WATER STRESS OF ALFALFA DURING STRESS AND RECOVERY

Abstract

Water status and stomatal activity of alfalfa (Medicago sativa L.) cultivars Cody and Sonora were evaluated under greenhouse conditions during water stress and recovery at the 7th leaf and full bloom developmental stages. Following onset of stress predawn LWP declined linearly and plants remained visibly wilted as potentials approached 1.8 MPa in both cultivars and developmental stages. Significant (P = 0.05) relationships were evident between predawn LWP and days after onset of stress (R 2 > 0.90) and between daily maximum leaf conductance (K L ) and predawn LWP (R 2 > 0.80) when averaged over both cultivars at each stage. Recovery of LWP of both cultivars was complete within 24 h after rewatering. Ability of stomatal activity to recover was similar for both cultivars and developmental stages and was attained within 32 h after rewatering. Results indicate that these cultivars, which differ in winterhardiness, do not differ in water status and stomatal activity with increasing water deficits.