Influence of gibberellic acid (GA₃) on growth, chlorophyll and seed yield of summer mungbean cultivars in Northwest of Bangladesh

Rawnak Ara Noor-E-Ferdous^1*, Md Shariful Islam² and Bikash C Sarker³

¹Bangladesh Stevia and Food Industries Limited, Dhaka-1216, Bangladesh, ² Bangladesh Sugarcrop Research Institute, Regional Sugarcrop Research Station, Thakurgaon-5102, Bangladesh, ³

Department of Agricultural Chemistry, Hajee Mohammed Danesh Science and Technology University, Dinajpur-5200, Bangladesh.

Article history: Received: 04.10.2020, Accepted: 24.12.2020, Published Online: 31.12.2020

*Corresponding author:rawnakara28@gmail.com

www.isciencepub.com

ABSTRACT

Mungbean is an important pulse crop and its productivity is highly sensitive to application of plant growth regulators. The experiment was carried out to investigate the effects of gibberellic acid (GA₃) on growth, leaf chlorophyll and yield of summer mungbean cultivars viz., V₁-Binamoog-5, V₂-BARI mung 6 and V₃-Binamoog-8 along with four treatments of H₁-control (without GA₃), H₂-50 ppm GA₃, H₃-100 ppm GA₃ and H₄-150 ppm GA₃ applied at 15, 30, 45 and 60 days after sowing (DAS). Data were recorded on plant height, number of leaves plant^-1, leaf area plant^-1, dry root weight, root volume, number of root nodule, chlorophyll content, proline content and seed yield. Plant height, number of leaves plant^-1, leaf area plant^-1 and seed yield were statistically different among the cultivars and also significantly influenced by the application of different concentrations of GA₃. The highest plant height, number of leaves plant^-1, leaf area plant^-1 and seed yield were obtained by applying 100 ppm GA₃. The interaction effect of cultivars and different concentrations of GA₃ were statistically significant on plant height, number of leaves plant^-1, leaf area plant^-1 and seed yield. The highest plant height, number of leaves plant^-1, leaf area plant^-1 and seed yield were obtained in Binamoog-8 by spraying 100 ppm GA₃. Therefore, it infers that foliar application of GA₃at the rate of 100 ppm and Binamoog-8 had the best yield potentiality in Northwest of Bangladesh for profitable summer mungbean cultivation.

Keywords: Chlorophyll, GA₃, growth, mungbean, seed yield

To cite this article: Noor-E-Ferdous RA, Islam MS and Sarker BC. 2020. Influence of gibberellic acid (GA₃) on growth, chlorophyll and seed yield of summer mungbean cultivars in Northwest of Bangladesh. Intl. J. Agric. Med. Plants. 1(1): 26-35.

INTRODUCTION

Mungbean (Vigna radiata (L) Wilczek) is one of the most important pulse crops of global economic importance. It originated in the South and Southeast Asia and widely grown in Bangladesh, India, Pakistan, Mayannmar, Thailand, Philippinnes, China and Indonesia. Mungbean has special important as an accommodative crop with short growing period along with N₂ fixation in soil (Ferdous et al., 2012). Plant growth regulators (PGRs) are being used as an aid to enhance yield of different crops (Nickell 1982, Sarker et al. 2009, Bakhsh et al. 2011). Gibberellins are plant hormones with a wide range of activities including seed germination and cell elongation (Miransari and Smith 2009, Hayashi et al. 2014). Hussain et al. (2018) stated that growth parameters showed increment with foliar spray with gibberellic acid. It .breaks seed dormancy, stems elongation, enhances germination, internodal length, hypocotyls growth and cell division in cambial zone and increases the size of leaves, flowers and pods (Deotale et al. 1998). It is well established that gibberellic acid causes a dramatic increase in growth of mungbean. It increases dry weight (Hore et al. 1988) as well as seed yield (Maske et al. 1998). So, favorable conditions may be induced by applying growth regulator like GA₃ exogenously in proper concentration at a proper time in a specific crop. Considering the above fact, the present study was undertaken with the response of mungbean to GA₃ inrelation to growth, yield and qualityat Northwest in Dinajpur region of Bangladesh for profitable cultivation.

