- ‘ ‘ . ’ HORNCULTURAL ASPECTS CONCERNED WITH THE PRODUCTION Q5 PKCKLENG CUCUMBERS FOB. ONCE‘OVER HARVEST Thais. fiat the beam of M. S. MiCHIGAN STATE UNWERSETY Alan R‘ Putnam 1963 a 13:: um; W ”I mun 1m 11 film 11:11» "E m 1111 I11 u m 93 LIBRARY Michigan State University OVERDUE FINES ARE 25¢ PER DAY PER ITEM Return to book drop to remove this checkout from your record. HORIICULTURAL ASPECTS CONCERNED WITH THE PRODUCTION OF PICKLING CUCUMBERS FOR.ONCE-OVER HARVEST AN ABSTRACT Submitted to Michigan State University in partied fulfillment of the requirements for the Degree of EASTER OF SCIENCE Department of Horticulture 1963 ABSTRACT HDRTICULTURAL ASPECTS CCNCERNED WITH THE PRODUCTION OF PICKLING CUCUHBERS FOR.ONCE-OVER HARVEST By Alan R. Putnan The survival of the pickling cucumber industry in Michigan may depend an the development of a successful mechanical harvesting system. I Research conducted from 1957 to 1960 indicated that mechanical har- vesters based on a multiple harvest approach more not successful. This study explored the possibilities of growing and harvesting cu- cumbers in a once-over’manner similar to the present systems used for peas and beans. The flowering and fruiting characteristics of a monoecious and a gynaecious variety were observed for 2 growing seasons. These varieties produced large indeterminant vines and developed only l-h marketable fruit at one time. ~Tvo successive crops of cucumbers were grown and harvested on the same land in 1961 and 1962. Spring plantings yielded much higher than plantings made after June 20 because of unfavorable environmental condi- tions in late summer. Several plant population and spacing experiments were conducted during both growing seasons. ‘High plant populations of up to h5,560 plants per acre resulted in higher once-over harvest yields. Plants spaced 1 foot apart in the row yielded higher than those spaced 6 inches apart reguardless of the plant pOpulation. Inhibition of further fruit development exerted by the fruit pre- viously set was a major factor limiting concentrated cucumber fruit production. Growth.measurements indicated that normally developing fruit increase in size rapidly from.the third to the seventh day after pollina- // tion. Inhibited fruit develop similarly until the third day after polli- nation, when the inhibition.is manifested. No further‘increase in size results until the previously set fruit are removed. Another phase of this study involved the evaluation of growth reg- ulator sprays as a means of increasing the nuaber of fruit per plant. Several types of growth regulator sprays uere applied to plants at var- ious stages of growth, both in the field and greenhouse. It was conclud- ed that these chemicals were not consistently effective in increasing once-over harvest yields of pickling cucumbers. HJRTICULTURAL ASPECTS CONCEMED WITH THE PRODUCTION OF PICKLING CUCUUBEPS FOR ONCE-OVER HARVEST By Alan R. Putnam A THESIS Submitted to Michigan State University in partial fulfullment of the requirements for the Degree of MASTER 0? SC IENCE Department of Horticulture 1963 - (74' _..~- 1 “ AC KN OWLEDGMEN TS The author wishes to express his sincere appreciation to Dr. S. K. Ries for his guidance, assistance, and encouragement in the planning and analysis of this study. Thanks are also due the mem- bers of the guidance committee: Dr. S. H. Wittwer. Dr. c. E. peterson. Dr. H. C. Beeskow, and Dr. B. A. Stout. Appreciation is also expressed to M. E..Austin for help with the field studies and for supplying temperature data. The author is also deeply indebted to his wife for encouragement and for as- sistance in preparing the manuscript. The financial assistance of the National Pickle Packers Assoc- iation is also gratefully acknowledged. TABLE OF CONTENTS ACKNOWLEDGMENTS.................................................. LIST OF TABLES................................................... LIST OF FIGURES.................................................. INTRODUCTION..................................................... REVIEW OF THE LITERATURE......................................... Taxonomy and morphology........................................ Flowering behavior............................................. Factors affecting sex expression............................... Factors affecting fruit development............................ The evolution of cucumber harvesters........................... STATEMENT OF THE PROBLEM......................................... MATERIALS AND METHODS............................................ SHOCOSSIYO planting studiel.................................... Plant pOPUICtiOD BtUdiO‘eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee Inhibition and pollination BtUdi‘Ueeeeeeeeeeeeeeeeeeeeeeeeeeeee O EV‘IU‘tiOn Of grOWth regulators................................ ESULTS AND DISC‘JSSIONOOCO00.0.0000...OOOOOOOOOOOOOOOOOOOO00.0.00 SUCCGSSi'. planting StadiOSQeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee 0 Plant pepulation 'tUdiOSeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee Inhibition and pollination BtUdiO’eeeeeeeeeeeeeeeeeeeeeeeeeeeee Evaluation or growth regulators................................ SUWHYOCICOOO00.000.000.000...OOOOOOOOOOOOOCOOOOCOOOOOOOOOOOOOO. LITERATUE CITEDOOOOOOOOOOOOOOOOOOOOOCOOOOOOOOOO0.00.0000...000.. 1 iii he \fl £? \N \N 10 /" LB 52 fifPEIDIXOOOOOOOOOOIOOO000.00.00.00...OCOOOOOOOOOOOO00.000.000.00. 57 ii LIST OF TABLES 1. The position on the vine and percent of fruit occurring at each node of 2 varieties..........................................29 2. Dollar yield per acre and number of days from planting to optimum harvest for 5 successive plantings (1961).................30 5. Dollar yield per acre and fruit per plant produced by 2 varieties grown at 2 different spacings..............................31 h. A typical harvesting sequence showing changes in bushels, dollars. and grades..................................................3l 5. Dollar yield per acre and number of days from.planting to optimum harvest for 7 successive plantings (1962).................52 6. .A comparison of the first and second harvests of Spartan Dawn and'Wisconsin SHE-18....................................3h 7. Dollar yield per acre and fruit per plant produced by 2 varieties grown at 2 different spacings............................5h 8. The effect of plant spacings on yield of Spartan Dawn and Wisconsin.SMR-lS....................................36 9. Dollar yields for different plantings and spacings of Spartan Dawn and Wisconsin SMR-lS.................................36 10. The effect of several spacings on yield of Spartan Dawn and Wisconsin SMR-lB....................................37 11. The inhibitory effect of developing fruit on subsequent fruit development................. .......................39 12. The effect of various pollination treatments on abortion 0f cumlmber Ovar1°8eeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee39 iii iv 13. The effects of growth regulator sprays on flowering and yields of‘Wisconsin SMR-lB cucumbers.............................h5 1h. The effects of growth regulator sprays on flowering and yields of'Wieoonein SfiR-la cucunbers.............................b6 15. The effect of growth regulator Sprays on flowering and fruiting of 2 varieties..........................................h7 16. Daily temperature data recorded frcnbthe Michigan State University Horticulture Farn..........................57 LIST OF FIGURES l. 1961 spacing trial for once-over harvest showing the plot design and the spacings used................................22 2. Flowering sequence and position of marketable fruit on a typical plant of the variety Spartan Dawn.......................28 3. Flowering sequence and position of marketable fruit on a typical plant of the variety Wisconsin SMR-lB...................28 14. A comparison of pistillate flowers at full bloom with inhibited fruit after 7 days and non-pollinated ovaries after 7 days...........h0 5. The growth of cucumber fruit after pollination..................Jll 6. A plant of the variety Spartan Dawn treated with 000 at 2000 ppm......................................................1J4 7. A plant of the variety Wisconsin Sim-18 treated with CCC ‘t 500 pm0000000OOOOOOOOOCOOCOOO0.0.0000...00.0.00.0000000000000M INTRODUCTION Michigan is the leading state in production of pickling cucumbers. In 1962, approxiamately 22,500 acres with a farm value of nearly 6 mil- lion dollars were harvested. This compares with a 10 year average (19 -1960) of 3L,920 acres with a farm.va1ue of about 5 million dol- lars.‘ Harvested acreage for the entire United States in 1962 was about 102,099_acres with.a farm value of 21.7 million dollars (2). At the present time, pickling cucumbers are harvested by hand. In Michigan the majority of the harvesting is done by migrant laborers, 65% of whom.are lexican.Nationa1s (58). In the past, laborers have been paid on a cr0p share basis, but in 1962 a new government regulation was established setting a 81 per hour minimum.wage for'Mexican Nationals. This action resulted in labor costs to farmers as high as 79% of the value of the crop, compared to a cost of about 50% of the value under the previous system.(57). The unfavorable economics of harvesting, a- long with an uncertain supply of labor and problems of recruiting, transporting, and housing, has resulted in a search for mechanical means of harvesting cucumbers. All successful mechanical harvesters used for horticultural crcps operate on a once-over or destructive harvest basis. The cucumber, un- like many other crepe, does not develOp a large number of marketable fruit at one time. In a once-over harvest operation, concentrated fruit 2 set is necessary to produce profitable yields. In the past 10 years, several investigators have carried on re- search with mechanical cucumber harvesters and harvesting aids using a multiple-harvest approach, A research pregram to study mechanical har- vesters was initiated at Michigan State University in 1957. Stout and Rise, and Bingley (5, 56) evaluated several machines and built an ex- perimental harvester using several promising components. In 1961, after Several years of disappointing performances, these researchers decided to evaluate the possibilities of a once-over harvest system for cucum- bars. This study e1plored the problems concerned with the once-over har- vest system. REVIEW'OF LITERATURE TAXONOMY All D MORPHOLOGY The cucumber, gucumis sativus L. is a member of the family Cucur- bitaceae which contains about 90 genera and 700 species. Members of this family are frost susceptible herbs with a trOpical or sub-trepical origin. The genus Cucumis contains about 30 species of trailing or climbing annuals and perennials which are generally menoecious (3). Spec- ies of the genus Cucumis that are grown commercially as annuals are: E: sativus 11., the cucumber; 2. 