H W N _—- S '7 7 1—: ___I .— _——— __—- I_J _— ._._— EFFECT OF A PLASTEC COATING ON C‘JT FLQWERS AND GREEN$ Thesis {or ”1e Degree o§ pl‘i. D. MECEEQAE STAYE UEWERSETY Charles Herbert Sherwood 1957 ‘— LIBRARY Michigan State University This is to certify that the thesis entitled THE EFFECT OF “A. PLASTIC COATING. ON cur FLOWERS AND GREENS presenteu l)” Charles H. Sherwood has been accepted towards fulfillment of the requirements for Ph .1). degree in HortiCUltum ’2' / Major professor Date May 2; 1957 0-169 EFFECT OF A PLASTIC COATING ON CUT FLOWERS AND GREENS By Charles Herbert Sherwood AN ABSTRACT Submitted to the School of Graduate Studies of Michigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Horticulture 1957 Mr Approved. 0 0000000000000 0 00000000000000. ABSTRACT The investigation relates some of the effects of a plastic coating, Vinyl latex 600, on cut flowers and florist's greens. The plastic material, mentioned above, had a specific gravity of 1.24 to 1.25 with a solid content of A9 to 51 percent, the average size of the particle being 0.2 microns. The observations indicated that the aqueous dilutions of 10 and 20 percent Vinyl latex were effective in reducing water loss and thereby maintaining the fresh appearance of the plant materials. The treatments were particulaly effective on gardenia, plume asparagus (asparagus plumosus) and the Ore- gon fern (Polystichum munitum). Respiration studies were also included. Special apparatus was de- signed for the purpose. A description of the same and the directions for its use are given in the text. The observations on excised rose petals, coated with 10 percent Vinyl latex 600, indicated carbon dioxide accumulation to be 0.8 percent or about 50 percent higher than those of untreated petals. Similarly, micro—manometric determinations were also made on various plant materi- als, coated with or without the Vinyl latex. Phytotoxicity and respiration abnormalities were also observed when latex, in excess of 10 percent, was allowed to dry slowly on the plant tissue. EFFECT OF A PLASTIC COATING ON CUT FLOWERS AND GREENS By Charles Herbert Sherwood A THESIS Submitted to the School Of Graduate Studies of Michigan State University of Agriculture and Applied Science in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Department of Horticulture 1957 II III IV VI TABLE OF CONTENTS INTRODUCTIONooooo000000000000000000000000000000000000000no. RETJIAM 0F LITERATURE.OOOOOOOOOOOOOOOOOO0.0....OOOOOOOOO.... A. General................................................ B. Cuticle................................................ C. Artificially Applied Protective Coatings............... D. Preservative Solutions................................. E. Cold Effects........................................... F. Gas Effects............................................ G. Metabolism............................................. H. Characteristics of Respiration......................... I. Measuring Respiration.................................. PROCEDURES AND RESULTS..................................... A. Lengthening The Life of Cut Flowers and Greens......... B. A Method Fbr The Rapid Determination of Carbon Dioxide. C. The Effect of A Plastic Resin on Carbon Dioxide........ D. Micro-manometric Determinations.......... ............ .. DISCUSSION................................................. SUMYO.OOOOOOOOOOOOOOO.O...O...00.00.000.0000000000000O.O LITERATURE CITlgDoooooe9.00.00.00.00.coco-cocooooooOooooOoo. Page 10 ll ll 11+ 15 15 19 30 37 A3 0 U o a I D I c e O I O I O O i I ‘ O D I v I I I. INTRODUCTION The handling, marketing, and storage of florist greens and similar living floricultural material are often costly because of the suscepti- bility of such materials to bruising, wilting and physiOIOgical aging. Procedures which may reduce bruising, retard aging, or prevent excessive dessication are worth investigating. Consequently, the value of the new plastic coating material, Vinyl 600, produced by the B. F. Goodrich Company appeared to be worthy of investigation as a promising approach toward the solution of these problems. II. REVIEW OF LITERATURE A. General It is recognized that a severed leaf, branch, or flower is more li— able to damage from.dehydration, mechanical injury or pathogens. Birch (I952), Laurie and Kiplinger (1948), and Post (1952) are among those re- ferring to such problems as important in the harvest and use of floral crops. A considerable volume of material is available regarding the pre- servation of cut flowers and greens, the recent summarization by Bowden (19h?) indicates that physiological aging remains an important problem. B. Cuticle In a very real sense the cutiCIe with its often naturally oily or waxy surface may be considered the last barrier or shield between the living part of the plant and its environment. Priestly (l9h3) summarized the cuticle in angiosperms. Schiefer- stein (1955) has recently integrated the literature pertinent to the cuticle and its waxy covering. It is especially noteworthy that although a cuticle is usually present on all above ground parts including flower, stems and even roots as reported by Lee and Priestly (192A), the over de- posit of wax may be undeveloped on a considerable part of the foliage as found by Schieferstein (1955). According to Bonner and Galston (1952) the cuticle proper consists of cutin which is essentially waxes such as esters of fatty acids with long chain alcohols, keystones, and hydrocarbons containing no oxygen. The exact composition and formation is in doubt. However, it is generally agreed that the chemical nature varies considerably from.plant to plant. The development of the cuticle is also believed responsive to differences in the condition of the plant, kind and age of part, as well as the ex~ ternal environment. This is predicated by Klebs' classic remark that any cell possesses from its parent a definite disposition of its inner con- ditions through which the chemical processes are maintained in certain directions (1909-10). Since this paper is concerned with the response of the protoplasm to artificial coatings exteriorto it, the distinction between living and non-living cell wall components and cuticle components is not as import- ant as their physiological relationships. However, it is considered pertinent that Schieferstein (1955) demonstrated that the cuticle proper is essentially varnish-like and so adherent to the exterior cell frame- work that pieces act as if embedded in it. His agreement with Mueller, Carr, and Loomis (195A) that the cuticle is uneven and undeveloped above where the underlying cells meet is in accord with the fissures of Crafts, Currier, and Stocking (l9h9) and the undeveloped parts of the cuticle de- scribed by Orgell (1955). Since the middle lamella may be considered ex- terior where two epiderman cells meet, it is also in accord with Roberts, Southwick, and Palmiter (1948) who state, "the amount and location of pectinaceous substances present in the leaves account for the entrance (passage) of water soluble materials such as minor elements, nitrogen, hormones, and organic fungicides sprayed on leaves." They considered this pectinaceous material as contiguous to the vascular system of the plant and to the exterior side of the cuticle. Skoss (1955) describes the cuticle as a framework of polymerized fatlike substance impregnated to variable degrees with wax. Skoss and many others like Bald (1952) consider the cuticle proper so impervious to materials such as spray chemicals and pathogens that the most likely passageways are the stomates. Conditions favoring positive and negative stomatal guttation cycles are considered particularly likely to result in spray injury or infection. Congestion or apOplexy of the foliage in particular is well known, the subsequent rupturing of the epidermis be- ing termed oedema. This exposes protOplasmiand favors infectious di- seases as shown by Johnson (19A7). Until more information is available, the cuticle may be visualized as a film or sheet-like protective armor. The analogy of cutin and chitin is pertinent in that the cuticle of plants or animals serves similar protective purposes. Because of the polymerized and practically insoluble nature of the surface in either instance, external contact is essentially limited to stomates, pores, hydathodes and other undeveloped "cuticular" surfaces between cells or cracks and other variously scarified areas. For the purpose of this paper the cuticle is visualized as plates of cutin extending over the surface of the epidermal cells. Although these plates may be undeveloped or scarified, stomates, hydathodes, and lenticles are large pores permitting protoplasmic contact with the ex- ternal environment. However, of equal if not more importance because of the greater exposure, are the junctions of epidermal cells where the cu- ticle is undeveloped and the primary cell walls (characterized by the pectins and cellulose strands of the middle lamella) are variously ex- posed affording a passageway for both fat and water soluble materials into the plant as described by Roberts, Southwick and Parker (19A8). The occurrence of waxes and oils on the surface of the cuticle proper may be due to this inability of polimerizable precursers of the cuticle to penetrate the cuticle. Their occurrence poses the important considera- tions of how the waxes penetrate (if they do, is it along strands of material or through unprotected pores?) and how resistance to wetting has been feund closely associated with injury from herbicides as shown by Staniforth and Loomis (l9h9). Since 2,A—D is soluble in either water or lipoids, the wetters could be functioning in channeling the material as well as insuring coverage. wylie (1930) in discussing