[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.