39312 1.1., the muskmelon; and E. anguria 11., the gherkin. Cucumis sativus E, is characterised by an extensive prostrate vine with several lateral branches. The root system is also extensive and ‘consiets of a long tap root which.may extend several feet into the soil with widely spread branch roots. The leaves are usually three-lobed, the middle lobe being large and pointed. Tendrils, which are defined as ”an outgrowth of the bud axis", may occur at each node. The flowers are borne in the axil of each leaf, the stamdnate flowers often occur- ring in clusters and the pistillate flowers usually appearing singularly. Hermaphroditic flowers may occur in some cultivars. \The fruits are tri- loculate pepoes, quite varible in shape with.numercus spines or hairs (3. 19)- Cucumber varieties for pickling purposes have been selected for several characteristics. Among these are: High yielding plants, disease h resistant plants, firm fruit, black spined fruit, and fruit with desir- able shape and color for processing. FLOWERING BEHiVIOR 0F CUCUMI§_SATIVUS 1? Most of the cultivars of Cucumds sativus L. are menoecious. Shifriss (50) has summarized the various types of sex expression as follows: moncecious- plants bearing both staminate and pistillate flowers on the same individual. gynoecious- individuals bearing exclusively pissillate flowers. heraphroditic- individuals bearing exclusively perfect flowers. andromenoecious- individuals bearing staminate and perfect flowers on the same individual. An androecious or all-staminate category was included by C. and H. Yampolsky (71) but Shifriss denied the existence of a true genetically male cucumber plant. Cultivars grown commercially are of the moncecious or gynaecious type. Many investigators have studied the flowering behavior of monoecious cucumbers. Heimlich (26) reported that the first staminate inflorescence is likely to occur in the first or second leaf axil, and may continue to develop in many leaf axils throughout the life of the plant. Several primerdia may be laid down in each leaf axil so that the flowers are 'borne in clusters. Judson (5h), in a morphological study of pistillate :flcwer formation, observed that the first primordia occurred several nodes from the cotyledonary node. Emerson (18) noted a sequence of phases in monoecious plants which became increasingly pistillate. Currence (1}) later observed that as the distance from the base of the stem increased, the percentage of female flowers increased. He stated that the cucumber, during development, changed from.a strongly staminate condition to a strongly pistillate condition. He also noted that the laterals were more pistillate than the main axis. Ritchigtf Elf (hS) reported essentially the same phe- nomenon in Cucurbita P°p°.£f' However, the first flowers formed were underdeveloped staminate, followed by several pregressive stages ending in the formation of pistillate flowers which develop parthenocarpically. These observations indicate that the typical monoecious plant goes through 3 phases; a staminate phase, a monoecious phase, and a pistil- late phase. Edmund (17) discussed the possible effect of staminate-pistillate ratios on yield. He concluded that excessive production of either flower type could result in losses to growers. FACTORS AFFECTING SEX ELPRESSION Tiedjens (61) and Emerson (15) both concluded frOm.their observa- tions that sex expression is a result of genetics and environment. In 1961,‘Wittwer and Bukovac (8) stated ”flower sex expression in the cu- cumber is subject to genetic, environmental, and chemical control." Genetiggfactors Extensive studies have been and are being conducted concerning the genetics of sex expression in Cucumis sativus L.. It is generally a- greed that several hereditary iactors are involved, however, there is still much to be learned. Evidence has been presented which indicates that two major genes and a complex of polygenes are present (21). Shifriss (52) stated at least 3 groups of factors are involved. ”A few qualitative genes determine the type of flowers which can be differen- tiated; polygenee govern the formation of a substrate which channels the expression of the genes for different kinds of flowers; an accelerator gene speeds up the rate of physiological processes controlled by the polygenes.” Nonpgenetic factors may also affect the substrate which channels the action of the genes. Gynaecicus plants have been discovered in several Japanese and Korean races of cucumbers (37).~ Tkachenko (62) reported that "female- ness" and 'maleness” are controlled by a pair of genes, and that ”fe- maleness” is dominant. In 1960, Peterson (uh) described a technique for breeding F1 hybrid gynoecious cucumbers. A homozygous gynaecious line (MSU 713-5) was produced by crossing a gynoecious segrate found in the Korean race Shcgcin and the pickling variety‘Wisccnsin SMR-lB, describ- ed hy‘Walker (63). Gynoecious varieties have shown promise for increas- ed yields and earlier and more concentrated fruit set. Environmental factors In 186b, Beyer (28) noted that the staminate to pistillate ratio oculd be altered by environmental factors. Many'investigators have stud- ied the effects of temperature and photcpericd using both.variables in the same experiment. Edmund (l6) grew several varieties in 3 different seasons and con- cluded that the number of pistillate flowers increased with a decreasing length of day. During the short days of winter, pistillate flowers often occurred in clusters at each node. Nitsch at} :1, (h5) reported that high temperatures and long days tend to keep the vines in a staminate phase, whereas low temperatures and short days speed up the pistillate phase. They were able to induce parthenocarpic pistillate flowers in 7 some varieties by exposure to short days and cool nights, and indicated that perhaps the night temperature was the more important. Shifriss and Galun (55) using several continuous plantings found a continuous increase in the number of staminate nodes preceding pistillate nodes from May to August. May plantings had 7 staminate nodes preceding pistillate nodes and August plantings had 16. Researchers in India also confirmed these results (11). Japanese workers obtained similar responses by altering temperatures and photoperiod and indicated that the period from 10-50 days following germination was the most critical in determining sex ex- ression (32). It was concluded that environmental factors change phys- iological conditions of the plant before flower differentiation. Under a given set of environmental conditions , the number of nodes from the cotyledonary leaves to the first pistillate flower was found to be quite constant within a variety (53). Nitrogen levels have been found to alter sex expression in the eu- cubits. Dearborn (15) reported that plants with a high nitrogen supply produced more pistillate and fewer staminate flowers than those with low nitrogen. Hall (25) confirmed these results using Cucumis snguris I? and obtained the response regardless of photOperiod. Miller (38) re- ported that both pistillate and staminate flower production was increas- ed but the staminate tc pistillate ratio was decreased when high nitrogen levels were maintained. Chemical factors In recent years much work has been accomplished on altering the flowering of cucurbits with growth regulating chemicals. The chemicals studied have been of two types, those which favor the develcpment of pistillate flowers and those which favor the develcpment of staminate flowers. Several researchers have reported the effects of indole-B- acetic acid and related compounds on flowering of cucumbers under green- house ccnditions (ll,3l,33,b6). Papers were published in the early 1950's stating that Indoleacetic acid (an) and Napthaleneacetic acid (MA) applied to the foliage as a spray or in lanolin paste would favor the formation of pistillate flowers (31). Researchers in India were able to obtain the same response by spraying 1AA and‘NAA in the field (ll,h6). lflttwer and Hillyer (29) found that foliar sprays of 2,3,SdrIBA at 25ppm increased the number of pistillate flowers and decreased the number of staminate flowers. Yield increases of up to 30% were later reported when .0025% 2,3.5‘TIBA was sprayed on greenhouse cucumbers (b7). In 1957, HelepAHarrison (27) concluded that sex expression is regulated by the level of growth substances present during flower development, and that the higher level favors pistillate flower formation. Galun (20) conducted extraction studies and could not find this difference in auxin levels, however, a higher concentration of growth inhibitor was extract- ed fromtthe old leaves of strongly male plants. Other chemicals have been shown to speed up the pistillate phase. In experiments with Cucurbita pepo .Ii' variety Acorn, mleic hydraside applied as a foliar spray completely suppressed staminate flower forma- tion (66). In 1960, the quarternary ammonium compounds, 2-chlcroethylo trimethyl ammonium.chlcride and others were shown to exhibit several effects on plants (68). Mitchell (bl) studied the effects of several quartenary ammonium compounds on flowering. Many of the chemicals, when applied to aerated solution cultures, exhibited the ability to in- duce the pistillate condition more rapidly; Allytrimethylammonium bromide at 5 x 10-“! proved most effective in increasing pistillate 9 flower fcnmation on several varieties of Cucumis sativus E., but also resulted in a marked suppression of vegetative growth. Gslun (20) was able to neutralize the effects of“RAA by using it in combination with Gibberellin.i3. During the past 15 years, several papers have been published concerning the effects of Gibberellins on Cucurbits. ‘Nittwer and Bukovac (67) reported that Gibberellin increased the number of staminate flowers preceding the first pistillate flower in two monoecious varieties of cucumbers. Gibberellin.A3 at 10'} molar applied to the root media was found to cause reversion from.pistillate to staminate up to the tenth nodes in gyncecious cucumbers (bl). In a breeding program.involving the selfing of gyncecious plants, staminate flowers were induced by Gibberellin.i at lSOOppm.applied as a foliar 3 spray (hb,h5). Two or 3 weekly applications were made beginning when the plants were in the second true-leaf stage. In 