INTRODUCTION Bitter gourd (Momordica charantia L.) is one of the important and popular cucurbitaceous vegetable grown in our country. It is considered as a prized vegetable owing to its high nutritive value, especially ascorbic acid, iron and medicinally important anti-diabetic property (Behera, 2004). Plant growth regulators (PGRs) have a great potential in increasing productivity in vegetables. Growth promoters / growth retardants can be used judiciously to maximize yield in several vegetable crops. Response of a plant or plant parts to exogenous growth regulators varies with fluctuations in endogenous hormonal levels in the plant, and the manner in which natural growth regulators interact with applied growth regulators. Though plant growth regulators have a great potential to influence plant growth and morphogenesis, their application and actual assessment needs to be planned well in terms of optimal concentration, stage of application, species- specificity, season, etc. These constitute a major impediment in exploiting PGRs applicability. In view of their effect on virtually every aspect of plant growth, even a modest increase of 10-15 per cent could bring about increment in gross annual productivity by 10-15 million tons. Effect of plant growth regulators on leaf biochemical characters and fruit yield components of bittergourd (Momordica charantia L.) cvs. MHBI-15 and Chaman Plus Biradar Geeta, M.B. Chetti and C.M. Navalgatti Department of Crop physiology University of Agricultural Sciences, Dharwad - 580 005, India Email: b4ugeeta@gmail.com ABSTRACT Effect of plant growth regulators on leaf biochemical parameters (chlorophyll pigments, sugars, nitrate reductase activity, total phenols) and fruit yield bitter gourd (Momordica charantia L.) was studied. The experiment consisted of foliar treatment with three plant growth regulators, GA3 (20, 40 and 60ppm), NAA (50ppm) and CCC (100 and 200ppm) in two bittergourd varieties, MHBI–15 and Chaman Plus at 45 days after sowing (DAS). Results revealed significant difference between treatments on chlorophyll, sugar, total phenol content as also on nitrate reductase activity. Foliar application of CCC (200ppm) recorded maximum amount of total sugars (18.03% over Control), total phenol content (10.93%) as also nitrate reductase activity (16.12%). Among the treatments, application of GA3 (20ppm) recorded maximum chlorophyll content (18.03% over Control). Highest increase in mean fruit yield over Control was recorded with application of GA3 (20ppm) (39.88%), followed by CCC (200ppm) (34.15%) in both the cultivars. Key words: Bittergourd, fruit yield, leaf biochemical characters, plant growth regulators Fruit yield in bittergourd depends upon accumulation of photoassimilates and their partitioning to different plant parts. Yield in bittergourd was found to be strongly influenced by application of different growth regulators, thus indicating importance of these compounds in increasing yield potential through an effect on various physiological and biochemical traits. With this background, the present investigation was undertaken to find suitable plant growth regulators for increasing yield potential and quality in bittergourd. MATERIAL AND METHODS A field experiment was conducted at Main Agricultural Research Station, University of Agricultural Sciences, Dharwad, during rabi 2007-08. The experiment consisted of treatment combinations involving three plant growth regulators, viz., GA3 (20, 40 and 60ppm), NAA (50ppm) and CCC (100 and 200 ppm) with two varieties of bittergourd MHBI–15 and Chaman Plus. Foliar treatments were imposed during flower initiation (45 days after sowing) in both the varieties, with three replications laid out in Factorial Randomized Block Design. Observations on leaf J. Hortl. Sci. Vol. 9(1):43-47, 2014 44 biochemical characters and fruit yield components were made using standard procedures. Extraction of chlorophyll was done following the method of Shoaf and Lium (1976) using dimethylsulfoxide (DMSO). Leaf material (250mg) was incubated for 30min at 65°C in 10ml of dimethylsulphoxide (DMSO) reagent. The supernatant was collected and volume made