Non-water-stressed baselines: A key to measuring and interpreting plant water stress

Abstract

A plant water stress index has recently been developed which employs a radiometric measurement of foliage temperature and a psychometric measurement of the vapor pressure deficit of the air. To utilize the index, it is necessary to know the relationship that exists between foliage—air temperature differential and air vapor pressure deficit for the plant in question when it is well watered and transpiring at the potential rate. This information is provided for 26 different species for clear sky conditions in the format of non-water-stressed baselines. For six of these plants, including one aquatic species, such information is also included for cloudy or shaded conditions; and two grain crops have results presented for both pre-heading and post-heading growth stages.