MATERIALS AND METHODS

The experiment was conducted at the Agricultural Farm of Hajee Mohammad Danesh Science and Technology University (HSTU), Dinajpur during the period from March to June 2011. The research site was located in Northwest of Bangladesh, an agriculturally important region. It is between 25.13º N latitude and 88.23º E longitude and at an elevation of 34.5 m above the mean sea level. The experimental land belongs to the Himalayan Piedmont Plain, Agro-ecological Zone (AEZ-1) and Ranishankail soil series classified by FAO (1988). The experimental field was a medium high land having sandy loam soil with pH 5.60. The experiment using three summer mungbean cultivars was considered as factor A (V₁-Binamoog-5, V₂-BARI mung 6 and V₃-Binamoog-8) while factor B were fourtreatments viz,. H₁-control (without GA₃), H₂-50 ppm GA₃, H₃-100 ppm GA₃ and H₄-150 ppm GA₃. The experiment was laid out in Randomized Complete Block Design (RCBD) with 2 factors. Twenty combined treatments were V₁ H₁ , V₁ H₂ , V₁ H₃ , V₁ H₄ , V₂ H₁ , V₂ H₂ , V₂ H₃ , V₂ H₄ , V₃ H₁ , V₃ H₂ , V₃ H₃ and V₃ H₄ ,respectively for the purposes.Crop management practices like fertilizer, irrigation and pest management were done properly as and when necessary. Three irrigations were applied where the first pre-sowing irrigation was done at the time of lime application@ 1.0 t ha^-1and were mixed with soil before two week of seed sowing (Ferdous 2016) for better germination, second irrigation was done after weeding and thinning, and third irrigation was done at flowering stage. Specific concentration of GA₃ for experimental treatments was prepared and applied in the form of foliar sprays at 25 and 45 DAS.

Yield and yield contributing characteristics: Three plants were selected randomly from each plot and plant height was measured from base of the plant up to the tip of the main stem. Plant heights of selected plants were taken at 15, 30, 45 and 60 days after sowing (DAS). Leaves (trifoliate) were counted on each sampled plant at 15, 30, 45, 60 DAS and mature stage. Three plants from each plot were collected carefully at 15, 30, 45, 60 DAS and at mature stage so that no root damage occurred. Root volume was measured by water displacing methods using 20 mL measuring cylinder followed by oven dried at 65^oC for 72 hours. The average dry root weight was calculated. The number of nodules in the root of each collected plants were counted and noted at 30, 45, 60 DAS and at mature stage.

Chlorophyll content: Fresh leaf samples from mungbean plants at the flowering stage were collected for chlorophyll estimation. Chlorophyll content of mungbean leaves was determined by following the method described by Arnon (1949).

Chl-a=12.21 A₆₆₃-2.81A₆₄₆ (mgg^-1 FW)

Chl-b=20.13 A₆₄₆-6.03A₆₆₃ (mgg^-1 FW)

Total carotenoid = (1000A₄₇₀- 2.05×Chl-a - 114.8×Chl-b) / 245 (mg g^-1 FW) by Porra (2002).

Proline content: Free proline content of leaves was estimated using the acid ninhydrin method described by Bates et al. (1973). Approximately 50 mg of fresh leaf sample (same leaf sample for chlorophyll estimation) at flowering stage was collected in a 2-mLEppendorf tube and extract was prepared using 3% sulfosalicylic acid. The optical density of solutions (sample solutions and standard solution) was measured at 520 nm wavelength using UV-visible spectrophotometer with the help of standard curve using proline standard series solution.

Seed yield: Seeds obtained from each unit plot were sun-dried and weighed carefully. The pod was collected by handpicking when full maturity came turning brown to black in color. Seed weights of sample plants were added to the respective unit plot yield to record the final seed yield per plot. Seed yield was expressed as kg ha^-1 after adjusting at 10% moisture level.

Statistical analyses: The obtained data on different parameters were statistically analyzed using the MSTAT-C program. The treatment means were compared by Least Significant Difference (LSD) followed by Duncan’s Multiple Range (DMRT) Test (Gomez and Gomez, 1984).

