Research Journal of Chemical Sciences ___ ______________________________ ______ ____ ___ ISSN 22 31 - 606X Vol. 2 ( 7 ), 72 - 74 , July (201 2 ) Res.J.Chem.Sci. International Science Congress Association 72 Short Communication Effects of Gibberellic Acid on Seedling growth, Chlorophyll content and Carbohydrate Metabolism in Okra ( Abelmoschus Esculentus L.Moench ) Genotypes under Saline Stress Jasmine Mary S. and John Merina A. Department of Chemistry, Government College for Women (Autonomous) Kumbakonam, INDIA Available online at: www.isca.in Received 3 0 th January 201 2 , revised 6 th April 201 2 , accepted 27 th June 2012 Abstract The effect of gibberellic acid on the counteracting of the Nacl 50, 100 and 150 mm induced deleterious effects on okra (Abelmoschus esculentus) genotype was studied. Effects of GA 3 on salt tolerance of okra were determined by measuring the growth parameters – shoot and root lengths, shoot and root fresh and dry weights and leaf area. The photosynthetic pigments (chlorophylls a,b and carotenoids) content and sugars level were invest igated. In response to the interactive effects of GA 3 and Nacl treatments. Nacl significantly reduced all growth parameters measured, photosynthetic pigments, as well as sugar contents. The effects of Nacl on the previous parameters were increased with Na cl concentrations. Exogenous application of GA 3 counteracted the Nacl deleterious effects on okra genotypes. GA 3 enhanced the okra salt tolerance in terms of improving the measured plant growth criteria. GA 3 appears to stimulate okra salt tolerance by acti vating the photosynthetic process. Key words: GA 3 , Okra, chlorophyll, polysaccharides Introduction Environmental stresses on salinity and drought reduce growth and agricultural productivity more than other factors 1 . Higher salinity levels caused significant reduction in growth parameters like leaf area, leaf length and root and shoot dry weights 2 . Water logging and sea water treatment decrease carotenoids in zeamays seedling and induce reduction in chlorophyll and photosynthetic acti vity 3 . Okra (Abelmoschus esculentus L.Moench) is a popular vegetable crop belongs to family Malvacea which is widely grown throughout the tropics and also well distributed in the Indian sub continent and East Asia. It’s grown from March to June in India an d it is very delicious vegetable. The young tender pods used for curries. When ripe the black and white eyed seeds are sometimes roasted and used as substitute for coffee. The stem of plant provides fiber, which is used in paper industry. The crop has hi gh nutritive value. Its production is not adequate to meet the growing demands of the increasing population. One of the constrains in the cultivation of okra is salinity. Salinity is an ever - alarming problem in Indian agriculture. The plant hormone plays an important role in regulating the plant growth under stressful environment. Gibberellic acid is a common plant hormone which is most favourable for promoting and improving plant growth and photosynthetic activity. The beneficial effect of gibberellic acid on different plant was recorded by Shedeed et al. on croton plants, Eraki on Queen Elizabeth rose plants. They concluded that GA 3 is used to regulating plant growth through increasing cell division and cell elongation. There are some reports which in dicate that GA 3 enhanced germination and seedling growth in chickpea . The evidence for hormone involvement comes from correlation of hormone concentration with specific development stages, effects of applied hormones and the relationship of hormones to m etabolic activities. The application of gibberellins increase the plant growth by attributing the fact that they increase the amino acid content in embryo and cause release of hydrolytic enzyme required for digestion of endospermic starch when seeds renew growth at germination. GA 3 acts synergistically with auxins, cytokinins and probably with the other hormone. The overall development of plant is regulated by the growth hormones nutrient and environmental factors. They also vary in their germination req uirement. It is not know that in which concentrations these hormones will cause a response in the cell under saline stress. This investigation with growth hormones will help in determining that which of hormonal concentration is suitable for plant growth under salinity. In view of the above background the present investigation was undertaken to study the influence GA 3 by different concentration on growth parameters, photosynthetic pigments and sugar levels under saline condition. Material and Methods A p ot experiment to study the response of okra to foliar GA 3 application during salt stress was carried out at the Department of Chemistry, Government Arts College (Autonomous), Kumbakonam. The experiment was laid down on a completely randomized block design earthen pots (25 cm in diameter), lined Research Journal of Chemical Sciences ___ _ _ _______________________________ ______________ _ ________ ISSN 22 31 - 606X Vol. 2 ( 7 ), 72 - 74 , July (201 2 ) Res.J.Chem.Sci International Science Congress Association 73 with polythene sheets were filled with 7 kg of acid washed sand seeds of Abelmoschus esculents (Arka anamika genotype) were procured from the Mercury seeds Corporation Ltd., Chennai, India Sterilized with 0.01% Hgc l 2 solution rinsed using double distilled water, and then sown in the pots. Five plants per pot maintained. Irrigation was carried out using 50% strength Hogland nutrient solution 4 . This continued till germination, after which the salt treatment was ini tiated concentration of 0, 50, 100,150 mM Nacl were maintained in the Hogland’s solution applied daily for 20 days following germination. The GA 3 were sprayed once on the leaves in the early morning when the plants had their fourth leaf completely expande d. A constant volume was sprayed in all cases with a manual pump. All determinations were carried out seven days after Gibbereliic acid treatment and 15 days after salt exposure. The plants were divided into four groups : i. c ontrol (50% Hogland nutrie nt solution) , ii. p lants treated with GA 3 (10 - 2 M) , iii. p lants received Nacl solutions 50, 100 and 150 mM. , iv. Plants treated with GA3 (10 - 2 M), with each of the salinity levels. All treatments were replicated there times. Half of the samples were rapidly dried in an oven at 80 o C to constant weight and then ground to fine powder, which was used for determination of dry weight and sugar fractions. The other half was used for growth data and extraction of pigments. Estimation of pigment contents was achieved by application of the method of Metznar et al. . 