Genotypic variation in peanut for transpiration response to vapor pressure deficit
Conservation of soil water resulting from decreases in stomata conductance under atmospheric high vapor pressure deficit (VPD) conditions is a possible approach for enhanced tolerance of water deficit by crops. Water deficit is usually a concern in peanut (Arachis hypogea L.) since it is frequently grown on sandy soils with low water-holding capacity. Seventeen peanut genotypes were studied to determine the response of their transpiration rates (TR) to VPD. The results of this study demonstrated variation among peanut genotypes with nine genotypes exhibiting a breakpoint in their VPD response at about 2.2 kPa, above which there was little or no further increase in TR. Therefore, these genotypes with a breakpoint have the possibility of soil water conservation when VPD exceeded 2.2 kPa. The remaining eight genotypes had a linear response in TR over the whole range of tested VPD. Also, the 17 genotypes could be separated into groups with differing rates of increasing TR at low VPD. The change in TR with increasing VPD may be important in determining the rate at which soil water is used under field conditions.