71."! V. - H: * 2 W l’ (i CREME CAL 3915.”? {EN OF SEX EXPRESS!CN F‘s ‘ J§CEC§QUS CUCU5§ BF Hi * US$538 SAV’WM 2.. :; W} H ET?“ .EF’HON W8 :5 ‘ BENZC‘? fiWfifiZULE ((2 We" \F-s EVE. fi:ft}1§g~?{ GE E33; "‘5 3.: am: ‘2‘: 2:7 ::::: Ci? ..:2:§2-: " ::::~~ :22:~2 «222:2» Jrfin {‘3- eu-‘Jt mintbi u 2t. i§*fi $¢fi L I B R A R Y Michig’ '1 State University L~m ABSTRACT CHEMICAL REVERSION OF SEX EXPRESSION IN DIOECIOUS CUCUMBER (CUCUMIS SATIVUS L.) WITH ETHEPHON AND A BENZOTHIADIAZOLE By Jimmy Jude Augustine Foliar applications of the chemicals, ethephon and S-methyl-7-chloro-A-ethoxycarbonylmethoxy-Z, l, 3-benzo- thiadiazole (MCEB), were used to substantiate the role of ethylene in its association with femaleness in cucumber (Cucumis sativus L.). The concn of ethephon (an ethylene releasing compound) for maximum female flower induction and the stage of growth at time of application on an androecious (all-male) cucumber were determined. In this study, the best treatment combination for induction of pistillate flowers without marked inhibition of growth was 50 ppm ethephon applied at the 3 to h leaf stage. The effects of MCEB (a prOposed inhibitor of ethylene action) and ethephon on sex expression were observed in androecious and gynoecious phenotypes of cucmber. MCEB had no effect in the androecious line while ethephon (50 ppm) induced pitillate flowers. The effect of MCEB on ethephon treatment was a marked reduction in the number of ethylene- induced pistillate flowers except when there was a #8 hr period Jimmy Jude Augustine between applications of MCEB and ethephon. This suggests that after #8 hr MCEB appears to be inactive and the ethylene effect is not reversible with MCEB. In the gynoecious phenotype, MCEB (75 ppm) induced staminate flowers, ethephon had no effect, and the effect of MCEB on ethephon: treatment was staminate flower production (nonsignificant) at relatively high concn of MCEB (ISO ppm). These results further indicate the role of ethylene in female sex expression and of MCEB as an inhibitor of ethylene action. CHEMICAL REVERSION OF SEX EXPRESSION IN DIOECIOUS CUCUMBER (CUCUMIS SATIVUS L.) WITH ETHEPHON AND A BENZOTHIADIAZOLE By Jimmy Jude Augustine A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Horticulture 1972 ACKNOWLEDGMENTS The author wishes to express his appreciation to Dr. L. R. Baker for his help and guidance throughout this study and to Drs. H. M. Sell and R. H. Herner for their valuable suggestions. Appreciation is also expressed to Amchem Co., Ambler, Pa. for supplying the ethephon, ”Florel”, and to Thompson-Hayward for the MCEB supplied under code TH 624l. Guidance Committee: Sections l and II are segments of related thesis research information condensed into formats suited and intended for publication in the Journal of the American Society for Horticultural Science. TABLE OF CONTENTS Page ACKNOWLEDGMENTS . . . . . . . . . . . . . . . . . . . . . i LIST OF TABLES. . . . . . . . . . . . . . . . . . . . . . iv LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . v SECTION I. FEMALE FLOWER INDUCTION ON AN ALL MALE (ANDROECIOUS) CUCUMBER, CUCUMIS SATIVUS L. Abstract . . Introduction . . . . . Materials and Methods. . . . . . . . . Results and Discussion . . . . . . . . . . . Summary and Conclusion Literature Cited . . . . ll. EFFECTS OF A BENZOTHIADIAZOLE AND ETHEPHON ON SEX EXPRESSION OF CUCUMBER, CUCUMIS SATIVUS L. mmthd Abstract . . . . . . . . . . . . . . . . . . I9 Introduction . . . . . . . . . . . . . . . . 20 Materials and Methods. . . . . . . . . . . . 22 Results and Discussion . . . . . . . . . . . 23 Summary and Conclusion . . . . . . . . . . . 3] Literature Cited ... . . . . . . . . . . . . 