Spring low temperatures are a serious natural threat to wheat production in the Huang-Huai wheat region, and they are often accompanied by weak light environments during the day. To elucidate the response patterns and adaptation mechanisms of winter wheat leaves to low-temperature and weak-light environments, we simultaneously measured prompt chlorophyll a fluorescence, delayed chlorophyll a fluorescence, and modulated 820 nm light reflection; moreover, we analyzed the effects of low temperature and weak light treatment for different duration (2 h and 4 h) on the donor-side activity of photosystem II (PSII), the degree of PSII unit dissociation, the efficiency of light energy absorption and capture by PSII, electron transfer to Q_A⁻ and PSI terminal, PSI activity and cyclic electron transport activity in isolated wheat leaves under controlled conditions. The results, which were corroborated using the three methods, revealed that in low-temperature and weak-light environments, the degree of PSII unit dissociation, and the efficiency of light energy absorption, capture, and electron transfer to Q_A⁻ decreased, while the donor-side activity remained unaffected. In contrast, the efficiency of electron transfer to the PSI terminal and the overall performance of photosynthetic electron transport increased. Comprehensive analysis suggests that the increase in the electron receptor pool at the PSI terminal under low-temperature stress is a crucial factor contributing to the enhanced electron transfer efficiency to the PSI terminal and the improved overall performance of the photosynthetic electron transport chain, which is also a crucial factor in the high cold tolerance of winter wheat.

Appropriate deep sowing holds significant potential in enhancing wheat production, particularly in dry and low-rainfall regions. Henan Province is a major winter wheat-producing area in China; evaluating the adaptability of wheat varieties to deep sowing through scientific methods is crucial to improve wheat production. This study investigates 26 wheat cultivars in Henan. By assessing key traits of seeds and seedlings at various sowing depths, we analyzed the effects of sowing depth on seed germination and seedlings. A comprehensive index for deep sowing tolerance was established using principal component analysis (PCA) and the membership function method, followed by the classification of the varieties according to their tolerance to deep sowing. The results indicated that, with increased sowing depth, seedling emergence time, coleoptile length, and coleoptile internode length increased, while seedling emergence rate, seedling height, leaf area, and shoot dry weight per unit area decreased. Based on PCA and membership function values, the 26 wheat varieties were classified into three categories: deep sowing tolerant, moderately tolerant, and intolerant, comprising 3, 19, and 4 varieties. This study provides valuable insights for optimizing wheat variety selection and improving sowing practices in Henan Province, offering both theoretical and practical contributions to local wheat production.