1962, the order of activity of the most active Gibberellins on staminate flower induction on gyncecious cucumbers was reported as A77Ah-A27 A9 (69) . Other factors affecting flpwering Tiedjens (61) in 1926 observed that the presence of develo;ing fruit exerted an inhibitory effect on further vegetative development and pro- duction of pistillate flowers. An increase in pistillate flower forma- tion has been obtained by defloration and by preventing pollination of 'flcwers (36). It was later reported from experience with several plant species, that flower buds often abscise before anthesis on plants which have produced fruit heavily (h2). The number of flowers produced was greatly enhanced by disbudding, deflcration, and defruiting, the greater effect being derived by disbudding. Galun (22), in a defoliation experiment, observed that the removal 10 of young leaves diminished the female tendency, and the removal of ma- ture leaves diminished the staminate tendency. He reasoned that this response was obtained because young leaves are active in producing growth substances, whereas mature leaves are acting in destroying them or count- eracting their effect. FACTORS AFFECTING FRUIT DEVEIDPlENT Environmental factors Temperature is a critical factor determining fruit set as it has been shown to affect anthesis, anther dehisoence, nectar secretion, and pollen germination (50,51). Temperatures of about 60°F. are required for anthesis to occur. If the day before anthesis would normally occur is below 60°F., the maturity of the blossom is delayed and a higher tem- perature following is necessary for both snthesis and dehisoenoe (51). Dehiscence and nectar secretion have been reported to start at about 62°- 63°F. and to reach an Optimun at temperatures between 65° and 70°?“ Germination of pollen will not occur at temperatures below 70°F. and the optimum has been reported as so°-ss°r. (50). Miller (38) reported that night temperatures of 60°F. produced fruits with a higher length to di- ameter ratio than those grown at a night temperature of 70°F.. It is generally agreed that high temperatures are favorable for rapid growth, which results in higher quality fruits. Pollinaticn is necessary for fruit set and develoPment of high quality fruit, except in a few unique varieties which naturally set fruit parthenccarpically. It has been reported that when flowers were not pollinated, 91$ aborted and that poor pollination results in many ”crooks" and "nubbin" fruit (50). Since pollen of cucumbers is rather sticky, natural pollination must be accomplished by insects (h). The 11 most important insect responsible for pollination is the honey bee (Apis mellifera £3) which collects nectar from pistillate flowers. A higher percentage of fruit set has been obtained with the use of bees than has been obtained with hand pollination. Chemical factors Several investigatiors have attempted to set cucumber fruit par- thenocarpically with growth regulators. ang (70) reported that napthaleneacetio acid at 1% applied to the cut style cap or as a .01% aqueous solution applied to the stigma was effective in setting fruit parthanocarpically, Gustafson (23) tried several chemicals and failed to obtain fruit set in cucumbers with all except NA}. However, only 3% of the‘NAA treated buds were set. Some other Cucurbits responded more favorably (9,12,23). Researchers in India applied two foliar sprays of gibberellin at lOppm.during the 1-2 leaf stage and during the 3-b.leaf stage. The first pistillate flowers formed had giant ovaries and de- veloped parthenocarpically at a more rapid rate than normally fertilized fruits on the control plants (11). In general, inducements of par- thenocarpy in Cucumis sativus E. by chemicals has not been successful, although success has been reported with other many-seeded fruits (23). Other factors Several other factors, because of their effect on growth and de- velopment of the cucumber plant have an indirect bearing on fruit pro- duction. Kotowski (35) conducted extensive experiments on seed ger- mination and observed that cucumber seed seldom germinates at soil tem- peratures below 52°F.. The optimum.was found to be 75°~85°F.. Seaton and Kroner (50) planted cucumbers in two different soil temperature en- vironments with the air temperature identical. After 30 days, plants in 12 soil at 60°F. were only 5 inches high whereas plants in soil at 85°F. were 30 inches high. Optimum temperature for plant growth has been reported as 65°-75°F. (h). High temperatures and high humidity are favorable conditions for the development of many foliage diseases. Since these conditions persist in the south, the more susceptible black-spined pickling cucumbers can- not be grown successfully there. Sunlight has been shown to be a limiting factor in the growth of greenhouse cucumbers during the winter months (60). When light intensity is low (100-1500 foot candles), the rate of photosynthesis is almost directly proportional to light intensity providing no other factors are limiting (5L). 4A plant may remain alive for long periods of time if enough photosynthesis occurs to balance the 2b hour respiratory loss, but no growth.will occur (7). lest plants which thrive in the sun re- quire a minimum.of h00~500 foot candles for maintenance and grow in- creasingly better at intensities up to 2500 foot candles. Higher in- tensities have no increased benefit. Improved plant growth has been reported from additional carbon dioxide added to the atmosphere. Bolas (6) reported increases in the growth of cucumbers in small enclosures by addition of carbon dioxide. Increases in fresh and dry weights and number of fruits developed were obtained by Hopen (29) when the atmospheric carbon dioxide level was increased. . Adequate soil moisture is necessary for maximum growth and yields. Excessive moisture at time of germination may expedite damping off (50). The rate of water absorption by roots in soils at 60°F. is about one- fifth that by roots in soils at 85°F. when the air temperature are equal. 15 Tiedjens (60) reported that although there is adequate water in the soil, cucunber plants may wilt because of imprOper soil structure or poor soil- root relationship. During dry periods, water may become a limiting fac- tor in growth, therefore irrigation may be beneficial. Miller 33. gl. (39) reported that pickling cucumbers are quite re- sponsive to small application of fertilizer but may be easily injured by it.. lbny researchers have studied fertiliser requirements for different soil types under several environmental conditions. Specific needs vary considerably from soil to soil. Rice and Carolus (£9) were able to obtain yields of over LOO bushels per acre on above average fields when 20 pounds of nitrogen, 160 pounds of phosphate and 80 pounds of potash were added. ‘Side dressings of nitrogen have proven effective on low fertility soils (1,65). Most researchers agree that well drained sandy loamrsoils of 5.5-6.5 are best for pickling cucumber production (A). Generally it is agreed that nitrogen is most often the important limiting nutrient factor in the growth of cucumbers. Dearborn (15) re- ported that plants receiving low'nitrOgen grew more slowly and produced fewer and smaller fruits than those getting liberal nitrOgen applications. It has also been reported that conditions which prevent plants from.ab- sorbing nitYOgen from the soil result in the production of poorly shaped fruits (60). The effect of nitrogen on flowering has been.discussed. Several researchers have reported the apparent inhibition of growth of cucumber plants by the developing fruit. Tiedjens (61) noted that varieties differ in their capacity to develop a number of fruits at one time. He theorized that simultaneously fertilised flowers developed equally well, but that less advanced ones were arrested in their develop- nwnt. The inhibition phenomenon was also reported in Citrullis (l2) and 1h in Cucumis EEEEHE? (9) to the extent that after the "crown set" the next series of flowers to appear absissed until finally another cycle of fruit setting occurred. Fertilisation (gametic union) has been shown to exert a stimulatory effect on vegetative growth for a short period of time. Inhibition con- tinues until the seed coats of the developing seeds begin to mature (6b). Host researchers believe that the developing fertilized ovaries produce a growth regulating substance which has a dominating influence on growth and further development of the plant (15,36,6h). Several experiments using varying plant population have been con- ducted. Mississippi workers have found that higher yields were obtained when plants were spaced 7.5 or 15 inches apart compared to 30 or h5 inch- es (1). It was also noted that more fertiliser was required to supply the larger number of plants. Rios (hB) obtained increased early yields with close spacings in a h.year study. It is generally agreed that crop plants should be distributed in such a manner so that the maximum area per plant leaf is exposed to sunlight, and that roots do not compete for moisture and nutrients (5h). Many other factors may affect the growth and subsequent fruit de- velopment of pickling cucumbers. Among these are insect and disease damage, damage from.the wind, lightning and hail, and weed competition. High yields are dependent upon vigorous growth throughout the season. THE EVOLUTION OF CUCUMBER HARVESTERS California researchers (2h) reported in 1956 that a harvesting aid which was constructed by a grower was effective in reducing harvesting time by one-half over regular hand picking. The device consisted of a motor driven vehicle with platforms extended on either side. The pickers 15 lay prone on the platforms and harvested onto a conveyor as the vehicle moved slowly through the field. Harvesting aids have been used with only varying degrees of success and still involve a large labor force. Stout and Ries (56) initiated a study of multiple-pick cucumber har- vesters in 1957. At that time, several patents for harvesters had been issued and several machines had been developed. Extensive tests were conducted using the existing machines and an experimental harvester built at Michigan State University (5). The performance of all machines tested was not consistent enough to label any one unit successful. Problems en- countered with multiple-pick harvesters as listed by Stout 323 Elf (57) are as follows: a. Accumulative damage to plants with resultant decrease in yields. b. Inadequate mechanical components for removing fruit set near the base of the plant. 