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

Effects of magnesium deficiency on the physiological indices,magnesium distribution and leaf ultrastructure of Citrus cultivars "shiranuhi" and "ponkan"

采用砂基培养法,研究缺镁胁迫下不知火"[Citrus reticulata×(C.reticulata×C.sinenesis)]和椪柑"(Citrus reticulata Blanco)的生理和形态结构变化,以及镁元素的分布特点.结果表明:1)镁缺乏使不知火"和椪柑"的生物量、根系活力、叶片叶绿素含量与超氧化物歧化酶(SOD)活性均显著下降,其中不知火"的下降幅度均明显高于椪柑";镁缺乏使二者叶片的过氧化物酶(POD)活性、丙二醛(MDA)含量及叶片相对电导率显著上升,其中不知火"的MDA含量和叶片相对电导率显著高于椪柑";在镁缺乏下不知火"叶片的过氧化氢酶(CAT)活性显著升高,而椪柑"的CAT活性与对照差异无统计学意义;2)不知火"和椪柑"各部位的镁含量均随营养液中镁浓度的增加而上升,且叶片镁含量随着叶龄的增长而呈明显下降趋势,在镁缺乏下不知火"各部位叶片镁含量均显著高于椪柑";3)叶肉细胞超微结构变化显著,在镁缺乏处理下不知火"细胞器受损程度较重,如叶绿体内基粒片层模糊、数目明显减少,淀粉粒增大,叶绿体膜与线粒体膜模糊;而椪柑"叶绿体变形、离壁,叶绿体内基粒片层数目明显减少,淀粉粒和质体小球增多.可见,镁缺乏对不知火"生理及形态结构的影响较椪柑"明显.

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＂.