Studies On The Low Temperature Sensitivity Of Flue-cured Tobacco Varieties And Effect Of Salicylic Acid

Temperature is one of environmental conditions that plants normal growth and development depend on, and it is main natural factor that affect plant morphological and geographical distribution. High or low temperature stress on plant will affect adversely the whole growth and development process. Low temperature in early spring often results in blocked growth and development and the tobacco normal production and quality can not be effectively guaranteed. Researching the chilling resistance mechanisms in flue-cured tobacco and finding out effective solutions become the most urgent task..The main culture flue-cured tobacco varieties Zhongyan100,NC82,K326 were treated with 2℃, 5℃and 8℃at 5th-leaf stage. The sensitive temperatures of flue-cured tobacco varieties were investigated according to the change laws of the biochemical indexes, such as relative electrical conductivity, malondialdelyole, Peroxidase, Superoxide dismutase and Proline. The results are as follows.(1) According to the change laws of the biochemical indexes in tobacco leaves, such as relative electrical conductivity, the content of MDA, POD and SOD activity and content of Proline , it was found that, relative electrical conductivity, the content of MDA and Proline, POD and SOD activity all appeared the obvious rise, and higher than normal temperature check , along with the grade of low temperature forces increased under the stronger low temperature forces; however the SOD activity was declined under low temperature force and higher than normal temperature check only in 8℃.(2) In the three tobacco varieties all the low temperature sensitivity were higher under 2℃and 5℃, and under T2-3 it was the most, then T5-7,T2-2,T5-5, and under T8-7 it was the lest. Zhongyan100 had stronger low temperature resistance than the two other tobacco varieties. Low temperature sensitivity was strongest in K326.(3)Under different low temperature forces, the sequence of low temperature sensitivity in Zhongyan100 was T2-3, T5-7, T2-2 and T5-5. In NC82 the strongest low temperature sensitivity was under T2-3, then T5-7 and T 2-2, however under that the difference was small.K326 has stronger low temperature sensitivity and the sequence of that was T2-3, T5-7, T2-2 and T5-5. Through the comparison and identification it was found that the three tobacco varieties had different temperature sensitivity, but the most sensitive temperature in each variety was the same. From strong to weak, the sequence of low sensitive temperature was T2-3, T5-7, T2-2.(4)Spray SA on Zhongyan100 and K326 tobacco leaves under low temperature, and the concentration of SA were 0.5mmol/L, 1.0mmol/L and 1.5mmol/L .The results showed that SA alleviated chilling damage effectively, lowered level of membrane lipid peroxidation, decreased leakage rate of plasma membrane in tobacco seedling leaves, however increased POD and SOD activity and content of Proline. Moreover, 1.0mmol/L was the most proper concentration of SA, that helped developing cold tolerance in flue-cured tobacco varieties under low temperature forces.(5) It was different between the ways of enhancement cold tolerance in Zhongyan100 and K326. SA can enhance cold tolerance more effectively in Zhongyan100, that was high cold tolerance variety, however under stronger low temperature stress. SA can enhance cold tolerance more effectively in K326, that was low cold tolerance variety, under weaker low temperature stress.