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Climate change has resulted in a continuous increase in the frequency, intensity, and duration of extreme low-temperature events and poses a serious threat to wheat production in China. To better understand the effects of low temperature on wheat photosynthetic production and yield formation, two-year temperature controlled experiments in phytotrons were performed with two different cold-sensitive winter wheat cultivars at five daily maximum/minimum temperature levels and three temperature durations—2, 4 and 6 days—at both jointing and booting stages. Except for its effect on mean net assimilation rate (MNAR) at jointing, low temperature level had significant negative effects on mean leaf area index (MLAI), mean net assimilation rate (MNAR), harvest index (HI), biomass per plant (BPPM) and grain yield per plant (GYPP), while photosynthetic duration (D) (except for Yangmai16 at jointing) was significantly positively affected. Moreover, low temperature duration and its interaction with low temperature level had negative effects on MLAI, MNAR, HI, BPPM and GYPP, but only the effects of low temperature duration on HI, BPPM and GYPP and the interaction effect on BPPM and GYPP reached a significant level. In addition, BPPM and GYPP were more sensitive to low temperature at booting than at jointing stage. Furthermore, significant negative linear relationships were observed between the accumulated cold degree days (ACDD) and MLAI, MNAR, HI, BPPM and GYPP, while a significant positive linear relationship was observed between ACDD and D in both cultivars. The contribution of BPPM to the variation of GYPP was greater than that of HI in both cultivars. However, for biomass, from the first day of low-temperature treatment to maturity (BPPT-M), the major variation was caused by MLAI when low temperature occurred at jointing and by MNAR when low temperature occurred at booting. These results could support the improvement of crop model algorithms under cold stress and assist in the wheat breeding with higher cold tolerance.
Liu et al. (Sat,) studied this question.