptance of packaging systems calculated from the criteria above. Plastic Carrier Racks Racks Table Comers and Stretch Plastic Wax Treated LITERATURE CITED Abeles, EB. 1973. Ethylene in Plant Biology. New York, London: Acad. ASTM Standard D-999. 1986. Standard Methods for Vibration Testing of Shipping Containers. The American Society for Testing and Materials Designation D-999. p. 190-193. Cunningham J.L., G.L. Staby. 1975. Ethylene and Defoliation of Ornamental Lime Plants in Transit. HortScience. 10(2):174-175. Funke, G.L., F. de Coeyer, A. dedecker, J. Maton. 1938. Response time to ethylene in tomato. Biol. Jaarb. 5:335. Marousky, FJ., B.K. Harbaugh. 1979. Interactions of ethylene, temperature, light, and carbon dioxide on leaf and stipule abscission, and chlorosis in Philodendron scandens subsp. oxycardiurn. Journal of the American Society for Horticultural Science 104(6):876-880. 83 "lllllllllllllllllll