The effect of seed presoaking with different concentrations of growth bio-regulators (indole acetic acid, gibberellic acid and kinetin) on productivity and some biochemical and physiological aspects of yielded seeds of cowpea ( Vigna sinensis L.) was investigated. Generally, application of growth regulators stimulated yield and yield quality of cowpea plants as compared to control plants through inducing a massive increase in number of pods/plants, seed biomass, pod length and number of seeds. In addition, results of this study showed that these growth regulators increased protein content and total soluble sugars in cowpea yielded seeds. Finally, it is evident from the present data that application of kinetin appeared to be the most effective hormone in stimulated productivity endogenous hormones and biochemical aspects in yielded seeds of cowpea plants.
Cowpea (Vigna sinensis L.) is one of the most popular and widely consumed vegetable crops all over the world, and high-quality yield is an essential prerequisite for its economic success in the Saudi Arabia. Cowpea is the most economically important indigenous legume crop [
Application of plant growth regulators to enhance growth and yield components of plants were studied [
Farghali and Hussein (1994) [
Foliar application of kinetin at 100 and 200 ppm caused a massive increase in shoot fresh weight of wheat plants [
Seeds of cowpea (Vigna sinensis L.) were obtained from Supermarket of Agricultural Research Center, Saudi Arabia. The selected seeds were surface sterilized in 5% sodium hypochlorite for 10 min, subsequently washed thoroughly with deionized water. The uniformed sterilized seeds (approximately one kilogram) were been divided into ten sets. Seeds of the 1st set were soaked in deionized water to serve as control, the 2nd, 3rd and 4th sets were soaked in different concentrations (25, 50 or 75 ppm) of gibberellic acid (GA3) for three hours respectively. The 5th, 6th and 7th sets were soaked in different concentrations (50, 100 or 150 ppm) of indole acetic acid (IAA) for three hours respectively. The 8th, 9th and 10th sets were soaked in different concentrations (25, 50 or 75 ppm) of kinetin for three hours respectively, then washed with distilled water. All these treated seeds were left to germinate for 5 days on a moistened filter paper in dark at 25˚C. Uniform germinated seedlings were sown in plastic pots (30 cm in diameter) containing equal amount of soil (Sand and Clay 2:1) and left to grow in a greenhouse under controlled conditions in a randomized complete block design at the research experimental farm of the Facility of Science, King Saud University, Riyadh. Soil characteristics used in this study were pH 7.18, electrical conductivity 1.81 ds cm−1, total organic matter 0.64%, total N: 98.0 mg kg−1, total P: 18.6 mg kg−1, Mg: 118 mg kg−1; K: 144 mg kg−1, and Ca+2: 565 mg kg−1. All plants were watered as needed with tap water to maintain soil moisture near field capacity (75% - 80%) and fed once weekly with 35 g potassium/m2 as superphosphate and 35 g nitrogen/m2 as potassium nitrate as a nutritive solution. Twelve weeks after sowing, six plants per each treatment were harvested.
Pod length, number of pods, number of seeds and 100-seeds weight of each treatment of cowpea plants were determined.
Harvest index = Grain yield/Above ground dry matter × 100 (Beadle, 1993).
Relative grain yield = Yield in treated plant/Yield in untreated × 100 (Beadle, 1993) [
Total soluble sugars (TSS) were determined after the extraction of dry seeds of each treatment in 10 ml of 80% (v/v) ethanol at room temperature with periodic shaking for 12 hours. TSS were determined using modifications of the method of Abdel-Fattah et al. (2002) [
Total protein in extracted seed yield of each treatment was determined by the method of Bradford (1976) [
A high performance liquid chromatographic (HPLC) method was developed to determine the four endogenous hormones including indole-3-acetic acid (IAA), abscisic acid (ABA), gibberellic acid (GA3), and kinetin in cowpea seeds. Methanol was chosen as the extraction solvent for the optimum conditions of separation. Then, the macerated extract was extracted by petroleum ether and ethyl acetate, and then purified with the Sep-Pak C18 column. The chromatographic conditions were as follows: Eclipse XDB-C18 reversed phase column (300 mm x 5.6 mm, 5 microm), the flow rate of 1 mL/min, the injection volume of 10 microL, and the detection wavelength of 240 nm were used for the separation of endogenous hormones. Methanol (A) and acetic acid aqueous solution (pH 3.6) (B) were used as the mobile phases with the linear gradient set as follows: 0 - 7 min 20% A, 7 - 10 min 20% A-28% A, 10 - 17 min 28% A, 17 - 19 min 28% A-40% A, 19 - 35 min 40% A. Extraction and purification was performance according the method of Terry et al. (1982) [
All data were subjected to statistical analysis using one-way analysis of variance (ANOVA). Using Duncan's multiple range tests, means were separated by the least significant difference (LSD, P ≤ 0.05) method using the Costat software (Cohort, Berkeley, Calif).
