Alterations in the Components of Peanut Leaf Water Potential during Desiccation

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Abstract
Changes in components of leaf water potential during soil water deficits influence many physiological processes. Research results focusing on these changes during desiccation of peanut (Arachis hypogeae L.) leaves are apparently not available. The present study was conducted to examine the relationships of leaf water ψl, solute ψs and turgor ψp potentials, and percent relative water content (RWC) of peanut leaves during desiccation of detached leaves and also during naturally occurring soil moisture deficits in the field. The relationship of ψp to ψl and RWC was evaluated by calculating ψp from differences in ψl and ψs determined by thermocouple psychrometry and by constructing pressure-volume (P-V) curves from the ψl and RWC measurements. Turgor potentials of ‘Early Bunch’ and ‘Florunner’ leaves decreased to zero at ψl of −1.2 to −1.3 MPa and RWC of 87%. There were no cultivar differences in the ψl at which ψp became zero. P-V curves indicated that the error of measuring ψs after freezing due to dilution of the cellular constituents was small but resulted in artefactual negative ψp values. Random measurements on two dates of ψl, ψs, and calculation of ψp from well-watered and water-stressed field plots consisting of several genotypes indicated that zero ψp occurred at ψl of −1.6 MPa. It was concluded that the relationships of ψp, ψl, ψs, and RWC of peanut leaves were similar to leaves of other crops and that these relationships conferred no unique drought resistance mechanism to peanut.