wounded leaves and Priestly (l9h3) empha- size that the cuticle is much more than a means of preventing water loss. Pathogen protection is an important function. Insect injuries have been found direct passageways for pathogens. The relationship of leafhoppers to aster yellows and of two-spotted mites to mildew is known even by commercial growers. Also known is the inordinate failure of insect- damaged plants to compete with unparasitized fellow plants. Injury is out of proportion to the cuticular damage, or secondary disease para- sitism. As indicated by Siefriz (l9h2), this regularly irritant injury may be more injurious than injury killing more tissue because of the shock duration time on the physiological activity of the protoplasm. c. Agtificially Applied Protective Coverings The use of supplementary protective coverings to retard "drying out" and infection of severed plant parts is not new. Austen (1657) describes the use of wraps and clay to protect scion wood for journeys of several days. In grafting he mentions that the clay is as valuable to keep moisture out as in. Most plantsmen have experimented with various mix~ tures containing beeswax, linseed oil, and asphalt for use as protective coatings. Commercial florists have associated mildew resistance with glossy foliage resulting from.oi1 sprays or linseed and grease mixtures placed upon hot heating pipes. . In this literature review, two classes of protective coatings are considered; the cuticle including those materials intimately supplement- ing or replacing the natural cutin and the less intimate coverings termed variously as sealed-pack, prepackaged, tight wrap, etc. The first class is applied by dipping, spraying, or vaporization. The coating substance may be in a water solution, a lipoid solution, or an emulsion. The same or other materials are commonly applied in wraps. Various papers, foils, and plastic films are available for such usage. Wildon recognized the value of melted wax coverings (1935). Chadwick (1936) describes the use of emulsified parrafins and vegetable oils. Miller, Neal, and Gardner (1945) explain the use of waxes and various wax emulsions to limit the dehydration of horticultural plants and as stickers and thinners for fruit sprays. Their paper brings together the early work Neilson started in 1928, that leading to the marketing of Dowax, and recent work regarding oil.and wax coatings. Dowax is shown to be effective in reducing transpiration and in increasing the effectiveness of some fungicides and repellents both in degree and in duration. Less phytotoxic products such as Florawax (Floralife) and Bloomwax (Flower Foods) have been developed for flowers readily damaged by Dowax (Dow). A non-lipoid material called Methylcell was credited by Felber and Gardner (l9hh) with protecting plants from excessive dessication. Although it did not attain much use for this purpose in horticulture, it has been recommended for facilitating heavier deposits of more impervious coatings. During the time these liquid wax coatings were being tried Cellophane (Du Font) and then Pliofilm (Goodyear) became available. Several shippers were using these sheet plastics for flowers such as acacia and gardenias during the late thirties. They were also using waxed cardboard extensively. At this time the author observed that molds were causing more damage of plant materials in transit or storage than dehydration. By l9h9, cellophane was used as a wrap for cut flowers by some retailers. After Wbrld war Two the use of sealed plastic overwraps was greatly emphasized. This was often termed pro-packaging and little or no effort was made to disguise this as other than a revolution in the merchandizing of flowers. Many florists invested heavily in materials and equipment. Few benefited and many are still critical of such packaging. After nearly ten years of development, problems in pro-packaging flowers remain frustrating and too many promising developments have been found but superficially or transitorily successful. In.the author's opinion, less than one percent of the flowers sold in 1955 were marketed as sealed pre—packaged units. Among many recognizing the potentials of pre-packaging were Dr. Ham- ner and the author. However, they felt that overwraps were weak in re- spect to the troublesome space between the protective covering and the surface of the plant. Liquid waxes, although eliminating the troublesome space, were soft and often injurious. In the immediate post-war period the B. F. Goodrich Rubber Company was interested in the potentialities of the synthetic rubber resins they called Geon. These latexes varied in exact composition and were being used in waterproofing and reinforcing paper, making raincoats, shower curtains, etc. They were applicable with plasticizers, dyes, etc. These polyvinyl latexes were usually heat cured, sometimes with a pre- heat period at about 200°F. before a final curing at higher temperatures (Goodrich). However, one of these, Vinyl 600, could be successfully used at 60°F. although a minimum of 70°F. was recommended. This Vinyl 600 was considered promising for use as an artificially applied protective cover- ing for cut flowers and greens as the film.produced upon drying was firm, transparent, and flexible. Bovey, Kolthoff, Medalia and Meehan (1955) found that vinyl 600 latex is comparable to natural latex in form and concentration. Baghadi and Smock (l9h3) used such latexes on apples. D. Preservative Solutions As surveyed by Tinker (1942) many articles refer to the addition of chemicals in waters used for cut flowers. He quotes calcium as one addi- tive of proven value for "topple". Commercially available "preservatives" such as Floralife (Floralife) and Bloomlife (Flower Foods) are useful for extending the life of cut flowers. Most of these contain a plant food such as sugar which tends to maintain the plants' metabolism. They also contain chemicals designed to control pathogens and keep the water con- ducting vessels functioning. Kelley and Sherwood (1955) found the better solutions resulted in a greater absorption of water. This was also mention— ed by Hitchcock and Zimmerman (1929). Bowden (1949) describes the use of amino acids in such solutions as a further aid in prolonging the natural beauty of certain cut flowers. Unfortunately these solutions are practical only when developed for average flowers under average conditions. Actually innumerable solutions would otherwise be necessary. As found by Kelley and Sherwood (1955). the kind of flower, the water used, and the additives made, interact to result in highly significant if sometimes unpredictable results. Neff (1937) indicated that the exposure of treated cut flowers influenced their response to treatment. This work led to modern packaging. It is not always practical to maintain severed material in solutions of any kind. E. Cold Effects In recent years, prolonged cold storage for an indefinite period was revived as a panacea for the storage problem of cut flowers and greens. The application of brominated activated charcoal described by Fisher and Keller (1951) is particularly pertinent. Fisher (1953) published an ex- cellent paper regarding near—freezing temperatures, pathogens, and toxic gases . This type of cold storage is not, as has been inferred, desir- able pre-conditioning. Prolonged storage is undesirable because some chemical processes are not appreciably retarded by such temperatures. Recent recommendations for roses have been modified from an Optimistic thirty to a realistic seven days of near—freezing storage. When suitable procedures are developed for sub-zero storage, the practical storage per- iod might be extended somewhat without seriously shortening the subsequent life after storage. Cornell (1951) has pioneered in quick freezing of flowers. The pre-conditioning of flowers by near-freezing temperatures has been recognized as a problem by commercial florists who have long used two general methods of treatment. One was bringing the temperature up 10 slowly by lOOF. stages. The other consisted of submerging the flowers in water (often cold but sometimes at room temperature). Since flowers taken from cold storage often absorb water slowly, Sherwood (1953) passed on Volz' (1928) old recommendation of conditioning wilted flowers by placing the stems in warm water and allowing the water to cool. In 1939, Maxon (1951) used vacuum to get water into thawed cuttings. Tukey, Hamner and Carlson (1945) adOpted this process of getting water into cut flowers. F. Gas Effects The study of the effects of gas concentrations, relative humidi- ties, and temperatures under practical conditions is complicated because each is inter-related. However, since the investigations of Kidd, West, and Briggs (1921), innumerable investigators have found that restricted oxygen availability or slightly raised carbon dioxide levels tend to prolong the life of seeds, bulbs, vegetables, meat, etc. Thornton (1930) reported that cut dahlia blooms kept at 50°F. in an atmosphere containing added carbon dioxide were not noticeably altered by a ten per— cent concentration of the carbon dioxide but were injured when the con- centration was fifteen percent or higher. Longley (1930) and Thornton (1933) found moderately raised carbon dioxide levels prolonged the life of cut flowers. Hitchcock and Zimmerman (1929) found a humidity of 98 percent beneficial. Sherwood (1955) found lower humidities desirable in the storage of isolated flowers and flower petals. Since flowers could not remain usable in actual equilibria with even a 98 percent relative hu- midity, one must assume such humidities are modified considerably in the interfacial zones existing between the protoplasm and the bulk of the ex- ll terior environment. A