32 Table Section I. Section I. LIST OF TABLES Effect of ethephon on sex expression of androecious line of cucumber . . Effect of ethephon and MCEB on an andro- ecious line of cucumber. . . . . . . . . Effect of MCEB on a gynoecious line of cucumber. . . . . . . . . . . . Effect of ethephon and MCEB on a gynoe- cious line of cucumber . . . . . . . Page 24 27 28 Figure Section I. LIST OF FIGURES The effect of ethephon on the number of pistillate nodes in an androecious line of cucumber. The effect of ethephon on the number of pistillate flowers in an androecious line of cucumber . . . . . . . The effect of ethephon on the percent pistillate flowers in an androecious line of cucumber Page ll lh SECTION I FEMALE FLOWER INDUCTION ON AN ALL-MALE (ANDROECIOUS) CUCUMBER, CUCUMIS SATIVUS L. ABSTRACT Ethephon, an ethylene releasing compound, when applied as a foliar spray causes USSR I, an androecious line of Cucumis sativus L., to produce pistillate flowers. The degree of conversion depends on the concn of ethephon and the stage of growth at time of application. In this study, concn of 50 ppm applied at the 3 to 4 leaf stage was observed to be the best treatment for optimum induction of pistillate flowers without marked inhibition of growth. INTRODUCTION Kubiciki (l6) reported an all-male, androecious pheno- type of cucumber (Cucumis sativus L.) controlled by a single recessive gene, a, Production of l00% gynoecious hybrid cucumber seed would be simplified by the use of such an androecious pollen parent rather than present monoecious (S) or proposed hermaphrodite (24) parents. However, before the androecious phenotype can be used, a method must be deveIOped to maintain and to increase the number of seeds of this non-fruiting type; that is, pistillate flowers for fruit and seed production. Plant growth regulators are widely used to alter sex expression in cucumbers (2, 7, l3, I9, 20, 23, 26). Studies suggest that an endogenous auxin-gibberellin balance deter- mines this sex expression (l, 2, 8, l0, ll, 22, 23). Modifi- cation of this balance in favor of auxin is associated with femaleness (7, 9, l2, l4, l7); conversely, an increase in gibberellin is associated with maleness (l0, ll, 12, 22, 23, 26). Rudich g£_§l. (27) suggests that the observed effects of auxin on sex expression result from auxin-induced ethylene formation and recently ethylene has been established as an endogenous regulator of sex expression of Cucumis melo L. (3). Ethephon, an ethylene releasing compound (6, 29), has been used to enhance femaleness in cucurbits (A, IS, 18, 25, 27, 28). Therefore, the objective of this study was to chemically induce pistillate flower formation in an androecious (all-male) line of cucumber. MATERIALS AND METHODS Two similar experiments were conducted October 15, l97l to December l3, l97l and December I, l97l to January 30, I972. Seed of the androecious line, USSR l, was obtained from Dr. E. T. Mescherov, All-Union Institute of Plant Industry, Leningrad, USSR. The seeds were sown in soil in 6.25 cm peat pots and grown in a greenhouse with supplemental fluores- cent lighting at 24° C during the night (IO hr) and 290 C during the day (IA hr). Plants were transplanted to IE cm clay pots after 12 days with four single plant replicates in a completely randomized factorial design. They were treated with a freshly prepared aqueous solution of 0, 6, 25, 50, lOO, and 200 ppm ethephon at the lst, 2nd, 3rd, and 4th true leaf stage. The ethephon solution was applied to the foliage with an atomizer until run-off. Flowers developed on the main stem were classified for sex expression through the 20th node; height was measured up to the same point. Statistical analysis of the data was done using Tukey's Multiple Comparison Test. RESULTS AND DISCUSSION Significant differences for all of the variables were observed between ethephon concn within growth stages (Table l). The control (0 ppm) and 6 ppm did not produce pistillate flowers; the concn of 6 ppm being inadequate for pistillate flower induction, regardless of stage of application. Signi- ficant differences between stage of inductive concn (25, 50, ICC, and 200 ppm) were observed for five of the six