Effect of GA3 on Some Biochemical Attributes and Yield of Summer Tomato

• M. S. Rahman, Md. Azadul Haque and Md. G. Mostofa

Abstract

An experiment was carried out in pots at Bangladesh Institute of Nuclear Agriculture, Mymensingh, during March to July 2012 to evaluate the influence of different concentrations of GA₃ on biochemical parameters at different growth stages in order to maximize the yield of summer tomato var. Binatomato-2. The concentrations of GA₃ used were 0, 25, 50, 75 and 100 ppm and they were applied at three stages, namely root soaking of seedlings before transplanting, vegetative and flowering stages. The experiment was laid out in a randomized complete block design with four replications. Results indicated that the highest chlorophyll and soluble protein contents were recorded when GA₃ was applied through root soaking followed by vegetative stage and the lowest was found at the flowering stage. In contrast, the highest nitrate reductase activity was observed when GA₃ was applied at the vegetative stage and the lowest activity was recorded at the flowering stage. The applications of 50-75 ppm GA₃ had significantly encouraged the bio-chemical parameters studied at 50 DAT. The amount of GA₃ applied at different stages had significant influence on the yield and yield attributes of summer tomato. The highest plant height was recorded when 50 ppm of GA₃ was applied at the vegetative stage. While, the longest time to first fruit setting was required when the roots of the seedlings were soaked in 100 ppm GA₃ solution. The application of 50 ppm GA₃ by root soaking had significantly increased the number of flowers, fruits and fruit yield per plant but similar performances were achieved when only 25 ppm GA₃ was applied at the flowering stage. The fruit yield of tomato per plant increased linearly with the increased number of flowers and fruits per plant.

Keywords: Concentration, Chlorophyll, GA₃, Soluble protein, Nitrate reductase activity

1. Introduction

Tomato (Lycopersicon esculentum) is one of the most popular and nutritious vegetables of Bangladesh. Tomato is cultivated all over the country due to its adaptability to a wide range of soil and climate. Normally tomato is grown in winter season due to its requirements for temperate climate. Hence, it is difficult to grow tomato in summer season due to adverse climatic conditions, such as high temperature, high rain fall, hailstorms, etc. Bangladesh Institute of Nuclear Agriculture (BINA) has developed some tomato varieties to cultivate in summer season. But the yield potential of these varieties can not be achieved due to the above mentioned climatic conditions. In summer season, tomato can however be successfully grown under glasshouse conditions. But it is not possible for the poor farmers to go for large scale production in glasshouses because it is highly expensive and need technical skills. The other option is the use of plant growth regulators to minimize the effect of harsh environments in order to maximize the yield of summer tomato. Results of some studies indicated that the application of Gibberellic acid (GA₃) had significantly increased the number of fruits per plant than the untreated controls (Tomar and Ramgiry, 1997). Adlakha and Verma (1964) reported that the application of GA₃ on flower cluster resulted in an increase in fruit weight. To increase the yield as well as to avoid flower and fruit dropping, application of GA₃ at optimum concentration and at right time is important. Gibberellic acid has great effects on plant physiological systems including fruit setting, leaf expansion, germination, breaking dormancy, increasing fruit size, improving fruit quality and in many other aspects of plant growth and thereby on crop production. Keeping the above circumstances in view, the present study was under taken to evaluate the performance of GA₃ on biochemical properties, growth and yield attributes and to determine the optimum time and concentration of GA₃ application in order to maximize the yield of Binatomato-2.

2. Materials and Methods

A pot experiment was conducted with tomato var. Binatomato-2 at the experimental site of Crop Botany Department, Bangladesh Agricultural University, Mymensingh, during March to July 2012. Five levels of GA₃ (Gibberellic Acid) viz. 0, 25, 50, 75 and 100 ppm were applied at (i) seedling stage by root soaking before transplanting (ii) vegetative stage [20 days after transplanting (DAT)] and (iii) flowering stage (40 DAT) by hand sprayer. The experiment was laid out in a randomized complete block design with four replications. Twelve kilograms of sun-dried sandy loam soil and cow dung, urea, TSP and MP @ 583.33, 2.9, 2.54 and 1.81 g/pot corresponding to 10 tons, 400, 350 and 250 kg/ha were applied in each pot. Before pot filling, full doses of TSP, MP and cow dung were thoroughly mixed with the soil. Half of the urea was applied during transplanting and the remaining half at vegetative stage. Intercultural operations were done as and when necessary. Data on yield and yield contributing characters were recorded at final harvest. Biochemical analyses viz. chlorophyll, soluble protein contents and nitrate reductase activities in leaves were estimated at 50 DAT following the methods of Arnon (1949), Lowery et al. (1951) and Stewart and Orebamjo (1979). Data were analyzed statistically to find out the level of significance using MSTAT-C package programme (Russel, 1986) and significant differences among the treatments were adjudged by Duncan`s New Multiple Range Test (DMRT) at 5% level of significance (Gomez and Gomez, 1984).