similar situation might prevail in the case of ox- ygen, or conversely, carbon dioxide. The elvironment of packaged cut flowers is largely unknown since it is extremely responsive to vectors and difficult to sample as found by Sherwood (1955). G. Metabolism Plagge, Maney and Pickett (1925) and later Plagge and Gerhart (1930), reported on the effects of storage conditions on the metabolism of apples. As a student the author assisted Dr. Plagge with later studies involving pre-war usage of plastic film overwraps on the respiration and aging of fruit. The importance of exact concentrations and consequently rapid measurements of many environments was readily observed. Much time was de— voted to obtaining representative samples, overcoming small sealing imper- fections, etc. During this period the value of analyzing smaller gas same ples more quickly was often discussed. The work of Brierly and Iandon (1942) on the smothering of strawberry plants emphasized the role of metabolism and the need for controlling res- piratory toxins. H. Characteristics of Respiration Respiration and growth have long been associated with temperature. It has been claimed that for every 10°C. change in temperature, the res- piration rate is doubled or halved. However, Loomis and Shull (1937) demonstrated that the character as well as the rate of respiration was affected. Hover and Gustafson (1926) found that estimating the effect of age on reapiration is complex. They found the characteristic might be high at first, then low, and finally high. They also found some plant tissue in which respiration increased with age and some in which it de- 12 creased with aging of the tissues. Donnely and Beck (19h5) stated that the amount of respiration of plant tissue decreases with the time of sectioning, age, and loss of food. Maskell (1928) and Denny (1933) found respiration affected by time of day with lower respiration rates at night. White (195h) found the rhythm of respiration considerably more complex with differences from seasonal effects as well as diurnal. Robertson, Turner, and Wilkens (19h?) and Whiteman and Schomer (l9h5) show how wounding can markedly Stimulate respiration for as long as ten days. Haas (1919) found that death caused in one or two hours from lethal doses of alcohol, formaldehyde, acetone, and ethyl bromide resulted in increased apparent respiration rates as long as two hours after death. He based death as the time when.the electrical conductivity jumped to six and two-thirds that of normal tissue. It is interesting to note that lethal drying resulted in the highest rates found, while death from 35°C. heat actually resulted in sub-normal rates. This was con- sidered possibly due to enzyme destruction. Whitehead (l93h) found disease affected the respiration rate, and Dmny (191.8) found surface microflora also raised the apparent rate with- out causing visual injury otherwise. The "bounce effect" in biology which is becoming more apparent as measurements becone more exacting, Aronof (1956),is further complicated by studies of various authors. wynd (l9h3) found the respiration of tobacco rose greatly the fourth day after the leaf was infected with mosaic and by the time the leaf itself was in- fectious, ten days later, the rate had declined to less than normal. Additives such as oils, nutrients, and growth regulators have been 13 found as capable of affecting the respiration rate as the solvents and laboratory chemicals previously mentioned. Stiles (1935) was one of the first to report that oils might cause either higher or lower rates. Childers (1935) pointed out that rate effects might also be apparent be~ cause the phloem translocation system was blocked by infiltrating oil. Prill, Barton and Solt (l9h9) found that surface active agents re- tarded the growth of wheat roots in solution and the author presumes this affected at least the accumulative respiration. Hamner, Carlson and Smith (19h?) found that 2,4-D treatment resulted in a significant rise in respira- tion the third day, with a maximum in ten days. Kelley and Avery (1949) and Mitchell, Burris, and Riker (l9h9) found 2,h—D at suitable concentra- tions might also reduce respiration. Both found other inhibitory sub- stances. Additive and pH effects were also noted. Barnes (1905) classified respiration as essentially aerobic, an- aerobic, or fermentive. There has been an increasing amount of litera- ture published where metabolic studies, Stiles and Leach (1952), were of critical value in living material in vivo or in vitro. Such detailed studies are invaluable in studying methods of increasing the useful life of cut flowers and greens. With such methods it may be possible to de- termine if growth regulating chemicals at different concentrations, times and places affect the plant material through primary or secondary effects such as the mobilization of normal plant solubles t0>the extent that toxic respiration by-products are locally accumulated in various quantities which then narcotize the tissue and prevent it from functioning normally. Radiobiochemistry as shown by Aronoff (1956) is especially promising. 1h 1. Measuring Heepiration Methods of measuring respiration and the necessary equipment are described by Loomis and Shull (1937). Some particularly interesting ones were those described by Denny (1948A, 1948B, l9h80). Donnely and Beck (19h5) describe a micro-reapirometer and Harrington and Crocker (1923) also describe a method suitable for small samples. The method offering the best results, if it could be mastered seemed to be that described by wynd (1952) as a micromanometric method using modified Barcroft apparatus. wynd (1952) describes the apparatus, calibration of it, and routine technique in detail. He points out that the limits of a significant difference are not biological but the smallest we can measure with certainty. Aronoff (1956) has also shown the need for more exacting measurements in relation to time. wynd also emphasizes the importance of the nature of the problem in the determination of sig- nificance. The apparatus was used to measure oxygen to a few millionths of a gram. This means it was considerably more sensitive than commer- cially available equipment. 15 III. PROCEDURES AND RESULTS A. Lengtheningthe Life of Cut Flowers and Floral Greens by the Use of Plastic Coatings The most promising latex available from the B. F. Goodrich Chemical Company was distributed under the designation Geon 31X. Later the desig- nation was changed to Vinyl 600. The early formulation was based on 25 percent solids in the vinyl resin latex. However, the bulk of the basic latex contained A9 to 51 percent total solids and had a specific gravity of 1.2h to 1.25. The specific gravity of the resin was 1.60 and its particle size averaged 0.2 microns. This is considered noteworthy be- cause latexes with a larger particle size would require proportionately thicker applications to achieve the same uniformity of coverage. As formulated, the pH of the latex was 6.5 to 7.5. This tended to become more acid with storage particularly at higher temperatures. Storage be- low 60°F. could result in gelatinization which could be treated bylwarm- ing the latex to 700 - 80°F. while agitating slowly to obviate coagulation. Material stored as long as a year might serve satisfactorily while other material stored only a short while under certain conditions, such as very cold temperatures, might coagulate. The basic manufacturer recommended storage at 60° to 80°F. and usage within 90 days. Since coagulation is favored by gear and close tolerance pumps their use was discouraged. Coagulation of these latexes were found to be favored by non-ionic and anionic systens. Therefore, Spreaders, wetters, stabilizers, fillers, 16 colors, etc., were recommended to be non-ionic (no charge) or anionic (negative charge) in the form of dispersions, enulsions, or solutions and at about the same temperature and pH of the latex concentrate with which they are being blended. Rubber lined storage containers were recommended. Although copper and brass is harmless to the latex, they are pitted by prolonged contact. Attempts to raise the pH with ammonia or ammonium salts may lead to discoloration of the films or coatings. However, the pH could be raised with a 10 percent solution of sodium carbonate, sodium bicarbonate, or trisodium phosphate. Striking results have been obtained with gardenias. In the addi- tional experiment 12 gardenias were used; A were dipped in a 10 percent solution of Vinyl 600, A in a 20 percent solution, and a left untreated. The flowers were then left out of water at noon temperature (700 to 80°F.) and observed at intervals. After A hours, untreated gardenia flowers began to wilt; and after 12 hours, in addition to being badly wilted, they had developed an ob- jectionable yellowish brown color. Flowers treated with a 20 percent solution of Geon remained turgid and in excellent condition for about 36 hours, after which deterioration was quite rapid. Flowers treated with a 10 percent solution remained fresh and attractive for 20 to 36 hours longer than untreated flowers. It appears from.this test that the 20 percent concentration of Vinyl latex 600 is best for gardenias. The treatment with Vinyl 600 in no way detracted from.the natural beauty and appearance of the flowers. It was felt by many observers that the appearance of the flowers was improved by the treatment. Some loss 17 in fragrance occurred from the treatment, but this loss was not great and was not undesirable. ' Water loss was reduced by the treatment, and this probably partially accounts for the fresh appearance of the flowers. Table 1 shows water loss at the end of 1+ hours. At this time the control flowers were be- ginning to wilt. Table 1. Water loss from gardenia flowers following treatment with Vinyl latex 600. Weight loss in percent I" t i l T t t a er a rea men 1. hours after treatment No Vinyl lat ex 0% 13.0 Vinyl latex 600 10% 6.2 Vinyl latex 600 20% MS Plume asparagus (Asparagus plumosus) is extensively used as a de- corative green. However, its tendency to lose "leaflets" (cladodes) short- ly after being cut is a major problem. Branches were selected, divided into 30 bundles and treated by dipping in water suspensions of Vinyl latex 600 at various conceltrations. Ten bunches were treat ed with 5 percent Vinyl latex 600, 10 bunches with 10 percelt, and 10 with 0 percent Vinyl latex 600. The branches were then placed in a warm room (85°F.) and the loss of weight recorded at intervals. Within 2 to 3 days, 20 to 30 per- cent of the cladodes dropped from the branches uncoated with Vinyl 600. The 10 percent Vinyl 600 treatment reduced shedding to a negligible amount over a 10-day period. As shown in Table 2, water loss was also retarded. 