Effects Of Low Temperature On Physiology Of Different Genotypes Phalaenopsis Spp.

Phalaenopsis is one kind of tropical flowers. At the Yangtze river region, the temperature has been an important factor on affecting the Phalaenopsis's growth and consumption. Our study use three phalaenopsis cultivars, they are'Hunyan','Jubao'and ZD-1, Which had been observed on the farm of Zhejiang University for a long time, they can represent the cold is better, worse and the medium. Physiological index were determined at 10,5,0αfor 12,24,48 h after pre-treatment. The results were as follows:1. The results showed that the electrical conductivity and MDA content in leaves were enhanced along with the increase of low temperature stress. Under the same treatment conditions,'Jubao'has the greatest increases in leaves, it show that its cell membrane had the most injury, 'Hunyan' is the least, ZD-1 is the medium. Therefore these two physiological indexes could be used as identification indexes of cold tolerance for Phalaenopsis plant.2. On the low temperature conditions of 10℃and 5℃, the contents of Chlorophyll(a+b), Chlorophyll a, Chlorophyll b, Carotenoids and Fv/Fm all has been significantly reduced in different degree. But on 0℃the reduced were not significantly, they all in a low level. 'Hunyan' has the smallest reduction,'Jubao' has the largest. Chl(a/b) had increased in some conditions, It is better for transform the light energy. Therefore these physiological indexes could be used as identification indexes of cold tolerance for Phalaenopsis plant.3. At the low temperature, there is no obvious change of soluble sugar content was detected in this study. The content of proline(pro) is lower than the CK, on 10℃and 5℃, it is higher than the CK on 0℃. The change of the content of soluble sugar and pro is different with the others, it need further study. There is a significantly increase of protein, and 'Hunyan' has the largest change, Therefore this physiological index could be used as identification indexes of cold tolerance for Phalaenopsis plant.4. The enzymatic systems of Phalaenopsis are studied superoxide dismutase (SOD), catalase (CAT) and with ascorbic acid-glutathione (AsA-GSH) cycle-related activity. The result show that, the activity of enzyme is higher than CK in low temperature conditions. The activity of SOD was the highest at the low temperature 10℃and 5℃, and APX had the highest activity at 0℃and the content of AsA in a highest level, we can see that the function of different enzyme can complement each other in various stress.'Hunyan' has the largest change, 'Jubao'is smaller than the others, so 'Hunyan' is cold tolerant,'Jubao'is cold susceptible, ZD-lis medium cold tolerant. The activity of enzyme could be used as identification indexes of cold tolerance for Phalaenopsis plant.5. At the low temperature, The content of ABA were enhanced along with the increase of low temperature stress. No obvious change of GA and IAA content was detected in this study. It needs further study.