镁缺乏对“不知火”和“椪柑”生理指标、镁分布及叶片超微结构的影响

Abstract

By using sand culture, the changes of physiological and anatomical features and the characteristics of magnesium (Mg) distribution of Citrus cultivars ”shiranuhi” [Citrus reticulata × (C.reticulata × C.sinenesis)] and ”ponkan” (C.reticulata) seedlings were studied in the Mg-deficient conditions. The results showed: 1) The deficiency of Mg decreased significantly the plant biomass, root viability, leaf chlorophyll contents and superoxidase dismutase (SOD) activities of both cultivars, especially for ”shiranuhi”. Mg deficiency increased significantly peroxidase (POD) activities, malondialdehyde (MDA) contents and relative conductivity of both plant leaves. Furthermore, MDA contents and relative conductivity in ”shiranuhi” were significantly higher than those in ”ponkan”. In addition, leaf catalase (CAT) activity of ”shiranuhi” in Mg-deficient condition increased significantly, but it wasn’t observed on ”ponkan”.2) Mg contents of both cultivars' leaves increased with increasing Mg concentration in solution, and they decreased obviously with the leaf aged. Furthermore, Mg contents of ”shiranuhi” were significantly higher than that of ”ponkan” under Mg-deficient condition.3) Ultrastructural observation of leaf structure and chloroplast showed that the organelle of ”shiranuhi” was damaged seriously under Mg-deficient condition, which was revealed by the vague thylakoid lamella with less number, drastic increase of starch grain volume, and the blurred membranes of chloroplast and mitochondria. As to ”ponkan”, distortion, plasmolysis and less grana lamella of chloroplast were observed, but the starch grain and plastoglobuli numbers were increased. Thus, it is suggested that the influences of Mg deficiency on physiological and anatomical features were more obvious in ”shiranuhi” than in ”ponkan”.