The Role of betaine foliar-application in retaining water and dehydration-tolerance of tobacco leaves

Chinese. 【目的】从保水和耐脱水这一新的角度，研究叶面喷施甜菜碱在烟草抗旱中的作用。【方法】烟草叶面喷施甜菜碱两周后，进行脱水和复苏处理。【结果】叶面喷施5～15 mmol・L. 1甜菜碱对水分适宜条件下的烟草株高和光合速率并未显著影响，但叶片叶绿素含量呈现增加的趋势；喷施20 mmol・L. 1甜菜碱的烟草株高却显著低于对照，叶片发黄，光合速率下降。喷施5～15 mmol・L. 1甜菜碱的烟草叶片在脱水过程中不仅能够保持较高的肉质化程度，而且其质膜及PSⅡ能保持更好的稳定性，其中喷施10～15 mmol・L. 1甜菜碱的效果最好；但喷施20 mmol・L. 1甜菜碱的叶片PSII活性小于对照。而喷施甜菜碱的叶片脱水24 h后的复苏能力都显著好于对照。【结论】叶面喷施甜菜碱的叶片保水和耐脱水能力显著提高，喷施甜菜碱的最适浓度为10～15 mmol・L. 1。

English. [Objective] The role of betaine foliar-application in drought-resistance of tobacco was analyzed in this paper in a new aspect of water-retaining and dehydration-tolerance. [ Method] The tobacco plants were sprayed with different concentrations of betaine for two weeks, and then the leaves were separated from the original plants and dehydrated under controlled conditions. Dehydrated leaves were resuscitated in distilled water-saturated cheesecloth. [ Results ] The results showed that foliar-application of 5-15 mmol・L. 1 betaine had no significant effects on the height and net CO2 assimilation rate of tobacco plants under normal condition Furthermore, its application （5-15 mmol・L. 1） enhanced the chlorophyll contents of tobacco leaves. However, the height of tobacco plants sprayed with 20 mmol・L. 1 betaine were lower than control plants obviously, so were the chlorophyll content and net CO2 assimilation rate. The betaine-sprayed leaves were dehydrated under controlled conditions. It was found that tobacco leaves, sprayed with 5-15 mmol・L. 1 betaine, can retain higher succulence degree and stronger stability of plasma membrane and photosystemⅡ. However, the activity of PSII in tobacco leaves foliar applied with 20 mmol・L. 1 betaine was less than control leaves. Furthermore, the activities of resuscitation of betaine-sprayed leaves were also higher than control plants. [ Conclusion ] The resuits above suggest that foliar-application of betaine have obvious effects on water-retaining and dehydration-tolerance, in which 10-15 mmol・L. 1 is optimum concentration.