Comparing to control plants, cowpea seeds presoaking in different doses of IAA (50, 100 and 150 ppm) significantly increased length of pod, pods number, pod weight, number of seeds, 100-seeds weight, relative seed yield and harvest index of cowpea plants (
Concerning the effect of GA3, the results reported in
Seed presoaked in kinetin at all concentrations (25, 50 and 75 ppm) significantly increased yield and yield parameters of cowpea plants by increasing pod length, number of pods, pod weight, 100-seeds weight and harvest index (
Parameters | Indole acetic acid (ppm) | |||
---|---|---|---|---|
Control | 50 | 100 | 150 | |
Pod length (cm) | 8.2c | 10.5b | 12.0a | 12.8a |
Weight of pod (g) | 0.95c | 1.10bc | 1.89b | 2.94a |
Number of pods/plant | 2.93bc | 3.55b | 3.87b | 4.98a |
Number of seeds/pod | 4.51c | 6.11ab | 7.34a | 8.01a |
Harvest index (%) | 200c | 410b | 450a | 455a |
100 seeds weight (g) | 9.21b | 10.5ab | 11.25ab | 12.50a |
Relative seed yield (%) | 1.14b | 2.90a | 3.11a | 3.20a |
*Values in each row followed by the same letter(s) are not significantly different at P ≤ 0.05 (Duncan’s multiple range test). Each value represents the mean of six replicates.
Parameters | Gibberellic acid (ppm) | |||
---|---|---|---|---|
Control | 25 | 50 | 75 | |
Pod length (cm) | 8.97b | 11.22ab | 12.0a | 12.50a |
Weight of pod (g) | 0.73b | 1.11ab | 1.54a | 1.74a |
Number of pods/plant | 1.93bc | 2.55b | 3.01b | 3.98a |
Number of seeds/pod | 3.51c | 6.33b | 8.24a | 9.11a |
Harvest index (%) | 190c | 310b | 350b | 477a |
100 seeds weight (g) | 9.31b | 11.80ab | 12.26ab | 13.88a |
Relative seed yield (%) | 1.25c | 3.44b | 3.91ab | 4.20a |
See footnote in
Parameters | Kinetin (ppm) | |||
---|---|---|---|---|
Control | 25 | 50 | 75 | |
Pod length (cm) | 8.25c | 12.56b | 13.00a | 14.18a |
Weight of pod (g) | 0.90c | 1.66bc | 1.99b | 2.98a |
Number of pods/plant | 1.93c | 4.05b | 5.88b | 6.77a |
Number of seeds/pod | 4.11c | 6.81b | 7.99ab | 10.50a |
Harvest index (%) | 199d | 520c | 640b | 785a |
100 seeds weight (g) | 9.11c | 11.54bc | 12.28b | 14.90a |
Relative seed yield (%) | 1.11c | 3.55b | 4.98b | 5.55a |
See footnote in
of the different determined yield components of cowpea plants.
Based on the obtained results here, kinetin at the different used concentrations is the powerful growth regulator for improving the productivity of cowpea plants when compared with the other growth regulator treatments (IAA or GA3). Thus, the higher values for the different yield components were observed in the plant treated with different concentrations of kinetin.
