Response of Droughted Wheat to Mid-Season Water Application: Recovery in Leaf Area and Its Effect on Grain Yield

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Abstract
Three varieties of wheat contrasting in drought resistance were sown in the field at two levels of soil moisture and water was applied on three occasions by the cumulative application of 75 mm or less water with a line-source sprinkler system. Application of water resulted in recovery of mean maximum leaf area index (LAI) from 0.5 to 3.0. Variety C306, known for its drought resistance, maintained maximum LAI around anthesis relative to other varieties. Since LAI was directly related to grain yield irrespective of the variety, we conclude that maintenance of high LAI at anthesis is desirable for obtain- ing high yield in stressed plants. Mid-season water application resulted in the recovery of flag leaf area (FLA) of the main shoot and the first tiller in all the varieties. However, only in C306 did FLA equal that of its irrigated control. The recovery of FLA resulted in a proportionately greater increase in the grain yield of the main shoot. By comparison, in the first tiller, increase in grain yield was much lower though its flag leaf area had considerably recovered. Grain yields of varieties did not differ in two drought situations - where all water was available at sowing or where 56% of the total water was available before sowing and the rest was supplied during vegetative growth. Among the varieties, only C306 showed a significant (30%) improvement in grain yield in the latter situation compared to the former.