‘麦香’桃叶片变色期色素含量及超微结构的变化

本文以桃的栽培品种‘麦香’（Prunus persica‘mai xiang’）为试材,在8月中旬其叶片由绿变紫红时,对其不同叶位的叶片色素含量进行了测定;以叶色维持绿色不变的品种‘照手姬’桃（Prunus persica‘terutehime’）为对照,并观察了这2个品种的叶片细胞超微结构。结果表明：当花色苷与总叶绿素、类胡萝卜含量的比值约为1∶3.86∶0.43时叶片开始转为淡紫色;当三者含量的比值达到1∶1.70∶0.18时,‘麦香’的整个叶片转变为紫色;当三者的比值大于1∶1.35∶0.16时,叶片的紫色加深变为紫红色。超微结构研究发现,‘麦香’的顶端嫩叶与‘照手姬’的存在显著差异,‘照手姬’桃叶绿体基粒片层清晰,而此时‘麦香’叶绿体基粒片层已表现出明显的松散,线粒体膜有降解现象,而且在上表皮细胞和栅栏组织的液泡中已存在不明物质,这种幼龄期表现的衰老迹象,可能是‘麦香’桃的早熟性决定的。在基部叶片的超微结构中,两品种都出现了相似的衰老现象,即叶绿体片层结构严重扭曲并出现解体现象、嗜锇颗粒增多变大、线粒体外膜解体,内嵴混乱。此外’麦香’叶片中还显示出特有的结构：栅栏组织细胞的液泡和上表皮细胞出现大量絮状或粒状的黑色物质。本实验结果表明,‘麦香’桃叶片的成色取决于花色苷和总叶绿素的比例,‘麦香’桃在变色期合成花色苷,然后可能运输到栅栏组织的液泡和上表皮细胞,使叶片呈现紫红色。

Changes of the content of pigments and ultrastructure of mesophyll cells during the leaf discoloration in Prunus persica 'mai xiang'

The contents of anthocyanins,chlorophylls and carotenoids in Prunus persica‘mai xiang’of different leaf position were examined in mid-August of 2008,and the ultrastructures of leave mesophyll cell were observed in both P.persica ‘mai xiang’and P.persica ‘terutehime’.The results indicated that the leaf color turn light purple when the ratio of anthocyanins to total chlorophylls and carotenoids was above 1∶ 3.86∶ 0.43;and it turn purple when the ratio was above 1∶ 1.70∶ 0.18;and it turn deep mauve when the ratio was above1∶ 1.35∶ 0.16.The results of experiment on sub-microstructure of blade cell showed that a series of chloroplast configuration changed,and the structure of grana and chloroplasts lamella appeared loose phenomenon.Some mitochondria membrane appeared disorganized phenomenon.Maybe the precocial feature decided its special morphology.P.persica ‘mai xiang’and P.persica ‘terutehime’appeared normal phenomenon of senescence leaves from the base of branches： Mesophyll cells and chloroplasts began to decompose.The number and the volume of plastoglobulis increased.Some mitochondria membrane disorganized and the vesicular sphere was visible under such concentration.There were a large number of black flocculent or granular material in vacuolar of the palisesade tissue cells and upper epidermis cells in‘mai xiang’.The results proved that the leaf color of‘mai xiang’depended on the ratio of anthocyanins and total chlorophylls.The leaves synthesized anthocyanins during the leaf discoloration and then it transported to the vacuolar and upper epidermis cells in order to make the leaves becoming purple.