As compared to control, treatment with growth regulators (IAA and kinetin) significantly increased total soluble sugars in the yielded seeds of cowpea plants (
Application of growth regulators increased the accumulation of protein in the
Treatments | Parameters | |
---|---|---|
Protein | Total soluble sugars | |
Control | 950e | 480d |
IAA | ||
50 | 1050e | 610cd |
100 | 1410cd | 835bc |
150 | 1580c | 892b |
GA3 | ||
25 | 1320d | 720c |
50 | 1560c | 725c |
75 | 1808ab | 740c |
Kinetin | ||
25 | 1530c | 922b |
50 | 1710b | 1038b |
75 | 1985a | 1316a |
See footnote in
yielded seeds of cowpea plants as compared to the control treatments (
Results of the changes in the endogenous auxins, cytokinins, gibberellins and abscisic acid contents in the yielded seeds of cowpea plants in response to application with IAA, GA3 or kinetin were recorded in
Three growth regulators were used in this study for improvement of some
Treatments | Parameters | |||
---|---|---|---|---|
IAA | GA3 | Cytokintin | Absisic acid | |
Control | 220d | 130c | 90d | 180a |
IAA | ||||
50 | 410b | 140b | 105c | 160b |
100 | 557a | 147b | 125b | 155b |
150 | 584a | 156b | 130b | 140c |
GA3 | ||||
25 | 250c | 135b | 98c | 155b |
50 | 278c | 142b | 110c | 130d |
75 | 310bc | 150b | 125b | 114ab |
Kinetin | ||||
25 | 505ab | 150b | 105c | 160b |
50 | 566a | 188a | 135b | 143c |
75 | 586a | 210a | 150a | 129d |
See footnote in
physiological activities and productivity of cowpea plants. From the results, it was observed that seed presoaking in different concentrations of IAA, GA3 or kinetin appeared to increase the different yield parameters (pod weight, pod length number of pods, number of seeds/pod, 100-seeds weight and relative growth yield) of cowpea plants when comparing with untreated control plants. The increase in cowpea productivity is probably due to the increase in rate of transpiration, and translocation of photosynthates from leaves to developing seeds caused by hormone treatments [
Growth regulators used in this study significantly increased total soluble sugars in the yielded cowpea seeds. These results are supported by the results of Khandaker et al. (2018) who stated that flower injection of IAA at 30 and 90 mg/L increased total soluble sugars of Abelmoschus esculentus. Furthermore, Kinetin application significantly increased soluble carbohydrates content and acid invertase activity [
From this study, it is clear that application of growth regulators significantly increased the protein content of developing cowpea seeds. IAA was reported by several investigators to cause an increase in protein and other nitrogenous compounds in several plant species [
It is clear from the present study that application of IAA increased endogenous auxins and gibberellins activities in the cowpea seeds. Similar effects was observed by Prajapati et al. (2015) who found that foliar application of IAA induced the up-regulated expression of gibberellin biosynthesis gene and produced more about polysaccharides so that growth may continue for longer periods. Furthermore, IAA initiates a signal transduction pathway resulting in production of secondary messengers that activate pre-existing H+-ATPases and stimulates the expression of several gens related to growth and development [
Kinetin application resulted in a significant increase in auxins, gibberellins and cytokinins of cowpea seeds. Such increase might have resulted from induction of influx of certain metabolites particularly sugars into seeds [
From the present obtained results, it can be concluded that seed presoaking with different concentrations of IAA, GA3 or kinetin increased yield quality of cowpea plants by inducing a remarkable increase in yield components as well as increases in protein content and total soluble sugars in yielded seeds. Also, it is evident from this study that kinetin application appeared to be the most effective hormone for improving productivity and endogenous auxins, gibberellin and cytokinin of cowpea plants. Further studies will be needed to investigate the effect of growth bio-regulators on some different metabolic pathways, molecular analysis and different enzymes in cowpea plants.
The author declares no conflicts of interest regarding the publication of this paper.
Al-Amri, S.M. (2018) Functional Activity of Some Growth Regulators on Yield Components and Endogenous Hormones of Cowpea Plants (Vigna sinensis L.). Agricultural Sciences, 9, 1229-1239. https://doi.org/10.4236/as.2018.910086