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Canopy temperature was measured on cotton plants , grown in 30 rows . The temperature difference (?t) between plant canopy (50 cm above the ground ) and air ( 200 cm above the ground ) were related to leaf water potential and soil water content, by making simultaneous and-daily measurments of these parameters . The data, obtained at 1400 hours , show that plant water potentials ranged from -15 bars at the day after irrigation , to -35 bars at the time of wilting . At the first day after irrigation , 4,t was high (5°c), however, it decreased ( to near zero ) , after wards . The results demostra ted a direct relation between ?t and leaf water potential and thereby place a firm foundation under the temperature difference method for sensing plant responses
to drought