Physiological Mechanism And Chilling Requirement Of Main Deciduous Trees In Southern Area Of Jiangsu Province

To satisfy Chilling requirement (CR) of deciduous fruit crops is an important guarantee for deciducxn fruit crops to sprout, blossom and bearing normally. If Chilling requirement of deciduous fruit crops is insufficient, production of deciduous fruit crops will be influenced because sprouting was delayed, floral organ became abnormal or abortion. So studying the physiological mechanism dormancy-release, chilling requirement of deciduous fruit crops and methods of dormancy-release are very important for protected cultivation of deciduous fruit crops and introduction of new varieties of fruit crops of southern area in china.Chilling requirement (CR) of main deciduous fruit crops in southern area of Jiangsu province were studied from November 2001 to February 2004. The results showed that CR of deciduous fruit crops, estimated by <7.2C chilling model ,0~ 7.2C chilling model and Utah model ,was difference between each other, while it was estimated by Utah model was less difference between different years. In one words ,values of CR measured of Pyrus pyrifolia and its hybrids were 340h~530h(0-7.2C chillingmodel), 340c.u~500 c.u (Utah model) and 530h~830h (< 7.2C chilling model) ,And those of apricot and nectarine varieties were 520h~900h(0~7.2C chillingmodel ), 590c.u~900 c.u (Utah model) and 840h~1300h (< 7.2C chilling model), and those of grape varieties were 770h~980h (0~7.2C chilling model), 820c.u~1000 c.u (Utah model) and 1200h~1350h (<7.2C chilling model) .Content of H2O2 and MDA, activities of antioxidant enzymes, and the respiratory ratio of grape and nectarine during nature dormancy-release were measured. The results showed that relative H2O2 content of grape and nectarine increased in early-dormancy stage, kept high level in deep-dormancy stage, and decreased later; content of MDA was high in early-dormancy stage and became a low level later; the change of SOD activities was same to that of H2O2.But the change of CAT activities was contrary to that of H2O2. POD activities increased in early-dormancy stage and reached the highest point in deep-dormancy stage, then decreased and kept at a low level later. Respiratory ratio increased in early-dormancy stage, the respiratory ratio of grape varieties reached a lowest point in deep-dormancy stage, while that of nectarine varieties was highest in deep-dormancy stage. A rise was found in stage of nature dormancy-release of grape and nectarine respiratory ratio. Chilling requirement between grape and nectarine has significant difference, but little difference between grape or nectarine.Content of H202 and MDA, activities of antioxidant enzymes, and the respiratory ratio of grape and nectarine, treated by CaCN2 and salicylic acid(SA) and glasshouse culture in different stage during nature dormancy-release, were studied. The results showed that CaCN2 and SA increased respiratory ratio, relative H2O2 content, POD activities, and decreased CAT activities, but has no significant effect on SOD activities. Treated by 25% CaCN2 from 3rd Jan. to 7th Feb. increased relative H2O2 content effectively, and satisfied the need of H2O2 content accumulation for buds to sprout, made sprouting ratio reach 41.6%~90%. Salicylic Acid had little effect on nature dormancy-release of grape; Treated by 10% SA from 3rd Jan. to 7th Feb to nectarine could regulate relative H2O2 content effectively, and satisfied the need of H2O2 content accumulation for buds to sprout, made leaf buds sprouting ratio reach 47%~88% and floral bud sprouting be advanced three to eight. CaCN2 had no significant effect on nature dormancy-release of nectarine.