Study On Physiological And Biochemical Characteristics In Juvenile Phase And Adulthood Of Xinjiang Precocious Walnut Leaves

Juvenile phase is the most important process in the transformation of fruit trees from nutritional to reproductive growth.Fruit trees have a serious impact on the early and late fruit set from sowing and sprouting to flowering and fruiting in a few years or decades.Therefore,it is important to study the child stage to shorten the reproductive cycle of fruit trees.The leaf blade is a crucial organ in the transition from childhood to adulthood of fruit trees,and there are few reports on the mechanisms related to childhood leaves.In this experiment,we compared the growth and development,microstructure,photosynthetic parameters and physiological and biochemical parameters of the leaves of the early fruiting walnut Wen185with those of the main varieties Wen185（7 a-bearing）,Xinxin2（7 a-bearing）and♀Wen185×♂Wen185 as the test material.The results of the experiment were as follows.The results of the experiment were as follows.（1）It was found that the leaf length,leaf width,leaf shape index,leaf area,petiole length and petiole thickness of adult leaves were larger than those of child stage through observation of juvenile phase and adult walnut leaves;further,through coefficient of variation analysis,leaf length,petiole length and petiole thickness in walnut leaf morphology could be used as reference indicators for live trees passing through child stage.（2）Using paraffin sections,we found that the thickness of upper epidermal cells,thickness of lower epidermal cells,thickness of fenestra tissue,thickness of spongy tissue,leaf thickness and fenestra ratio were all greater in adult walnut leaves than in juvenile phase;the tissue structure laxity and tissue structure tightness were greater in juvenile phase walnut leaves than in adult leaves.Combined with the principal component analysis,the leaf thickness and tissue structure laxity were the key factors to distinguish the juvenile phase from the adult stage,and the tissue structure tightness and fenestra ratio were the secondary factors to identify the plants passing the child stage.（3）By measuring photosynthetic parameters of leaves in juvenile phase and adulthood,we found that the relative chlorophyll content,net photosynthetic rate（P_n）,stomatal conductance（G_s）,transpiration rate（T_r）and intercellular CO₂concentration（C_i）were higher in adult leaves than in juvenile phase.（4）Proline（Pro）,soluble protein,peroxidase（CAT）and DNA concentrations in adult leaves were all greater than those in juvenile period,and malondialdehyde（MDA）,catalase and superoxide dismutase（SOD）contents in juvenile phase leaves were all higher than those in adult phase.