INFLUENCE OF AIR TEMPERATURE, LIGHT INTENSITY, SOIL MOISTURE STRESS AND SOIL AERATION ON MOISTURE USE BY WHEAT

Abstract

In growth chamber experiments, it was found that total and rate of moisture use by wheat were directly proportional to light intensity, except under conditions which restricted growth.Increasing the day temperature from 21° to 27 °C reduced the total moisture use. This was attributed to the greater vegetative dry matter produced at 21 °C. Under high soil moisture stress, (0.2 to 15 atm), plants used less water at a slower rate than at the lower stress (0.2 to 1.4 atm), but the moisture treatment had little effect on moisture use per gram of dry matter Apparently, under the conditions of this experiment the most important cause of reduced transpiration at high moisture stress was reduced plant growth.At about the late tillering to stem-extension stage, wheat was surprisingly insensitive to changes in moisture stress. An increase in soil moisture stress during this period did not result in the usual reduced rate of moisture consumption.Irrespective of the growth stage at which the stress was changed (increased or decreased), stress had little influence on moisture use per unit of straw dry matter. If the soil was "wet" (0.2 to 1.4 atm) at about the stem-extension stage, poor seed set occurred and thus moisture use per gram of seed was increased. When plants were provided with adequate aeration, moisture use per gram of seed was one-third that of plants grown under poor aeration.