Objective In recent years, high temperatures occur frequently in the south of China, and the high-temperature environment has become an important limiting factor for the growth and development of Camellia oleifera. In order to investigate the physiological response to high-temperature stress and differences in heat tolerance of different C. oleifera varieties, for selecting the the varieties suitable for planting in high-temperature areas.

MethodsBased on the 3 year-old grafted seedlings of 15 varieties currently planted in various provinces (regions) of China, the relative leaf water content, dry matter content, photosynthetic pigments, osmotic regulators and antioxidant enzyme activities of 12 physiological and biochemical indexes of the varieties under the high-temperature stress (temperature increase of the plastic film) were investigated and measured. And the principal component analysis and the affiliation function methods were used to comprehensively analyze the tolerance ability assessment.

ResultsUnder high temperature stress, the relative water content and dry matter content of leaves of the varieties decreased; the content of photosynthetic pigments decreased, and most of them havd significant differences (p＜0.05); the content of malondialdehyde, antioxidant enzyme activity and osmotic regulating substances increased; and the analysis of the affiliation function showed that there were differences in the heat tolerance of the 15 varieties, and the variety Hwajin had the highest heat tolerance, followed by Ganzhouyou, Huashuo, Cenruan NO.2, Xianglin NO.210, Ganwu NO.2, Changlin No.53, Yueshao NO.75-2, Yueshao NO.77-1, Changlin NO.4, Cenruan NO.3, Huaxin, Changlin NO.40, and Ganzhouyou NO.7, Ganshi NO.83-4.

Conclusion Among the 15 varieties, Huajin, Ganzhouyou NO.1, Huashuo, Cenruan NO.2, Xianglin NO.210have strong heat resistance and are suitable for planting in high-temperature areas.