The Effect of Soil Moisture Stress to Various Fractions of the Root System on Transpiration, Photosynthesis, and Internal Water Relations of Peach Seedlings1

Abstract

Peach [ Prunus persica (L.) Batsch] seedlings were grown in large sectional boxes with root systems divided into 4 separate quadrants. Groups of peach seedlings with 3, 2, 1, and 0 quadrants of the root system deprived of water for 3 weeks, were further subjected to moisture stress in all quadrants by withholding water for 5 days, and they were then rewatered. In another treatment, seedlings were subjected to 2 cycles of water stress, applied 3 weeks apart, by completely depriving all quadrants of water until the plants wilted. Transpiration, photosynthesis, stomatal conductance, and xylem pressure potential were measured. Subjecting a large portion of the root (50%) to stress by withholding water only caused a small reduction (17%) in transpiration, photosynthesis, and stomatal conductance. Subjection of various fractions of the root system to severe moisture stress did not affect the shoot:root ratio. The reduction in root growth in dry quadrants was accompanied by the production of more roots in wet quadrants and less transpiring leaf surface and branch growth. The rate of recovery of transpiration and photosynthesis from water stress was greatly influenced by the duration and intensity of wilting as well as by the rate of regeneration of new root systems.