18 Table 2. water loss from Asparaggs plumosus following treatment with Vinyl latex 600. Weight loss in percent Material Treatment Nov. 18 Nov. 19 Nov. 20 Asparaggs plumosus 0% Vinyl latex 600 0 35 66 5% Vinyl latex 600 0 18 #3 10% Vinyl latex 600 0 5 23 Oregon fern (Polystichum munitum) is a decorative plant material that would be used more extensively if it would last longer. Fronds from Oregon ferns were divided into 30 bundles. Ten bundles were dipped in a 10 percent Vinyl latex suspension, 10 in a 5 percelt suspension, and 10 in a 0 percmt Vinyl latex solution. The bundles were again exposed in a warm room.(85°F.) and records taken at intervals (Table 3). After about 12 hours most fronds were Obviously wilting and shriveling. By 2h hours, those uncoated were past using. Those treated with 10 percent Vinyl latex 600 lasted 2A to 36 hours longer. Table 3. water loss from Polystichum munitum following treat- ment with Vinyl latex 600. Material Treatment Weight 1°33 inpercentt; Nov. 20 Nov. 22 Oregon Fern 0% Vinyl latex 600 0 60 5% Vinyl latex.600 0 A6 10% Vinyl latex 600 0 #2 19 A later eXperiment showed that 20 percent Vinyl latex 600 was much more effective than 5 percent or 10 percent concentrations. Although the 20 percent latex left a markedly glossy surface this was not objection- able on the fern. In experiments concerning the application of Vinyl 600 latex to cut flowers and greens, it was‘fbund that seriously injured areas turned brown within 12 hours. The latex.over these areas often dried a milky white indicating coagulation. Interaction of the drying latex with the plant material was suspected since immature plant material or slow drying in an enclosed atmOSphere favored the difficulty. Since drying rapidly at room temperatures for at least 15 minutes precluded visible injury, work was continued on respiration rather than on investigation of phytotoxic pro- perties. Since larger samples might dry slower and more unevenly, it was postulated that large samples should not be enclosed for at least 30 minutes after they appeared entirely dry. It is also noteworthy, although not surprising, that two applications of 5 percent resin latex were more effective than one at 10 percent. B. A Method for the Rgpid Dgtermination of Carbon Dioxide in Small Samples of Gases1 As shown by Loomis (1937) and Neff (1937), the carbon dioxide content of the atmosphere exterior to cut flowers and greens has been found an im- portant factor in storage considerations. As mentioned previously, the author was familiar with the techniques by Plagge, in obtaining data as reported by Plagge and Haney (19h1) and Plagge and Fischer (l9h2). In 1“Journal article No. 876 (n.i.) of the Michigan Agricultural Experiment Station. 20 general the optimum perceltage of carbon dioxide exterior to stored plant material is between five and ten percent with the exact concentration de- pendent upon temperature, variety, etc. Often, as when intimate wraps are used, the analysis of small sam- ples of atmosphere adjacent to the plant material is desired. None of the various methods of determining carbon dioxide concentrations as described in the literature were considered suitable for quick analysis of numerous small samples stored in various environments. Lung and Ambler (1931.) stated that an error not exceeding 0.5 percent of the total volume of the sample is obtainable in analyzing for carbon dioxide in samples no larger than one ml. in size. Although most carbon dioxide analyzing equipment features the packed tower or other complexities, Sherwood (1937) stated that the simple and ineXpensive "bubble tower" is practical for small gas samples. Schafer (1938) measured carbon dioxide concentrations to 0.1 percent in leaf atmospheres with hydroxide absorption within 30 seconds. The apparatus described by Berg (19A6) has the advantage of being usable for the analysis for several gases in the same small sample. Unfortunately it requires over tax minutes a sampleald it is not readily usable for re- peated analyses outside of the laboratory. In some instances it is important that sudden changes in the carbon dioxide concentration be detected. Approximate values obtained by frequent testing may, in such cases, serve a better purpose than more accurate re— sults determined at longer intervals. The purpose of this study was to develop equipment and a procedure which permitted the determination of the approximate carbon dioxide con— tent of one m1. samples of gas at the rate of about one a minute. 21 The essential parts of the apparatus (Figure l) consist of a pipette, an absorbing chamber, and a syringe sampler. Other parts were added to facilitate repeated analysis. To make the apparatus (Figure 1) insert one m1. pipette, graduated in hundredths, into the base of the glass T with a bit of rubber tubing serving as a collar. Attach a two and one-half inch length of thick, pre- ferably transluscent rubber tubing to the lower arm of the glass T and in- sert a glass plug into the free end of this tube. To the other arm fasten a glass stopcock and then a 15-inch length of rubber tubing terminated with a glass mouthpiece. At the other end of the pipette attach a capillary tube bent in a hook shape as shown in Figure 1. A cylindrical reservoir made by removing and discarding the bottom from.a test tube is attached to the capillary tube with a one-hole rubber stopper. The apparatus is mounted with the pipette horizontal, the glass valve above, the glass plug below, and the reservoir in an upright position. This mounting can be accomplished by attaching clamps below the glass valve, on the lower arm of the glass T, and at the union of the capillary tube and pipette. To ready the apparatus for use, put a one-inch column of mercury in the tube above the glass plug. Add a five percent solution of potassium hydroxide through the reservoir by applying suction through the mouthpiece until the solution is about one inch below the valve. Remove the excess from the reservoir and by means of the mouthpiece draw a little air in the pipette to form.one or two small bubbles. Then close the glass valve. Now add a one to five percent solution of hydrochloric acid to the reser- voir and draw it through the pipette by means of the mouthpiece until only 22 a one-fourth inch air bubble remains trapped in the pipette. Again close the glass valve. Add sufficient acid solution to half fill the reservoir vial and adjust the bubble with the glass valve (stOpcock) until it just touches the zero scale mark. The level of the liquid in the reservoir should now be about that under the glass valve. A pH indicator may also be added if desired. A one m1. syringe and a No. 26 needle make a satisfactory sampler. A tuberculin syringe marked as the pipette and of the same capacity is convenient. Since the accuracy is dependent upon the syringe and its manipulation, trial runs and necessary adjustments should be made. Out- side air should be used for insuring proper sample volumes. Known concen- trations of carbon dioxide gas can be used to insure accurate operation. The author found samples of exhaled breath convenient to periodically check operation under field conditions, particularly when tested samples were found surprisingly low. The mercury serves to protect the syringe from contamination with the reagent while the sample is being injected into the apparatus through the rubber tube wall just above the glass plug. Rinsing the syringe with a one percent solution of hydrochloric acid before each sampleing will in- sure that the syringe will remain tight and free of alkali. The needle should be withdrawn as soon as the sample is injected as minute mercury droplets may otherwise wonk into the syringe. Results of representative trials as shown in Table A indicate the comparative accuracy of the Micro-analyzer and the Orsat apparatus. The per-run time for the micro-analysis was less than one minute. 23 Directions: To use the apparatus, set the bubble at zero. Then insert the syringe needle into the sample source and fill the syringe a little past the 1 ml. mark. Withdraw the syringe and inject the desired gas quantity into the mercury column. Withdraw the needle and ascertain the scale reading as indicated by the bubble. Open the valve and re- adjust the bubble to zero. The use of the mouthpiece makes possible more rapid readjustment. Close the valve ail another sample can be run immediately. Precautions: l. The fittings must be tight. 2. The needle should be injected into the mercury. Special care in rinsing is necessary if the potassium hydroxide solution gets into the syringe. 