INFLUENCE OF THE DURATION OF FAVORABLE MOISTURE BETWEEN DROUGHTS ON WHEAT

Diverse effects of 3,6, 9 and 12 days of favourable moisture between two drought cycles on wheat (Triticum aestivum L. cv. Kalyan sona) have been reported here. The first cycle of drought imposed for a period of 10 days on separate sets of plants at 51, 54,57 and 60 days after sowing (DAS) caused comparable reductions in plant water potential (psi plant), relative turgidity (RT%) and grain yield. All these plants were simultaneously subjected to a second cycle of drought at 73 DAS for a uniform period of 9 days. Observations on psi plant, RT, stomatal resistance and also contents of free amino acids, free proline and soluble protein, at the end of the second drought cycle and 48 h after irrigation, indicated that the adverse effects of water stress were more severe in plants which were given shorter (3 and or 6 days) compared to longer (9 and 12 days) periods of adequate soil moisture between two droughts. Changes in the activities of amylase, nitrate reductase, malate dehydrogenase and glucose-6-phosphate dehydrogenase generally revealed a similar trend. Notwithstanding a larger decline in grain yield under two, as compared to one cycle of drought, the grain yield was also depressed more under shorter (3 and 6 days) as compared to longer (9 and 12 days) period of adequate water supply between the stress events. Evidences provided here show that, among other factors, the period of favourable moisture between droughts has a significant influence on metabolism and crop performance.