Drought acclimation in field growing subterranean clover plants

Abstract

The slow-induced drought response of subterranean clover plants was studied under field conditions. Soil and plant water status, leaf growth and photosynthetic characteristics were determined in simulated microswards with irrigation and with withholding watering. In response to soil water depletion, stomatal conductance was quickly reduced to 50% of controls without any significant change in water relation, later achieving extremely low values (0.1 mol m-2s-1). The evaporation rate was also reduced to 35-40% of irrigated plants, but the photosynthesis rate remained at 50%. A steep drop in water relations as well as leaf size and specific leaf dry weight was apparent by the 32nd day of water stress in the first group of mature leaves fully developed under drought. An osmotic adjustment in response to soil water depletion was clear. The reduction in leaf appearance rate as well as in single leaf area effectively contributed to the increase in water economy in the canopy. © 1994.