| In order to avoid the late frost damage of walnut, spraying experiments on 'Qingxiang' and 'Zhonglin 1'were done after havesting fruit by using GA3 at different concentrations (0,50,100,200,300 mg/L) and mixture which was composed of 200 mg/L GA3 and ETH solution at different concentration (0,50,100 mg/L). The germination rate of the top and lateral bud on the dormant branches, the nutrition changing rules and the hardiness of the upper branches were observed and analysed. The results were as follows.1?With increasing the concentration of GA3, the trend of the damage level and the cold injury index were increased in 'Qingxiang', while the germination rate of the first sprouted bud decreased. During the process of germination, compared with the control, there were no significant influence on the cold injury index and the electrolyte leakage at the 50,100 mg/L GA3 treatments (P< 0.01); compared with the control, the 200,300 mg/L GA3 treatments had significantly influence on the damage level, the cold injury index, the concent of MDA and starch (P< 0.01), which increased 93.11% and 205.41%,2.00% and 2.12%,23.76% and 30.96%,32.76% and 47.23% respectively; while compared with the control, the 200,300 mg/L GA3 treatments had significantly influence on the germination rate, the concent of water and soluble sugar, as well as the acticities of POD and SOD (P< 0.01), which decreased 62.27% and 66.47%,21.29% and 27.60%,30.09% and 35.15%,28.75% and 32.23%,30.12% and 36.30% respectively.2 s With increasing the concentration of GA3, the trend of the damage level and the cold injury index were increased in 'Zhonglin 1', while the germination rate of the first sprouted bud decreased. During the process of germination, compared with the control, there were no significant influence on the damage level, the cold injury index, the concent of proline and MDA at the 50,100 mg/L GA3 treatments (P< 0.01); compared with the control, the 200,300 mg/L GA3 treatments had significantly influence on the damage level, the cold injury index, the electrolyte leakage and the starch concent (P< 0.01), which increased 224.93% and 247.49%,1.75% and 2.50%,44.11% and 82.30%,21.33% and 30.30% respectively; while compared with the control, the 200,300 mg/L GA3 treatments had significantly influence on the germination rate, the concent of water and soluble sugar, as well as the acticities of POD and SOD (P< 0.01), which decreased 20.04% and 59.98%,20.33% and 30.68%,39.53% and 41.95%,20.98% and 20.63%,14.49% and 30.12% respectively.3?With increasing the concentration of ETH, the damage level of'Qingxiang' decreased, while the germination rate of the first sprouted bud increased. During the process of germination, compared with the control, the 50,100 mg/L ETH treatments had no significant influence on the cold injury index and the concent of proline, GSH and soluble protein (P< 0.01); compared with the control, the damage level and the electrolyte leakage had significantly decreased 47.52% and 56.50%,13.76% and 20.60% respectively (P< 0.01); while the germination rate, the concent of water and soluble sugar, as well as the acticities of POD and SOD had significantly increased 21.59% and 38.84%,19.44% and 8.37%,11.81% and 5.63%, 23.22% and 47.30%,6.97% and 14.06% respectively (P< 0.01).4?With increasing the concentration of ETH, the damage level of 'Zhonglin 1'decreased, while the germination rate of the first sprouted bud increased. During the process of germination, compared with the control, the 50,100 mg/L ETH treatments had no significant influence on the germination rate, the cold injury index, the electrolyte leakage and the concent of MDA and GSH, as well as the acticities of SOD (P < 0.01), while the damage level had significantly decreased 19.08% and 22.51%(P< 0.01).5?Therefore, GA3 could reduce the cold resistance of branches by decreasing the protective enzyme activity, increasing the cold injury index and the electrolyte leakage, decreasing the concent of water and soluble sugar, leading to the death of the bud on the upper branches and the germination delay of the bud on the middle and lower segments of branches;the GA3+ETH could raise the cold resistance of'Qingxiang' branches, decrease the cold injury index, increase the concent of proline and soluble sugar due to increase the protective enzyme activity, lead to the lower mortality of the bud on the upper branches and the early germination of the top and lateral bud; However, the effect of the GA3+ETH on raising the cold resistance of 'Zhonglin 1'branches and the early germination of the top and lateral bud was not obvious.In conclusion, GA3 could delay germination of walnut bud, but it reduced the cold resistance of branches which led to the death of the bud on the upper branches and the germination delay of the bud on the middle and lower segments of branches. Therefore, it could not be applied to agricultural production widely. GA3+ETH could weaken the effect of GA3, and raise the cold resistance of the walnut, thus reducing the degree of frozen injury and promoting early germination of the top and lateral bud. It provided a new way to solving the problem of the late frost or the frozen injury of branches. |
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