observed variables; viz., number of pistillate nodes (except 200 ppm), number of pistillate flowers (except ICC and 200 ppm), number of staminate flowers, percent pistillate flowers, and plant height. Node number of the lst pistillate flower generally decreased within a stage with the increase in inductive concn, with the exception of ICC and 200 ppm which caused blind nodes or abortion of the floral buds at the lower nodes. Plants sprayed at the 3 and A true leaf stage produced pistillate flowers, on the average, lower than the second node indicating that the ”labile period”, or stage of development sensitive to modifying factors (l3) such as chemicals, had not been passed. This might be caused by the pistil being differentiated last in the floral primordia (2l). .0000 c00_cmanu m_a_u_:z m_>mx30 >0 .m>o_ N. 0:» pm >.ucmu_0_cm_m 0000.6 .o: 6.6 000000. coeeou £0_3 0:53.00 c_Lu_3 mammzw _ 0.00 00 0.00 00 0.0. 000 0.0. 000 0... 000 0.. 000 .00 0.00 00 0.00 00 0.0. 000 0.0. 0000 0.0. 000 0.0 00. .00 0.00 0 0.00 0 0... 0.0.00 00 0.0. 000 0.. 00 00000 0.00 000 0..0 000 0.00 0000 0.0. 000 0.0 00 0.0 00 000 0.00 0 0.0 00 0.00. 0 0.0 0 0.0 0 0.0 0 0 0.0.. 0 0.0 0 0.00. 0 0.0 0 0.0 0 0.0 0 00: 00 0.00 00 0.00 000 0.00 0000 0.0. 000 0.0. 00 ..0 000 .000 0.00 00 0.00 0000 0.00 000 0.0. 000 0.0. 000 0.. 00. .000 0.00 00 ..00 00 0.0. 00 0.00 0 0.0. 000 0.0 00 00000 0.00 000 0.00 000 0.00 0000 0.0. 000 0... 00 0.0 00 000 0.00 0 0.0 00 0.00 0 0.0 0 0.0 0 0.0 0 00 0.00. 0 0.0 0 0.00. 0 0.0 0 0.0 0 0.0 0 0.0 .00 ...0 000 ..00 000 0.00 0000 0.0. 000 0.0 0 ..0 000 00000 0.00 00 0.00 0000 0.00 000 0.0. 0000 0.0. 000 0.. 00. 000000 ..00 000 0.00 00 0.00 0000 0.0. 000 0... 000 0.0 00 00000 0.00 000 0.0. 000 0.00 0000 0.0 000 0.0 00 0.0 00 00 0.00. 0 0.0 0 0.0.. 0 0.0 0 0.0 0 0.0 0 0 0.0.. 0 0.0 0 0.00. 0 0.0 0 0.0 0 0.0 0 000 0000 0.00 000 0.0. 000 0.0: 000 ..0. 000 0.0 00 ..0 000 00000 ..00 000 0.0. 000 ..00 000 0... 00 0.0 000 0.. 00. 0000 0.00 00 0.0 000 0.00 000 0.: 00 0.: 000 0.. 00 00000 0.00 0 0.. 000 0.00, 00 0.. 0 0.. 00 ... 00 0 0.0.. 0 0.0 0 0.0.. 0 0.0 0 0.0 0 0.0 0 00 0.00. 0 0.0 0 0:00. 0 0.0 0 0.0 0 0.0 0 00. mcmzo_m AEUV mcozo_m 00630—0 mcozo_m oum___um_a 0030—0 AEQQV moo: :uON ou mum.__um_m mumc.Emum oum___um_a ;u_3 mono: oum___um_a cucou mmmum u;m_m; 0cm.¢ Hemogom mo .02 mo .02 mo .02 um. 00 0602 cosmosum mood ilii ifll Ili IIIIP ~.LonE:u:u 00 o:.. m:o_ooocncm mo co.mmmgaxm xmm co cozamzuo mo uoomwm ._ m_QMF The number of nodes with pistillate flowers increased between stages for each concn (Figure l) with the exception of a decrease in number at the 4 leaf stage when using concn of 25, 50, and IOO ppm. The response within stages with increasing concn is a bell shaped curve with the exception of the l leaf stage which gives a linear increase. The greatest number of nodes with pistillate flowers (l6.3) was obtained 4 with 50 ppm applied at the 3 leaf stage (indicated by the arrow). Pistillate flowers developed through the l6th node. Since ethephon is quickly broken down ifl_vivg (29) it is unlikely that ethephon was available to induce changes in initiation and/or differentiation of primordia for more than a few days. A continuous supply of ethephon was probably not present from the time of application to the time of production of the l6th node; hence, several initiating and/or differentiating primordia must have been present at the 3 leaf stage. The number of pistillate flowers increased with each stage for each concn of ethephon (Figure 2). A bell shaped response was obtained within each stage with increasing concn. The greatest number of pistillate flowers (20.8) was induced with 50 ppm applied at the 4 leaf stage (indicated by the arrow). The higher concn, lOO and 200 ppm, caused blind nodes and, therefore, fewer total pistillate flowers. Conversely, a concomitant decrease in the total number of staminate flowers between each stage for each concn of ethephon was observed. FigUre l. The effect of ethephon on the number of pistillate nodes in an androecious line of cucumber. 