0. Inability to remove and retrieve all the marketable fruit from certain commerical varieties. d. Lower yields because of wide row spacing required by machine. e. Pulling of plants from the soil when vine growth is luxuriant or anchorage poor. f. Small acreage capacity for a machine because of the necessity of repeatedly harvesting the same plants. In 1961, studies began on the develoPment of a once-over harvester. Delong (16) tested several mechanisms for removal of fruit from the vine. A component consisting of two flat rubber belts arranged on parallel rol- lers was successful in removing a high percentage of fruit. Feasibility studies based on production costs of $50 per acre and predicted costs of 3 different types of once-over harvesters show that it 16 will be necessary to harvest at least 100 acres of cucumbers per season with a machine costing no more than 86,000 (57). Once-over yields of at least 70-80 bushels of high grade fruit will be necessary to make once- over harvesting feasible. STATBENT OF THE PROBLEM Since all successful harvesters for horticultural craps operate on a once-over harvest basis, and since a multiple harvest approach has not proven feasible, a study of once-over harvesting of cucumbers was initi- ated e The objectives of this research were to study the basic horticul- tural problems encountered in once-over harvesting, to evaluate methods of increasing yields, and to determine the feasibility of this system with the present varieties. The following factors were studied: b. 0e d. The flowering and fruiting characteristics of a monoecious and a gyncecious variety. Successive plantings throughout the growing season and the possibility of 2 crops in the same year. Plant populations and spacings as they affect yields. Fruit inhibition as a major factor limiting yields. An evaluation of growth regulators as a means of increasing fruit set and yield. 17 KATERIALS AND METHODS During the 1961 season, the experimental plots were located at the Michigan State University Horticulture Farm on a'Wauseon fine sandy loam soil. In 1962, the plots were located at the Michigan State University Forestry‘fiursery on a Hillsdale sandy loam soil. Prior to planting, 500 pounds per acre of 12-12-12 analysis fer- tilizer was broadcast and disked into the soil. On plots where success- ive plantings were made, an additional 500 pounds per acre of 12-12-12 was broadcast and disked in prior to planting the second crop. Late plantings also received a side dressing of 200 pounds per acre of amm- onium nitrate applied when the plants were at the 2-3 true leaf stage. Irrigation was applied as needed during both growing seasons. Each plot was 25 feet in length with guard plants at both ends of the row. All harvests were destructive or once-over harvests. The plants were pulled from the soil by hand and all of the marketable and cull fruit removed. The fruit were weighed and counted and then graded on a portable grader with openings corresponding to the various grade sizes. Yield data were converted to bushels and dollars per acre and fruit per plant. The fruit grades and values for both years were as follows: Grade Size (inches) Value per 100 pounds 196113.62 196i“1 1‘" ) 1962 1 1 up to 116 5.00 6.00 18 19 Grade ' Size (inches) Value per 100 pounds (dollars) 1961 1962 1961 1962 2 2 1.1. - 132- 2.00 2.50 v 16 3 5 1% - 2 1.00 1.25 oversize h. greater than.2 ---- .50 culls culls crooked, nubbin or yellow fruit ---- ---- Seed of the gyncecious hybrid variety Spartan Dawn, which was used in all experiments, contained 10 percent monoecious pollen parent to as- sure an ample supply of pollen. These plants were included in the yield records but were not observed for flowering and fruiting characteristics. Data were statistically evaluated by analysis of variance and mean differences were compared by the least-significant difference and Duncan's multiple range tests.‘ I. Successive planting. :tudies Six successive plantings were made in 1961 in which several factors were studied. The plots were seeded on.lay'2h, June 5, June 2b, July 2h, August 2, and August 10. The 3 later plantings followed earlier plantings on the same plot. After harvest, vines from the preceding orcp were al- lowed to dry out for 2 days and fertilizer was then broadcast and disked in with the vines. The plots were arranged in a split plot design, the order of ran- domisation being varieties, spacings, and harvests. ~Each treatment was replicated 3 times. The varieties Spartan Dawn and Wisconsin SHE-18 were planted in 3 harvest rows spaced 5 feet and 2fi-feet apart. Guard rows ‘were planted between each block and bordered the entire plot. After emergence the plants were thinned to étinches apart in the 5 foot rows 20 and 1 foot apart in the 2% foot rows to give equal plant populations Four plants from.each replicate were selected and the flowering sequence was observed at 2-3 day intervals until harvest. The first harvest was conducted when a few fruit were lé-inches in diameter. The second and third harvest rows were taken at 2-3 day inter- vals following the first harvest. In 1962, 7 successive plantings were made to establish a sequence of harvests throughout the entire season. The criteria used to determine the time of planting was the time when the first true leaf of plants from the preceding planting had begun to enlarge. The plots were seeded on May 17, May 25, June 8, June 19, June 89, July 10, and July 20. The 2 later plantings followed earlier plantings on the same plot. A split plot design was employed with the order of randomisation being varieties, spacings, and harvests. Each treatment was replicated h.times in the first 3 plantings and 2 times in the last h plantings. The varieties Spartan Dawn and Wisconsin SMR-lB were planted in 2 her- vest rows spaced h and 2 feet apart. After emergence the plants were thinned to 6 inches and 1 feet apart in the row to give equal plant populations with each spacing. The June 8 planting was employed to determine if higher yields could be obtained from the second picking than were obtained from the first picking. Marketable fruit were removed from.the intact vines in- stead of employing a destructive harvest. Four days later the second harvest was made by pulling the vines in the usual manner. Plants from the guard rows of each variety were harvested and the node position of the fruit was recorded. The percent of fruit occurring at each node was calculated. 21 II. Plant population_studies In 1961, 3 spacing trials were planted on June 5, July 26, and August 7. The plot design was a split plot with the order of randomiza- tion being variety, spacing, and harvest date. Each spacing was repli- cated 2 times within each variety. The plots were seeded in rows h, 2, and 1 foot apart with a V-belt seeder using the varieties Spartan Dawn and Wisconsin SHE-15. Three harvest rows were included in each spacing block with guard rows planted between blocks as shown in Figure 1. After emergence the plants were thinned to give spacings of h x %, 2 x g, 2 x l, and l x 1 feet. Four plants in each replicate were selected at random for flowering observations. The number of pistillate flowers produced on plants at each spacing was recorded at 3qh day intervals. The time of harvest was determined as described in the preceding study. In 1962, a spacing trial was planted on May 28 using the varieties Spartan Dawn and Wisconsin SEE-16. The plot design was similar to that used in 1961. The Spacings used were 3 x 1, 3 x t. 2 x 1, 2 x a, 1 x 1, and l x % feet. III. Inhibition and pollination studies In 1961, the guard rows of the spacing trials were used as a source of plants for other studies. A study of the inhibition of further fruit enlargement by the fruit previously set was initiated with the May-2h planting. Six plants from.eaoh of h guard rows were selected at random and observed as follows. On July 19, the number of marketable fruit on each plant was recorded and the plants were divided into 2 groups. The marketable fruit were removed iron 1 group of plants and no fruit were removed fron.the other group. After 7 days, the number of marketable on a'._s.. seamen op puma seam .veew m K 4 and .m x m .H K H .H K H .voms m .r 0: tr? c «swam new use swamps poflm exp mewsonw vmobaea aoponoono new asap» afloemm Homfi .H onzmwm 25 fruit on both sets of plants was recorded. Plants in the guard rows of the June 5 planting were used in an at- tempt to determdne if a real inhibition from.the enlarging fruit existed, or if the failure of more fruit to develop was merely due to a lack of pollination. Ten pistillate flowers from.each of 3 replicates were treated in 5 different ways. The control group was allowed to be pol- linated in the usual manner by bees. Anather group was hand pollinated and allowed to be pollinated by bees. The third group was covered with capsules just before anthesis to prevent pollination. Ten days later observations were made on the number of fruit set and the number of ovaries which aborted. Plants for the fruit growth study conducted in 1962 were selected from.guard rows of the June 8 planting of Spartan Dawn. Ovary measure- ments to the nearest tenth.mm were made on 10 flowers at anthesis with a direct reading caliper gage%/ The measurements recorded were the great- est diameter, and the length from the base of the calyx to the junction of the peduncle. The ovaries of 25 pollinated flowersxwere measured daily for 7 days after pollination. The data were transformed into volume (om?) assuming a cylinder as the approximate fruit shape. IV. Evaluation.g£ growth regulators Two replicated experiments and a non-replicated test were conducted in 1961. On May 17, 2 variety blocks of Spartan Dawn and Wisconsin 8MB- 18 were planted in rows 5 feet apart. After emergence, the plants were thinned to approximately 6 inches apart in the row. Treatments were laid out in'a randomized complete block design with 3 replicates for L/'Federal Products 00., Providence, Rhode Island. 24 Wisconsin Sim-18 and none for Spartan Dawn. Treatments were applied as foliar sprays when the plants were at the 2-3 true leaf stage. The chemicals were applied with a small plot sprayer using quart bottles as containers and carbon dioxide cylinders as a source of pressure. Tween- 20 (.0575) was used as a wetting agent in all treatments and the leaves were sprayed to the point of run-off. Three plants from each replicate were selected at random for obser- vation. The number and position of pistillate flowers was recorded at 2-14 day intervals. Five plants were harvested from each plot when the first grade 3 fruit were observed. The second planting was seeded in rows 1; feet apart on July 21;, us- ing the variety Wisconsin SHE-18. The plots were randomized as before with 3 replications, and the chemical treatments were applied on August ll, when the plants had 3 true leaves. 