Studies On Heat Tolerance In Cyclamen

The heat tolerance in 9 different cultivars of cyclamen stocks which were chosen from 5 series of France, Japanese, Holland, American and common variety fragrant smell cyclamen, was studied. Firstly, the impact of temperature on cyclamen seedling growth was studied, and the physiological traits of the heat tolerance and heat tolerance index in seedling stage were analyzed. Secondly, the heat tolerance among ages of different seedlings and the different varieties of cyclamen were compared. Finally, using antioxidant, preliminary chrictiristic to improve the heat tolerance of cyclamen was researched. The main results were as follows:1. Under high temperature, growth was inhibited severely, the membrane structure was damaged, root vitality and photosynthesis were decreased, the degradation of proteins was accelerated, and the metabolism of the active oxygen was increased.2. After heat stress, the relative membrane permeability of leaves, the root vitality, as well as the contents of O₂-, MDA and protein correlated obviously with temperature, suggesting that they can be regarded as the biochemical index of physiology for heat tolerance qualification in seedling stage of the cyclamen. Meanwhile, the fibrous roots, the number of leaves, the thickness of leaves and epidermis of leaves in cyclamen seedlings could be used as their morphological index for heat tolerance qualification. The mortality of cultivars of France and Japanese with strong heat tolerance was relatively low, whereas the mortality of Holland variety with weak heat tolerance was relatively high, indicating that mortality can be applied as an indirect index.3. Cyclamen seedlings could tolerate temperatures under 35-39℃, and there was a higher tolerance within short time. With a treatment of different time to the cyclamen seedling under 40℃, the content of protein in the leaves reduced notably in the 6h treatment. It indicated that the longest time to tolerate high temperature in cyclamen seedlings was 5h under 40℃ Results showed that in recent years cyclamen had certain adaptive capacity to the bad environment of higher temperature.4. The heat tolerance among ages of different seedlings and varieties in Cyclamen was compared by means of the test of the relative membrane permeability of leaves and the observation of leaf microstructure. The results indicated that heat tolerance of variety of French and Japanese series was relatively stronger than that of other variety series, while heat tolerance of Holland series was the weakest. The relative membrane permeability of leaves was not a suitable trait to identify the heat tolerance of different ages of Cyclamen.