5 e d O N .0... no T .m m I 0. ...0 ... ... P .o I h. .. 0. o I ... m. .—v 4. pl: 5.2.. .d ‘ . &.r Nam 80! .< o o .04 )0, m mm 00 .00 ~00 m0zmuzo: 8:333:03 A 203 V lO Figure 2. The effect of ethephon on the number of pistillate flowers in an androecious line of cucumber. 11 Flowers 0 (05 '3 (iii-u- m G N we l .. .. .. .. .ou. .... f _O l 0. 0 ll 0. N H- 4. $.24 a w 009 a, I an o N <9 9 0 .2. .4 mm 00 _00 ~00 qumuzo: 00:00:03.8: A 003. l2 There was a general decrease within each stage with increased concn with the exception of 50 ppm which gave the greatest reduction when applied at the 3 (15.9) and A (ll.8) leaf stage. This decrease in staminate flower numbers resulting from ethephon treatment agrees with Rudich g£_gl. (27). An increase in percent pistillate flowers was seen between stages for each concn of ethephon (Figure 3) except 25 ppm applied at the A leaf stage. Generally there is a bell shaped response within each stage with an increase in concn with the exception of the 1 leaf stage which exhibited a linear increase over all concn. The greatest percent of pistillate flowers was obtained with 50 ppm applied at the 3 (56.l%) and A leaf (63.9%) stages. Plant height decreases with the increase in stage of growth for each ethephon concn and within stages with increase in concn. So, the greater the concn and the later it was applied the greater the inhibition of growth. Increased deveIOpment of secondary laterals was also noted with applications of 200 ppm ethephon. l3 Figure 3. The effect of ethephon on the percent pistillate flowers in an androecious line of cucumber (wad) uououuaouoo uoudauia OOI 09 93 003 .14 % PistIllate Flowers 01-50le —N 0000000 ll lllllllTlIT .i. N 3 Q <90 04 " 3. 5)- ‘2? 9 SUMMARY AND CONCLUSION The optimum concn of ethephon for maximum pistillate flower production was 50 ppm. The stage of application was critical; the application of 50 ppm at the 3 to A leaf stage resulted in twice the pistillate flower production than at the 2 leaf stage. Application in the 3 leaf stage gave less inhibition of growth, but in the A leaf stage resulted in a greater percentage of pistillate flowers. In conclusion, ethephon, an ethylene releasing compound, caused a reversion in sex expression from staminate to pistillate flowers in an androecious line of cucumber. Whether this effect was related to auxin, gibberellin, or ethylene, per se, is not known. l5 I. IO. ll. LITERATURE CITED Atsmon, D.,A. Lang, and E. N. Light. I968. Contents and recovery of gibberellins in monoecious and gynoecious cucumber plants. Plant Physiol. A3z806-8l0. Bukovac, M. J. and S. H. Wittwer. l96l. Gibberellin modification of sex expression in Cucumis sativus L. Advan. Chem. Ser. 28:80-88. Byers, R. E., L. R. Baker, H. M. Sell, R. C. Herner, and D. R. Dilley. I972. Ethylene: A natural regulator of sex expression of Cucumis melo L. Proc. Nat. Acad. Sci. (US) 69(3):7l7-720. Cantliffe, D. J. and R. W. Robinson. I97l. Res onse of cucumber to soil application of (2-chloroethyl) phosphonic acid. 'HortScience 6(A):336-337. Connor, L. J. and E. C. Martin. l97l. Staminate-pistillate flower ratio best suited to the production of gynoecious hybrid cucumbers for machine harvest. Hort- " Science 6(A):337-339. Cooke, A. R. and D. J. Randall. I968. Induction of flowering by 2-haloethanephosphonic acid. Nature 2l8:97A. GaIUn, E. I959. Effects of gibberellic acid and naphthaleneacetic acid on sex expression and some morphological characters in the cucumber plant. Phyton (Buenos Aires) I3:l-8. : Y- Jung, BDd A. Lang. I963. Morphogenesis of floral buds of cucumber ifl_vitro. Nature I9A;596-598, , S. Izhar, and D. Atsmon. I965. Determination of relative auxin content in hermaphrodite and andro- monoecious Cucumis sativus L. Plant Physiol. AO:32I-326. Hayashi, F., D. Boerner, C. E. Peterson and H. M. Sell. I97]. The relative activity of gibberellin in seedlings of gynoeciousand monoecious cucumber (Qucgmj§_sativg§). Phytochemistry I0:59-62. Hemphill, D. 0., Jr., L. R. Baker and H. M. Sell. I972. Different sex phenotypes of Cucumis sativus L. and C. melo L. and their endogenous gibberellin activity. Euphytica 2I:285-29I. I6 I2. l3. IA. IS. I6. I7. I8. I9. 