RESULTS AND DISCUSSION

Plant height: Plant height increased gradually with the advancement of the growth stages (15 -60 DAS) of the plants in all the cultivars (Table 1). Significant variations (P<0.05) were observed on plant height among the cultivars. The highest plant heights (10.36, 21.60, 43.59 and 66.29 cm) were observed in V₃ (Binamoog-8) and the lowest plant height were observed in 9.30, 19.92, 39.70 and 61.50 cm in V₂ (BARI mung-6) at 15, 30, 45 and 60 DAS, respectively. Plant height was significantly influenced by different concentrations of GA₃ at all growth stages of mungbean (Table 1). Applying 100 ppm GA₃ had the significant effect to stimulate more cell divisions in increasing height at 30, 45, 60 DAS and at maturity stages except 15 DAS, and the lowest dry root weight was observed in control. The interaction effect of cultivars and different concentrations of GA₃ were also statistically significant at different days after sowing (Table 1). The highest (10.73, 24.87, 45.93 and 70.68 cm) and the lowest (8.91, 17.75, 36.78 and 57.12 cm) plant heights were obtained in V₃H₃ (Binamoog-8 × 100 ppm GA₃) and V₂H₁ (BARI mung 6 × with no GA₃ application) treatments at 15, 30, 45 and 60 DAS, respectively. From theabove observation, it was found that plant height was increased with the 100ppm GA₃in Binamoog-8 variety. It is observed that GA₃ caused remarkably increase of plant height of' BARI mung 2 (Haque 2001). He reported that 100 mg L^-1 of GA₃ was more effective in stem elongation in mungbean.

Table 1. Effect of GA3 on plant height of summer mungbean and their interactions

Number of leaves per plant: Number of leaves plant-1 differed significantly (P<0.05) among the cultivars at different days after sowing. The highest number of leaves plant-1 (4.17, 5.51, 8.19, 10.49 and 9.42) was recorded in the Binamoog-8 (V3) which were statistically different among the cultivars and the lowest number of leaves plant-1 (3.32, 4.84, 6.37, 7.78 and 7.4) were in BARI mung 6 (V2) variety at all stages, respectively (Table2). Significantly the highest number of leaves (3.96, 5.62, 7.90, 9.95 and 9.00) was found spraying 100 ppm (H3) GA3 due to its biochemical activities. The lowest number of leaves (4.78, 6.48, 8.34 and 7.51) was observed in control plants at 30, 45, 60 DAS and mature stages, respectively except 15 DAS. Interaction effect of cultivars and different concentrations of GA3 was found in Table 2. A significance different was found with the interaction effect among the cultivars and different concentrations of GA3. The highest number of leaves plant-1was observed in V3H3during the entire growth stages. The lowest number of leaves plant-1 (3.16) was recorded in V2H4 at 15 DAS but the lowest number of leaves plant-1was found during whole growing period. Similar results was observed in Sarkar et al. (2002), who found that GA3 using 100 ppm in soybean plants produced higher number of leaves at the later stages of 60 and 80 DAS. Noor et al. (2017) found that GA3 at 50 ppm concentration in treated french bean plants produced higher number of leaves at the later stages of 48 and 58 DAS. It might be GA3 that stimulates cell enlargement and cell division and enhances plant height, number of branches and number of leaves in the present studies.

Table 2. Effect of GA3 on number of leaves plant-1 of summer mungbean and their interactions

Leaf area per plant: Effects of GA₃of different cultivars of mungbean was significantly differed on leaf area plant^-1 at 15, 30, 45, 60 DAS and mature stage (Table 3). The highest leaf area plant^-1 was found in V₃ plants and the lowest was observed in V₂ plants at 15 DAS. Leaf area plant^-1 was significantly influenced by the application of different concentrations of GA₃ at all growth stages of mungbean (Table 3). Significantly the maximum leaf area plant^-1 was observed while spraying 100 ppm GA₃ at 30, 45, 60 DAS and mature stage, respectively. The lowest leaf area plant^-1 was found spraying H₁ at 30, 45, 60 DAS and mature stage, respectively. A significant variation was found on leaf area plant^-1 at 15, 30, 45, 60 DAS and at mature stages by the interaction effect between cultivars and different concentrations of GA₃ (Table 3). Significant maximum leaf area plant^-1 was observed by applying V₃H₃ at 30 DAS to mature stage except at 15 DAS. Similarly, the lowest leaf area plant^-1 was obtained in V₂H₁at 30 DAS from mature stage. GA₃ induced higher leaf areas were reported in mungbean plant by Rahman et al. (2018), in rice plants (Liu et al. 2012) and tomato plants (Khan et al. 2006).

Dry root weight per plant: There was a significant variation of dry root weight plant^-1was observed except 15 DAS (Table 4). Dry root weight was the maximum in Binamoog-8 and BARI mung 6 during the whole growth stages using different levels of GA₃. Spraying 100 ppm GA₃ had the significant effect to produce more biomass in root at all stages except 15 DAS and the lowest dry root weight was observed in control. Dry root weight showed significant difference among the interaction effect between cultivars and different concentrations of GA₃ at 30 DAS to mature stage except 15 DAS (Table 4). Among the interaction effect, the highest dry root weight was observed in V₃H₃ (Binamoog-8 × 100 ppm GA₃) of 0.14, 0.53, 1.08 and 0.86 g at 30, 45, 60 DAS and mature stage, respectively. Similarly, significantly the lowest dry root weight was observed in V₂H₁ (BARI mung 6 × without GA₃) treatment of 0.05, 0.15, 0.36 and 0.32 g at 30, 45, 60 DAS and mature stages, respectively. Root dry weight was increased with increasing with NAA concentration (Ferdous et al. 2012) in mungbean plant and similar result was observed in Wang and Deng (1992) in rice plant.