3. Results and Discussion

There were significant differences among the treatments in respect of chlorophyll content, soluble protein content and nitrate reductase (NR) activities in tomato leaves at 50 DAT (Table 1). The highest chlorophyll content in leaves was obtained when the roots of seedlings were soaked in GA₃ solutions before transplanting, which was identical to the application of GA₃ at vegetative stage. The lowest chlorophyll content was found in plants when GA₃ was applied at the flowering stage. Chlorophyll content in leaves was influenced significantly due to the application of different concentrations of GA₃. The highest chlorophyll content was found from 100 ppm GA₃ followed by 75 ppm and the lowest was found from the control, which was identical to those obtained from the application of 25 and 50 ppm of GA₃. Chlorophyll content increased with increased concentrations of GA₃.

The application of GA₃ through root soaking of seedlings and at vegetative stages resulted in the highest but similar soluble protein contents in tomato leaves and the lowest was found when it was applied at the flowering stage. The soluble protein content in leaves was also significantly influenced by the application of variable levels of GA₃. The highest content was recorded with 50 ppm and the lowest content was recorded with 100 ppm GA₃ which indicated that soluble protein content in leaves increased significantly until the application of 50 ppm and thereafter decreased with further increase in GA₃ concentrations. Adlakha and Verma (1964) also reported that 50 ppm GA₃ had appreciably increased the protein content in leaves.

The maximum nitrate reductase activity was recorded at vegetative stage. The lowest was observed in flowering stage and this was similar to the activity performed when GA₃ was applied through root soaking. Nitrate reductase activity was significantly influenced by the application of different concentrations of GA₃. The maximum nitrate reductase activity was recorded with 75 ppm GA₃ and the minimum was found from the control. Spraying of 50 and 75 ppm GA₃ did not show any difference in NR activities at 40 days after planting.

The applications of GA₃ at different stages of plant growth resulted in significant influence on yield and yield attributes of summer tomato. The highest plant height was recorded when GA₃ was applied at the vegetative stage and the lowest height was recorded at the flowering stage. GA₃ had significant influence on plant height. It increased until the application of 50 ppm and declined remarkably with further increase in GA₃ concentrations. The interactions between stage and concentrations of GA₃ indicated that the application of 50 ppm of GA₃ at the vegetative stage encouraged vigorous plant growth and thereby resulted in the highest plant height.

There was no significant difference among the stages of hormone application in respect of time to first fruit setting. The maximum number of flowers, fruits and fruit weight per plant was produced when GA₃ was applied through root soaking followed by the vegetative stage. All those parameters showed the lowest results when GA₃ was applied at flowering stage. Similar result was also reported by Kaushik et al., 1974. They applied GA₃ at vegetative stage and obtained increased fruit weight per plant. Sanyal et al. (1995) observed that foliar application was more effective than root soaking of seedlings. GA₃ concentrations had statistically significant effect on plant height, time to first fruit setting, number of flowers, fruits and fruit weight per plant. The highest plant height was found with the application of 50 ppm GA₃ which was identical to 25 ppm and the lowest was found from the control. The maximum time for first fruit setting was required when GA₃ was applied at 100 ppm and the lowest time was required with lower concentrations of GA₃. The maximum number of flowers, fruits and fruit weight per plant was produced with 50 ppm GA₃ application and the lowest was recorded with 100 ppm. Saleh and Abdul (1980) reported similar result from their experiment. They found that GA₃ at 50 ppm decreased the total number of flowers per plant but increased the total yield. Hossain (1974), Adlakha and Verma (1995) found that the application of 50 ppm GA₃ had increased the fruit setting, while Saleh and Abdul (1980) observed that GA₃ at 25 or 50 ppm had increased the total yield of tomato compared to the control. Sanyal et al. (1995) also found that 50 ppm of GA₃ had profound effect on the yield of tomato.

