Metabolic Physiology Of Glycinebetaine And Molecular Biology Of Salt-resistant Response In Mulberry (Morus Alba L.)

Glycinebetaine (GB) is one of the nontoxic osmoregulators in plants, which is directly related to stress-resistance in many plants. To explore theory basis and application routines of exogenous GB for possible cultivating of mulberry trees under salt stress, we studied the metabolic physiology of GB and molecular biology of salt-resistant response in mulberry (Morus alba L.).By using the technology of 1H-NMR for quantitative analysis, the variations of GB contents in leaf samples at different leaf positions and from different mulberry cultivars were examined to understand the metabolic characteristics of endogenous GB in mulberry trees. The results indicated that GB could be detected in leaves from all the five tested cultivars of mulberry, though different amounts of GB were found to be accumulated in different cultivars. For the GB contents in leaves at different leaf positions in each cultivar, it was showed that GB accumulated more in upper (younger) leaves than in lower (older) leaves. It was also found that salt stress could result in the changes of endogenous GB accumulation in mulberry, showing the increment of GB content in leaves.To develop possible new cultivation measures for mulberry trees under salt stress, the changes in growth and development, and physiological responses of mulberry seedlings were investigated after applying exogenous GB to salt-stressed seedlings through root system. The results revealed that application of exogenous GB at a certain concentration could increase the levels of chlorophyll, soluble sugars, and proline in leaves, maintained the leaf water content, regulated K+/Na+ ion equilibrium, reduced the content of MDA, and thereby alleviated inhibition of mulberry growth under salt-stress. Moreover, it was found that the GB concentration at 2.5~5.0 mmol·L-1 was suitable for root application.