| Apricot tree is liable to be injured by spring frost because of its early flowering .It is necessary to evaluate the cold hardiness of different apricot varieties and select the harder ones, to set up an effective evaluating technology system and select varieties that are late flowering and cold hardiness .The freezing-resistance mechanism of apricot has been studied using twigs in dormancy and the cold hardiness was evaluated. The main results are followed:1. It is one of the most exact and credible ways to judge the cold hardiness of fruit trees through investigation in the fields. Flowers of apricot trees were injured by springfrost (?----- ℃) in the north of China on march 28th,2001. The freezing injury oftwenty varieties of apricot were investigated in the principal cultural areas of apricot in Shandong province and their freezing resistances were evaluated. The results showed that: ㊣njuring was lower in middle and top of slope, the same to the top site of crown.?Flowers of apricot in peach rootstock were injured lighter than in the apricot rootstock. 〢ccording to the researching result , it was obvious that the difference of freezing resistance in apricot or sweet cherry varieties. "Hongfeng" and "Honghebao" were the most freezing resistance apricot cultivars in the researching varieties. This offered good germplasm to freezing resistance breeding.2. In the study of freezing-resistance mechanism of apricot, we have gotten that: (DThe difference of water content in twigs of apricot during the dormancy is notnotability in different varieties. The rates of free water content to tied water are in great difference. This rate can be used to measure the ability of anti-freezing, more is the rate and less is the ability. The is no correlation between the content and the rate of free water content to tied water.(2)In this experiment the relative conductions of all varieties become more and more bigger as the decreasing of the temperature. There is an acute increase at one temperature , the temperature is about -30 ℃. There are great difference The numbers of relative conductions in hardiness varieties are always lower than the others.(3)In this experiment the change trend of SOD activity is "high-low-high-low", there are two 'peaks' in the line and the first one is bigger than the second one. The change trend of POD activity is "high-low-high", there is one 'peak' at least in the line. The33activity begins to increase at the lowest temperature and the increasing range is bigger in the strong one . The change trend of CAT activity is flat in former phase , there is one acute increase at last.(4)The soluble protein content became more and more higher as the droping of temperature, a sudden increase at -40 ℃. It is more clear of the change trend of hardiness variety.(5) The change of proline content is increase during the treat of low tempatures.(6)The soluble sugar content became more and more higher as the droping of temperature, the temperatures of -20 ℃ and -20 ℃ are important ones. The shape of the change line is like "S". The increasing quantum of soluble sugar content is higher in hardiness variety.3.Through the pr i nc i pa I component ana lysis , the rate of free water content to the tied water content, the relative conduction , SOD activity , soluble sugar content are testified having good relativity with the other targets. The ability of freezing resistance of Jifengerhao , Damaihuang, Honghebao, Hongfeng are higher, and Jintaiyang, Badanshuixing and Katy is lower. |
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