Abstract: 【Objective】To investigate the physiological responses and differences in cold tolerance among Phalaenopsis under low-temperature stress,and provide support for improving cold-tolerance traits and breeding new cold-tolerant cultivars.【Methods】Three Phalaenopsis cultivars（P. Big Chili,P. Little Gem Stripes,and P. Wedding Promenade） were used as experimental materials and subjected to low-temperature stress（10,5,0 ℃） and non-stressed（CK,25 ℃） conditions. The activities of peroxidase（POD）,catalase（CAT）,superoxide dismutase（SOD）,and the contents of proline（Pro） and malondialdehyde（MDA） in detached leaves under these conditions were measured. The cold tolerance was comprehensively evaluated using the membership function method.【Results】Under low-temperature stress,the physiological responses of the tested Phalaenopsis cultivars differed significantly from those under non-stressed conditions. In the P. Wedding Promenade cultivar,the activities of POD,CAT,SOD,and the contents of Pro and MDA exhibited a gradual decline with decreasing temperature,peaking at 10 ℃ with values of 220.73 U/（g·min）,44.00 U/（g·min）,261.19 U/g,and 289.31 μg/g,44.00 μmol/g,respectively. For the P. Big Chili and P. Little Gem Stripes cultivars,the activities of POD,CAT,SOD,and the contents of Pro and MDA exhibited an initial increase followed by a decrease,all peaking at 5 ℃. The comprehensive membership function values for P. Wedding Promenade,P. Big Chili,and P. Little Gem Stripes were 0.540,0.447,and 0.357,respectively.【Conclusion】The three Phalaenopsis cultivars exhibited different levels of tolerance and physiological responses to low-temperature stress,with cold tolerance ranked as P. Wedding Promenade>P. Big Chili>P. Little Gem Stripes,which is consistent with their performance in actual cultivation.

Key words: Phalaenopsis, Low-temperature stress, Physiological response, Cold tolerance, Membership function method