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Guangxi is the main sugarcane producing region in China, however, drought is an important factor to limit the sugarcane productivity. Therefore, it is especially important to solve the problem of drought in sugarcane production. Adaptation of sugarcane plant to drought stress could be expressed in morphological physiological, biochemical and molecular characteristics. In the present experiment, plants of6sugarcane varieties, ROC16, ROC22, GF98-296, B8, GT21and GT28, were grown in greenhouse, and the treatments of normal watering (CK), drought stress and re-watering after drought were designed and done. The physiological and biochemical parameters of the plants, i.e., growth, green leaves/plant, membrane permeability, contents of chlorophyll, MDA, soluble sugar, and soluble protein, and activities of peroxidase (POD) and superoxide dismutase (SOD) in leaves were analyzed. The main results were as follows.1. The changes in growth speed were highly significant among the treatments of drought for40d, drought for80d, and re-watering for80d after drought. At the early stage of drought treatment, ROC16showed the worst in loss of growth speed, growing ability after drought, recovery of green leaves/plant, stalk diamer, millable stalks/plot, brix and cane yield recovery. ROC22and GT28had a strong growing ability after drought, and they still retained8green leaves/plant, which is good for maintaining the ability of photosynthesis and metabolism and recovering stalk growth. At the late stage of stress, the largest decrease in green leaves/plant was observed in the variety GF98-296, which decreased by51%. The variety B8showed the best performance in brix and cane yield recovery capability.2. ROC22and GT28performed well during severe drought, which showed the smallest decrease in chlorophyll content, net photosynthetic rate and photochemical efficiency. ROC16and B8showed significant decrease in the three parameters.3. GT28and ROC22also showed stronger ability of drought resistance and recovery after rewatering. GT28and B8showed relatively lower cell membrane permeability during whole duration of drought treatment, and that in GT28increased only26.6%, the least change in all the tested varieties. At80th day of drought stress, GT28showed the highest increase in soluble sugar content, B8showed highest water loss, and ROC22showed the strongest water keeping ability. Under severe drought, SOD activity was inhibited, and that in ROC16declined the most. At the re-watering stage, GT28and B8showed lower cell membrane permeability than others, which is good to adapt to adverse environment. GT28and GF98-296showed significantly lower POD activity while ROC16showed opposite compared to CK; ROC22showed the largest decrease in SOD activity. Most varieties showed higher or close water potential compared to CK.4. Growth speed, green leaves/plant, cell membrane permeability and contents of chlorophyll, soluble sugar, and MDA could be used as the indexes of drought resistance of different sugarcane varieties. The order of drought resistance for the six sugarcane varieties from strong to weak is:GT28>ROC22>GF98-296>GT21>B8>ROC16; and the order of compensation during re-watering after drought for the six sugarcane varieties is:ROC22>GT28>GF98-296>GT21>B8>ROC16.
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