Polyethylene glycol induced water stress in maize seedlings and evaluation of antioxidant defense mechanisms

Maize is one such crop, the production of which is highly challenged due to water shortage and soil water losses. The present study was undertaken on artificially induced water stress of maize in vitro, where stress was applied with PEG-6000 on one week old seedlings of four varieties BN 10, Dhanya. Kaveri-Super 244, and Swarna for 3, 5 and 7 days. The activity of antioxidative enzyme like peroxidase, catalase, ascorbate peroxidase, glutathione reductase and superoxide dismutase was assayed in the stressed and control plants. Peroxidase activity decreased on the 7th day in Dhanya and Swarna but in BN 101 and Super 244 the activity decreased slightly on the 5th day and increased again on the 7th day. Ascorbate peroxidase and superoxide dismutase showed a similar trend where the activity decreased after a certain period of stress. Similar trend was seen for GR activity too in case of Dhanya and Swarna. But in BN 101 and Super 244 there was an increase in the activity with the increase in the period of stress. Catalase activity declined during stress in Dhanya and Swarna while the other two varieties showed an increase during stress. Other than enzymatic activities, various biochemical analyses like proline, ascorbate, chlorophyll was also carried out. With the increase in intensity of drought there was an increase in both proline and ascorbate content in all. A significant increase in the ascorbate content was observed in BN 101 and super 244, H202, accumulation and lipid peroxidation showed an increase during stress in Dhanya and Swarna but no increase was seen in the other two varieties. Chlorophyll content showed a decline during the period of drought when compared to the control plants of all varieties. Enzymatic activity and biochemical tests show that Dhanya and Swarna are susceptible to drought stress than super 244 and BN 101 which are the tolerant varieties.