Effect of Low Temperature on Photosynthetic Characteristics, Senescence Characteristics, and Endogenous Hormones of Winter Wheat "Ji Mai 22" during the Jointing Stage

To investigate the effects of low-temperature (LT) stress on photosynthetic properties and senescence characteristics of winter wheat leaves during the jointing stage, an environmental temperature control experiment was designed at Nanjing University of Information Science and Technology in 2023, using Triticum aestivum L. cv. "Ji Mai 22" as the test material. Four different temperature levels were set: 18 degrees C/8 degrees C (daily maximum/daily minimum temperature; CK), 13 degrees C/3 degrees C, 10 degrees C/0 degrees C, and 7 degrees C/3 degrees C. The duration of each treatment was 2, 4, and 6 days, respectively. The experimental findings reveal that the changes in physiological parameters of winter wheat leaves under low-temperature stress treatments are nonlinear. Under the 3 degrees C LT treatment, the photosynthetic parameters and endogenous hormone levels of wheat leaves significantly decrease after 6 days of stress. Under the 0 degrees C LT treatment, the photosynthetic parameters, leaf pigment content, and endogenous hormones of wheat decrease significantly, while under the -3 degrees C LT treatment, all the parameters of winter wheat leaves show a significant decline. Generally, the "Ji Mai22" wheat cultivar has a lower growth temperature limit of -3 degrees C during the jointing stage.