20. 2I. 22. 23. I7 HesIOp-Harrison, J. I957. The experimental modification of sex expression in flowering plants. Biol. Re. (Cambridge Phil. Soc.) 32:38-90. and Y. Hesl0p-Harrison. I957. Studies on flowerTng pTant growth and organogenesis. II. The modification of sex in Cannabis sativa by carbon monoxide. Proc. Roy. Soc. (Edinburgh) B66:A2A-A3A. Ito, H. and T. Saito. I956. Factors responsible for the sex expression of Japanese cucumber. III. The role of auxin on the lant rowth and sex expression. J. Hort. Assoc. (Japan) 27(I :IOI-IIO. Karchi, Z. and A. Govers. I972. Effects of ethephon on vegetative and flowering behavior in cucumber (Cucumis sativus L.). J. Am.° ,Soc. Hort. Sci. 97(3): 357-365. Kubiciki, B. I969. Investigations on sex determination in cucumber (Cucumis sativus L.) VI. Androecism. Genetica Polonica‘T0:87-99. Laibach, F. and F. J. Kribben. I957. Der Einfluss von Wuchsstoff auf die Bildung mannlicher und weiblicher Bluten bei einer monezischen Pflanze. Ber. Deut. Bot. Ges. 62:53-55.‘ McMurray, A. I. and C. H. Miller. I968. The effect of 2-chloroethaneph05phonic acid (ethrel) on the sex expression and yield of Cucumis sativus L. J. Am. Soc. Hort. Sci. 9A:A00-A02. Mitchell, W. D. and S. H. Wittwer. I962. Chemical regulation of sex expression and vegetative growth in Cucumis sativus L. Science 136:880—88I. Naugoljnyh, V. N. I955. Changing the sex character in cucumber to increase their productivity. Botan. Zh. AO:7I5-7I9. Nitsch, J. P. I965. Physiology of flower and fruit development. EncyI. Plant Physiol. l5(I):lS37-I6A7. Peterson, C. E. and L. Anhder. I960. Induction of Staminate flowers on gynoecious cucumbers with gibberellin A3. Science l3I:I673-I67A. Pike, L. M. and C. E. Peterson. I969. Gibberellin Au/A7 for induction of staminate flowers on the gynoecious cucumber (Cucumis sativus L.) Euphytita I8zl06~I09. 2A. 25. 26. 27. 28. 29. I8 and W. A. Muldey. I97I. Use of hermaphrodite cucumber lines in deveIoBment of gynoecious hybrids. HortScience 6(A):339-3 0. Robinson, R. W. and S. Shannon, M. D. deLaGuardia. I969. Re ulation of sex expression in the cucumber. BioScience I9?2):lAl-IA2. Rodriquiez, B. P. and V. N. Lambeth. I972. Synergism and antagonism of gibberellin and growth inhibitors on growth and sex expression in cucumber. J. Am. Soc. Hort. Sci. 97(1):90-92. Rudich, J. A.,H. Halevy, and N. Kedar. I969. Increase in femaleness of three cucurbits by treatment with Ethrel, an ethylene releasing compound. Planta (Berl.) 86:69'76. , N. Kedar, A. H. Halevy. I970. Changed sex expression and possibilities for FI-hybrid seed production in some cucurbits by ap lication of Ethrel and Alar (3-995). Euphytica I9: 7-53. Warner, H. L. and A. C. Leopold. I969. Ethylene evolution from 2-chloroethylphosphonic acid. Plant Physiol. A2:I56-I58. SECTION II EFFECTS OF A BENZOTHIADIAZOLE AND ETHEPHON ON SEX EXPRESSION OF CUCUMBER, CUCUMIS SATIVUS L. ABSTRACT The effects of 5-methyl-7-chloro-A-ethoxycarbonyl- methoxy-Z, l, 3-benzothiadiazole (MCEB), a proposed inhibitor of ethylene action, and ethephon (an ethylene releasing compound) on sex expression were observed in androecious and gynoecious phenotypes of cucumber (Cucumis sativus L.). MCEB had no effect in the androecious line while ethephon (50 ppm) induced pistillate flowers. The effect of MCEB on ethephon treatment was a marked reduction in the number of ethylene-induced pistillate flowers except when there was a A8 hr period between applications of MCEB and ethephon. This suggests that after A8 hr the MCEB is inactive and the ethylene effect is not reversible with MCEB. In the gynoecious