| This experiment was carried out to evaluate the drought resistance of 11 kinds of grape rootstocks and 11 kinds of varieties of different origins and to study their physiological and biological responses to slight, mild and severe water stresses with soil relative water content of 55% ~ 60%, 40%~ 45% and 30%~35%, respectively. Two-year-old potted grapevine rootstocks or varieties were used as materials and the experiment was carried out in the small orchard of Shandong Agriculture University. The main results are as follows:1.According to the cluster analysis of drought injury index and relative growth of shoot (RG), the drought resistance of grapevine rootstocks and varieties could be divided into five classes. The most resistant rootstocks, 1103Paulsen, 5BB and 3309C , could normally grow under mild drought stress. Even after 40d's severe drought stress, they still sustained high RG at 21.1% -26.7% with slight injury symptom. SO4, DOG, Shuangyou, Beihong, Beta were in the second class, which could endure long-term mild water stress with 40.2%~48.1% RG. Hongshuangwei, Cabernet Sauvignon N, Zexiang and Ruby Seedless were in the third class enduring short-term mild water stress. 420A, 225A, Gaoqi, Centennial Seedless, Kyoho, Rizamat and 8B were less resistant varieties, which could grow normally only under slight water stress. Heixiangjiao and Riparia were very sensitive to water stress, which could just endure short-term slight water deficit.2. Grapevine responses to water scarcity were complex, involving adaptive changes and/or deleterious effects. Water stress had different degrees of negative influence on the growth of shoot. After 40d's slight water stress, the most resistant rootstocks sustained more than 80% RG, the second-class drought-resistance varieties 50%~60%, the third about 40%, the other classes just about 25%. After 40d's mild drought stress, RG of the most resistant rootstocks was also above 50%, while that of the second-and third-class drought-resistance grapevine varieties was between 30% and 50% and others below 20%. RG of all the varieties was seriously reduced by severe water deficit, even the most resistant rootstocks only got about 25% RG.3. After long-term mild and severe drought stress, the storage of starch per unit in root of 3309C increased, but that of Cabernet Sauvignon decreased.4. After 30d's slight water stress, WUE of all the varieties improved, especially one of the first-class resistant rootstocks 5BB.5. As drought progressed, the peak of Pn occurred much earlier than that of contrast, but its value was much lower than contrast. During mid-morning and noon, Pn declined to values close to zero, even to negative values for Cabernet Sauvignon, Rizamat and 1103P. Photosynthetic noon break advanced greatly, especially relatively less resistant cultivars such as Cabernet Sauvignon and Rizamat. The decline of Pn of all the vatieties in mild and severe drought stresses could be explained as the result of the non-stomatal limitation.6. As drought progressed till 21d, Pn of all the grapevine varities declined increasingly, then kept at the lowest level, but the most resistant rootstocks 1103P and 5BB declined less than Heixiangjiao and Cabernet Sauvignon But second-class resistant variety Shuangyou was very peculiar, for its Pn declined rapidly after one week1 mild water stress, but after 14ds, its Pn restored, then kept at a higher level. After re-irrigation, Pn of all the varieties restored swiftly, especially that of the three rootstocks, 1103P, 5BB and 3309C.7. After 20d's mild water stress, ABA content in 3309C leaves increased much more than that in Cabernet Sauvignon leaves.8. SOD activities in the leaves of 3309C and 5BB were higher than contrast after 30d's mild water drought, but similar to contrast after 30d's severe drought, while SOD activities in the leaves of Cabernet Sauvignondecreased significantly as the stress progressed. In the normal water condition, POD activities in the leaves of grape rootstocks were much lower than th...
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