Changes in plant water relations of wheat and soybeans after relief of water stress

Abstract

The ability of a crop to recover from a mild or severe water stress and the rate of recovery are of importance for irrigation management and are also linked to the drought resistance and water use efficiency of the crop. The present study was conducted on soybean and wheat crops, and involved daily monitoring of various plant water status parameters both before and after irrigation. Leaf water potential (ψL) and stomatal diffusive resistance recovered to the levels of a well-watered crop within a matter of days after relief of a mild stress, but took considerably longer following a severe stress. For example, soybean ψL recovered in 1 day, while wheat ψL. took 2 days following a mild stress, whereas thé ψL. of the severe treatment never quite recovered to the control value. The osmotic potential (ψL) on the other hand, remained lower than that of the well-watered control for several weeks after stress in both crops, thus maintaining a higher préssure potential. The degree of osmotic adjustment indicated by the lowered ψL and rates of recovery were related to the severity of the water stress experienced. Results indicate that the intensity and duration of water stress experienced by a crop affects the recovery after irrigation, and that these effects need to be considered in crop water use and modelling studies.