| Tobacco(Nicotiana tobacum L.) is an important cash crop in China, which is very sensitive to the changes of ecological environment. Effects of temperature and water status on the quality of tobacco are considerable, and they are the important factors affecting tobacco quality and yield. Therefore, comprehensive and in-depth studying responding mechanism of tobacco plants to drought and low temperature stress and the effect of growth temperature on the quality of tobacco leaves are urgent problems to be solved. This paper taking the tobacco plants as materials, studied:(1) Comparison of metabolic difference of trehalose under drought and chilling stress in tobacco seedlings;(2) Effects of different temperature on the non-structural carbohydrate metabolism of tobacco plants;(3) Effect of different temperature on non-structural carbohydrate metabolism in different growth stages of tobacco leaves. 1. Comparison of metabolic difference of trehalose under drought and chilling stress in tobacco seedlingsUsing tobacco seedlings( cv. Yunyan 203) as material, treated under drought and low temperature stresses, the changes of trehalose content, their metabolism related enzyme activities and gene expression were detected during the drought and chilling stress at 4℃ in the tobacco leaves. The results indicated that trehalose content increased firstly, achieved the maximum level in 2 d, then decreased during drought and chilling stress for 6 d, and the trehalose content in the leaves under drought stress all maintained higher level than that under the chilling stress. Similar to the change of trehalose content, TPS, TPP activity was increased first and then decreased, and showed higher under the drought stress. On the other hand, THase activity demonstrated persistent increase under the drought and chilling stress, and was higher under chilling stress than that under drought stress. The expression level of TPS, TPP, THase genes was higher in the drought stress than the control, but the expression level under chilling stress was lower than the control. These results indicated that drought and chilling stress can induce the accumulation of trehalose, the drought stress can lead to relatively higher level of trehalose content, related enzyme activities and gene expression, impliying that response of trehalose to drought stress is more sensitive than that to chilling stress. 2. Effects of different temperature on the non-structural carbohydrate metabolism of tobacco plantsUsing tobacco plants growing in artificial climate chamber simulating different environment temperature as materials, the effect of different growth temperature(mean temperature of 30.5 ℃, 23.5 ℃, and 16.5 ℃) on soluble sugar, reducing sugars, sucrose content, starch content, enzyme activity and the expression of related genes were stuied in leaves and roots of tobacco plants.The result showed that, the soluble sugar, reducing sugars, sucrose and starch accumulation had significant difference in leaf and root under different temperature, they all showed that 16.5℃>23.5℃>30.5℃; in leaves, the SPS was positively related with the content of sucrose, the SuSy and Inv was negatively correlated with the sucrose content; in the roots, the SPS and SuSy had positive correlation with sucrose content and the Inv had negative correlation with sucrose content. The AGPase, SSs and SBE in leaves were rising gradually, also showed 16.5℃>23.5℃>30.5℃; the 3 enzyme activities in roots were also higher at 16.5℃; the activity of amylase was higher at 30.5℃. The related genes expression were consistent with enzyme activites overall in different temperature, every gene expression had obvious differences, by their coordinated expression to achieve the enzyme activity regulation. Above all, temperature can influence the expression of related genes, the enzymes activity and the sugar accumulation, ultimately the quality of tobacco had been affected. 3. Effect of different temperature on non-structural carbohydrate metabolism in different growth stages of tobacco plantsUsing Yunyan 87 as material, growing in artificial climate chamber simulating different environment temperature(Jiangchuan in Yunnan, Zunyi in Guizhou and Xiangxian in Henan province) in the period of transplanting to resettling stage, resettling to squaring stage and mature stage, studying the effects of growth temperature on tobacco soluble sugar, reducing sugar, sucrose, starch content, enzyme activity and metabolism related genes expression. The results showed that, the soluble sugar, reducing sugar, sucrose and starch content increased with the continuous growth of tobacco, SPS activity was higher in the transplanting to resettling stage and mature stage period, the gene expression was also higher; SuSy and Inv activity were higher in transplanting to resettling stage, then decreased. The soluble sugar, reducing sugar and sucrose content were accumulated and the SPS activity was rose in the temperature conditions of Yunnan Jiangchuan area of each period. The temperature of Henan Xiang County in resettling to squaring stage was beneficial to the accumulation of sucrose and the SPS activity increase. Temperature of Guizhou in Zunyi in each period the sugar accumulation is less, the SuSy and Inv which decomposition sucrose were relatively high. The temperature of Guizhou Zunyi area was beneficial to the accumulation of starch and the AGPase activity increase in the stage of transplanting to resettling stage; the temperature in Yunnan Jiangchuan area was conducive to the accumulation of starch content and the AGPase, SSs activity raise in resettling to squaring stage and mature stage; the starch accumulation under the temperature of Henan Xiang area in each period were less, and the Amylase activity was higher in transplanting to resettling stage and mature stage. The above results showed that, the temperature impacting genes expression, thereby affecting the enzyme activity and the metabolism, transport of sugar, ultimately have a certain influence on the formation of tobacco leaves style. |
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