'Since inconsistent results were obtained in 1961, another growth regulator test was conducted in 1962. Variety blocks of Spartan Dawn and Wisconsin Sim-18 were seeded in rows 14 feet apart on June 12. After emergence, the plants were thinned to 6 inches apart in the row. The treatments were arranged in a randomized complete block design with 3 replications. The chemicals were applied on July 2, when the plants were at the 2-} true leaf stage. Three plants from each replicate were chos- en for pistillate flower observations. Yield records were obtained from 10 plants in each plot. Another experiment was conducted in an attempt to increase fruit production. Six plots, 25 feet in length, were selected at random in a field of Spartan Dawn. Three replicates were sprayed with potassium gibbsrellats at 1000 ppm using Tween-20 (.0591) as a wetting agent, when 25 the first flowers were opening (August 7). The remaining plots were de- signated as controls. Fifteen days later the fruit were harvested. In the fall of 1962, a greenhouse study was initiated to determine if gibberellin applications might induce the development of partheno- carpic fruits. Seeds of the variety Spartan Dawn were sown in 50 6-inch pets on October 2. Five pots were also planted to the variety'hinnesota Dwarf XII to assure an adequate pollen supply. The plants were maintain- ed at a 65°F. night temperature with no supplemental light. Shortly after emergence, the plants were thinned to 1 plant per pot. Soluble fertiliser was applied weekly after the appearance of the first true leaf. The plants were staked and grown to the flowering stage. Forty uniform.plants were selected and the first 2 pistillate flowers on each plant were treated. The treatments were arranged in a split plot design, the main plots being pollination vs. no pollination. A check and 3 gib- berellin treatments were included in each pollination treatment, and each was replicated 5 times. Hand pollination was accomplished by de- taching the staminate flowers, tearing back the petals, and rubbing the anthers over the stigma of the pistillate flowers. The nonppollinated flowers were covered with capsules at anthesis. The gibberellin treat- ments were executed the same day as the pollination treatments. Potas- sium gibberellate was applied by three different methods as follows: a. Applied to the ovary in a ring of lanolin paste. (1 ml of 100 ppm solution in 10 m1 lanolin) b. Sprayed on the ovary with a hand atomizer (100 ppm). 0. Injected .05 so into the ovary with a hypodermic needle (100 pm). \ Fruit set observations were made 7 days later. RESULTS AND DISCUSSION 1. Successive planting studies The flowering sequence data recorded from 12 plants of each variety in 1961, were summarized and from.this an “average” plant was drawn for each observation date. Spartan Dawn produces only 1 or 2 staminate flowa ers under normal field conditions. The first pistilIate flower may occur at the cotyledonary node and usually is not set. Pistillate flowers may occur at each succeeding nods throughout the life of the plant (Figure 2). I The variety Wisconsin SMR-IS goes through a staminate phase for the first 8 to 9 nodes, after which it becomes monoecious and remains so until har- vest. The laterals produce chiefly pistillate flowers, the first of which usually become marketable fruit (Figure 3). Two varieties showed distinctive differences in fruiting habit. The variety Spartan Dawn set a high percentage (80%) of its fruit along the main stem. The most concentrated region was from node 2 to 8. A large number of fruit also occurred on node 1 of the lateral branches. lflsconsin SHE-18 developed 69% of its fruit on laterals, 61% on node 1 of the laterals (Table 1). Fruit occurred on the main stem of this variety in the region of node 6 to 11, and this was rarely more than 1 fruit per plant. ' In 1961, late season plantings produced dollar yields much lower than the earlier plantings (Table 2). This may be accounted for at least in part by the severe damage to the later plantings by angular leaf spot (10). 26 PO .‘3 Two crOps were grown to maturity on the same plot during 1 growing sea- son. The latest planting to mature was made on August 2. A planting made on August 10 was destroyed by frost on September 29 about 5 days be- fore maturity. An average of 51 days was required from.p1anting to the maxium har- vest with a range of h7-57 days for the variety Spartan Dawn. Wisconsin SHE-18 produced its maximum.yield on an average of 52 days from.p1anting with a range of h8-60 days. The maximum.yield usually occurred at the second harvest or about 2 days following the appearance of grade 5 fruit. Plants spaced 1 foot apart in the row yielded consistently higher dollar per acre and fruit per plant yields than those spaced 6 inches apart at the same plant population (Table 5). There was no difference between varieties in the dollar yield per acre produced, although Spartan Dawn consistently produced more fruit per plant. Bushels per acre was found to be an unreliable estimate of the act- ual yield especially when comparing a sequence of harvests in the same planting. High bushel yields are often.misleading because of the pres- cenoe of many low grade fruit. The bushel yield, dollar yield, and grade changes in 3 successive once—over harvests of the same planting indicate dollar yield was a much.more reliable figure because it considers not only the weight of the fruit, but also the grade and corresponding value (Table h). Seven plantings of cucumbers were successfully harvested in 1962. No statistical comparison of plantings could be made, but it was observed that the early plantings (May 17-June 19) yielded higher than the later plantings (Table 5). The average number of days from.p1anting to the Optimum harvest date with Spartan Dawn was L9 days, with.a range of h6— [‘0 C“ MSU’TlB-S x:Spartan 27 Figure 2. Flowering sequence and position of marketable fruit on a typical plant of the variety Spartan Dawn. Wisconsin SEE-18 FR» Farketable fruit TIT—- Fruit has set X — Pistillate flower 0 - Staminate flower -o 2.9 o -o o -o -o oo -o r; s Figure 5. Flowerirg sequence and position of marketable fruit on a typical plant of the variety Wisconsin SEE-18. Table 1. The positi;n on the vine and percent of fruit occurring at each 1 node of 2 varieties? Main Stem Spartan Dawn 29 Wisconsin SMR-lB_ # _1_./ Calculated from 1011 fruit harvested-from 180 plants of each variety. .— --- ifide 1 0.6 0.2 2 7.7 0.6 3 12.5 0.2 1; 11.9 0.1. 5 13 .7 0.6 6 15.14 2.2 7 8.1 5.7 8 y 5.9 8.3 9 2.11 6.9 10 1.8 3.2 11 0.2 2.8 (Kain Stem Total 80.2 31.1 Laterals N13. 16.0 60.7 2 3.0 6.5 3 0.11 1.6 L; 0.14 0.1 Lateral Total 19.8 68.9 Table 2. Dollar yield per acre and number of days from planting to Optimum harvest for 5 successive plantings (1961). Numbe r Crop Date Variety Harvested Dollar Planted of days Yield 2/ IL. May 211 Spartan Dawn July 21 57 131 SIR-18 July 21.. 60 911 In June 5 Spartan Dam July 28 52 1d; Sim-18 July 28 52 79 111 June 28 Spartan Date August 18 50 70 sun-18 August 21 53 11.3 132/ July 2h Spartan Davin Septunber 11 ha 59 Sim-18 September 11 118 115 1132/ August 2 Spartan Dam September 18 1.17 1414 8101-18 September 20 1.9 38 Average Spartan Dawn 51 82 SIR-18 52 80 _1/ rm. 1. with a spacing of 2% x 1 feet. 2/ Planted on the same plot after a preceding cucumber crop was removed . 31 Table 3. Dollar yield per acre and fruit per plant produced by 2 varie- ties grom at 2 different spacings (plant population 17,1420). 1/ h Dollars per acre “EamgswmfetT Varieties x 1 5 a: % Average 2/ 'lisconsin.SMR-18 65.5 52.8 h8.l Average 63 06 57 09 Fruit per plant Spartan D3“ 2e6 1e? 2.2 Wisconsin Sim-18 1.8 1.1 1.5 Average 2/ 2 .2 l .14 1/ Average of all harvests. ( 2/ P value for varieties not significant. 3/ P value for difference between spacings significant at odds of 99:1. Table 1;. A typical harvesting sequence showing changes in bushels, dollars and grades (Spartan Dawn planted May 214) . I Bushels Dollars Grade 1% by wig-1t) Oversize, Harvest per acre per acre 1 2 3 culls 1 (7/19) 37 hé 23 61 16 - II (2/21) 130 83 5 21 65 11 111(7/2h) 25h 67 2 10 30 58 Table 5. Optimum harvest for 7 successive plantings (1962). Dollar yield per acre and number of days from planting to Crop IA IIA III 113 _3_/ Ave rage Date Variety Harvested Number Dollar planted of days yield 3/ lay l7 Spartan Dawn July 7 50 160 Sim-18 July 9 52 1141 May 25 Spartan Dawn July 12 ' 148 121; SIR-18 July 16 52 169 June 8 Spartan Dawn July 25 146 15).; SIR-18 July 30 51 1514 June 19 Spartan Dawn August 6 148 172 sun-18 August 9 51 11:0 June 29 Spartan Dawn August 20 51 53 SIR-18 August 22 53 56 July 10 Spartan Dawn August 29 149 63 sun-16 September 1 52 72 July 20 Spartan Dawn September 13 53 35 SIR-18 September 13 53 b0 Spartan Dawn 19 109 SIR-13 52 110 1/ This is with a spacing of 2 x 1 feet. 2/ nail on August 10 severely injured this and succeeding plantings. 2/ Planted on the same plot after a preceding cucumber orOp was remved. 35 53 days. 'Wisconsin SEE-18 reached the optimun.harvest stage on.an.aver- age of 52 days after planting and the range was only 51-53 days. The criteria used for determining the time of'planting gave a satisfactory sequence of harvest throughout the season. (A.hail storn_on.August 10 severely injured the June 29 and all later plantings. Several cool nights occurred in August and September as shown in the table of temperature data (Table 16). These temperatures were unfavorable for cucumber growth.and deve10pment, hence the percentage of cull fruit produced in the last 3 plantings was in the magnitude of 35- 58%. Two crops of cucumber were successfully grown in 1 season on the same plot, although the second crop yields were very low. In a study involving the comparison of yields obtained from.the first and second pickings, no difference between pickings was found at either spacing or variety (Table 6). The plants spaced 1 foot apart in the row again produced more fruit per plant and higher dollar yields. 