Changes in xylem water potential (XWP) of three wheat varieties (KSML 3, WG 357 and WL 410) grown in a field under different soil moisture regimes were examined. The crop was given light and severe stress at crown root initiation and flowering stages and the resultant effect on the XWP of plant leaves was compared with that in the non-stressed crop and that remaining totally rainfed. The potential decreased at the maximum rate of 0.2 bar/min for 20 to 30 minutes after sunrise but within an hour the rate became slow. At sunset, the rate of recovery in XWP was more in rainfed than in irrigated wheat. Changes in XWP around sunrise and sunset corresponded to variations in air temperature. XWP of the irrigated crop remained higher till mid-day but thereafter it dropped below that of the rainfed wheat leaves. The pattern of diurnal variations in the XWP of the three wheat varieties was almost similar though the absolute values were different. Differences in the XWP of irrigated and rainfed wheat leaves decreased with ageing indicating thereby the inherent ability to adapt to conditions of moisture stress.
Soil moisture regime, wheat, xylem water potential
