Effects of exogenous trehalose on filling characteristics and sugar component content of wheat under high temperature stress during the filling period.

Taking the heat-sensitive wheat variety 'Fanmai 5' (FM5) and the heat-tolerant variety 'Huaimai 33' (HM33), which were screened out in the previous experiments, as experimental materials, we conducted a field experiment with passive heat-enhancing shelters to simulate post-flowering high-temperature environment (average temperature increase of 5.13 ℃) during 2021-2022. During the filling period, we analyzed the effects of exogenous trehalose (10, 15 and 20 mmol·L-1) on the filling characteristics and sugar fraction under high temperature, with no spraying at ordinary temperature as control (CK). The results showed that treating without spraying exogenous trehalose at high temperature (H) significantly reduced wheat grain yield and grain weight during the filling period, and spraying exogenous trehalose alleviated the reduction of grain yield and grain weight at the filling stage under high temperature stress. Compared with the H treatment, grain yield and grain weight of HM33 and FM5 wheat varie-ties increased by 3.5%, 6.7% and 4.2%, 5.4%, respectively. High temperature stress significantly increased the trehalose content and trehalase (THL) activity in flag leaves of both wheat varieties, and decreased the fructose and glucose contents. Spraying exogenous trehalose increased the contents of trehalose, fructose, and glucose in flag leaves, and decreased the trehalase activity in flag leaves compared with H treatment, which could improve the glucose metabolism capacity of wheat at filling stage. The increasing effect of FM5 was higher than that of HM33. High temperature stress significantly reduced starch content of flag leaves and grains, while spraying exogenous trehalose alleviated the decrease of starch content of flag leaves and grains under high temperature stress, which was profit able for the substance accumulation of wheat grains under high temperature stress. Under the conditions of this experiment, spraying 15 mmol·L-1 trehalose at flowering stage was the best treatment for the two wheat varieties.

[Effects of low temperature stress on photosynthetic performance of different genotypes wheat cultivars].

Different genotypes wheat cultivars (spring wheat Yangmai 18, semi-spring wheat Zhengmai 9023, and semi-winter wheat Yannong 19) were chosen to study their photosynthetic and chlorophyll fluorescence characteristics at tillering and stem elongation stages under low temperature stress. After treated with low temperature (-10 degrees C at night) at tillering stage for 2 days, the net photosynthetic rate (Pn), stomata conductance (g(s)), maximum quantum yield of PSII (Fv/Fm), photochemical quenching (q(P)), non-photochemical quenching coefficient (NPQ), and acyclic photosynthetic electron transfer rate of PSII (ETR) of Yannong 19 were significantly higher than those of Yangmai 18 and Zhengmai 9023, the g(s), Fv/Fm, qP, and NPQ of Zhengmai 9023 were significantly higher than those of Yangmai 18, while the intercellular CO2 concentration (Ci) of Yannong 19 was significantly lower than that of Zhengmai 9023 and Yangmai 18. In addition, the minimal fluorescence (Fo) of Yangmai 18 was significantly higher than that of Zhengmai 9023 and Yannong 19. Similarly, after treated with low temperature (0 degrees C at night) at stem elongation stage for 3 days, the Pn, g(s), qP, and Fv/Fm of Yannong 19 were significantly higher than those of Yangmai 18 and Zhengmai 9023, and the NPQ and ETR of Yannong 19 were significantly higher than those of Yangmai 18. In addition, the Pn, g(s), Fv/Fm, and qP of Zhengmai 9023 were significantly higher than those of Yangmai 18, the Fo of Zhengmai 9023 was significantly higher than that of Yannong 19, and the Ci and Fo of Yangmai 18 were significantly higher than those of Zhengmai 9023 and Yannong 19. It was suggested that under low temperature stress at tillering and stem elongation stages, semi-winter wheat Yannong 19 had the highest photosynthetic activity and the best self-protection mechanism, followed by semi-spring wheat Zhengmai 9023, and spring wheat Yangmai 18.