关键词: 干热河谷, 光合特性, 光合限制, 抗旱策略

Abstract: 【Aims】The contradiction between water and heat is prominent in the dry–hot valley, where extreme drought in May severely restricts vegetation restoration. However, the photosynthetic limitation mechanisms and adaptive strategies of different plants under water stress remain unclear. To elucidate the differences in drought resistance, this study systematically analyzed the photosynthetic physiological responses of Leucaena leucocephala, Pueraria montana, and Crotalaria pallida to water stress.【Methods】A pot experiment was conducted with four water treatments: normal watering (CK, soil relative water content 75%–80%), mild drought (T1, 60%–65%), moderate drought (T2, 45%–50%), and severe drought (T3, 30%–35%). Physiological indices and photosynthetic parameters of the three plant species were measured, and their drought resistance was comprehensively evaluated using principal component analysis (PCA) and membership function analysis. 【Results】 With increasing water stress, plant height, ground diameter increment, and net photosynthetic rate of all three species decreased significantly. Distinct photosynthetic limitation strategies were observed: photosynthesis of L. leucocephala and C. pallida was mainly dominated by stomatal limitation, whereas that of P. montana was primarily restricted by non-stomatal factors. Under severe stress, proline content in C. pallida and L. leucocephala accumulated sharply, and malondialdehyde (MDA) content increased significantly in C. pallida, while osmotic regulation and oxidative stress responses in P. montana were relatively weak. PCA results indicated that the drought resistance of the three species followed the order: L. leucocephala > C. pallida > P. montana.【Conclusion】 Water stress had significant effects on the physiological and photosynthetic characteristics of the three plant species. It is suggested that L. leucocephala be used as the dominant species and C. pallida as an accompanying species in vegetation restoration of dry–hot valleys, while P. montana should be planted only in areas with relatively favorable water conditions.

Key words: dry-hot valley, photosynthetic characteristics, photosynthetic limitation, drought strategy