up to a known quantity (10ml) and absorbance read at 645 and 663nm. Using spectrophotometer (Spectro UV-VIS dual beam UVS-2700, Labomed Inc., USA), total chlorophyll, chlorophyll ‘a’ and ‘b’ were calculated and expressed as mg/g fresh weight. Sugars were estimated following Nelson (1941). Reducing sugar content was estimated using copper and arsenomlybdate reagents. Colour development was read et 510nm using the spectrophotometer. Total sugars were estimated using anthrone reagent. Colour developed was estimated measuring absorbance at 630nm. Results were expressed as mg/g fresh wt. Nitrate reductase activity (NRA) in vivo was estimated following Saradhambal et al (1978) by leaf disc method using NNEDA and sulphanilamide. Pink colour development was read using a spectrophotometer at 540nm. Activity of nitrate reductase was expressed as nmoles of NO2 formed per gram fresh weight per hour. Estimation of total phenols was done by Folin Ciocalteau Reagent method (Sadasivum and Manikam, 1992). Results were expressed as mg/g fresh weight. Total fruit yield was calculated by multiplying plant population per hectare by yield per vine in three randomly labeled plants. Total number of fruits was counted on each vine. Data were subjected to analysis of variance as per Panse and Sukhatme (1967). RESULTS AND DISCUSSION Biochemical parameters Plant growth regulators had a profound influence on chlorophyll content in the leaf. Significant differences were observed among treatments, but interaction effect was found to be non-significant between treatments and varieties with respect to chlorophyll ‘a’, ‘b’ and total chlorophyll content in the leaf (Table 1). Maximum increase in chlorophyll ‘a’ (18.9%), ‘b’ (14.4%) and total chlorophyll (18.03%) over the Control was recorded with GA3 @ 20ppm. In general, chlorophyll content was significantly lower in cv. MHBI-15 compared to that in cv. Chaman Plus in all treatment combinations, including the Control. Foliar application of GA3 (20ppm and 40ppm) resulted in higher chlorophyll content. Increase in photosynthetic rate due to GA3 application has been attributed to enhanced ultra-structural morphogenesis of plastids and increase in Rubisco activity (Arteca and Donga, 1981). Variation in chlorophyll content due to growth regulator application may be attributed to decreased chlorophyll degradation and or increased chlorophyll biosynthesis. Data on reducing, non-reducing and total sugars indicated significant differences between varieties and treatments (Table 2). Significant increase in reducing sugars was noticed with application of CCC. Maximum reducing sugar content (22.1%) in leaf was recorded with CCC (200ppm). Non-reducing sugars (13.6%) also increased with foliar spray of CCC (200ppm). Foliar application of CCC (200ppm) also registered significantly high increase Table 1. Influence of plant growth regulators on chlorophyll ‘a’, ‘b’ and total chlorophyll (mg/g fresh wt.) in bittergourd leaf Treatment Chlorophyll ‘a’ Chlorophyll ‘b’ Total chlorophyll V1 V2 Mean V1 V2 Mean V1 V2 Mean T1 - Gibberellic acid (20ppm) 0.956 1.006 0.981 0.222 0.239 0.230 1.178 1.245 1.211 T2 - Gibberellic acid (40ppm) 0.913 0.950 0.931 0.215 0.229 0.222 1.128 1.179 1.153 T3 - Gibberellic acid (60ppm) 0.883 0.905 0.894 0.210 0.220 0.215 1.093 1.125 1.109 T4 - Naphthalene acetic acid (50ppm) 0.935 0.797 0.866 0.215 0.230 0.222 1.150 1.027 1.088 T5 - Cycocel (100ppm) 0.898 0.915 0.906 0.210 0.217 0.213 1.108 1.132 1.120 T6 - Cycocel (200ppm) 0.864 0.883 0.873 0.205 0.212 0.208 1.069 1.095 1.082 T7 - Control 0.821 0.830 0.825 0.198 0.204 0.201 1.019 1.034 1.026 Mean 0.895 0.898 0.896 0.210 0.221 0.216 1.106 1.119 1.113 For comparing means of S. Em± CD (P=0.05) S. Em± CD (P=0.05) S. Em± CD (P=0.05) Varieties 0.011 NS 0.003 0.009 0.017 NS Treatments 0.022 0.065 0.004 0.012 0.031 0.092 V x T 0.031 NS 0.005 NS 0.044 NS V1: MHBI-I5 V2: Chaman Plus NS: Non-significant J. Hortl. Sci. Vol. 9(1):43-47, 2014 Biradar Geeta et al 45 in total sugars (18.5%) over the Control and in other treatments. In general, higher sugar content was recorded in cv. Chaman Plus compared to cv. MHBI-15 in all the treatments. Higher