3. The operation of the syringe should be checked occasionally. A change of 0.01 ml. in the setting may be necessary depend- ing upon the syringe, how it is read, and the temperature. A. The injection area should occasionally be squeezed to dis- courage bubbles near the valve which might otherwise be drawn into the suction line. 5. The potassium hydroxide and hydrochloric acid solutions must be maintained. Although five milliliters of solu- tion is adequate for hundreds of samples, it should be changed monthly or as indicated by other than immediate adjustment of the bubble after injection. Questions to keep in mind: 1. Is the sample as injected, nearly the temperature of the apparatus? 2. Is the sample representative? 3. If the bore of the pipette is rather large, will unusually rapid injection result in low readings? Because of the small size of the sample and the rapid shuttling of the bubbles, no delay in absorption resulting from slow diffusion of the carbon dioxide in the gas phase is apparent. Reaction time, dilution of the potassium hydroxide or humidity of the sample are unlikely sources of measurable error. The dilute hydroxide is recommended as it is less dangerous than the more concentrated solutions which are frequently used. The hydrochloric acid serves to retard etching of the scale and for rins— ing the syringe. Greater accuracy might be obtainable by modifications such as using a sampling pipette instead of the syringe. Smaller samples could be more accurately analyzed by using a smaller bore pipette for the scale and bubble. Other gases could be analyzed in similar samples by the use of different reagents. The apparatus (Figure 1) can be used with an accuracy of about 99 percent of the total sample. The use of triplicate samples will result in a greater degree of accuracy, as will extreme care. C. The Effect of a Plastic Coating,,Vinyl 600, on Carbon Dioxide Accumulation under Excised Rose Petals The Vinyl 600 coatings on floral products as described earlier were considered by Sherwood.and Hamner (19A8) to be effective largely because they reduced the loss of water. However, since some treated flowers kept longer than untreated flowers when water loss was not excessive, the possibility of the retardation of physiological aging because of the accumulation of carbon dioxide under the coating was also Considered. It was assumed that an external atmosphere in equilibrium with that within 25 0.0 0.3 a 0.0 0. mm mm a 0.0 4.0 H N.v N.mm mm m 08 {a H we m.m~ em a. m.m mime H 0.0 m.mm mm o ox as H 0.0 mam mm m m.mH mafim H o.mH H.HN mm .4 m.mH 91m H m.oH w.om mm m mH m.@ H 4.0H 0.8 mm N o 0.2 a o 0.3 mm a unsound onueou .He ouHm essence onUwou .Hs ouHm ooasom m8 Hesse seesaw N8 asses ode—am seesaw aoNhHeoeIOLOH: venue LI 259393. 320 one use 30323:?“on on» an 3932:. N00 oifiamofioo .4 e33. 26 the petal would be more closely associated with the response of the flower than other measurements. It was hoped that the gaseous carbon dioxide content of such an atmosphere would be obtainable. The rose petals were obtained from.two partially open roses of the Better Times variety'which had been kept in water at room temperature for six.hours after being removed from refrigeration. Each petal was removed in sequence, the outer petals being considered the older and more mature. Sixteen vials 2.2 cm. in diameter and 5.5 cm. in length were given a coating of rubber cement on the lip and numbered with fingernail polish. Sixteen numbered smaller vials 1.3 cm. in diameter by 5 cm. were sealed by cementing paper discs to the lip with fingernail polish. Eight of these were dipped so the paper received a coating of 10 percent Vinyl 600 emulsion. After drying, the smaller vials were inserted into the larger ones with the disc side up. Sixteen corrugated cardboard washers four cm. square were prepared by punching round holes 1.5 cm. in diameter through the center of corru- gated cardboard squares. A moist chamber was prepared from.a covered can of the type used for preserving cake by putting shredded wet paper under the rack within it. The micro-gas analyzing equipment described by Sherwood (19h6) was used for determining the carbon dioxide concentrations after different exposures. Holes in the petals made by the Number 26 needle of the sampler were sealed with a minute dab of Vinyl 600. Sixteen rose petals were arranged in groups of four in sequence of removal from the two roses so that one group represented the older and one group the younger petals of each rose. 27 All petals within the particular group were randomized and two coated with ten percent Vinyl 600 on the edges and upper or inner side. This coating was allowed to dry for 30 minutes after which the large vials were covered by centering the petals on the lip with the outer side adjacent to the interior. They were further secured by centering the cardboard washers on top and securing the whole with two rubber bands, as shown in Figire 2, with firm but not crushing pressure. An additional seal of 50 percent Vinyl 600 was then run around the vial where it contacted the rose petal. The petals which had been coated with 10 percent Vin31.600 on the upper side were then given another coat on the lower side. Each group then included two coated and two un- coated petals one of each in a large vial containing a small vial with a treated disc and one of each with an uncoated disc. The assemblies were then put into the culture chamber and kept at 25°C. for 48 hours. All received a drOp of water on the petal at 24 hours as a few untreated petals appeared to be wilting a little. A few vials were sampled at 12 and 24 hours by injecting the needle through the petal which was resealed with a minute dab of Vinyl 600. The concentrations after 48 hours were barely measurable with the method used (Table 5). The data for a lesser period is not presented. Unfortunately, the petals were not considered in a good enough condition to attenpt a longer period. However, as averaged, the concentration found under the older petals was 0.6 percmt carbon dioxide while that found under the younger petals was 0.7 percent. The conceltration of the inner vials as compared to the outer showed no differences under either old or young petals. However, 28 coating the covering on the small vials resulted in a carbon dioxide concentration double that of comparable uncoated vials. The average readings for petals coated with Vinyl 600 was almost 0.8 percmt carbon dioxide or about 50 percent higher than the 0.5 per— cent found under those not coated. The difference was greatest under the younger petals. The carbon dioxide conceltrations found seem consistent with the treatments made. The 50 percent higher concentrations found under coated petals is comparable to the nearly 50 percent average decrease in carbon dioxide assimilation found under Vinyl latex coatings by Kramer (1948). It is also reasonable that the younger petals should be found to have a concentration 15 percent higher than that under the older petals. Since these younger petals were at least eight petals re- moved from the oldest it is not surprising that the Vinyl latex had pro- portionately more effect on them since the cuticle was less developed. Although it was expected that coating the covering on the inner vial would result in higher readings of samples from the outer vial, the high- er readings of sanples from.the coated inner vials could indicate that the levels in the larger vials had been higher prior to the test or that the sample obtained from the large vials was being diluted by incoming air mixing with it as it was withdrawn. The use of a longer needle is indicated. Since the inner vial was sampled in place, the replacement air came only indirectly from outside. It is also indicated that the procedure is far from developed since an adequately small environment should, in the author's Opinion, attain levels exceeding 5 percent under such coated petals before injury from Table 5. The Effect of Plastic (Vinyl 600) Coatings on CO2 Accumulation Under Treated Rose Petals (Better Times) During a 48 Hour Period After Treatment. Age of rose petal treated - Percent C02 Treat- Older Ybunger Total Average ment* Large Inner Large Inner Large Inner vial vial vial vial vial vial l 0.8 0.0 0.2 0.0 0.5 0.0 0.3 1.0 0.9 0.1 0.6 0.6 Ave. 0.6 0.5 0.6 0.1 0.6 0.3 2 0.2 0.5 0.3 0.3 0.3 0.4 0.7 0.1 007 1.0 007 0.6 Ave. 0.5 0.3 0.5 0.7 0.5 0.5 3 0.0 0.1 0.2 0.2 , 0.1 0.2 0.7 1.0 0.8 0.9 0.8 1.0 Ave. 0.4 0.6 0.5 0.6 0.5 0.6 4 0.5 1.2 0.4 0.9 0.5 1.1 0.8 0.5 1.5 1.6 1.2 1.2 Ave.. 0.7 0.9 1.1 1.3 0.9 1.1 * Treatments: 1. Check (neither petal nor small.via1 treated). 2. 10 percent Vinyl 600 coating on petal only. 3. 10 percent Vinyl 600 coating on small vial only. 4. 10 percent Vinyl 600 coating on petal and small vial. the imperviousness of the coat would be found. Schafer (1938) found carbon dioxide levels approaching four percent in leaf atmospheres. 