The Relations of Stomatal Conductance, Water Consumption, Growth Rate to Leaf Water Potential During Soil Drying and Rewatering Cycle of Wheat (Triticum aestivum)

Abstract

The wheat, Triticum aestivum, was used to study the relationships among stomatal conductance, water consumption, and growth rate to leaf water potential during a soil drying and rewatering cycle. Stomatal conductance of wheat steadily decreased with decreases in the days of drying and leaf water potential. Upon rewatering, leaf water potential rapidly returned to the control levels, whereas the reopening of stomata showed an obvious lag time. The length of this lag time was highly dependent on times of the drying and rewatering cycle. The result proved that the drying-rewatering alternation had a significant aftereffect on wheat stomata that could reduce wheat transpiration. The results of the trial showed that the slowly intensified soil water deficiency and the following recovery of soil moisture could decreased the osmotic regulation of wheat, keep wheat leaves turgid and growing under water deficient conditions, and decrease the threshold of leaf water potential below which wheat growth would slow much more rapidly. The fact that, at the same leaf water potential, the wheat growth rate after the recovery of soil moisture was higher than before indicates that the osmotic regulation induced by the drying and rewatering alternation could keep wheat growing and wheat soil water use efficiency significantly increasing under drought conditions. The decreased wheat water consumption mainly resulted from the decreased stomata conductance and transpiration rate. During the recovery of soil moisture, the transpiration through stomata, although wheat growth rate was able to return to normal, did not completely recover. This showed that the drying and wetting alternation had after-effects on wheat growth. Meanwhile, the drying and rewatering alternation increased the ratio of root dry weight to shoot dry weight.