phenotype, MCEB (75 ppm) induced staminate flowers, ethephon had no effect, and the effect of MCEB on ethephon treatment was staminate flower production (nonsignificant) at relatively high concn of MCEB (ISO ppm). These results further substantiate the role of ethylene in female sex expression and of MCEB as an inhibitor of ethylene action. I9 INTRODUCTION Ethylene per se has been associated with increased femaleness in cucurbits (A, 5). Thus, endogenous levels of ethylene are higher in the gynoecious phenotype of cucumber than in the monoecious (A, 5) and the exogenous application of ethephon, an ethylene releasing compound, induces pistillate flowers on an androecious (all-male) phenotype of cucumber (I). Ethylene was demonstrated to be a natural regulator of sex expression by growing a gynoecious phenotype of muskmelon under hypobaric ventilation for removal of endogenous gases by diffusion, with a resulting induction of perfect flowers (A). Another method for the study of ethylene in sex expression was the chemical inhibition of ethylene action. The chemical, 5-methyl-7-chIoro-A-ethoxycarbonylmethoxy-Z, l, 3-benzo- thiadiazole (MCEB), was reported to be an apparent inhibitor of ethylene action when foliar applications on tomato plants prevented 2,A-D induced epinasty (6); epinasty presumably caused by ethylene production (2). MCEB has also been reported to induce perfect flowers on gynoecious muskmelon (3) and staminate and perfect flowers on gynoecious cucumber (A). This study attempted to determine if MCEB inhibits ethylene action in sex expression of cucumber by observing the effects of ethephon and MCEB on androecious (all—male) 20 2I and gynoecious (all-female) phenotypes and to determine the concn of MCEB necessary for induction of staminate flowers on gynoecious cucmber. MATERIALS AND METHODS Seed of USSR I, an androecious line obtained from Dr. E. T. Mescherov, All-Union Institute of Plant Industry, Leningrad, USSR, and 7l3-5, a gynoecious line, were planted March 2A, I972. The seeds were sown in soil in 6.25 cm peat pots and grown in a greenhouse with supplemental fluorescent lighting at 2A0 C during the night (I0 hr) and 290 C during the day (lA hr). Plants were tranSplanted to IE cm clay pots after I5 days with two single plant replicates in a completely randomized factorial design. They were treated at the 3 to A leaf stage (I) with freshly prepared solutions of 0 and 50 ppm ethephon and 0, 25, 75, ISO, and 300 ppm MCEB. Two orders of application (ethephon then MCEB and the reverse) at each concn were sprayed 0, 3, l2, and A8 hr apart. Both materials were applied as aqueous solutions to the foliage with an atomizer until run-off. Flowers were classified for sex expression through the 20th node and height was also measured through the 20th node. Statistical analysis of the data was analyzed using Tukey's Multiple Comparison Test. No signi- ficant differences existed between order of application of ethephon and MCEB; therefore, the data were presented as means of four replicates in Tables I and 3 with the mean for 0 ppm ethephon representing one random observation for each time interval. 22 RESULTS AND DISCUSSION Androecious phenotype. As expected, MCEB applied in the absence of ethephon resulted in no significant differences for any of the variables observed; viz., number of pistillate flowers, number of staminate flowers, percent pistillate flowers, and plant height (Table l). Ethephon (50 ppm) applied in the absence of MCEB at O, 3, I2, and A8 hr intervals induced I8.5, l9.6, I7.A, and l8.3 pistillate flowers per 20 nodes, respectively. There were 22.8, 2A.9, 22.l, and 2A.A percent pistillate flowers for 0, 3, I2, and A8 hr intervals, respectively. For these time intervals and this concn of ethephon, there were no significant differences in either femaleness or plant height. The effect of MCEB (5, 25, 75, I50, and 300 ppm) on ethephon treatment (50 ppm) was observed