accumulation of sugar in CCC treated plants might be due to higher biosynthesis of chlorophyll and photosynthesis. Our results also confirm the earlier findings of Uprety and Yadavs (1985) in oat plants. Plant growth regulators exhibited significant differences in nitrate reductase activity (NRA) in the leaf (Table 3). The enzyme activity increased by 16% with foliar application of CCC @ 200ppm compared to that in Control. Nitrate reductase a key enzyme in nitrogen metabolism, is known to be regulated by various environmental factors apart from presence of its substrate viz., nitrate. The enzyme catalyses reduction of nitrate to nitrite (Vadigeri et al, 2001). Similarly, Lawlor and Fock (1975) suggested that CCC- induced increase in photosynthesis was associated with an increase in NR activity. It is generally believed that nitrate reductase activity depends upon the activity of substrate and proteinaceous compounds. Therefore, it is suggested that application of plant growth regulators results in enhanced nitrate uptake by plants (Kuchenberg and Jung, 1988). Similarly, Goswami and Srivastava (1989) also reported increase in nitrate reductase activity to the application of growth regulators. Data on total phenols as influenced by plant growth regulators indicated wide differences among the two genotypes and treatments. Cultivar Chaman Plus recorded higher total phenols compared to MHBI-15 (Table 3). All the growth regulators used significantly increased total phenol content. Among the treatments, CCC (200ppm) recorded significantly higher increase in total phenol content (10.93%) over the Control. Plant phenolic compounds have been widely reported to be substances stimulatory to plant growth and function as promoters (Ghareib et al, 2010). This, as reported by other workers, is made possible by mobilization of metabolites like carbohydrates and total phenols (Talaat, 2005; Talaat and Balbaa, 2010). These data indicate that total phenol content can be enhanced with application of PGRs in bittergourd. Yield and yield components Number of fruits per plant was significantly higher with foliar spray of GA3 @ 20ppm (11.6%), followed by CCC @ 200ppm (9.6%) compared to Control (Table 4). Fruit yield per plant and fruit yield per ha were also Table 2. Influence of plant growth regulators on reducing sugars, non-reducing sugars and total sugars (mg/g fresh wt.) in bittergourd leaf Treatments Reducing sugars Non-reducing sugars Total sugars V1 V2 Mean V1 V2 Mean V1 V2 Mean T1 - Gibberellic acid (20ppm) 2.05 2.29 2.17 4.86 6.07 5.46 6.93 8.36 7.64 T2 - Gibberellic acid (40ppm) 1.98 2.25 2.11 4.87 5.95 5.41 6.85 8.20 7.52 T3 - Gibberellic acid (60ppm) 1.91 2.11 2.01 4.83 5.97 5.40 6.74 8.08 6.99 T4 - Naphthalene acetic acid(50ppm) 2.03 2.22 2.12 5.02 6.26 5.64 7.05 8.48 7.96 T5 - Cycocel (100ppm) 2.08 2.28 2.18 5.08 6.31 5.69 7.16 8.59 8.08 T6 - Cycocel (200ppm) 2.16 2.36 2.26 5.17 6.34 5.75 7.33 8.71 8.25 T7 - Control 1.78 1.92 1.85 4.55 5.57 5.06 6.33 7.49 6.96 Mean 1.99 2.2 2.1 4.91 6.06 5.48 6.91 8.27 7.59 For comparing means of S. Em± CD (P=0.05) S. Em± CD (P=0.05) S. Em± CD (P=0.05) Varieties 0.01 0.03 0.01 0.03 0.1 0.29 Treatments 0.02 0.05 0.02 0.06 0.19 0.54 V x T 0.02 NS 0.03 0.09 0.27 0.77 V1: MHBI-I5 V2: Chaman Plus NS: Non significant Table 3: Influence of plant growth regulators on nitrate reductase activity and total phenols in bittergourd leaf Treatment Nitrate reductase activity Total phenols (nmolNO2 g -1fr.wt. hr-1) (mg g-1 fresh wt.) V1 V2 Mean V1 V2 Mean T1 - Gibberellic 118.9 179.3 149.1 13.90 14.91 14.40 acid (20ppm) T2 - Gibberellic 117.6 175.8 146.7 13.96 14.73 14.34 acid (40ppm) T3 - Gibberellic 115.6 173.4 144.5 13.86 14.64 14.25 acid (60ppm) T4 - Naphthalene 121 181.9 151.5 13.95 14.79 14.37 acetic acid(50ppm) T5 - Cycocel 122.9 184.3 153.6 14.07 14.95 14.51 (100ppm) T6 - Cycocel 125.8 186.9 156.3 14.24 15.38 14.81 (200ppm) T7 - Control 108.6 160.6 134.6 12.94 13.76 13.35 Mean 118.6 177.4 148 13.84 14.73 14.28 For comparing S. Em± CD (P=0.05) S. Em± CD (P=0.05) means of Varieties 1.3 3.6 0.02 0.05 Treatments 2.4 6.8 0.03 0.09 V x T 3.3 NS 0.04 0.13 V1 : MHBI-I5 V2: Chaman Plus NS: Non-significant