EFFECT OF PLANT GROWTH REGULATORS ON REVERSAL OF REPRODUCTIVE CHARACTER IN SECHIUM EDULE (L.) LEADING TO CROP IMPROVEMENT

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1 Indian J. Agric. Res.., 47 (6) : , 2013 AGRICULTURAL RESEARCH COMMUNICATION CENTRE / indianjournals.com EFFECT OF PLANT GROWTH REGULATORS ON REVERSAL OF REPRODUCTIVE CHARACTER IN SECHIUM EDULE (L.) LEADING TO CROP IMPROVEMENT Neelanjana Baruah * and C.M. Sarma 1 Department of Botany Birjhora Mahavidyalaya, Bongaigaon , Assam, India Received: Accepted: ABSTRACT An experiment was conducted to study the effect of plant growth substances on reversal of reproductive character in Sechium edule L. Foliar spray of ethrel at 50, 100, 250, 500 and 1000 µg/ml was made to seedlings of S.edule. The spray of ethrel significantly increased female flowers over male which led to increase in fruit number. Number of female flowers gradually increased and ethrel at 250µg/ml was the optimal concentration recording 39.7 number of female flowers as against 13.2 at control. On the contrary the number of male flower at 250 µg/ml was 30.7 as against 15.5 at control. CCC was also applied at 50, 100, 250, 500 and 1000 µg/ml to S.edule (L.) The femaleness was increased and 250 µg/ml of CCC emerged as optimum concentration recording 26.5 number of female flower against 14.9 at control. At the respective concentration the number of male flower was 13.1 against 16.3 at control. Thus excessive vegetative growth in S.edule L was reduced by both ethrel and CCC. The experiment established reversal of male flower to female leading to increase in number of fruits. Key words: CCC, Ethrel, Sechium edule (L.), Sex reverse. NTRODUCTION The effect of spraying and pre-sowing treatment of seeds with plant hormone solutions on shifts in sex expressions have been investigated by most authors. The treatment of cucumber plants with auxin greatly increases the ratio of female to male flowers (Laibach and Kribben, 1950 a, b). It was discovered that auxin increases the production of ethylene the actual sex modifying agent by the plants. It was reported that auxin treatment of hemp, increased the number of female individuals (Heslop- H arrison,1956,1957). Auxin effects on sex expression were also found in maize (Molotkovsky, 1960, 1968). Later it was shown in cucumber (Heslop-Harrison, 1963) and hemp (Mohan Ram and Jaiswal, 1970) that sparying with ethrel, a compound releasing ethylene changes sex expression in the female direction, whereas in contrast treatment of hemp with gibberellic acid caused a change in the male direction (Atal, 1959, 1963; Kohler, 1964 ; Khryanin, 1969). Growth retardants have been shown to increase femaleness in many cases (Sadhu * Corresponding author s neelanjanabaruah@gmail.com 1 BotanyDepartment, Gawhati University, Jorhat, Assam, India. and Das, 1978). Early flowering due to growth retardants was also reported by Stuart (1961) and Cathey (1964). Plant growth regulators readily affect sex expression in cucumber besides other factors such as temperature, day length, nutrition and chemicals (Heslop-Harrisson 1957,1963). There are more reports of numerous experiments which have been done with the application of growth retarding chemicals. Scientists are now concentrating their field of works on higher productivity of agricultural and horticultural crops using growth retardants. Extensive works with conventional retardants like CCC, SADH, AMO 1618, 2, 4-DNC, Phosphon-D etc. have already been done. Dixit et al (2001) working on watermelon reported that different growth regulators markedly suppressed the number of male flowers and enhanced the female flowers over control treatment. It was reported by Saimbhi, and Thakur (1973) that in Citrullus vulgaris var. fistulosus the application of TIBA 25 and 50 mg/l and CCC 500mg/l did not affect the staminate flower production but increased the