30 D. Micro-manometric Determinations Plant materials coated with various concentrations of the Vinyl 600 latex occasionally and unpredictably developed areas which were off- color or even necrotic. It was considered possible that a sensitive method of measuring respiration might be of value in determining whether or not abnormal metabolic conditions existed following treatment and, if so, their character. wynd's respirometer (1952) was activated and used under his direction. The experimental plant materials were rose petals of the variety Better Times and Norway Spruce needles. The procedure used consisted of pairing the samples, one lot for treatment and another non-treated for each of the three pairs of manome- ters. In the case of rose petals, discs 1 cmt in diameter were punched from each side of the petal, numbered, and by random placed in either a check or treatment lot. Therefore, the manometer pair received a disc from either the left or right side of each rose petal. By trial it was found that about 6 discs were Optimum.for the equipment used. The discs were then treated with 0 percent to 20 percent concentration of Vinyl 600 latex and then dried at least 15 minutes before use unless otherwise noted. Spruce needles were taken from the same twig, paired or removed and treated in the manner described for the rose discs. Generally six needles were used per manometer. In many instances the apparatus required final temperature adjust- ments or other care and this resulted in more than 15 minutes drying time before the samples were sealed in the vessels. As a point of caution, it is suggested that all major activities such as preparing the vessels be accomplished in advance unless a surplus of comparable vessels calibrated 31 for each manometer are available. As soon as possible after an adequate drying time the vessels were capped and secured in position. The apparatus was the31run for at least fifteen minutes before the arms were closed and readings begun. When the readings appeared atypical, as they rarely did, the data was scrutin- ized to see if the starting time was adequate and characteristic diffi- culties could be easily traced to a loose connection, contamination of the sample with reagent, a plugged line, etc. The fluid in the nanometers was readjusted after five hours of sampling. Sulfuric acid was used to maintain drying conditions in the vessels. This controlled fungi found troublesome at higher humidities but it usually limited total run times of uncoated controls to less than 48 hours. The absorption of oxygen by uncoated samples indicated the samples were uniform. However, 20 percent Vinyl latex coated samples were quite variable with samples dried 25 minutes before enclosure being associated with medium low oxygen absorption rates, those dried 20 minutes with higher rates, and those dried but 10 minutes with the lowest rate of oxygen absorption (Table 6). Determination of the effect of drying time was run with 10 percent Vinyl latex coatings on spruce needles with 10, 20, and 30 minutes dry- ing times before enclosure. As shown in Table 7, there was no significant difference attributable to even a short 10-minute drying time when 10 per- cent Vinyl 600 was used. Even the preliminary temporary reduction in oxygen absorption was not as apparent when using dilute concentrations. The 20 percent concentrations were especially consistent for short 32 periods when all needles appeared undamaged at the end of the experiment concerned. As shown in Table 8, the data for the full run time is quite variable. Determinations were made to see if the 30—minute drying time pre- viously mentioned as adequate. Insofar as immediate post-treatment is concerned, 30 minutes is sufficient drying time but some lack of uni- formity in oxygen absorption was found. Treated discs from.rose petals absorbed oxygen more erratically than spruce needles. The absorption of oxygen was usually low immediately after treatment, than high, and finally low again (Table 9). The data presented were based on dry weight. However, the data based upon fresh weights, when graphed, showed similar trends due to treatment. Fresh weights were obtained by briefly soaking in tepid water and blotting dry before weighing. All data reported produced straight line graphs when plotted on the basis of millionths of a gram of oxygen absorbed for peri- ods of several hours and often for consecutive periods throughout the ex— periment. As shown in Table 10 the Norway Spruce needles lost moisture on drying to 66 hours with differences in weight due to treatment of ten to fifteen percent. The actual film of latex was less than one percent difference in weight in all concentrations used. 33 Table 6. Effect of Drying Time of 20% Vinyl Latex Coatings on Oxygen Absorption on Norway Spruce Needles. Run Dura- Minutes Drying Time in Open Air Date Time tion in Control 20% Vinyl 600 Control Minutes 20 20 15 10 15 July 29 1:10 pm 70 9.20* 10.64 9.67 5.36 9.47 80 10.48 11.98 10.74 6.27 10.76 90 11.56 13.31 12.04 7.07 11.93 100 12.62 14.39 12.98 8.21 12.75 July 29 5:00 pm 100 8.34 2.18 3.54 1.48 14.04 110 9.41 2.66 4.25 1.82 15.21 230 28.99 17.54 12.86 7.07 28.43 250 30.28 20.08 13.33 7.41 29.95 July 30 8:10 am 10 1.07 0.847 0.59 0.57 1.64 20 2.99 1.81 1.77 1.14 3.51 30 5.13 3.27 2.30 1.94 5.26 40 5.78 5.08 3.06 2.74 6.90 *Based onul. of 0 2 absorbed/10 mg. dry weight of Norway Spruce needles. 34 Table 7. (bcyge’l Absorption inpl. in Norway Spruce Needles as Affected by Protective Coatings, 10 and 20 Percent Vinyl Latex 600. Results Expressed as Percent of Control. Drying Time Before Enclosure and Date Time V.L. Percent Oxyge’l Absorbed inul. Conc. Minu- Oxygen Minu- Oxygen Minu- Oxygen % tes Percent tes Percent tes Percent July 29 1:00 pm 20 20 114 15 101 10 64 5:00 pm 20 66 m. 25 87 48 40 July 30 11:OO;am 117 25 1.4 August 8 6:00 pm 10 30 107 20 97 10 104 August 9 11:00 am 106 90 104 10:00 pm 106 94 103 35 Table 8. Oxygen Absorption as Influenced by 10, 15 and 20 Minutes Dryb ing Period in Norway Spruce Needles Coated with 20 Percent Vinyl Latex 600. Observations Recorded at Various Intervals- and the Results are Experssed as.fll. of Oxygen/1 gm. Dry weight /10 Min. M1. of Oxygen Absorbed at Different Date Interval Drying Time Interval in Minutes Peri“ o 10 15 20 July 30 1:00 pm 1.43 4.86 4.02 6.88 6:00 pm 2.42 0.92 0.41 1.14 July 31 3:00 pm 1.89 1.31 1.07 1.09 August 1 10:00 am 1.99 1.51 1.14 1.25 Table 9. Oxygen Absorption of Rose Petals,/1 cm. disc/5 hours, after Treatment with Vinyl Latex 600. Results are Expressed as Percentage of water Dipped/1 cm. disc. Oxygen Absorption in.u1./lcm. disc. Date Time Replications Interval l 2 July 22 3:00 pm 76 87 8:00 pm 99 93 July 23 10:00 am 54 88 Table 10. Weight/(mgs) of 12 Norway Spruce Needles as Affected by 10 and 20 Percent Vinyl Latex 600 Concentration Treatment. Observations Recorded After Various Time Intervals. weight (mgs) of the Treated Needles After Treatment 18 24 30 42 66 Check 101 106 96 91 80 10 % Vinyl Latex 600 104 101 100 96 88 20 5% Vinyl Latex 600 107 105 103 100 95 37 IV. DISCUSSION An effective, though artificial, protective coating on cut flowers and greens could be obtained with sprays or dips containing a plastic disperson, Vinyl latex 600. The use of rubber latex concentrations of 5 to 20 percent were satisfactory with the more apparent results at the higher concentrations. Injury, especially to juvenile plant material was reduced with the use of lower latex concentrations and quick drying in the open air. Data obtained indicated that 20 percent latex concen- trations affected the oxygen absorption of treated spruce needles most with those dried but 10 minutes before enclosure and least those dried 20 minutes. Since the 10 percent latex treatment had little effect on respiration as measured by oxygen absorption of material dried from 10 to 20 minutes, it is considered likely that drying 10 percent treated ma- terial 10 minutes and 20 percent treated material 20 minutes after they appeared dry would be sufficient before enclosure of such material. Un- less treated material is visibly dry within 10 minutes, the author con- siders drying conditions inadequate. The reason for'injury is unknown. The latex may concentrate more of its solubles against the plant surface while drying slowly. This con- centration combined with additional penetration time before drying could well result in a greater liklihood of injury. It is also possible the cuticle itself is attacked by the latex. Another possibility is the free- ing of active chlorine or other anion greatly increasing acidity with re- sultant phytotoxicity. The injury, appearing to be contact in character, 38 indicates the possibility of caustic action. Whatever the cause, prolonged exposure of the plant surface to a latex suspension favors the injury. The coagulation of the wet latex noted on enclosed plant material may be due to excessive concentration of the latex or it may indicate one or more of the emulsifiers or a pro- tective coating on the latex particle had diffused away or become in- activated. The use of two applications of 5 percent or an initial application of 5 percent, followed by a stronger one is desirable. The protective coating is more effective than one application of 10 percmt latex and the liklihood of phytotoxicity is reduced. The use of a small amount of tri- sodium phosphate in the first coat to insure a pH of 6.5 to 7.0 may be ad- vantageous. Leeper (1955) suggested the inclusion of a small amount of a scavenger, such as organic tin added to the latex, might be helpful in re- ducing troubles due to excess acidity. The erratic absorption of oxygen by treated plant material was associ— ated with high latex concentrations and long drying times. However, even the supposedly favorable concentrations and drying times tended to suppress, raise, and then lower the rate of oxygen absorption. It is possible a transitory toxic effect was involved. A lipoid solvent possessing an ap- preciable vapor pressure at ordinary room temperatures might be suspected. An unsaturated hydrocarbon may be involved. The chemical or chemicals re- sponsible might be residues or contaminants of processing. It is note- worthy that Vinyl latex 600 formulations are regularly improved (Hamner 1955) and these results were with material available by 1954. Processing the latex with one of the positive exchange resins might 39 be of value if short chains of acid rubber molecules are involved. This might also avoid coagulation. Placing the latex under high vacuum for several hours might prove of value if volatiles such as acetone are involved in the phytotoxic proper- ties. Treating material while cooling might increase difficulties and