Table 3. Effect of GA3 on leaf area plant-1 of summer mungbean and their interactions

Table 4. Effect of GA3 on dry root weight of summer mungbean and their interactions

Number of root nodule: The giberellins are also able to regulate the legume nodules production indicated recently. Hayashi et al., (2014) reported that the GA3 is important at two different growth stages of nodulation including the early stage of root colonization and the late stage of nodule production and maturity. A significant difference in number of root nodule was observed at all growth stages among three cultivars of summer mungbean (Table 5). Number of root nodule was the maximum (25.03, 49.69, 94.46 and 63.64) in V3 (Binamoog-8) and minimum (20.81, 35.50, 79.14 and 49.53) was observed in V2 (BARI mungbean) at 30 to 60 DAS and mature stage, respectively (Table 5).Number of nodule plant-1 differed significantly among four concentrations of GA3 at different days after sowing (Table 5). GA3 at 100 ppm had significant effect on Binamoog-8 producing of root nodule at 30 to 60 DAS and at mature stage while the lowest number of nodule was observed in control. The interaction effect of cultivars and different concentrations of GA3 were also statistically significant at different days after sowing (Table 5). Developments of root nodule are mainly dependent on phosphorous availability and the function of root nodule forming bacteria. Growth regulators cause increase in activity of root system and enhances biotic activities in the rhizosphere. Similar findings were reported, who stated that the foliar application of nutrients and growth regulators found to increase in the morpho-physiological parameters, number of root nodules plant-1 and dry weight of nodule in soybean by the foliar application of hormones and nutrients (Raut et al. 2017, Ketki and Thakare 2006). Foliar application of GA3 induced this effect at all the concentration applied. The present finding was in good agreement with Uddin (2009). The greater numbers of root nodule are beneficial for fixing atmospheric N2 by rhizobium bacteria resulted in N supply in soil. The present study indicated that the higher root nodulation produced by foliar spraying of GA3 might nourish N requirement for the mungbean plants, which might have supported N nutrition. Higher nodule formation in summer mungbean roots applying NAA application was reported by Ferrdous et al. (2012).

Table 5. Effect of GA3 on number of root nodule of summer mungbean and their interactions

Root volume: Root volume was recorded from 15 to 60 DAS. Significant maximum root volume was observed in V3 (Binamoog-8) treatment at 45 and 60 DAS (5.88 and 8.47cm3). Significant the lowest root volume was observed in V2 (BARI mung 6) at 15to 60 DAS (1.18, 2.34, 4.57 and 7.12 cm3) treatment (Table 6). The highest root volume was observed in H3 (1.16, 3.58, 5.83 and 8.52 cm3)at all growth stages and the lowest root volume was observed in control at 15 to 60 DAS(0.94, 1.93, 4.55 and 6.43cm3), respectively. The interaction effect of cultivar and different concentrations of GA3 for root volume was significant at 15 to 60 DAS. It is clear from the results that the highest root volume was observed in V3H3 treatment and the lowest was observed in V2H1 at 15 DAS and 60 DAS. Ferdous et al.(2012) revealed that NAA induced higher root volume in mungbean plants, which conformed the present study.

Table 6. Effect of GA3 on root volume of summer mungbean and their interactions

Chlorophyll content: There was no significant effect on chlorophyll-a content in leaves among the cultivars but levels of GA₃ (Table 7). It is noted that a significant effect was observed in the interaction among the cultivars and levels. The highest chlorophyll-a (1.37 mg g^-1FW) was found in with the application of 100 ppm GA₃ and the lowest (1.14 mg g^-1 FW) was observed in control (H₁) treatment. The highest amount of chlorophyll-a was obtained (1.39 mg g^-1 FW) in V₂H₃ leaves and the lowest chlorophyll-a (1.13 mg g^-1 FW) was in V₂H₁ leaves. Chlorophyll-b was maximum in V₃but minimum in V₂ treatment. Considering levels of GA₃, the highest chlorophyll-b content (0.54 mg g^-1 FW) was obtained in H₃ while the lowest content was 0.42 mg g^-1FWin H₁ (Control).The highest chlorophyll-b (0.58 mg g^-1 FW) was obtained in V₃H₃ and V₁H₃treatments, while the lowest chlorophyll-b (0.38 mg g^-1 FW) was observed in V₂H₁ leaves.