2 518 INDIAN JOURNAL OF AGRICULTURAL RESEARCH percent femaleness. The CEPA (2 chloroethyl phosphonic acid) decreased while both TIBA and 50mg/l and CCC 500mg/l increased the number of fruits per plant and the yield. The demand for vegetable crop has been increasing day by day. Squash ( Sechium edule L ) belonging to the family Cucurbitaceae is popular vegetable of North Eastern region of India. This crop can be cultivated successfully both on plains and hilly slopes. The crop grows well on a wide range of soil and can tolerate a wide range of rainfall. The agro climatic condition of Assam is favourable for cultivation of various plants under cucurbitaceae family. Cucurbitaceous members bear unisexual monoecious flowers having the number of male flower is always more than the female ones. This is the reason behind in production of less number of fruits in members of cucurbitaceae. The application of plant growth regulators proved significant in producing greater number of fruits in comparison to untreated ones. Increase the number of female flowers per plant increases the production of the crop. Therefore, it was considered necessary to study the effect of plant growth regulators on reversal of sex which leads to crop improvement. MATERIALS AND METHODS A field experiment was conducted at Bongaigaon for three consecutive years on a sandy loam soil of ph 5.10, 1.84 p.c organic matters. The experiment was carried out in randomized block design (RBD) with six treatments of PGRs including an untreated control. Each treatment was replicated three times. Ethrel was applied at five concentrations namely 50 µg/ml, 100 µg/ml, 250 µg/ml, 500 µg/ml, 1000 µg/ml and one control (distl.water treatment). Similarly CCC was also made to seedlings of squash at 50, 100, 250, 500 and 1000 µg/ml by foliar spraying of the solutions. The spray was done twice at 30 days after sowing and again after 7 days of first application. At the flowering stage the number of male and female flowers was recorded. RESULTS AND DISCUSSION Ethrel treated plants showed positive response towards sex reversal. Ethrel proved to be very effective in increasing the number of female flowers in S.edule L. After first, second and third year application at the optimum concentration (50 µg/ml) of ethrel the numbers of male flower was recorded as 36.7 as against 15.5 at control (Table 1). After application of ethrel the numbers of male flower was recorded as 36.7, 33.2, 30.7, 20.0 and 11.6 at 50, 100, 250, 500 and 1000 µg/ml respectively. At higher concentration of ethrel the number of male flower gradually decreased to 33.2, 30.7, 20.0 and 11.6 at 100, 250, 500 and 1000 µg/ ml. The number of female flowers was recorded as 30.3, 35.1, 39.7, 23.9 and 7.0 at 50, 100, 250, 500 and 1000 µg/ml respectively as against 13.2 at control (Table 3). The stimulatory effect of ethrel in enhancing femaleness is summarized in Figure 1. The statistical analysis of the pooled data reveals the effect of ethrel to be highly significant (Table 2). The time effect and the interaction between time and ethrel did not emerge as significant establishing the fact that there was not much variation in response during different time intervals and that too in response to different concentrations (Table 4). The same range of concentrations of CCC was tried on S.edule (L.) The mean Table (Table 5 and 7) exhibited the identical trend of stimulation TABLE 1: Effect of ethrel on Sechium edule L.(Mean of male flowers for 3 consecutive years). Ethrel(µg/ml) Time Mean for Cone Mean for time CD for Ethrel (n= 9) at 5% probability level= 3.92 at 1% probability level= 5.15CD for Time (n= 18) at 5% probability level= 2.77, at 1% probability level= 3.64

3 Vol. 47, No. 6, FIG. 1: Effect of Ethrel on Sechium edule (L) TABLE 2: Analysis of Variance for effect of ethrel on male flower of S.edule (L.) Ethrel ** Time Interaction (5 2)= (ethrel time) Error Total TABLE 3: Effect of ethrel on Sechium edule ( L.) (Mean of female flowers for 3 consecutive years). Ethrel(µg/ml) Time Mean for Conc Mean for time CD for Ethrel (n= 9) at 5% probability level= 3.43, at 1% probability level= 4.51 CD for Time (n= 18) at 5% probability level= 2.43, at 1% probability level= 3.19 TABLE 4: Analysis of Variance for effect of ethrel on female flower of S.edule (L.) Ethrel ** Time Interaction 10= (5 2) (ethrel time) Error Total

