田野菟丝子寄生对薇甘菊光合特性的影响

目的]薇甘菊（Mikania micrantha）不同叶位对田野菟丝子（Cuscuta campestris Yuncker）的寄生行为会产生不同的寄生效应。方法]连续3d从野外取样,采用叶绿素成像技术和分光光度计,测定寄生影响。结果]寄生显著降低了薇甘菊第4、5片叶PSⅡ的最大光化学效率（Fv/Fm）,对低光诱导下的qP和NPQ均无显著影响,却显著降低了第8、9片叶子的光合电子传递相对速率（ETR）。寄生也改变了寄主叶片的均质性。寄生非显著地降低了寄主薇甘菊第4～9片叶的叶绿素总量和类胡萝卜素含量,显著地降低了第6、7、9片叶的叶绿素a/b值。田野菟丝子茎内的色素含量均非常低,叶绿素a/b却保持与寄主薇甘菊相似的水平。结论]田野菟丝子的寄生对寄主产生的胁迫直接影响寄主的光化学中心的活性,从而影响其光合进程。

Chlorophyll Fluorescence Response of Mikania micrantha to the Infection by Cuscuta campestris with Imaging Fluorescence Technique

Objective]There were different effects of infection by Cucuta campestris on Mikania micrantha leaves at different leaf position.Method]Chlorophyll imaging technology and spectrophotometer were adopted to determine the effect.Result]The negative effects were significant in the maximum efficiency of PSII photochemistry Fv/Fm of the 4th and 5th leaf,and also in the relative rate of electron transport ETR of the 8th and 9th leaf.However,there was no significant effects on the photochemical quenching coefficient qP,non-photochemical quenching coefficient NPQ and the maximum rate of electron transport ETRm of the host.Meanwhile,infection changed the spatial homogeneity of fluorescence parameters.The total contents of chlorophyll and carotenoids of the 4th-9th leaves were lower in the infected host than in the control non-significantly,but significantly lower in the chlorophyll a/b ratio of 6th,7th and 9th.Conclusion]These results indicated that the infection of C.campestris may reduce the activity of PSII photochemistry of the host M.micrantha,which would influence the host photosynthesis.