Effect of PGRs on leaf biochemistry and yield in bittergourd J. Hortl. Sci. Vol. 9(1):43-47, 2014 46 significantly higher with foliar application of GA3 @ 20ppm, followed by CCC @ 200ppm. Lowest fruit yield was recorded in the Control. Higher fruit yield was obtained as a result of higher number of hermaphrodite flowers per plant and better vegetative growth observed by us in our earlier study (Geeta et al, 2010). Similar results were reported by Dostogir et al (2006) and Ram Asrey et al (2001). Significant increase in number and weight of fruits and total yield was observed in peach with application of CCC @ 500ppm (Mahajan and Sharma, 2000). Increase in fruit yield of treated plants may be further attributed to the fact that plants remain physiologically active to build up sufficient amount of assimilates for developing flowers and fruits, thereby, leading to higher yield. Improvement in yield could come about in two ways, i.e., by the existing varieties adapting to grow better in their environment, or, by altering the relative proportions of different plant parts to increase the yield of only the economically important parts (Pankaj et at, 2005). In addition, crop yield depends not only on accumulation of photosynthates during crop growth and development, but also on its partitioning to desired storage organs. These, in turn, are influenced by efficiency of the metabolic processes within a plant. Growth retardants are capable of redistributing dry matter in the plant, thereby bringing about yield improvement (Chetti, 1991). From these results, it can be concluded that all PGR foliar treatments differed significantly for both the varieties in all the traits studied with reference each other and in Control plants. Among the different treatments, GA3 @ 20ppm enhanced chlorophyll content. Significantly higher NRA, reducing, non-reducing and total sugars, and, total phenols were recorded with CCC (200ppm), and the lowest was recorded in Control. However, maximum number of fruits per plant was recorded with GA3 (20ppm) followed by CCC (200ppm) and various treatments differed significantly with respect to fruit yield (kg/plant and t/ha), with GA3 (20ppm) showing highest values compared to all other treatments. REFERENCES Arteca, R.N. and Donga, C.N. 1981. Increased photosynthetic rates following gibberellic acid treatments to the roots of tomato plants. Photosynth. Res., 2:243-249 Behra, T.K. 2004. Heterosis in bitter gourd. J. New seeds., 6:217-222 Chetti, M.B. 1991. Evaluation of Chamatkar on groundnut. 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Influence of plant growth regulators on yield and yield components in bittergourd Treatment No. of fruits / plant Fruit yield(kg/plant) Fruit yield(t/ha) V1 V2 Mean V1 V2 Mean V1 V2 Mean T1 - Gibberellic acid (20ppm) 16.4 18.3 17.3 1.203 1.417 1.310 8.113 9.249 8.681 T2 - Gibberellic acid (40ppm) 15.7 17.5 16.6 1.087 1.318 1.202 7.650 8.922 8.286 T3 - Gibberellic acid (60ppm) 15.2 16.8 16.0 1.059 1.252 1.155 7.398 8.579 7.988 T4 - Naphthalene acetic acid(50ppm) 15.6 16.7 16.1 1.100 1.164 1.132 7.770 8.625 8.197 T5 - Cycocel (100ppm) 15.9 17.8 16.8 1.116 1.266 1.191 7.834 8.745 8.289 T6 - Cycocel (200ppm) 16.1 18.0 17.0 1.173 1.359 1.266 8.004 9.029 8.518 T7 - Control 14.9 16.1 15.5 0.883 1.013 0.948 6.806 7.619 7.212 Mean 15.6 17.3 16.4 1.088 1.255 1.171 7.653 8.68 8.165 For comparing means of S. Em± CD (P=0.05) S. Em± CD (P=0.05) S. 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Physiological Response of Sweet Basil plants (Ocimum basilicum L.) to putrescine and trans-cinnamic acid. American- Eurasian J. Agril. Environ. Sci., 8:438-445 Uprety, M. and Yadava, R.B.R. 1985. Effect of CCC on lodging, yield, and grain quality of Oat (Avena sativa) cultivar Kent Indian J. Plant Physiol, 28:103-106 Vadigeri, B.G., Madalgeri, B.B. and Sheelavantar, M.N. 2001. Effect of ethrel and gibberllic acid on yield and quality of two cucumber varieties. Karnataka J. Agri. Sci., 14:727-730 (MS Received 04 April 2013, Revised 04 November 2013, Accepted 20 January 2014) Effect of PGRs on leaf biochemistry and yield in bittergourd J. Hortl. Sci. Vol. 9(1):43-47, 2014