Effect of water deficit during vegetative growth periods on post-anthesis photosynthetic capacity and grain yield in winter wheat (Triticum aestivum L.)

Determining the effect of water deficit during vegetative growth periods on grain yield will provide reasonable strategy for water-saving management of winter wheat (Triticum aestivum L.). Pot experiment was conducted using winter wheat cultivar (Yangmai16) to investigate the effects of water deficit during vegetative periods on post-anthesis photosynthetic capacity and the relationship with grain yield formation during the growing season of 2013-2014. Water deficit consisted of moderate (leaf water potential of -1.20 to -1.40 MPa) and severe (leaf water potential of -1.80 to -2.20 MPa) levels during tillering and jointing growth stages, respectively. Moderate water deficit during tillering significantly increased grain yield through an enhanced yield capacity per stem and moderate water deficit during jointing resulted in similar grain yields as compared to control, while severe water deficit during both periods significantly reduced grain yield due to strong reduction in number of spikes as compared to control. Moderate or severe water deficit during tillering had no effect on flag leaf area but reduced it significantly when it occurred during jointing. Water deficit treatments during jointing and tillering increased net photosynthetic rate (P-n) of flag leaves, the treatment during jointing being the most stimulatory. The maximum photochemical efficiency of Photosystem II, actual photochemical efficiency, the maximum carboxylation rate and photosynthetic electron transport rate increased in ways similar to Pn in response to water deficit but non-photochemical quenching decreased. We conclude that improved photosynthetic capacity by moderate water deficit during vegetative growth period highly contributes to grain yield, especially during tillering period, while grain yield decreased by the limitation of leaf area and spikes under severe water deficit.