as a marked reduction in the number of induced pistillate flowers and percent pistillate flowers for the first three time intervals (0, 3, and I2 hr) but not in the fourth (A8 hr). For a given time interval there were no significant differences observed for different concn of MCEB; that is, all concn of MCEB were equally effective in negating the action of ethephon (ethylene). MCEB reversed ethephon (ethylene) action with the lower concn at the 0 and 3 hr intervals. However, at the I2 hr. interval almost complete reversal occurred regardless of the MCEB concn. When A8 hr was the time interval between 23 2A p o o m 0.0 p o o. m 0.0 oom opm m.m0 o m.o opm m.:m m 0.0 om. onm 0.0m m m.o onm m.0o_ o m.o m0 pm ..JO. mp m.o onm o.-_ mp 0.. mm m m.._. m 0.0 opm m.mo_ m 0.0 m 0m ..mo. poem ..NN poem :._0 0m :.0. o m. po m.m_ mponm N.m po m.0N mp w.~ oom poem ..Nm mponm ..m poem m.om mpo m.: om. poem m.om opo ..m opm 0.:0. mpo m.m m0 m m.... mp m.. onm m.oo_ mp m.. mN mm 0.00. m w.o pm m.oN. mp 0.. m 0m N.0o. m m.:~ poem N.mm m 0.m o m poem m.mm ponm ~.: poem m.0m mp m.~ oom onm 0.0m mponm m.0 onm m.mm mpo m.0 om. opm 0.4m mpon 0.m onm o.mm opo m.m m0 onm m.mm mp N._ opm o.mm mp 0.. mm nm 0.0.. m 0.0 opm 0.00. m 0.0 m pm o.mo_ opm m.NN poem m.~m mm m.@ o 0 0m onm m.om m 0.0 opm m.0w o 0.0 oom onm 0.mm m 0.0 m m.-_ o 0.0 Om. onm m.mm m 0.0 m m.m~_ m 0.0 m0 m m.___ m 0.0 nm 0.0.. o 0.0 mN m :..~_ m 0.0 pm o.m_. m 0.0 m m ..0_. m 0.0 pm 0.o~_ o 0.0 o m:-o o mEov mcmzo_m mLmzo_m 00030.0 08am. A800. 0: .0; mom__.om_a oumc.Emum mom___om_a cocoo Aesv cocoo yam—a ocmoemm mo .02 mo .02 mmuz 05.0 cozamcom ~.LmnE:o:o 00 o:.. mso.omochm cm co mmuz pcm cocamcom mo uommwm ._ m_nmp 25 .ommh c00_cmanu m.a_o_:z m_>mx:k >0 .m>m. N. 050 om >.ocmo_w_cm_m Lemm_p o0: p_p mLmoom_ :oEEoo £o_3 mcE:_oo c_;o_3 memo:q pop ..0: opm m.mw po m.om mpon m.m 00m onm ...“ mponm m.:_ ponm m.mo poem m.__ om. onm m.:0 onm m.mu popm m.~: onm m.m_ mm pm 0.:m mponm m.m onm m.0m mpon m.m mm pm m.mm poem ..NN ponm m.mm pm m.0_ m cm m.mo_ nm :.:N poem w.0m pm m.m_ o m: Eov mcmzo_m mLm30_m mcmzo_m AEQQV AEQQV u; .o; mom.._ommd oomc_Emom mom___om.Q cocoo “cc. cocoo yam—m ucmocmm 00 .02 mo .02 mwuz mE_h cozamzum .ocoo ... m_nmh 26 applications, MCEB appeared to be inactive when applied prior to ethephon and when MCEB was applied after ethephon, MCEB did not appear to reverse the ethephon effect. Means of the number of staminate flowers were not signifi- cantly different with applications at different time intervals or at different concn of MCEB, except the phytotoxic concn of 300 ppm. The trend was a greater reversion to staminate flowers with S and 25 ppm MCEB. There were no plant height differences between time intervals of application, but a linear decrease resulted with increasing concn, 300 ppm being phytotoxic, sometime causing death. Gynoecious phenotype. In the absence of ethephon, MCEB (75 ppm) induced a significant number of staminate flowers (l6.8) in the gynoecious line of cucumber over all time intervals observed (Table 2). This caused a significant reduction in the percent (53.7) of pistillate flowers. At 300 ppm MCEB a significant reduction in number of pistillate flowers (8.5) was caused by a significant reduction in plant height (55.A%). As expected, ethephon (50 ppm) had no effect on any of the variables observed (Table 3). Overall, few significant differences were observed with MCEB on ethephon (50 ppm) treatment. The only significant effect of MCEB on ethephon treatments on number of pistillate flowers was a reduction using 300 ppm with A8 hr between applications. This was attributed to a significant reduction 27 Table 2. Effect of MCEB on a gynoecious line of cucumber.Z MCEB No. of No. of Percent Plant concn pistillate staminate pistillate hei ht (ppm) flowers flowers flowers (cm 0 I8.I aY 0.0 b IO0.0 a 97.8 a 5 l7.8 a 0.0 b I00.0 a 89.7 a 25 20.0 a 2.0 b 90.9 a 88.A a 75 l9.5 a l6.8 a 53.7 b 80.0 a ISO 15.3 ab 3.0 b 83.6 a 52.8 b 300 8.5 b 0.3 b 96.6 a l6.0 b yMeans of four replicates of four plants. zMeans within columns with common letters did not differ significantly at the I% level by Tukey's Multiple Comparison Test. 28 mpo 0.00 pm 0.0m m.o opm o.N. OOm ponm m.mm pm m.mm m.: onm m..