Zhang Hai-Xia, Li Huie
College of Agriculture, Guizhou University, Guiyang, Guizhou, 550025, China.
J Plant Res. 2025 May;138(3):433-446. doi: 10.1007/s10265-025-01620-0. Epub 2025 Feb 8.
The summer heat is a vital factor limiting the introduction of relatively large-leaf Rhododendron plants to low-altitude areas, making it crucial to evaluate the resistance of different germplasm to summer heat. A pot experiment was conducted in 2023 to investigate the temporal changes in the photosynthetic characteristics, physiological and biochemical characteristics, and chlorophyll fluorescence characteristics of 14 representative relatively large-leaf Rhododendron germplasm. The results showed the R. irroratum and 'Hotspur Red' exhibited the highest heat damage index (HDI), while R. jiulongshanense and 'Moser Maroon' had the lowest HDI among the 14 Rhododendron germplasm. The photosynthesis rate and F/F (maximum photochemical efficiency) initially decreased and then recovered in all germplasm except R. irroratum. In contrast, the leaf transpiration rate, stomatal conductance, and chlorophyll content gradually increased. Hydrogen peroxide concentration first decreased and then increased, while malondialdehyde concentration initially increased and then decreased. Additionally, the superoxide anion content gradually increased. The activities of superoxide dismutase, peroxidase, and catalase (CAT) initially increased and then decreased. The HDI was positively correlated with CAT activity (r = 0.28, P < 0.05) but negatively correlated with photosynthesis rate (r = -0.26, P < 0.05), leaf transpiration rate (r = -0.27, P < 0.05), and F/F (r = -0.43, P < 0.001). Variation in summer heat resistance, as indicated by HDI, was observed among the 14 Rhododendron germplasm. This heat resistance was mainly associated with leaf transpiration rate and F/F. The indirect role of antioxidant enzymes in maintaining reactive oxygen species homeostasis in summer heat resistance was observed. The results provide a reference for introducing and cultivating relatively large-leaf Rhododendron plants to low-altitude areas.
夏季高温是限制相对大叶杜鹃属植物引种到低海拔地区的一个重要因素，因此评估不同种质对夏季高温的抗性至关重要。2023年进行了盆栽试验，以研究14种有代表性的相对大叶杜鹃属种质的光合特性、生理生化特性和叶绿素荧光特性的时间变化。结果表明，在14种种质中，露珠杜鹃和‘霍斯珀红’的热害指数（HDI）最高，而九龙山杜鹃和‘莫泽栗色’的HDI最低。除露珠杜鹃外，所有种质的光合速率和F/F（最大光化学效率）最初下降，然后恢复。相比之下，叶片蒸腾速率、气孔导度和叶绿素含量逐渐增加。过氧化氢浓度先下降后上升，而丙二醛浓度先上升后下降。此外，超氧阴离子含量逐渐增加。超氧化物歧化酶、过氧化物酶和过氧化氢酶（CAT）的活性最初增加，然后下降。HDI与CAT活性呈正相关（r = 0.28，P < 0.05），但与光合速率（r = -0.26，P < 0.05）、叶片蒸腾速率（r = -0.27，P < 0.05）和F/F（r = -0.43，P < 0.001）呈负相关。在14种种质中观察到HDI所表明的夏季高温抗性存在差异。这种耐热性主要与叶片蒸腾速率和F/F有关。观察到抗氧化酶在维持夏季高温抗性中的活性氧稳态方面的间接作用。研究结果为相对大叶杜鹃属植物引种到低海拔地区及栽培提供了参考。