'No difference was found between the two varieties (Table 7). II. Plant population studies The total of pistillate flowers produced per plant and the flowering sequence were not affected by plant population in 1961. iHowever, the number of marketable fruit per plant and dollar per acre yield was in- fluenced by different spacings as shown in Table 8. The number of fruit per plant was consistently greater when the plants were spaced 1 foot apart in the row campared to those spaced 6 inches apart. Plant pOpula- tions of h3,560 plants per acre resulted in higher dollar yields than pepulations of 21,780 plants per acre. Data for 3 plantings indicate that spring plantings yield higher 31.; Table 6. A comparison of the first and second harvests of Spartan Dawn and Wisconsin sun-18. Dollar yield per acre 5 Plan? s pacing‘ffeet) Harvest ‘ 2 x 1 11 1: k Average 1/ 1 177 1 123 150 2 153 127 1145 Average 170 125 V y P value for difference between harvests not significant. _/ P value for difference between spacings significant at odds 99:1. Table 7. Dollar yield per acre and fruit per plant produced by 2 varie- ties grown at 2 different spacings (plant population 21,780). _1_/ Dollars per acre Plant spacing (feetf Varieties 2 x 1 11 x % Average 2/ Spartan Dawn 110e5 88s? 99e5 Wisconsin SIR-18 112.1 82.6 97 .14 Average 2/ 111.2 85.7 Mpflli‘ruit per plant Spartan Dawn 3 .7 2 .9 3 .3 Wiscons in Sim-18 3 .0 2 .0 2.5 Average 3/ 3 .14 2 .5 1/ Averages of .the highest yielding harvests. 2' P value for difference between varieties not significant. / P value for difference between spacings significant at odds of 99.1. 55 than mid-summer plantings (Table 9). The late plantings were severely infested with angular leaf spot which resulted in reduced fruit production. The increase in once-over harvest yields with high plant populations was in agreement with reports by.Anderson (l) and Rios (hB) for increased early yields on multiple harvest varieties. The spacings had no apparent effect on flowering but did affect the plant growth. Since plants spaced 1 foot apart in the row yielded higher than those spaced 6 inches apart in the row, regardless of the distance between rows, it appears that root and vine distribution may be important factors. Plants spaced in this manner may be more favorably situated to obtain the maximum.amount of light, water, and nutrients. The problem of deteriorated fruit at close spacings as reported by Hopen (30) did not appear in 1961. Plants grown for once-over harvest do not remain in the field to the point where such a thick mat of vegeta- tion is formed as would be the case for multiple harvest. In 1962, plant populations of h5,560 and 87,120 produced higher dollar per acre yields than the lower plant populations, however, no in- creased yield was obtained at plant populations over h3,560 (Table 10). Plants at each row spacing produced more fruit per plant when spaced 1 foot apart in the row rather then 6 inches. This was not reflected in higher dollar yields because of a 2-fold difference in plant population. Both varieties responded similarly to the spacings used. The results of the spacing studies were in agreement with those ob- tained in 1961. With the present indeterminant varieties, there was no increased benefit obtained by increasing the plant population over 145,560. Advantages\may be obtained by the development of detenminant, dwarf-type plants which may be grown successfully at higher plant pepulations. 56 Table 8. The effect of plant spacings on yield of Spartan Dawn and Wiscons in sum-15 . Spec E Plant Fmfi Stat. m S 11‘ Se Between In population per signi f. (dollars signif . rows rows plant per acre) (feet) (feet) 1/ 2/ l/ __ 2/ u a 21 ,780 1 .7 . 39 . 2 s- h3.56o 1 .8 . 59 bc 2 l 21 ,7’80 2 .7 b 51 a c 1/ Average of 8 different harvest dates of both varieties. 2/ lieans with unlike letters are significantly different, odds 99.1. Table 9. Dollar yields for different plantings and Spacings of Spartan Dawn and Wisconsin SMR-lS. _l_._/ PIant spacing feet) Planting 1.1 x g 2 1g 2 x l 1 x 1 Average I. June 5 86 96 103 914 95 11. July 28 37 76 61 9h 67 111. August 2 26 62 141 6b. b9 Average _2_/ 50 a 78 b 68 b 811 b n‘ _— _ ‘- n _L l/ Average of the highest harvests of each plantings. 2/ Means with unlike letters are significantly different, odds 19:1. 37 Table 10. The effect of several plant spacings on yield of Spartan Dawn and Wisconsin SEAR-18 (Average of 14 harvest dates). spacings (f—e'etT jun? s . e a . Between In papulation per signif. (dollars signif. Rows -_ Rowe plant 1/ Aper airs) 2/ 3 1 114.520 3-5 a 93 a 3 t 29.0w 2.0 b 101 a 2 1 21,780 2.7 a 108 a 2 1 113.560 1.6 ' b 121 . b 1 1 1.13.560 1.9 b 162 b 1 5‘ 87,120 1.1 c 125 . b 1/ Means with unlike letters are significantly different, odds 99:1. _2_/ Means with unlike letters are significantly different, odds 1911. 58 III. Inhibition and pollination studies. Studies conducted in 1961 indicated that further fruit development was arrested on plants when the marketable fruit were not removed. After a period of 7 days no appreciable fruit development occurred when the original fruit were left on the plant. However, when the marketable fruit were harvested, other inhibited fruit continued to develop into marketable size (Table 11). Data from the pollination study indicated ..in an indirect manner that a true inhibition existed, and that the lack of further fruit development was not due to a lack of pollination. When flowers were not pollinated, 91% aborted within 10 days (Table 12). Inhibited fruit do not abort to a great extent, but may remain on the plant in an arrested condition for at least 2 weeks. A large percentage of the unfertilized ovaries had shriveled and undergone abscission in this period of time. Natural pol- lination by bees resulted in 83% fruit set, and no significant increase was achieved by additional hand pollination. It was noted in 1961 that many fruit are set and make an initial burst of growth.and then are inhibited from further development. .A study of fruit growth was conducted in 1962. Of the 25 flowers selected for measurements, 11.; developed into marketable fruit, 8 became inhibited after about 3 days growth, and 3 shriveled and later abscised. Ovaries at full bloom inhibited fruit after 7 days, and non-pollinated ovaries after 7 days are shown in Figure 1.1. At the third day after pollination, the inhibition effect was first observed in the data. No increase in size of the inhibited fruit occurred from the third to the seventh day after pollination as shovm in Figure 5. The fruit which became marketable continued to grow at a rapid 59 Table 11. The inhibitory effect of developing fruit on subsequent fruit deveIOpment. Number of marketable fruitgper plant 1/ *“A Feafineflzs Date Harvested Not harvested July 12 (before harvest) 2.9 3.1 July 19 (harvested) h.3 3.3 Total fruit produced _2_/ 7.2 3.3 3/ Average of 12 plants. 3/ I" value for difference between treatments significant at odds 9931. -Table 12. The effects of various pollination treatments on abortion of cucumber ovaries. A m Treatments 1% ovary abortion 1/ Stat. signif. g/ Field pollinated 17 a Field and hand pollinated 13 a No pollination 97 b 3/ Average of 30 flowers per trea‘haent. g/ Means with unlike letters are significantly different, odds 99:1. WV .mth h germs and pasta «when .nm fine 4 .J casuan ==_E.____=____.=.___=_.=__..___.___=_.=______r._.=_____.__._u_.=_____._.__..n_._._._=___=_.a_==__=__=;_p_~; Ca an nu .« ICDCDW VOLUME-CM3 6 l1 fl —- NORMAL -- INHIBITED l j l l I t r I 2 3 4 5 DAYS AFTER POLLINATION Qui- VJL. Figure F. Growth of cucumber fruit after pollination. b2 rate until the seventh day. The growth curve obtained was similar to that reported by Sinnott (55) for other cucurbit fruits. IV. Evaluation .93. growth regulators The results obtained with chemical sprays in 1961 were inconsistent in 2 different plantings with 2 different sets of environmental condi- tions. Non-replicated treatments on the lay l7 planting of Spartan Dawn resulted in 2 apparent responses. Plants treated with ethylene glycol monobutyl ether gibberellate fomed staminate flowers up to node 5 of the main stem. The vines were also more extensive in growth. Plants treated with 2-chloroethyltrimethy1emnonium chloride (000) at 2000 ppm appeared to yield more fruit per plant than any of the other treatments (Figure 6). The monoecious variety Wisconsin Sim-18 exhibited several responses as shown in Table 13. 000 at 2000 ppm hastened the appearance of pistil- late flowers, increased the number Of pistillate flowers formed, and in- creased the yield over that of the control plants. The number of pistil- late flowers and yield was also increased with the 500 ppm treatment (Figure 7). The plants treated with ethylene glycol monobutyl ether gib- berellate at 1000 ppm remained in the staminate phase longer and produced fewer fruit per plant, although the bushel yield was not different from the control. Naphthalene acetamide and benzothiasole-2-oxyacetic acid at both rates used increased the number of pistillate flowers, fruit per plant, and bushel yield per acre. Although maleic hydraside at 500 ppm and (2-chlcrophenylthio) propionic acid at 100 ppm exhibited no effect on the number or position of pistillate flowers, it did result in in- creased yields compared to the control plants. No injurious effects were observed from any of the treatments. No difference existed between any treatments applied August 11 1.3 .voeu & H m veesme epseaa ma mo ewsaehd_\l .evnMHn o omens» om m6 m5 «.4 com .35 a. 93 mm ”.m o.m a... .. Ammo. .oméosrs 3% 8 tn 3m .3 com .3333 33.: epeHHeae 3 man new 33 com .53. .23. 1.388 3.23m 83.3». evsaaoao om m.m m.H h.ma oooH Inndw heave nhpsnencs mochaw oneahspe HS mum o.m Nam com .332. §32§3§.§S%§.2.E.-m 8 3.4 m3 m6 ooom .333. 52.5.3.3..fiufibsofiozoum mm tn 4.. who 02 3.. 3.3.2.:.Efiafififiofloamv R man a...“ .6 8m 3.. 3.3a...£3fi~a§fi83§-fl 33 34 m3 mé cm 3.. .3....?...m..3...3.3..m mm vs: m.4 map om vase capeoshuovmueaousunpcueom no m.m w.m .N.o om ecuaepeos eneaenpmmsz 0... 9m tn 0.. 2: 33.»... 83239.2 \Maeaes hen \N #539 \a :2»on \H cowaseoo .339: 753 1-11 I I! 3....3 .3. 