Abstract: Two wheat varieties differing in spring cold-sensitivity Yannong 19 (YN19) and Xinmai 26(XM26) were used as experimental materials. During the anther differentiation period, two temperature treatments of 4℃ and−4℃were set up in the smart climate box. At the same time, the average temperature of the ambient temperature was 10℃ as the control (CK). After the treatment, effects of low temperature stress during the anther differentiation period on leaf anatomical structure and photosynthetic characteristics of wheat were observed. The results showed that: (1) low temperature stress during the anther differentiation period significantly increased the SOD, POD, CAT enzyme activities and MDA content of functional leaves of the two wheat varieties, and the CAT enzyme activity increased the most. Compared with CK, XM26 increased by 48.68% and 87.55% at 4℃ and −4℃, while YN19 increased by 76.59% and 110.39%, respectively. Overall, the increase in antioxidant enzyme activity of YN19 was greater than that of XM26, and it had a strong ability to eliminate reactive oxygen species. (2) Low temperature stress destroys the chloroplast structure of wheat functional leaves. Compared with CK, the chloroplast number and chloroplast area of XM264℃ and −4℃ decreased by 12.43%, 24.97% and 57.68%, 5.88%, respectively, and YN19 decreased by 14.56%, 16.69% and 25.88%, 61.90%, respectively. With the decrease of temperature (4℃→−4℃), the number and thickness of grana lamellae in the leaves of the two tested wheat varieties also decreased significantly, the cell membrane was damaged to different degrees, and the grana lamella began to disintegrate. (3) With the deepening of low temperature stress, the contents of chlorophyll a (Chla), chlorophyll b (Chlb) and Chla+Chlb of the two tested wheat varieties decreased, and XM26 decreased by 26.97%, 27.39%, 31.78% compared with CK under −4℃ low temperature stress, while YN19 decreased by 34.36%, 23.81%, and 26.91%, respectively, indicating that low temperature stress destroyed the internal structure of leaves and reduces chlorophyll content. (4) Compared with CK, the net photosynthetic rate (Pn) of functional leaves of wheat under low temperature stress decreased gradually, and the intercellular CO2 concentration (Ci) increased gradually. The Pn of XM26 decreased by 31.84% and 92.04%, while that of YN19 decreased by 17.42% and 89.62% on the day of low temperature stress at 4℃ and −4℃, respectively, indicating that the decrease of Pn in wheat leaves was mainly caused by non-stomatal limiting factors. To sum up, the low temperature stress during the anther differentiation period will damage the wheat leaf function and reduce its photosynthetic capacity. Therefore, the cultivation and management measures should be strengthened in field production to improve the cold resistance of wheat and reduce the damage caused by late spring cold to wheat.

Key words: Wheat, Low temperature stress, Leaf anatomical structure, Photosynthetic characteristics