| Abstract: | Aims Water use efficiency (WUE) and drought tolerance of crops are important in arid and semiarid areas. Our objective was to investigate the effects of root pruning at the regreening stage on drought tolerance and WUE of winter wheat (Triticum aestivum) in late growing stage. Methods We manipulated root size by root pruning regreening plants grown in pots. In a light root pruning treatment, we partially cut off the secondary lateral roots along one side of the plant. In a heavy root pruning treatment, we partially cut off the secondary lateral roots along four sides of the plant. Control plants (CK) were left intact. Important findings Both the root pruning treatments reduced the root system significantly, but their root/shoot ratio remained similar. The values of chlorophyll fluorescence parameters, i.e., the maximum photochemical efficiency of PSⅡ (Fv/Fm), PSⅡ potential activity (Fv/Fo), effective PSⅡ quantum yield (ΦPSⅡ), apparent rate of photosynthetic electron transport (ETR), coefficient of photochemical quenching (qP) and coefficient of non-photochemical quenching (NPQ), were significantly higher in both treatments than the control 8 days after withholding water at anthesis. This means that root pruning improved drought tolerance of wheat, resulting in improved photosynthetic capability. Light root pruning had no significant effects on grain yield under wet condition, but improved yield under moderate drought stress. Therefore, light root pruning wheat produced a higher index of drought resistance compared with the control. Light root pruning improved WUE of wheat under two water conditions. Heavy root pruning did not improve WUE or the index of drought resistance due to a reduced shoot density and grain yield. The study showed that reducing root size moderately through breeding or agricultural measures would be beneficial to improving drought tolerance and WUE in winter wheat. |
