Pre-anthesis night warming improves post-anthesis physiological activity and plant productivity to post-anthesis heat stress in winter wheat (Triticum aestivum L.)

Global warming is asymmetric, with the increase in temperature at night being greater than that during the day. In this study, we conducted night warming treatments using a passive heating device on the wheat variety 'Yangmai 1' grown in culture pots in an experimental field. The night warming treatments were performed from the tillering stage to the jointing stage (NWT-J), from the jointing stage to the booting stage (NWJ-B), and from the booting stage to the anthesis stage (NWB-A). A non-warming treatment was used as a control (NN). Post-anthesis heat (H) stress was performed during the grain-filling stage. The results showed that treatments NWT-J and NWJ-B significantly enhanced grain yield by increasing the 1000-grain weight, while the NWJ-B treatment showed the highest impact. Night warming treatments at early growth stages significantly prevented the grain-yield reduction caused by heat stress during grain filling. NWJ-B treatment increased the sucrose content and sucrose phosphate synthase (SPS) activity of the flag leaves under heat stress during grain filling, which increased the ability of the plants to convert post-anthesis photoassimilates into sucrose, providing a basis for the accumulation of sucrose in the grains. Meanwhile, NWJ-B treatment increased the ability of the plants to assimilate and utilize nitrogen by increasing the nitrogen content and activity of nitrate reductase (NR) and glutamine synthetase (GS) of the flag leaves under heat stress during grain filling. Post-anthesis assimilation products and the activities of the enzymes related to carbon and nitrogen metabolism in wheat plants subjected to night warming treatments maintained at a higher level, which promoted the formation and conversion of proteins and starches in the grains at the late growth stages. Night warming treatments from the jointing to booting stage effectively improved post-anthesis physiological activity and plant productivity, which reduced yield loss caused by heat stress during grain filling.