this would suggest that direct absorption is involved. Lipoid solvents might be expected to injure more at higher temperatures. That the film from latex treatments protects the plant is incontro- vertible. Both water loss and oxygen absorption of treated material are appreciably-reduced. )Wrno‘M-flnywiflbL' .7 3F '} However, Thornton (1933), Plagge (1940) and others found that very high carbon dioxide concentrations can result in injury of the type found. The author (1940) found injury following the sudden cooling of Saintpaulia foliage which he could explain only on the possibility that respiration by- products, nontoxic at warmer temperatures, accumulated at the "rings" where injury occurred. The author also found similar injury more favored by acid than by alkaline solutions. The possibility of toxic accumulations of carbon dioxide even momen- tarily occurring under a film abnormally gas tight because of a slow dry- ing time has not been proven. The accumulation of carbon dioxide in the latex during storage is considered unlikely. It is a coincidence that Kramer (1949) Who discussed the cold-water problem with the author in 1940 also worked with Vinyl latex. He found that treated plants were briefly retarded in visible growth but that the eventual growth and yield might even exceed that of untreated plants. Us- ing Vinyl latex 600 at 10 to 12% percent with Dreft as a wetter, he found 4O transpiration of treated plants reduced as much as 55 percent the first day. However, yellow poplar transpired 10 percent more. He also found that carbon dioxide absorption was reduced over 60 percent the first day and up to 25 percent after a week. This confirms that the coat retarded the passage of both water and carbon dioxide. Since oxygen is restricted more than carbon dioxide by these films, the marked effect upon carbon dioxide assimilation may be partially eXplained by an over accumulation of oxygel. Toxins such as oils have an even more marked effect on carbon dioxide accumulation than they do on reSpiration. Chloroplasts can be converted to leucoplasts by treatments without such marked effects on other cell pro- toplasm (Sherwood 1940). Therefore, the pronounced retardation of carbon dioxide assimilation fbllowing an application of a comparatively low latex concentration is acceptable. The additive effect of the Dreft is also a possible factor as Staniforth and Loomis (1949) found 2,4-dichlorophenoxy- acetic acid was more injurious when used with a wetter. The intimate nature of the coat is illustrated by Hamner and Chi-kien (1948) finding Vinyl latex also increased the effect of 2,4—dichlorophenoxyacetic acid concentrations. They found that one, five, and ten percent concentrations of Vinyl latex alone had no ascertained effect on the beans treated under greenhouse conditions. This emphasized that the coat is beneficial only when useful in protecting the plant from drying winds or other adverse factors. Although the coat could be expected to hold more chemical, the marked effect is ordinarily obtainable only by placing the 2,4-dichloro- phenoxyacetic acid treated control plant in a sealed container. The effect can also be partially explained as the premise that the latex, like a hl wetter, favored mechanical penetration through cracks, etc. in the weaken- ed cuticle and through the stomata. Hamner, Gartner and O'Rourke (1948) found the material V.L. 600 of decided value in retarding the water loss from.cut foliage. They recommended its use to improve the keeping quality of spruce, Chinese arborvitae, and mistletoe. A later publication by Gartner, O'Rourke, and Hamner (l9h9) describes the latex's value in trans- planting. Vinyl latex 600 has been successfully used to coat many horticultural plants since this work was begun. Recommendations based on these studies involving its use on severed plant materials and other studies have been assembled by various distributors of the latex concentrate. The variously modified latex concentrates are now sold under such trade names as Plant Coat, Wilt Pruf and Plant Shine. The material has been recommended for use as a spray extender and for use in foliar fertilization (Bitty 1953). Sherwood and Raun (1950) found a five percent application effective in controlling red spider. Other applications recommended utilize the film strength. Sherwood and Beck (l9h8) found that although the tearing strength of cloth was markedly en— hanced, the unfortified V.L. 600 did not appreciably increase rot-retardant proterties. The cloth was not heat cured during coating as is done commer- cially'with paper. The important horticultural use of Vinyl latex 600 would seem to be as a protective coating where plants are likely to be exposed to adverse factors such as dehydration after cutting or transplanting, wind or sand burn, unusual drought conditions, and some insect and disease organisms. For example, the spraying of corn fields to prevent sand cutting during h2 emergence, treating red spider infested evergreens to control the spider and aid plant recovery, and usage in budding and grafting to reduce water loss and mold infections. Maxon (1951) used Vinyl latex 600 with various dyes to both protect and color cut flowers. Use with newer chemicals is being tested on cut flowers as reported by Giles (1953). This would seem promising where the chemicals, though prolonging life, do not adequately protect against dessication or mechanical damage. It is noteworthy that similar coatings in sheet form are again being adopted to commercial us- age in horticulture as shown by Sweet (1952) and Mahlstede (1953). The extensive use of the more intimate protective coatings, such as are available with Vinyl 600 latex, is imminent. Information regarding more convenient and safer techniques of application should be developed before extensive promotion is encouraged. :7. Orv.1-'t _ J-lfi‘ o_‘.‘:, 2:25 1.3 V o SUI'Ifi'lARY The effect of a plastic coating, Vinyl latex 600, on certain cut flowers and florists greens was investigated. An aqueous dilution of the latex in concentrations of ten and twenty percent as a foliar application was effective in retarding moisture loss. The keeping quality of the plant material was enhanced as a result of treatment with the vinyl latex. Phytotoxicity and respiration abnormalities were observed, when the vinyl latex, in excess of ten percent, was allowed to dry slowly on the plant tissue. An apparatus was designed for obtaining and measuring micro—quantities of oxygen in respiration determinations. VI. LITERATURE CITED Aronoff, Sam. Techniques of radiobiochemistry. Iowa State College Press. Ames. 1956. Austen, R. A. Treatise of fruit trees. 2nd ed. Hall-Robinson. Oxford. 1657. Baghadi, H. A. and R. M. Smock. The comparative value of certain plastic materials and waxes in checking moisture loss from apples. Proc. Amer. Soc. Hort. Sci. h2z238—246. l9h3. Bald, J. G. Stomatal droplets and the penetration of leaves by plant pathogens. Amer. Jour. Bot. 39:97-99. 1952. Barnes, C. R. The theory of respiration. Bot. Gaz. 39:81-98. 1905. Berg, W. E. A microanalyser for very small gas samples. Science 10h: 575-576. 19A6. Birch, R. A. The modern florist. Pearson Ltd. London. 1952. Bonner, J. and A. W. Galston. Principles of plant physiology. Freeman. San Francisco. 1952. Bovey, F. A., I. M. Kolthoff, A. I. Medalia, and E. J. Meehan. Emulsion and polymerization. High polymers Vol. IX. Interscience N.Y. 1955. Bowden, R. A. A study in maintaining the red color in roses. Thesis M.S. Michigan State University. l9h9. Brierly, W. G. and R. H. Landon. Experimental smothering of dormant strawberry plants. Proc. Amer. Soc. Hort. Sci. 40:361-366. 19A2. Chadwick, L. C. Data on the use of emulsified paraffins and vegetable oils. Nursery Notes 5:1—5. 1936. Childers, N. F.‘ Some effects of sprays on the growth and transpiration of tomatoes. Proc. Amer. Soc. Hort. Sci. 33:532-535. 1935. Cornell, Pardon. Personal communication. 1951. Crafts, A. S., H. B. Currier and C. R. Stocking. Water in the physiology of plants. Chronica Botanica. waltham. 19A9. Denny, F. E. Bases for calculations in measuring changes in leaves during the night. Contr. Boyce Thomp. Inst. 5:181-19h. 1933. L. 1.1-I a... .- 45 Denny, F. E. Effect upon plant respiration caused by changes in the 02 concentration at the range immediately below that of normal air. Contr. Boyce Thomp. Inst. 15:61-70. 19h8A. Denny, F. E. Semi-micro method for measuring the amount of O consumed and 002 produced in plant respiration. Contr. Boyce Thomp. Inst. 15:A7-50. 19483. Denny, F. E. Suggested methods for measuring the carbon dioxide production of a large number of simultaneous samples. Contr. Boyce Thomp. Inst. 15:141-151. 19A8C. a~ Delny, F. E. The role of the surface microflora in measurement of the respiration rate of germinating seeds. Contr. Boyce Thomp. Inst. Donnely, W. and W. A. Beck. The respiration of growing plant cells. Plant Physiol. 20:hh8-452. 1945. Dow Chemical Company, Midland, Michigan E. I. Dupont DeNemours & Co. Inc., Wilmington, Delaware. Felber, I. M. and V} R. Gardner. Effect of a hydrophyllic colloid of high viscosity on water loss from soils and plants. Mich. Agr. Exp. Sta. Tech. Bul. 189. l9hh. Fischer, C. W. Longterm holding of cut flowers. Proc. Amer. Soc. Hort. Sci. 61:585-592. 1953. Fischer, C. W. and J. R. Keller, Prevention of decay of horticultural products by the use of brominated activated charcoal. Proc. Amer. Soc. Hort. Sci. 57:432-438. 1951. Floralife, Inc. 1A33-39. S. wabash Ave., Chicago, Ill. 1956. Flower Foods, Inc. P. O. Box 106, Maywood, Ill. 1956. Gartner, J. B., F. L. O'Rourke and C. L. Hammer. The influence of a plastic resin in increasing survival with summer-transplanted ever- greens under severe conditions. Proc. Amer. Soc. Hort. Sci. 5h: 508-510. 