Effect Of Water Stress On Protein And Protease In Leaves Of Sugarcane Varieties With Different Drought Resistance

Sugarcane is a popular sugar crop and most promising regenerative energy crop, but drought is the most important limitation factor for its yield. Based on the previous studies of drought stress resistance in sugarcane, now the drought resistance could be well evaluated by integrated morphological and physiological indexes. For sugarcane production in upland fields, it is very important to improve the irrigation condition and to select drought resistant varieties, and cultivation measures including chemical regulations have been proven very effective in improving the drought resistance of sugarcane plants. Further investigations of substance bases and their physiological functions at molecular level will be helpful to create new drought resistant genotypes of sugarcane through biotechnology.In this research, three sugarcane varieties, ROC16, GT21, ROC22, were used as the experimental materials, which were brought up in pots. The plants were treated with 25% (W/V) polyethylene glycol 6000 (PEG6000) for simulating drought stress at the seedling stage and the elongation stage respectively. The purpose is to study the effects of drought stress on protein and protease in leaves of sugarcane varieties with different resistance at the two stages. The results were as follows:1. The plants showed stronger drought resistance at seedling stage than at elongation stage. The drought resistant abilities showed very little diversity among different sugarcane varieties at the seedling stage, but significant at the elongation stage.2. The water potential in leaf +1could not completely represent the extent of drought stress of sugarcane.3. The free amino acid content and the free proline content could sensitively reflect the extent of drought stress on sugarcane, and the drought sensitive variety accumulated amino acid earlier. It was observed that the increase of free proline content always lag the increase ofΔ'-pyrroline-5-carboxylate synthase (P5CS) activity.4. A reliable SDS-PAGE technique was developed for studying the proteins in leaves of sugarcane. The patterns of soluble protein showed remarkably different among different sugarcane varieties with different drought resistance as well as in different treatments. Especially, the proteins of 48kDa and 36kDa had high correlation with the drought resistance of sugarcane.5. The endopeptidase activity and endopeptidase isozymes were applied in research on drought stress in sugarcane. There were some correlations between endopeptidase activity and drought stress. The lower endopeptidase activity it showed, the stronger drought resistance ability it had. The bands of endopeptidase isozymes could be divided into 4 types. There were some correlations between the changes of the bands and the extent of drought stress, but their orderliness was not remarkable.