Recovery of root water uptake of winter wheat after water stress

Experiments conducted with winter wheat in greenhouse show that root water uptake is reduced by water stress，and can not recover to the control level even after the relief of stress．The degree of the recovery after rewatering is affected by growth stage at which stress occur，stress level and stress duration．Under the same stress level root water uptake recovers to a lower degree if stress occurs at an earlier stage and to a higher degree if it occurs at later stages．Prolonged stress duration further reduces the recovery of water uptake．The severe stress at different growth stages affects the recovery in a different way．The recovery after severe stress started from three-leaf stage can surpas that after moderate stress，suggesting that earlier severe stress has no more negative effect on the recovery than the moderate stress．At other growth stages，stress level has negative effect on the recovery．Co mparative study of the maximum root dry weight and the maximum root water uptake indicates that recovery of water uptake under moderate stress mainly depends on recovery of the activity of the existing root system ，while that under severe stress mainly depends on the regrowth of new roots．The incapability in recovery of root water uptake represents the main factor for the decreased productivity．