19A9. Giles, J. M. The effect of maleic hydrazide on the keeping quality of cut roses. Greenhouse Gossip 12:6. June, 1953. Dept. Hort. O.A.C., Guelph, Ontario. ~ B. F. Goodrich Chemical Co., 2060 East Ninth St., Cleveland, Ohio. 1953. Goodyear Chemical Co., Akron, Ohio. A6 Haas, A. R. C. Respiration after death. Bot. Gaz. 67:3A2—366. 1919. Hamner, C. L. Personal communication. November, 1955. Hamner, C. L., R. F. Carlson, and F. G. Smith. Changes in food reserves and respiration capacity of bindweed tissue accompanying herbididal action of 2,A-D. Plant Phys. 22:58—65. 19h7. Hamner, C. L., J. B. Gartner and F3 L. O'Rourke. A non-toxic plastic coating to improve the keeping quality of cut foliage. Mich. Agr. EXp. Sta. Bul. 30:3. 191.8. :- Hamner, C. L. and Kiang Chi-Kien. Use of a plastic material to increase the action of the sodium salt of 2,4-D. Science 107:572—573. 19h8. Hamner, C. L., R. F. Carlson and H. B. Tukey. Improvement in keeping qual- ity of succulent plants and cut flowers by treatment under water in partial vacuum. Science 102(26h8):332-333.» 19h5- Harrington, G. T. and W. Cmcker. A new and efficimt respirometer for seeds and other small objects. Directions for its use. J. Agr. Res. 23:101-115. 1923. Hartridge, H. A survey of methods and apparatus for micro gas analysis. J. Sci. Instr. 16:317-32h. 1939. Heilbrunn, L. V. Dynamics of living protoplasm. Academic Press N. Y. 1956. Hitchcock, A. E. and P. W. Zimmerman. Effect of chemicals, temperature and humidity on the lasting qualities of cut flowers. Amer. Jour. Bot. l6:A33—h40. 1929. Hover, J. M. and F. G. Gustafson. Rate of absorption as related to age. J . Gal 0 Phys. 10:33-39 0 1926 0 Johnson, J. Water congestion in plants in relation to disease. Wisc. Agr. EXP. Sta. Bul. 160:1-35. 19h7. Kelley, J. and C. H. Sherwood. Effect of chemicals and waters on the keeping qualities of cut roses and snapdragons. Presented at A.S.H.S. Meeting Fall, 1955. Kelley, S. and G. S. Avery. The effect of 2,4-dichlor0phenoxyacetic acid and other physiologically active substances on respiration. Amer. Jour. Bot. 36:A21-A26. 19A9. Kidd, F., C. west and G. E. Briggs. A quantitative analysis of the growth of Helianthus annuus. Part I. The respiration of the plant and of its parts throughout the life cycle. Proc. Roy. Hort. Soc. B. 92: 368‘38h. 1921. A7 Klebs, G. Alterations in the development and forms of plants as a result of environment. Proc. Roy. Hort. Soc. 82B:5h7-558. 1909-1910. Kramer, Paul. Letter to B. F. Goodrich Chem. Co. Sept. 26, 1949. Laurie, Alex.and D. C. Kiplinger. Commercial flower forcing. Blakiston. Philadelphia. 19A8. Lee, Beatrice and J. H. Priestly. The plant cuticle I: Its structure, distribution and function. Ann. Bot. 38:525-5A5. 1924. Leeper, Robert. Personal communication. Nov. 1955. Longley, L. E. Some effects of storage of flowers in various gases at low temperatures on their keeping qualities. Proc. Amer. Soc. Hort. Sci. 30:607-609. 1933. Loomis, W. E. The relation of polymerization reactions to meristematic development. Proc. Amer. Soc. Hort. Sci. 35:860—863. 1937. Loomis, W. E. and C. A. Shull. Methods in plant physiology. MCGraw-Hill. 1937. Lunge, George and H. R. Ambler. Technical gas analysis. Gunney and Jack- son, London. 193A. revision. Mack. W. B. The relation of temperature and partial pressure of oxygen to respiration and growth in germinating wheat. Plant Physiol. 5: 1-69 0 1930 o iaxon, Marcus. Personal communication. 1951. Mahlstede, John and L. K. Kirk. Ia. Nurserymen's research program 1953. Presented at annual Ia. Nurserymen's conv. 1953. Maskell, E. J. Experimental researches on vegetable assimilation and respiration XVII. The diurnal rhythm of assilation in leaves of cherry laurel as "limiting" concentrations of carbon dioxide. Proc. Roy. Hort. Soc. B,lOZ:A67-488. 1928. Miller, E. J., A. L. Neal and V. R. Gardner. Emulsions for horticultural sprays. Mich. Agr. Expt. Sta. Quart. Bul. 27:338-351. 19A5. Miller, E. J., J. A. Neilson and L. S. Bandemer. wax emulsion for spraying nursery stock and other plant materials. Mich. Agr. Exp. Sta. Spec. B111. 282. 1937. Mitchell, E. J., R. H. Burris and A. J. Riker. Inhibition of respiration in plant tissues by callus stimulating substances and related com, pounds. Amer. Jour. Bot. 36:368-378. l9h9. A8 Mueller, L. E., P. H. Carr and W. E. Loomis. The submicroscopic structure of plant surfaces. Amer. Jour. Bot. 41:593-600. 1954. Neal, A. L. and Gardner, V. R. Influence of oil wax emulsion sprays on cherries. Jour. Agr. Res. 77:261-270. 1948. Neff, Marshall. Problems in the storage of cut carnations. Plant Physiol. 14:271-284. 1939. Orgell, Wallace H. The isolation of plant cuticle with pectic enzymes. Plant Physiol. 30:78-80. 1955. Plagge, H. H. Progress made in gas storage of fruits, vegetables. Food Industry. 12:46-48, 106. Oct. 1940. Plagge, H. H. md D. V. Fischer. Pectic changes in Jonathan apples as a measure of ripening under differential carbon dioxide treatments. Proc. Amer. Soc. Hort. Sci. 40:169-171. 1942. Plagge, H. H. and Fisk Gerhardt. Acidity changes associated with the keep- ing qualities of apples under various storage conditions. Ia. Agr. m. 81:30 Res. Ell-1.. 131, 1930. Plagge, H. H. and T. J. Maney. Some responses of apples in storage to pliofilm liners and wrappers. Ice and Refrigeration. 101:201-205. 1941. Plagge, H. H., T. J. Maney and B. S. Pickett. Functional diseases of the apple in storage. Ia. Agr. Exp. Sta. Bul. 329. 1925. Post, Kenneth. Florist Crop production and marketing, Orange Judd. N.Y. 1952. Priestly, J. H. The cuticle in angiosperms. Bot. Rev. 9:593-616. 1943. Prill, E. A., Lela V. Barton and Marie L. Solt. Effects of some surface- active agents on the growth of wheat roots in solutions. Contr. Boyce Thomp. Inst. 15:311-318. 19A9. Ritty, P. M. The uses of a water dispersible plastic as an aid in park maintenance. Paper given at Florida Park and Rec. Training Inst., Sebring, Florida, April 16, 1953. Roberts, E. A., M. D. Southwick and D. H. Palmiter. A microchemical examr ination of Molntosh apple leaves showing relationship of cell wall constituents to penetration of spray solutions. Plant Physiol. 23: 557-5590 19658. Robertson, R. N., T. S. Turner and M. J. Wilkins. Studies in the metabolism of plant cells. V. salt respiration and accumulation in red beet tissue. Australian Jour. of Expt. Biol. and Med. Sci. 25:1—8. 1947. A9 Schafer, J. Effect of light on CO2 in leaves. Plant Physiol. 13:141— 1560 1938. Schieferstein, R. H. Formation of wax deposits on leaves. M.S. Thesis. Iowa State College. 1955. Sherwood, C. H. A method for the rapfid determination of carbon dioxide in small samples of gases. Presented at A.S.H.S. Meetings. 1946. Sherwood, C. H. Packaged environment as affecting the life of cut flowers. Part 1. Sample significance. Presented A.S.H.S. Meeting Fall, 1955. Sherwood, C. H. The effect of aeration and water relationships on the growth of potted plants. M.S. Thesis, Ohio State University. 1940. Sherwood, C. H. and G. Beck. Unpublished studies on rot retardants. 1948. Sherwood, C. H. and C. L. Hamner. Lengthening the life of cut flowers and floral greens by the use of plastic coatings. Mich. Quart. Bul. Sherwood, C. H. and E. S. Raun. Unpublished studies on pesticide value of Vinyl 600 Latex concentrations. 1950. Sherwood, Thomas K. Absorption and extraction. McGraw-Hill, N.Y. 1937. Siefriz, W. (Ed.). Symposium on the structure of protoplasm. Ia. State Col. Press. Ames. 1942. Skoss, Jesse D. Structure ami composition of plant cuticle in relation to permeability. Bot. Gaz. 117:55-72. 1955. Staniforth, D. W. and W. E. Loomis. Surface action in 2,4—Dichlor0phenoxy- acetic acid (type) sprays. Science 100:628-629. 1949. Stiles, w. Respiration. Bot. Rev. 1:249-268. 1935. Stiles, W. 3x1 W. Leach. Respiration in plants. Third ed. John Wiley and Sons. 1952. Sweet, D. V. Use of polyethylene film.in the propagation and culture of certain horticultural plants, Mich. Agr. Expt. Sta. Quart. Bul. 35: Thornton, N. 0. Life of cut flowers. Am. Jour. Bot. 17:623. 1930. Thornton, N. C. Carbon dioxide storage. IV. The influence of carbon di- oxide on the acidity of plant tissue. Contr. Boyce Thomp. Inst. 5: 50 Tinker, A. H. Care of cut flowers. Jour. Roy. Hort. 500. 67:373-380 & 392”3950 19420 Volz, E. C. Studies on keeping qualities of cut flowers. M.S. Thesis. Cornell Univ. Ithaca, N.Y. 1918. - White, P. R. The cultivation of animal and plant cells, Ronald Press. 1954. Whitehead, T. The physiology of potato leaf-roll. 1. On the respiration of healthy and leaf-roll infected potatoes. Ann. App. Biol. 31:48— 77- 193A. Whiteman, T. M. and H. A. S. Schomer. Respiration and internal gas con- tent of injured sweet potato roots. Plant Physiol. 20:171-182. 19A5. Wildon, C. E. Dahlias. Mich. Agr. Exp. Sta. Spec. Bul. 266. 1935. wylie, R. B. Acatrization of foliage leaves. 1. Wbund responses of cer- tain meSOphytic leaves. Bot. Gaz. 90:260-278. 1930. wynd, F. L. Respiration of mosaic-infected tobacco plants. Plant Physiol. Wynd, F. L. The technique of the application of micro-manometric methods to problems of biology. Lloydia 15:1-33. 1952. 15”7u¢ber tube Y .IflflCSVTWfiE! ,/” 5t0PC “W / 5% ”a. 10““ zmviv wl7v fl7Jv‘fl730.a210 o H <— wwwwwwwwwwwwwwwwwwwww \ babbl - snake e cap/liar} Mk 1 ml. pipette mercury g 2 imanywwy ‘ Fig. 1. Qu/c/r C 0; evaluation eywpment Pctd/ or /ca.f 2.0' .h."~- *I ..~ A_I. ‘ - ‘ I , N N \.\\\ \\\\\\\\\\\\ q '_ l'li c \ N N N N N N N N N N N N N N N N N N \ N N N \ N Paper Walker @3122 cc My (0;: for“; +1.62»: Ina/c \ J‘lle// vx2z/ 2 2 x6? .5' C177. ‘ \ Pepe, a’llrc \ forow‘ 5 \ .5726” V/d/ E 1.3x 56/72. § Rubber bar/0’ \\\\\\\\‘\\\‘ fig. 2. C 02 _&ccumu/a tor for text/”y .. eff/bee y of :arkce coa My! -————- .. Date Due 3 9 2 . O C m e D