~ Om. pm ..mm pm :.0m 0.: m m.m~ m0 pm m.mm pm 0.0m m.o opm o.m. mN m o..o. m 0.00. 0.0 opm m.0. m cm :.mm m 0.00. 0.0 opm ..0. o N. mpon :..: .pm o.mm m.~ opm m.:. 00m oponm 0.0m pm m.om. m.. onm o.m. om. poem 0.00 pm N.om m.o onm m.om m0 pm n.mm pm m.mm m.o onm m.m. mN m m.om m 9.00. 0.0 onm 0.0. m m m.Nm m 0.00. 0.0 opm N.@. o m o m.m. m 0.00. 0.0 o m.m 00m onm n.m0 pm ..mm o.m. opm m.o~ 0m. onm w.ow m 0.00. 0.0 onm m.m. mm onm o.~w pm m.00 m.: onm m.0. mm m 0.:m m 0.00. 0.0 onm m.@. m pm m.mm m 0.00. 0.0 onm m.0. o 0 0m mpon ..o: pm 0.:m m.o on w.m oom oponm m.~0 pm w.~w ..m opm m.:. Om. onm 0.00 0 :.00 0.0. o0m 0.00 00 pm ..mm pm 0.0m ~.~ onm 0.m. mm pm :.mm m 0.00. 0.0 onm :.m. m m m.mm m 0.00. 0.0 onm w.m. 0 male 0 Meo. mcmzo.m 00030.0 00030.0 .Eaa. .Eaa. o; .m: mom.._um.a momc.Emow mum...om.a cocoo ALL. cocoo ocm.¢ ocmocmm .02 mo .02 mmuz mE.p cozamcou N.cmnE:o3o 00 m:.. 0:0.oooc>m m :0 mmuz pcm cosamzum Lo oommmm .m m.pmh 29 .ummh cem.LmQE00 m.a_u.:z m.>mxsh >3 .m>m. N. mzu um >.ucmo...cm.m mem.v “0: 0.0 mgmuum. coEEou 50.3 mcE:.ou c.5u.3 mcmmzw m0 m.wm m 0.00. on 00m muonm ..00 am m.m0 gm 0m. mvunm ..Nm pm N.Nm m mm onm m..m am N.mm onm mm m m.00. am 0.00 unm m cm N.0m m 0.00. unm 0 m: Meu. mgmzo.. mLm30.. mLm30.m .Eaa. .800. u; .m; mum.._um_a mumc.Empm mum...um.a cucou ALL. cocoo 0cm.m ucmogmm .0 .oz .0 .oz 000: ME.F cozamcum |l I'll .ucou .m w.nmh 30 in growth. The gynoecious cucmber has a high level of endogenous ethylene (h, S) and the biologically active concn of MCEB needed for inhibition of ethylene may be phytotoxic for other plant processes and growth. Staminate flower production (nonsignificant) occurred at relatively higher concn of MCEB (150 ppm) than when MCEB (75 ppm) was applied in the absence of ethephon. A linear decrease in plant height was observed for each time interval but no significant differences existed between time intervals. SUMMARY AND CONCLUSION In the androecious line of cucumber, MCEB in the absence of ethephon had no effect on sex expression. Conversely, ethephon (50 ppm) in the absence of MCEB induced pistillate flowers. When MCEB was added a marked reduction in the number of ethephon-induced pistillate flowers resulted. In the gynoecious phenotype, MCEB (75 ppm) in the absence of ethephon induced staminate flowers, ethephon in the absence of MCEB had no effect, and the effect of MCEB on ethephon treatment was staminate flower production (nonsignificant) at relatively high concn of MCEB (lSO ppm). In conclusion, MCEB and ethephon treatments demonstrated the inhibitory effect of MCEB on ethylene action, which in turn substantiates the role of ethylene in female sex expression in cucumber. 3] LITERATURE CITED Augustine, J. J., L. R. Baker, and H. M. Sell. Female flower induction on an all-male (androecious) cucumber, Cucumis sativus L. (In preparation). Burg, S. P. and E. A. Burg. I968. Role of ethylene in fruit ripening. Plant Physiol. 37:l79-l89. Byers, R. E., L. R. Baker, 0. R. Dilley, and H. M. Sell. l972. Chemical induction of perfect flowers on a gynoecious line of muskmelon, Cucumis melo L. Hort- Science 7(3):283-28h. Byers, R. E., L. R. Baker, H. M. Sell, R. C. Herner, and D. R. Dilley. l972. Ethylene: A natural regulator of sex expression of Cucumis melo L. Proc. Nat. Acad. Sci. (u.s.) 69(3):7l7-720. Rudich, J. A., H. Halevy, and N. Kedar. l972. Ethylene evolution from cucumber plants as related to sex expression. Plant Physiol. h9:998-999. Van Daalen, J. J. and J. Daams. I970. Substituted aldoxy-carbonyl-methoxy-2, l, 3-benzothiadiazoles. A new group of synthetic growth regulators. Naturwiss. 8:395. 32 MICHIGAN STATE UNIVERSITY Ll RARIES 3 1193 03082 4902