Variations in Physiological Response, Lipid Peroxidation, Antioxidant Enzyme Activities, Proline and Isoflavones Content in Soybean Varieties Subjected to Drought Stress.

Drought stress is one of the crucial factors
affecting the global plant growth and crop productivity. In
the present study, Indian soybean varieties (cv. JS 335 and
cv. KHSb-2) were examined for the changes in their antioxidant
enzyme activity, total isoflavone content and also
the influence on its growth under drought stress. Several
physiological responses, malondialdehyde, proline contents
and antioxidant activities of superoxide dismutase, catalase,
peroxidase, ascorbate peroxidase and glutathione
reductase were estimated under mild drought stress and
recovery stage respectively. Mild water deficit stress for
5 days during late vegetative stage increased total superoxide
dismutase activity in KHSb-2 than in JS 335 variety.
Water deficit stress triggered the activities of catalase,
peroxidase, ascorbate peroxidase and glutathione reductase
enzymes in KHSb-2 than in JS 335. High accumulation of
proline and lower level of lipid peroxidation were also
observed in KHSb-2 than in JS 335. The root and shoot
fresh and dry weight along with leaf relative water content
of cultivar KHSb-2 exhibited lesser reduction than in JS
335. The partial recovery of antioxidant enzyme activities,
elevated relative water content and growth parameters in
both varieties were compared to stress plants. Moderate
enhancement in total isoflavone content was observed in
KHSb-2 (3.44 % increase) and JS 335 (2.84 % increase) in
seeds subjected to mild stress. From nutraceutical point of
view, the results investigated would be vital for development
of soybean cultivar with drought tolerance and
moderate enhancement of isoflavone content under drought
stress.