4 520 INDIAN JOURNAL OF AGRICULTURAL RESEARCH TABLE 5: Effect of CCC on Sechium edule (L.) Mean of male flowers for 3 consecutive years). CCC(µg/ml) Time Mean for Conc Mean for time CD for CCC (n= 9) at 5% probability level= 1.92, at 1% probability level= 2.52 CD for Time (n= 18) at 5% probability level= 1.36, at 1% probability level= 1.78 TABLE 6: Analysis of Variance for effect of ethrel on male flower of S.edule (L.) CCC ** Time Interaction 10= (5 2) (CCC time) Error Total in CCC treated plants of S.edule (L.) CCC proved to be highly effective in S.edule L. The plants produced less number of male flowers in comparison to the control. After application of CCC the number of male flowers were reduced recording 13.6, 13.6, 13.1, 11.9 and 10.3 at the concentrations of 50, 100, 250, 500 and 1000 µg/ml respectively (Table 5). On the contrary femaleness was enhanced showing increased number of female flowers (figure 2). The number of female flowers was in the order of 19.3, 22.3, 26.5, 23.0 and 11.6 at the concentrations of 50, 100, 250, 500 and 1000 µg/ml against 14.9 at control (Table 7). CCC at 250 µg/ml was found to be optimal. Statistical analysis (Table 6 and 8) of experimental data reveals that CCC was highly significant in reducing and increasing the number of flowers. The change in reproductive character did not vary during different time intervals and hence time effect did not emerge as significant. FIG. 2: Effect of CCC on Sechium edule (L)

5 Vol. 47, No. 6, TABLE 7: Effect of CCC on Sechium edule (L.) (Mean of female flowers for 3 consecutive years). CCC(µg/ml) Time Mean for Conc Mean for time CD for CCC (n= 9) at 5% probability level= 3.65 at 1% probability level= 4.79 CD for Time (n= 18) at 5% probability level= 2.58, at 1% probability level= 3.39 TABLE 8: Analysis of Variance for effect of ethrel on female flower of S.edule (L.) CCC ** Time Interaction 5 2= (CCC time) Error Total 54-1= The present investigation on squash revealed that plant growth regulators increased femaleness over male and control. This finding corroborates the works of Gomez et al (2004) who also observed sexual expression of squash is in control of ethylene. Release of ethylene or simi lar unsaturated hydrocarbon in the plant system because of ethrel application might be responsible for the flower induction (Randhawa et al 1970). That the application of CCC induces greater number of flowers had also been reported by Tawagen and Hassan (1974), Sharma et al (2001), Talukdar and Paswasn (1995). Acceleration of flowering by CCC application was also elucidated by Thukral et al (1993). Present investigation thus, has strengthened the fact that plant growth regulators can reverse reproductive characters in squash which lead to crop improvement. CONCLUSION In the present study plant growth regulators have been shown to control sex in Sechium edule L. The growth retardants ethrel (2-chloroethyl phosphonic acid) and CCC (2-chloroethyl trimethyl ammonium chloride) are effective in enhancing femaleness on Sechium edule L. It was noted that the higher concentrations of plant growth regulators applied were ineffective in producing female flowers. This finding also establishes the fact that by the application of plant growth regulators the productivity of Sechium edule L can be increased to such an extent which would solve the problems of farmers. The effective concentration of ethrel for foliar application (at seedling state) has been determined at 250 µg/ml to obtain the maximum female flowers, simultaneously reducing the number of male flowers, to increase the number of fruits. Number of male flowers produced by S.edule L under 50 and 100 µg/ml of ethrel concentrations were at par and significantly higher than the treatments that received high concentration of ethrel ( 250, 500 and 1000 µg/ml ) at 5% probability level. Male flower production under 250 µg/ml of ethrel concentration showed 30.7 ( ranging from 36.7 to 30.7) reduction from the treatment that received 50 µg/ml ethrel concentration but had at per results with 100 µg/ml ethrel concentration. In contrary 250 µg/ ml of ethrel concentration had produced the highest number of female flowers (39.7) of S.edule L which was significantly higher than other treatments, both at 5% and 1% probability level. ACKNOWLEDGEMENT The authors are thankful to Dr.Iswar Chandra Baruah, Head of Agronomy Department, Assam Agricultural University, Jorhat, Assam for his valuable suggestions and inspiration.

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