The interaction between GA₃ concentrations and stages of application indicated that the highest number of flowers, fruits and fruit weight per plant were produced when GA₃ was applied through root soaking of seedlings at 50 ppm which was identical to the application of 50 ppm at vegetative stage or 25 ppm at flowering stage. A positive and linear relationship was found between the number of flowers per plant and fruit weight per plant (r = 0.96**) (Figure 1), number of fruits per plant and fruit weight per plant (r = 0.99**) (Figure 2) which indicated that the fruit yield of tomato is highly influenced by the production of flowers and the retention of fruits per plant irrespective of the stage and amount of GA₃ applied in tomato plants.

4. Conclusion

It was revealed from the study that application of GA3 at the rate of 50-75 ppm by root soaking and at vegetative stage increased biochemical properties as well as increase the number of flowers, fruits and fruit yield per plant of Binatomato-2. It can be concluded that foliar application of 50 ppm Gibberelic acid on Binatomato-2 variety provide the best result in terms of biochemical attributes and yield.

5. References

Adlakha, P. A. & Verma, S. K. (1964). Effect of gibberellic acid on the quality of tomato fruit. Punjab Horticulture Journal. 4 (3-4), 148-151.

Adlakha, P. A. & Verma, S. K. 1995. Effect of gibberellic acid on fruiting and yield of tomatoes. Science and Culture 31, 301-303.

Arnon, D. I. (1949). Copper enzymes in isolated chloroplasts, polyphenol oxidase in Beta vulgaris. Plant Physiology. 24, 1-5.

Briant, R. E. (1974). An analysis of the effect of gibberellic acid on tomato leaf growth. Journal of . Experimental Botany. 25, 764-771.

Gomez, K. A. & Gomez, A. A. (1984). Statistical Procedures for Agricultural Research. (2^nd ed.). International Rice Research Institute. John Wiley and Sons, New York, p. 139-240.

Hossain, M. A. E. (1974). Studies on the effect of parachlorophenoxy acetic acid and gibberellic acid on the production of tomato. M. Sc. Ag. Thesis, Dep. of Horticulture, Banglaesh Agricultural University, Mymensingh.

Hunt, R. (1978). Plant growth analysis studies in biology. Edward Arnold Ltd. London, p. 67.

Kaushik, M. P., Sharma, J. K. & Singh, I. (1974). Effect of alpha naphthalene acetic acid , gibberellic acid , kinetin and morphactin on yield of tomato. Plant Science. 6, 51-53.

Lowerry, O. H., Roserrough, N. J., Farr, A. L. & Randall, R. J. (1951). Protein measurement with the folin phenol reagent. Journal of Biology and Chemistry 193, 265-275.

Rusell, D. F.(1986). MSTAT-C Package Programme. Crop and Soil Science Department, Michigan State University, USA.

Saleh, M. M. S. & Abdul, K. S. (1980). Effect of gibberellic acid and cycocel on growth, flowering and fruiting of tomato (Lycopersicon esculentum Mill.) plants. Mesopotamia Journal of Agriculture 15(1), 137-166.

Sanyal, D., Kar, P. L. & Longkumar, M. (1995). Effect of growth regulators on the physico-chemical composition of tomato (Lycopersicon esculentum Mill.). Advances in Hort. And Forestry, 4, 67-71.

Stewart, G.R. & Orebamjo, T.O. (1979). Some unusual characteristics of nitrate reduction in Erythrina senegalensis DC . New Phytology 83, 311-319.

Tomar, I. S. & Ramgiry, S. R. (1997). Effect of growth regulators on yield and yield attributes in tomato (Lycopersicon esculentum Mill.). Advance Plant Science 10 (2), 29-31.

Table 1. Effect of GA₃ application at different stages of plant growth on bio-

chemical parameters of summer tomato var. Binatomato-2 at 40 DAT

In a column, figures having similar letter(s) do not differ significantly at 5% level of probability by DMRT.

Table 2. Effect of GA₃ application at different stages of plant growth on yield and

yield components of summer tomato var. Binatomato-2

In a column, figures having similar letter(s) do not differ significantly at 5% level of probability by DMRT.

Significant at 5% level, ** Significant at 1% level