80% acetone extract was calorimetrically assayed at 452, 644 and 655 nm. The procedure of Naguib was used to determine the sugar fractions. Plant extract plus arseno molybdate solution develops the c olour, which was calorimetrically measured at 700 nm. The results presented in the tables are the mean of three replications. The data were statiscally analysed using the least significant differences (LSD) test as described by Snedecor & cochran 5 . Resu lts and Discussion Applications of the test levels of Nacl to Okra plants adversely influenced their growth pattern (shoot and root length, fresh and dry weights of shoots and roots and leaf area), as compared with control plants ( t able 1 ). These results are in agreement with those of Ghoulam et al ., who showed that Nacl salinity caused a marked reduction in growth parameters. (leaf area, fresh and dry weight of shoots and roots of sugar beet plants). GA 3 treated Okra plants exhibited an increase in tolera nce to salt treatment. This increase in salt tolerance was reflected in the measured growth criteria. Fresh and dry and length of shoots and roots as well as leaf area were increased comparing with plants received Nacl only ( t able 1 ). Gutierrez et al. 6 , also reported a similar increase in the growth of shoots and roots of soybean plants in response to Gibberellic acid treatment. Dhaliwal et al. 7 , and Zhou et al. 8 , also indicate that GA 3 increases the leaf area in sugarcane plants, which is consistent wi th out results in okra plants. Table - 1 Growth characteristics of okra seedlings in response to treatment with Nacl in presence and absence of gibberellic acid. Each value is the mean of three replicates. All treatments are significant at 1% level of their controls Gibberellic Acid (M) Nacl (mM) Length (cm) Fresh Weight (g) Dry Weight (g) Leaves Area/Plant (cm 2 ) Shoot Root Shoot Root Shoot Root 0.0 0.0 43.0 13.1 16.28 3.03 2.63 0.40 193 50 42.5 14.0 15.07 2.80 2.45 0.36 182 100 37.0 10.1 13.17 2.64 2.09 0.33 168 150 30.03 6.7 10.09 1.89 1.52 0.25 160 10 - 2 0.0 47.3 15.8 20.07 6.18 3.35 0.81 215 50 45.5 16.0 18.74 7.01 3.00 0.90 210 100 44.7 13.8 17.40 4.75 2.74 0.53 200 150 38.9 9.2 14.82 3.82 2.28 0.47 194 LSD 1% 1.4 1.3 1.2 0.9 1.3 0.05 2.6 Table - 2 Changes on pigments of Okra seedlings in response to treatment with Nacl in presence and absence of gibberellic acid Gibberellic Acid (M) Nacl (nM) Pigments (mg/g Fresh Weight) Chlorophyll a Chlorophyll b Carotenoids 0.0 0.0 4.13 1.92 0.97 50 3.71 1.64 0.71 100 3.02 1.13 0.48 150 1.91 0.98 0.30 10 - 2 0.0 6.04 3.12 2.15 50 5.12 2.71 1.73 100 4.51 2.02 1.42 150 3.90 1.71 1.01 LSD 1% 0.28 0.18 0.12 Research Journal of Chemical Sciences ___ _ _ _______________________________ ______________ _ ________ ISSN 22 31 - 606X Vol. 2 ( 7 ), 72 - 74 , July (201 2 ) Res.J.Chem.Sci International Science Congress Association 74 Table - 3 Changes in carbohydrate content of okra seedlings in response to treatments with Nacl in presence and absence of gibberellic acid. Each value is the mean value of three replicates. All treatments are significant at 1% level of their controls Gibberellic Acid (M) Nacl (mM) Carbohydrates (mg/g Dry Weight) Soluble sugars Polysaccharides Total 0.0 0.0 77.9 178.6 256.5 50 83.4 179.3 283.7 100 90.1 158.9 249.0 150 98.7 144.7 243.4 10 - 2 0.0 72.3 195.0 267.3 50 75.7 188.4 264.1 100 81.5 179.6 261.1 150 87.9 158.9 246.8 LSD 1% 2.1 2.5 2.0 Table 2 shows that the pigments (chlorophyll a,b and cartenoids) content of Nacl treated okra plants was significantly decreased below that of the controls. Similarly, Dela - Rosa and Maiti 9 found an inhibition in chlorophyll bio synthesis in sorghum plants because of salt stress. GA 3 treated plants exhibited higher values of pigment concentration than those of control or salinity treated samples (Table II). In soybean plants treatment with GA3 increased pigments content as well as the rate of photosynthesis 10 . Sinha et al. 11 pointed out that chlorophyll and carotenoids contents of maize leaves were increased upon treatment with GA 3 taking together, the results of the previous authors support our findings. Okra plant submitted to Nacl salinity treatment show ed a progressive increase in their soluble sugar content with increasing the salinity level, while an opposite trend was obtained with respect to polysaccharide concentration ( t able 2 ). GA 3 treatment caused a significant decrease in the content of soluble sugars below that of untreated samples ( t able 3 ). GA 3 increased, however the control plants ( t able 3 ). In this regard soluble sugar content was also increased in tomato plants in relation to salt stress 12 . It is suggested that GA 3 application might acti vate the metabolic consumption of soluble sugars to form new cell constituents as a mechanism to stimulate the growth of okra plants reported in this study. GA 3 treatment might also be assumed to inhibit polysaccharide. 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