Carotenoid content: Results in Table 7 showed that carotenoid content differed significantly among the cultivars. Binamoog-8 (V₃) observed the highest carotenoid content (0.35 mg g^-1FW), which was statistically different from other cultivars and carotenoid content (0.32 mg g^-1FW) was found from BARI mung 6. This variation might be due to the GA₃ effect on different physiological activities. Carotenoid content was significantly influenced by application of different concentrations of GA₃ (Table 7). The highest carotenoid content (0.38 mg g^-1FW) was obtained in H₃, while the lowest content (0.31 mg g^-1FW) was found in H₁ treatment. The interaction effect of cultivars and different concentrations of GA₃ was statistically significant on carotenoid content.

Proline content: Proline content was non-significant among the cultivars and ranged from 1.35 to 1.41 mg g^-1 FW but was significantly influenced by the application of different concentrations of GA₃ (Table 7). The highest proline content (1.41 mg g^-1 FW) was obtained in H₄ while the lowest (1.33 mg g^-1 FW) was obtained in H₃ (without GA₃). The interaction effect of cultivars and different concentrations of GA₃ was also statistically significant on proline content (Table 7). The highest proline content (1.45 mg g^-1 FW) was obtained in V₃H₄ while the lowest proline content (1.31 mg g^-1 FW) was observed in V₂H₁. From the present investigation, important role of GA and proline was observed when applied as foliar spraying on mungbean. Proline application results in its rapid uptake and coupled with its synthesis in plant, thereby increasing the endogenous level of proline and also plays an important role for osmotic adjustment against various stresses (Ahmed et al. 2011). In addition to the role of osmo-protection, proline protects the enzymes, protein structure, cell organelles and membranes by checking lipid peroxidation and facilitates the energy supply for plant growth, and effective quencher of ROS formed through life cycle of plant and enhanced the activity of antioxidant enzymes. and therefore, proline increases resistance to unfavorable climatic conditions (Ashraf and Foolad 2007).

Seed yield: Seed yield differed significantly among the cultivars (Table 7). Binamoog-8 (V₃) showed the highest seed yield (1.29 t ha^-1), which was statistically different from other cultivars. Seed yield was significantly influenced by the application of different concentrations of GA₃ (Table 7). The highest seed yield (1.53 t ha^-1) was obtained in H₃ (100 ppm GA₃) while the lowest (1.02 t ha^-1) was obtained in H₃(without GA₃). The interaction effect of cultivars and different concentrations of GA₃ were found the highest seed yield (1.66 t ha^-1) in V₃H₃followed by V₁H₃ (1.56 t ha^-1). The lowest seed yield (0.98 t ha^-1) was observed in V₂H₁. The greater seed yield by applying 100 ppm GA₃ due to increased chlorophyll production and higher leaf area which might help in enhance photosynthesis in mungbean. GA₃ with different concentrations significantly enhanced seed yield in many crops as reported by a number of researchers (Beall et al. 1996, Uddin1999, Sarkar et al. 2002, Tiwari et al. 2011, Alam et al. 2018, Rahman et al. 2018, Sanjida et al. 2019).

Table 7. Effect of GA₃ on chlorophyll, carotenoid,prolineand seed yield of summer mungbean and their interactions

CONCLUSION

It is concluded that gibberellic acid (GA₃) had the positive stimulatory effect on growth, chlorophyll and seed yield production. The highest number of leaves plant^-1, leaf area plant^-1along with greater amount chlorophyll production enhanced seed yield obtained applying 100 ppm GA₃. The interaction among the cultivars with different concentrations of GA₃ showed statistically significant variation on the growth and yield parameters. The highest plant height, number of leaves plant^-1, leaf area plant^-1 and seed yield were obtained in Binamoog-8 by thrice exogenous spraying 100 ppm of GA₃. It is evidently suggested that Binamoog-8, a summer munbean cultivar in Bangladesh boosted up its yield potentiality by exogenous foliar application of GA₃ @ 100 ppm. Therefore, the findings infer thatGA₃ might help in producing more summer mungbean seed yield in Old Himalayan Piedmont Plain soil especially in Northwest of Bangladesh for environment friendly management practices.

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