The Screening To Low Calcium And Mechanism Of Chinese Cabbage To Tip-Burn

This text studied the screening and identifying methods and the physic-biochemical indexes and cytological changes of tip-burn in Chinese cabbage. We summarized and improved screening and identifying methods of tip-burn, and tested the content and the activity changes of protein, soluble sugar, MDA, photosynthesis and enzyme. We also studied the changing process of leaf's internal tissue and organization, and got these conclusions as follow: 1. We got 14 high resistance varieties, 40 resistance varieties, 107 toilerant varieties , 22 sensitive varieties and 14 high sensitive varieties. 2. It is 2mmol/L EDTA-Na2 which is proper to screening of detached leaves; to evaluate material's resistance to low calcium, one should based on spots and rots as the same time; the starting position of tip-burn is mainly on leaf stalk; the results indicated that the distribution of main symptoms of tip-burn are all "T"shape; different varieties has different resistance to tip-burn. 3. We studied 3 different identifying methods of tip-burn, the results show that: the method of insertion of detached leaves is adapt to screening for many varieties roughly and it is a simple, convenient and quick method; seedling identification is adapt to screening for few varieties precisely, this method has high accuracy and typical symptom, it is both economical and practical method at present; we do not advocate field identification because of low accuracy and many inhibiting factors. 4. When calcium deficiency, the content of soluble sugar, MDA and membrane leakage, are increased, the activity of root, Ca2+-ATPase, POD and the content of protein, chlorophyll, Vc and photosynthesis rate are dropped; the electrophoresis result shows that there is no change on protein when calcium deficiency, the electrophoresis of POD of the leaf indicates that there are different between CK and treatment, two weak lines are disappeared in treatment, this means the activity of POD of leaf reduced. 5. The research of cytology shows that there are dramatically morphological and structure changes in the leaf: the cells of mesophyll array loosely and parenchyma cells reduced, cambium becomes thinner and degree of xylem becomes more serious, the content of chlorophyll dropped; the changes of conducting tissue and stoma structure affect transport and allocation of water and nutrient, hinder leaf growth and disturb regular metabolism of leaf, at last lead to wilt, rot and become crisp papyraceous.