3.33.3 3.333. .23 .fia H.355 ‘mHmmhr pusah_ aegfiwzu nmmm, mmeammmmaT; .matmxm nauseous: no auaewh was wnauescnu no change aovsaswoa meson» no evoeuao any .mH eases Figure 6. A plant of the variety Spartan Dawn treated with CCC at 2000 ppm. In comparison, control plants produced 3.L fruit per plant. ' . c I Figure 7. A plant of the variety Wisconsin SHE-18 treated with CCC at 500 ppm. In comparison, control plants produced 3.1 fndtperphmt. (Table 11;). Staminate flower induction with gibberellin in an early planting was in accord with reports by Mitchell (Ll) for greenhouse applications and by Peterson (h5) for applications in the field. The effects of CCC on flower expression were also similar to that reported by'Hitchell. The flower responses obtained with the auxin-like compounds were similar to those reported in the literature. Since maleic hydraside and (2-chloro- phenylthio) propionic acid did not affect pistillate flower formation, their effect on increasing yield is difficult to explain. It is possible that several of these compounds may have had an effect on the inhibition mechanism in the cucumber. Inconsistency in the results from.2 experiments indicated that per- haps environmental and physiological factors at the time of application had an important effect on the absorption, translocation, and effective- ness of these compounds. Other factors may overcome any effect that the chemicals might have had. This is typical of the problems encountered with growth regulators under field conditions. In 1962, growth regulators applied as foliar sprays at the 2-3 true leaf stage had no effect on the fruit per plant or bushel yield. (Table 15). Gibberellin induced staminate flower formation on the first few nodes of Spartan Dawn but did not reduce the total number of pistillate flowers produced. More variability in flowering occurred among plants in the same treatment than was observed in 1961. Failure to obtain favorable responses from chemical sprays under another set of environ- mental conditions'indicated that these treatments were not a reliable means of increasing yields in the field. A gibberellin spray of 1000 ppm applied at anthesis did not increase b6 Table 11;. The effect of growth regulator sprays on flowering and yield of Wisconsin Sim-18 cucumbers. Trim.“ :fimbor T‘Cmit fisher. Chemical Rate pistillate per per (ppm) flowers 1/ plant 2/ acre 2/ None (Twe en-2O , .05%) - 3 .9 3 .2 55 Bensothiazole-2-cxyacet- 100 3.2 2 .3 140 is acid Benscthiascle-2-oxyacet- 20 14.0 3.1 66 is acid Bensothiasole-2-oxyaoet- 5 3.0 2.14 36 is acid 2-chlcroetlwltrimethyl- 2000 14.6 2 .9 62 anioniun chloride 2-chlorcethy1t rimethyl- 500 3 .8 2 .7 65 annoniun chloride 2-chloreethyltrimethy1- 100 14.2 2.7 39 amoniun chloride Maleic hydrazide 1000 2 .8 2 .8 LL6 Maleic hydraside 500 3 .2 2 .9 76 Male 10 hydra: 1d. 250 5 e8 3 e1 60 1.51) at odds l9 s 1 NS NS NS _l_/Average of 9 plants observed 5 days before harvest. 3/ calculated from yields of 30 plants spaced ’4 x 1 feet. 147 .voom .w H 4 ocean. owns—”m on we amass. \ua. .33de m «o eweueb< \m m2 m2 m2 m2 mz m2 :9 .35 a. 93 3 m4 ~.m 3 4.“ g 2 2:3 5 33 322258 on m.m o.m om m.m m; 02 $5.. 5 39. 328258 mm tn N.m .3 m.m m5 cm 33 oflpooamuoéuoaosfifioueom cayenne gauge mm lam o.n mo m.m fl: om .ssflafiofla pinpoouozod afidkogo gdfla 3 Qm m.» we QM 92 com .fiflafioatfiafiofiozod S fin flu 8 +3 Tm om 32:23 3.32 om msm mam R m.m Na 8m . .3332 3.1: we o.m m.N 1:. 1m +70 I Sumo. .omuaoelav eaoz e a“ \N the exams .fi \N 2 finds a“ 3.5 euemesm wmsam yea—«Er» snag Gunman In 3003.3 para? .3352 Even :9.“st $033.35 or» we manage.“ was waisted.“ no change ace-Howe." fibeaw mo veemme 22. .mn canes b8 the fruit per plant or dollar yield per acre over that produced by the untreated plants. The control and gibberellin treated plants yielded an average of 3.1 and 3.3 fruit per plant and 106 and 117 dollars per acre respectively. The 1962 greenhouse study indicated that gibberellin treatments un- der the conditions used, were not effective in the inducement of partheno- carpic fruit development. When pollination was prevented, no flowers were set regardless of the gibberellin treatment. All of the non-polli- nated flowers had aborted after a period of 7 days. Forty percent of the hand pollinated flowers were set and no increase was obtained with the gibberellin.treatments. Flowers at later node positions might respond emore favorably to these treatments, as the first flowers formed often show a natural tendancy to undergo abcission. SUMMARY The horticultural aspects concerned with the production of pickling cucumbers for once-over harvesting have been studied for 2 growing sea- sons. The flowering and fruiting characteristics of a gyncecious and a monoecious variety of pickling cucumbers were studied in relation to a once-over harvest. The varieties used produced large indeterminant vines typical of those now'grown for'multiple harvesting, and did not develop a large number of fruit at one time. Successive planting studies were conducted in which plantings were made from mid-Hay until mid-August. During both growing seasons, the earlier spring plantings yielded much higher than the later plantings, because of unfavorable environmental conditions in late sun-nor. With the varieties used, once-over harvesting was accomplished in approximate- ly 50 days after planting. Because of the shortened growing season, 2 crOps of cucumbers were successfully grown on the same soil in one year. The data obtained from the successive harvests indicated that the time of harvest is a very important factor in obtaining the maximum yields. The grade and value of fruit declined rapidly in a period of 2 days. Bushels per acre was found to be an unreliable indication of the true yield. Several plant population and spacing studies were conducted. High plant populations of up to L3,560 plants per acre resulted in higher once-over harvest yields. Plants spaced 1 foot apart in the row were b9 50 found to produce more fruit than those spaced closer tOgether. Fruit deterioration was not a problem at the close spacings. Pollination was found to be essential for fruit set in both.varie- ties as no pollination resulted in ovary abortion and abscission. Fruit inhibition by the fruit previously set was found to be a major factor limiting concentrated fruit production by the cucumber. 'No increase in the number of fruit on plants occurred for a period of 1 week when the marketable fruit were not removed. Growth measurements of normally de- veloping fruit and inhibition fruit showed similar growth for the first 2 days after pollination. After the second days, the rate of growth of inhibited fruit was decreased, and after the third day no increase in size was made. Fruit inhibition appears to be phenomenon which the cu- cumber has deve10ped throughout its evolutionary processes which assures that at least 1 fruit will develop at the expense of others. Several types of growth regulating chemicals were applied to plants in the field and the greenhouse at various stages of growth. The ob- jective of these treatments was to alter the flowering and fruit setting capabilities of the plants in a favorable manner. Inconsistent results were obtained under varying environmental conditions with all the com- pounds tested exoept the gibberellins, which did not produce a beneficial effect. It was concluded that chemical applications were not an adequate means of increasing once-over yields of pickling cucumbers. These studies indicated that the varieties used could be success- fully once-over harvested only if a low cost machine was available as re- ported by Stout 223.:i' (57) and if a large acreage could be grown keep- ing production costs at a minimums High fertility levels and irrigation will probably be required. The ultimate success of once-over harvesting 51 may depend upon the production of determinant varieties with concentrat- ed fruit setting ability, which are adapted to high plant populations. LITERATURE CITED 1. Anderson. W. S. 19h3. Close spacing, medium fertilizer rates most profitable for pickling cucumbers. Miss. Farm Res. 6 (3): 8. 2. Anonymous. 1962. VegetablesdProcessing, Annual Summary. U.S.D.A. Statistical Reporting Service, Washington, D. C. 3. Bailey, L. H. 19h9. Manual of Cultivated Plants. Revised Ed. 95he955. Macuillan Co.N ”Yo—k. h. Banadyga, A. A. 19h9. Cucumbers for Pickleg. National Pickle Packers Association, Oak Park—”IllinOIs. 5. Bingley, G.‘W} 1959. Construction, Evaluation, and Efficiency Studies of a Mechanical Cucumber'Harvester. Thesis for the Degree of M.S. Mich- igan State University. 6. Bolas, B. D. and F.Y. Henderson. 1928. The effect of increased at- mospheric carbon dioxide on the growth of plants. Ann. Bot. LE: 509.523, 7. Bonner, J. and A. W. Galston. 1959. Principles bf Plant Physiology. Freeman Press, San Francisco. 8. Bukovac, M. J. and S. H. Wittwer. 1961. Gibberellin modification of flower sax expression in Quounis sativus L. Adv. Chem. Ser. 28: 80-88. 9. Burrill, P. C. and T. W. Whitaker. 1939. The effect of indoleaoetio acid on fruit setting in muskmelon. Proo. Amer. Soc. Hort. Sci. 37: 829- ' 830. 10. Carsner, E. 1918. Angular leaf spot of cucumber: dissemdnation, overwintering, and control. Jour. Agr. Res. (U.S.) 15: 201-220. 11. Choudhury, B. and S. C. Phatak. 1959. Sex expression and sex ratio in cucumber (Cucumis sativus L.) as affected by plant regulator sprays. Indian Jour. fisrt. 16(3): 162-169. 12. Cunningham, C. R. 1939. Fruit setting in watermelons. Proc. Amer. Soc. Hort. Sci. 37: 811-81h. l3. Currence, T. M. 1932. Nodal sequence of flower type in cucumber. PI‘OOe Aster. SOOe Hort. SOie 293 h77‘h79e 1h. Danielson, L. L. l9hh. Effect of daylongth on growth and reproduc- tion of the cucumber. Plant Physiol. 19: 638-6h8. 52 53 15. Dearborn, R. B. 1936. iNitrogen nutrition and chemical composition in relation to growth and fruiting of the cucumber plant. Cornell Univ. Agr. Expt. Sta. Memoir 192. 26 pages. 16. Delong, H. M. 1962. Development and Evaluation of a Fruit Detach- ment Principle for Once-Over Mechanical Cucumber Harvesting. Thesis for the Degree of M. S. Michigan State University. h2 pages. 17. Edmund, J. B. 1930. Seasonal variations in sex expression of cer- tain cucumber varieties. Proc. Amer Soc. Hort. Sci. 27: 329-332. 18. Emerson, R. A. 192h. A genetic review'of sex expression in the flowering plants. Science. 59: 176-182. 19. Fernald, et :1. 1950. Gray's Manual of Botany. 8th Ed. l3u9. Amer. Book Co.—'New York. 20. Galun, E. 1959. The role of auxins in the sex expression of the cucumber. Physiol. Plantarum. 12: hb-61. 21. . 1961. Study of the inheritence of sex expression in the cucumber. The interaction of major genes with modifying genetic and non- genetic factors. Genetica. 32: 13h-163. 22. . and D. Atsmon. 1960. The leaf-floral bud relationships of genetic sexual types in the cucumber plant. Bull. of the Res. Coun. of Israel. 9(1): h3-50. 23. Gustafson, F. G. 19L1. Probable causes for the difference in fac- ility of producing parthenocarpio fruits in different plants. Proc. Amer. Soc. Hort. Sci. 38: h79-h81. 2L. hall, 8. J. and J. H. MacGillivray. 1956. Mechanized cucumber picking. Calif. Agr. 25. Hall, W. C. l9h9. Effects of photoPeriod and nitrogen supply on growth and reproduction in the gherkin. Plant Physiol. 2L: 753-769. 26. Heimlioh, L. F. 1927. The development and anatomy of the stan- inate flower of the cucumber. Amer. Jour. Bot. lbs 227-237. 