Keywords: 
• plant physiology /
• Salvia splendens /
• heat resistance /
• salicylic acid /
• resistance

Abstract: To increase heat resistance with Salvia splendens, one of the most important bedding plants in south China where high summer temperatures decrease its growth, this study measured the effects of high temperature （39 ℃ day/30 ℃ night） on heat damage indexes, relative electric conductivity （REC）, antioxidant enzyme activities, and chlorophyll fluorescence parameters in two cultivars of Salvia splendens: Hangtian No. 5 and Zhanwang. The experimental design consisted of a control （25 ℃, day and night） and three treatments （high temperature, 0.01 molL-1 SA spraying, combination of high temperature and SA spraying） was arranged in a randomized, complete block design with 3 replicates, giving a total of 48 plants, and statistical assays were carried out by analysis of variance （ANOVA） using SAS software. Results showed that by the 6th day compared to control plants, spraying with SA significantly （P＜0.05） decreased the heat index inHangtian No. 5andZhanwang. Also with high temperature stress, SA significantly decreased （P＜0.05） leaf relative electrolyte leakage increases for both cultivars. Furthermore, SA increased （P＜0.05） ascorbate peroxidase （APX） and catalase （CAT） activities as well as soluble protein content more in the heat sensitive cultivar Hangtian NO. 5 than Zhanwang. In addition, SA treatment along with high temperature stress significantly （P＜0.05） decreased superoxide dismutase （SOD） and peroxidase （POD） activities and increased maximum efficiency of Photosystem Ⅱ （Fv /Fm） in both cultivars. These results indicated that the increase in heat tolerance using SA could be related to the enhancement of antioxidant enzyme activity and the decrease of oxidative damage and photo-damage of PS Ⅱ with high temperature.［Ch, 8 fig. 20 ref.］