Morphological responses induced by walnut leaf scorch
[Objective]To investigate the morphological changes in walnut trees during the occurrence of walnut(Juglans regia L.)leaf scorch.[Method]The study utilized one-year-old fruiting branches of the predominant walnut cultivar'Wen185'(J.regia'Wen185')from the Aksu region in the Southern Xinjiang Basin.Quantitative measurement techniques were employed to assess changes in branch length,basal diameter growth rate,and xylem specific hydraulic conductivity during the onset of leaf scorch.Microscopic observation techniques were used to qualitatively examine the structural changes in leaves,petioles,and branches affected by the disease.[Result]The walnut leaf scorch severely affected the growth and structure of the annual fruiting branches in'Wen185'walnut trees.The length increment,basal diameter increment,and xylem water conductivity of the diseased branches were significantly reduced(P＜0.05).The length increment was 63.42 mm in healthy branches and 48.68 mm in diseased branches;the basal diameter increment was 2.98 mm in healthy branches and 2.17 mm in diseased branches;the xylem water conductivity was 9.00 kg·m-1·s-1·MPa-1 in healthy branches and 2.55 kg·m-1·s-1·MPa-1 in diseased branches.The results of multiple comparison of leaf anatomical structure showed that leaf thickness,palisade tissue thickness,spongy tissue thickness and upper epidermis thickness decreased with the increase of leaf scorch disease grade.Healthy leaf cell structure intact,no cavity and epidermal damage.However,mesophyll cells of infected leaves were broken,spongy tissue had holes and free cells were damaged.With the increase of the grade of scorched leaf disease,epidermal cells were distorted and deformed.In severe cases,the upper epidermis was seriously distorted,spongy tissue had more holes,mesophyll cell damage was intensified,and the lower epidermis was broken.At the same time,the surface of the pitted membrane on the petiole of the infected leaves became rough and white particles appeared,and in severe cases,it broke.At the same time,particulate matter and succulent structure appeared in the threaded catheter of xylem of susceptible branches,which led to blockage of the catheter and affected the transport of water and nutrients.[Conclusion]During the onset of walnut leaf scorch,the growth of the annual fruit branches of J.regia'Wen185'was hindered,the leaf structure was damaged,and the thread pipe of xylem was blocked,which led to the decrease of xylem specific water conductivity.
walnut leaf scorchgrowthxylem conductance in stemsleaf structure
万方数据
维普