27. Heslop-Harrison, J. 1957. The experimental modification of sex expression in flowering plants. Biol. Rev. Cambridge Phil. Soc. 32: 3b-90 e ‘ 2b. Heyer, F. lboh. Untersuchungen uber das Verhaltnis des Geschlechts bei einhausigen und zweihausigen Pflanzen. Ber. D. Landw. Instit. d. UniVe H‘llee 53 1-1520 29. Hillyer, I. G. and S. H. Wittwer. 1959. Chemical and environmen- tal relationships in flowering of Acorn squash. Proc. Amer. Soc. Hort. 801 e 7h: 558-5660 5h 30. Hopen, H. J. 1962. Environmental Factors Affecting the Growth of Cucugis sativus L. with Special Reference to Carbon Dioxide. Thesis for the Degree of Ph. D. Kichigan State University. 93 pages. 31. Ito, H. and T. Saito. 1956. Factors responsible for the sex expres- sion of Japanese cucumber. III. The role of auxin on the plant growth and sex expression. Jour. Bert. Assoc. Japan. 25: 101-110. 32. . and . 1957. Factors responsible for the sex expres- sion of Japanese cucumber. VI. Effects of the daylongth.and night temp perature unsuitable for pistillate flower formation, artificially con- trolled during the various stages of the seedling development in the nursery bed. Jour. Hort. Assoc. Japan. 26: 1-6. 33. . and . 1957. Factors responsible for the sex expres- sion of Japanese cucumber. VIII. Effects of long day and high.night temperature treatment of short duration, accompanied by the growth sub- stance application on the sex expression of cucumber. Jour. Hort. Assoc. Japan. 26: 209-21h. 3b. Judson, J. E. 1929. The morphology and vascular anatomy of the pistillate flower of the cucumber. Amer. Jour. Bot. 16: 69-66. 35. Kotowski, F. 1926. Temperature relations to germination of vege- table seeds. Proc. Amer. Soc. Hort. Sci. 23: 176-163. 36. McCollum, J. P. 193k. Vegetative and reproductive responses as- sociated with fruit development in the cucumber. Cornell Agr. Expt. Sta. Memoir 163. 27 pages. 37. Header, E. u. Personal communications. 1961. 36. Miller, C. H. 1957. Studies on the Nutrition and Physiology of Pickling Cucumbers. Thesis for the Degree of Ph. D. Michigan State University. 69 pages. 39. . R. L. Carolus, S. K. Rice, and W. W. McCall. 1958. Some factors influencing pickling cucumber production. Proc. Amer. Soc. Hort. Sci. 71: h66-h75. ho. . and s. x. 121... 1958. The effect of environment on fruit development of pickling cucumbers. Proc. Amer. Soc. Hort. Sci. 71: h75~h79o ' Ll. Mitchell, W. D. 1962. Physiological and Biochemical Aspects of Flower Sex Expression in Cuourbits with Special Reference to Cucumis sativus L. Thesis for the Degree of Ph.D. Michigan State University. pages. b2. Murneek, A. E. and S. H. Wittwer. 19h2. Relation of sexual repro- duction to development of horticultural plants. I. General effects of flower and fruit production. Proc. Amer. Soc. Hort. Sci. ho: 195-205. 55 1A5. NitOCh, Je Po. Ee Be Kfirtz' Je Le Livom, and Fe We Went. 1952e The development of sex expression in cucurbit flowers. Amer. Jour. Bot. 39: 324.3. Lb. Peterson, C. E. 1960. A oeoious inbred line of cucumber. Mich. Agr. Expt. Sta. Quart. Bul. h5figx b0-h2. AS. ‘_3 and L. D. Anhder. 1960. Induction of staminate flowers on gyncecious cucumbers with gibberellin A3. Science. 131: 1673-167L. h6. Phatak, S. C. 1959. Studies on floral biology, sex expression and sex ratio in cucumber(Cucumis sativus L.). Thesis for the associateship of Indian Agr. Res. Inst., New Delhi. h7. Podesva, J. 1956. Studies on the use of growth substance solutions for spraying forced vegetables. (English, Russian, and German summaries) Sborn cs1 Akad. Yemed Ved Rostl. vyroba. 29: 737-7h6. LB. Rise, 8. K. 1957. The effect of spacing and supplemental fertiliz- er applications on the yield of pickling cucumbers. Mich. Agr. Expt. Sta Quart. Bul. 10(2): 375-381. 19. . and a. L. Carolus. 1958. The effect of nutrient level zn)growth of pickling cucumbers. Mich. Agr. Expt. Sta. Quart. Bul. LO 5 8 659-6&e 50. Seaton, H. L. and J. C. Kremer. 19h1. Effects of,c1imatological factors on yield and quality of cucumbers. Canner. 92(15): 22. 51. . and . 1938. The influence of climato- logical factors on anthesii'and anther dehisoence in the cultivated cu- curbits. Proc. Amer. Soc. Hort. Sci. 36: 627-631. 52. Shirley, H. L. 19h5. Light as an ecological factor and its meas- urement. Bot Rev. 11: 1497-532. 53. Shifress, 0. 1961. Sex control in cucumbers. Jour. of Hered. 52 (1): 5-11. 5h. . and E. Galun. 1956. Sex expression in the cucumber. Proc. Amer. oc. Hort. Sci. 67: L79-h86. 55. Sinnott, E.‘W. 19h5. The relation of growth to size in cucurbit fruits. Amer. Jour. Bot. 32. 1139-1116. 56. Stout, B. A. and S. K. Rice. 1959. A pregress report on the devel- opment of a mechanical cucumber harvester. Mich. Agr. Expt. Sta. Quart. Bu1e 141(3)‘ 699.7180 57. . and _‘ . and A. R. Putnam. 1963. The feasi- bility of a once-over mechanical harvester for pickling cucumbers. Mich. Agr. Expt. Sta. Quart. Bul. (in press). 56 58. Stuckman, N. W. 1959. Michigan pickling cucumbers-the grower, the picker, and the WYRF. Mich. Agr. Expt. Sta. Qmart. Bul. L2: 2-23. 59. Thompson, H. C. 1959. Vegetable Crops. 5th Ed. 513-523. McGraw- Hill, New York. 60. Tiedjens, V. A. 1926. Some observations on the response of green- house cucumbere to certain environmental conditions. Proc. Amer. Soc. Hort. Sci. 23: lob-109. 61. . 1928. Sex ratios in cucumber flowers as affected by different conditions of soil and light. Jour. Agr. Res. 36: 721-7h6. 62. Tkachenko, N. N. 1935. Preliminary results of a genetic investi- gation of the cucumber. (Russian, English summary). Bul. Appl. Bot. Genet. and Plant Breed. 9: 311-356. 63. Walker, J. C. 1958. Two new pickling cucumber varieties resistant to scab and mosaic. Plant Disease Reporter. h2: 1337-1338. 6h. Wittwer, S. H. and A. E. Murneek. 19L2. Relation of sexual repro- duction to development of horticultural plants. II. Ph siological in- fluence of fertilization. Proc. Amer. Soc. Hort. Sci. 0: 205-208. 65.‘ ___ . and J. Tyson. 1950. Yields of pickling cucumbers as influenceHHby rates of fertilizer application, fertilizer placement, and nitrOgen side dressing. Mich. Agr. Expt. Sta. Bul. 32(h): 555-559. 66. . and I. G. Hillyer. 195h. Chemical induction of male sterility in cucurbits. Science. 120(3126): 893-89b. 67. A . and M. J. Bukovao. 1958. The effects of gibberellin on economic crops. Econ. Bot. 12(3): 213-255. 68. . and N. E. Tolbert. 1960. 2-chloroethyltrimethylam- monium chloride and related compounds as plant growth substances. V. Growth, flowering, and fruiting responses as related to those induced by auxin and gibberellin. Plant Physiol. 35: 871-877. 69. <__. and M. J. Bukovao. 1962. Staminate flower formation on gyncecious cucumbers as influenced by the various gibberellins. Die Naturwissenschaften. Heft 13. e 305/06. h9 Jahrgang. 70. Weng, C. Y. 1939. Induced parthenocarpy of watermelon, cucumber, and pepper by the use of growth promoting substances. Proc. Amer. Soc. Hort. 801e 363 632‘636e 71. Yampolsky, C. and H. Yampolsky. 1922. Distribution of sex in phanerogmmic flora. Bibliotheca Genetics. 361-362. fit. .1! grit wfiiflei-s “IA... I" u. I II... . ,- _ taunt“ A1 ‘PEND IX Table 16. Daily temperature data recorded from the Michigan State Lniversity Horticulture Farm. Date 1961 1962 Ha}: . 13in . Mean TEX . an . Wear. 1112\3- 15 76 60 ()8 e0 " ' "' 16 63 L2 52.5 9h 61 77.5 17 ch 30 5L.0 95 59 77.0 18 55 67 51.0 9b 6b 79.0 19 63 38 50 .5 93 59 76-0 20 63 LL. 53.5 03 68 75.5 21 62 b5 53.5 73 53 03.0 2 5 35 b7.0 81 as 63.0 2L 75 38 50.5 67 55 66.0 25 70 51 60.5 80 L5 62.5 20 bl 33 37.0 69 L5 57-0 27 62 31 ho.5 7h 37 55.5 25 7C (48 59 so 814 (47 65 e5 29 6b LB 56.0 93 60 76.5 30 71 35 53.0 81 65 73.0 June 1 71 56 63.5 68 50 59.0 2 77 62 69.5 68 an 56.0 3 70 b9 59.5 78 39 58.5 h 80 51 65.5 85 55 70.0 5 88 50 69.0 80 6h 72.0 6 78 50 6h.0 76 57 66.5 7 79 52 65.5 80 1.6 63 .0 8 77 63 70.0 85 ho 65-5 9 80 58 69.0 79 60 69.5 10 86 60 73.0 78 65 71.5 11 91 60 75.5 61 60 70.5 12 95 68 80.5 69 52 60.5 13 90 69 79.5 7h A9 61.5 1L. 71 52 61.5 82 sh 68.0 15 70 00 57.0 86 50 68.0 16 77 b3 60.0 88 51 69.5 17 53 L15 a-teo 92 & 77 e0 18 8h. b9 66.5 88 on 76.0 19 2 56 69.0 80 58 69.0 20 68 L6 57.0 75 51 63 .0 22 75 50 62.5 83 61 72.0 23 62 51 56.5 81 61 71.0 57 Temperature data continued 58 _ g 1961 1962 Date? 15.x . Min? Me an Max: Mini” 26 70 LA 57.0 81 59 25 71 50 60.5 85 56 26 82 L5 63.5 80 56 27 87 51 69.0 85 67 28 93 66 78.5 90 51 29 95 67 81.0 91 60 5o 96 67 81.5 90 67 July 1 92 63 77.5 83 59 2 85 69 76.0 77 58 3 75 57 66.0 76 57 L 77 hi) 62 05 80 5h. 5 86. 51 67.5 85 60 6 87 SL 70-5 93 57 7 77 . St. 65.5 91 61 8 77 63 65-0 89 67 9 80 1.8 611.0 78 58 10 80 51 65.5 82 50 11 68 59 73-5 96 63 12 89 59 7h.0 86. 61 13 75 57 66.0 81 53 lb. 80 59 69.5 82 63 15 87 65 75.0 80 52 16 80 60 70.0 85 55 17 83 55 69.0 85 56 18 88 59 73.5 88 52 19 , 86 62 76.0 at 55 20 57 6h 7505 76 6h 21 88 60 7L.0 79 61 22 86 69 77.5 72 56 25 86 éh 75.0 73 59 2h 87 66 75.5 80 50 25 77 62 69.5 80 58 26 90 59 714-5 76 (49 27 88 60 7h.0 81 65 28 82 62 72.0 66 52 29 87 65 76.0 78 61 5o 88 6h 76.0 82 62 31 81 66 72-5 79 59 August 1 67 61 66.0 BL Sb 2 81 65 72.0 8h. 67 3 66 58 72.0 87 56 L 82 61 71.5 89 63 5 71 61 66.0 88 62 6 76 62 69.0 72 61 7 81 53 67.0 89 59 8 85 60 72 e5 8 3 65 9 88 67 72.5 78 53 10 86 65 75 e5 62 (45 66.0 7005 75-5 78.5 67.5 67.0 Temperature data continued L951 __ _ 1962 We Max . 1a. . Mean — — _A Max . lain: Mean 11 85 68 76.5 83 £17 65.0 12 80 57 68.5 79 60 69.5 13 71 M. 57-5 66 58 62-0 m 86 50 68.0 78 56 67.0 15 85 60 72.5 81 1.5 62.0 16 8L. 56 70 .0 83 60 71 .5 17 811 51 67-5 76 67 61.5 18 88 52 70.0 85 1.1. 65.5 19 85 58 71 -5 90 56 73-0 20 70 51. 62.0 81 61. 72.5 21 72 1.9 60.5 8b. 59 71 -5 22 81 1.7 68.0 82 55 67.5 25 63 59 61.0 90 52 71.0 211 73 . 60 66.5 91.- 58 76.0 25 76 62 69.0 78 65 71.5 26 77 60 68 .5 ‘ 7o 65 66.5 27 85 61 72 .0 80 5 5 66.5 - 25 88 68 78 e0 90 56 73.0 29 86 6!. 75.0 89 60 711.5 50 90 62 76.0 90 58 711.0 31 89 60 711.5 8t 68 76.0 S eptenber 1 81 68 711.5 81 62 71.5 2 82 69 70.5 85 118 66.5 5 87 71 79e0 83 66 71405 t 86 68. 77.0 ab, 65 714.5 5 85 70 77.5 81 1.5 65.0 6 85 61. 711.5 73 31 52-0 7 86 61 73-5 77 35 56-0 8 87 59 73.0 78 115 61.5 9 89 60 711-5 76 61 68.5 10 91 68 79e9 77 a) 6805 11 89 71 80.0 73 115 59.0 12 75 65 68.0 87 1.9 68.0 15 86 66 76.0 87 62 711.5 11. 75 60 67.5 78 58 68.0 15 611 h? 55 .5 76 51 63 .5 16 73 146 59 05 78 50 ateO 17 75 1.6 60.5 76 59 67-5 18 76 115 60-5 69 87 58-0 19 78 L5 60.5 65 1.2 52.5 20 75 55 65.0 56 33 1.21.5 21 82 61 71.5 66 29 1.7.5 22 86 611 75.0 23 73 59 66-0 214 76 59 66.5 25 65 50 57-5 26 611 116 55.0 27 69 112 55.5 28 5h 39 1.6.5 29 61 50 05.5 "I11,1@1’111'171'11'1111117 ITS