Field Pea Transpiration and Leaf Growth in Response to Soil Water Deficits

No quantitative functions exist to describe transpiration rates and leaf expansion rates of drought‐stressed field pea (Pisum sativum L.) plants relative to well‐watered plants. Such functions are especially important in analyses of the effects of water deficit periods on crop yield under a range of field conditions. Pot and field experiments were conducted to develop and evaluate drought‐stress functions for transpiration and leaf area expansion. These functions were obtained in a dehydration cycle where plant response was monitored as the soil dried progressively. The level of water deficit was characterized as the fraction of transpirable soil water (FTSW). Transpiration and leaf area expansion did not change appreciably until FTSW reached = 0.4, and then decreased linearly through FTSW equal to 0. Drought response functions obtained for transpiration and leaf area expansion in a pot study also well represented the results obtained in independent pot and field studies.