Compensative effects of chemical regulation with uniconazole on physiological damages caused by water deficiency during the grain filling stage of wheat

Chemical regulation using plant growth regulators has proved to be potentially beneficial in water-saving agriculture. This experiment was conducted with winter wheat (Triticum aestivum L. cv. 'Jingdong 6') to study the effect of chemical regulation on alleviation of water deficit stress during the grain filling stage. Uniconazole, a plant growth regulator, was foliar sprayed at 85% (adequate irrigation) and 60% (deficit irrigation) field capacity. Results showed that the distribution of H-3-H2O in roots and flag leaf, characteristics of vascular bundle in primary roots and internode below spike, roots activity, transpiration rate and stomatal conductance of flag leaf were negatively affected by deficit irrigation after flowering. Foliar spraying at the early jointing stage with 13.5 gha(-1) uniconazole was able to relieve and compensate for the harmful effects of deficit irrigation. Both the area of vascular bundle in primary roots and internode below the ear were increased by uniconazole, while root viability and their ability to absorb and transport water were increased. In the flag leaf, stomatal conductance was reduced to maintain the transpiration rate and water use efficiency (WUE) measured for a single wheat plant was higher. Uniconazole increased WUE by 25.0% under adequate and 22% under deficit irrigations. Under adequate irrigations, the C-14-assimilates export rate from flag leaf in 12 h (E(12)h) was increased by 65% and 36% in early and late filling stages, while under deficit irrigations, the E(12)h of uniconazole-treated plants exceeded that of control plants by 5% and 34% respectively. Physiological damages caused by water deficiency during the grain filling stage of wheat was alleviated by foliar spraying with uniconazole.