叶色黄化突变体甜瓜叶片内部生理生化变化 的研究

从薄皮甜瓜白莎蜜1 号中筛选出一个生长发育正常的自发型叶色黄化突变体93 88-1，以突
变亲本白莎蜜1 号为对照，对其光合色素含量、叶绿素生物合成前体物质含量、叶绿素荧光参数以及叶绿
体超微结构进行研究。结果显示：9388-1 光合色素含量显著低于白莎蜜1 号，而叶绿素a 与叶绿素b 的
比值显著高于白莎蜜1 号；叶绿素合成受阻于胆色素原（PBG）与尿卟啉原Ⅲ（Urogen Ⅲ）之间；荧光参
数F₀、P_n、ФPS Ⅱ和ETR 显著低于白莎蜜1 号，而qN 和NPQ 显著高于白莎蜜1 号，Fm、FV/Fm 和qP 与
白莎蜜1 号无显著差异；突变体9388-1 的叶绿体内部基粒片层垛叠数有所减少，基粒排列不整齐，呈线
条状，基粒片层间距离大，排列疏松，内含物混浊，淀粉粒少，而白莎蜜1 号基粒片层结构紧密排列，结
构完整，淀粉粒多。表明叶绿素的生物合成受阻，导致叶绿体内部结构发育缺陷，从而影响光合色素的稳
定性，改变叶绿体各种色素的含量与比例，最终引起叶色黄化。同时，突变体能及时地耗散过剩的光能，
对光合机构起一定的保护作用，维持植株正常生长。

Studies on Internal Physiological and Biochemical Changes of Xantha Mutant in Melon Leaves

Xantha mutant 9388-1，a spontaneous mutant，was screened out from a normal green
leaf melon（Cucumis melo L.） variety‘ Baishami No.1’．Its contents of photosynthetic pigment and Chl
synthesis precursors，chlorophyll fluorescence kinetic parameters and ultra-structure of chloroplasts
were studied with mutant parent‘ Baishami No.1’ as contrast．The results showed that photosynthetic
pigment content in mutant leaves was significantly lower than that in‘ Baishami No.1’，while the ratio
between chlorophyll a and chlorophyll b was significantly higher than in‘ Baishami No.1’．Chlorophyll
biosynthesis was hampered at conversion from prophobilinogen（PBG） into uroporphyrinogen
（Urogen Ⅲ）．Compared with chlorophyll fluorescence kinetic parameters of‘Baishami No.1’，F₀，
P_n，ФPS Ⅱ and ETR were significantly lower，while qN and NPQ were notably higher than that of
‘Baishami No.1’．There were no significant differences in Fm，FV/Fm and qP ．Under transmission
electron microscopy，9388-1 leaves were found with underdeveloped chloroplast，containing aberrant
thylakiods，fewer graum and starch grains than that of‘Baishami No.1’．Grana lamellae were deranged
with a line shape and less stacked，but grana lamellae was crowed together in normal one．These
results indicated that the biosynthesis chlorophyll was hampered，leading to aberrant chloroplast and the
photosynthetic pigments content changed，and then affected their stability．The mutant kept a higher
heat dissipation capacity，which could prevent photosynthetic apparatus from damaged by excessive
light energy and maintain the normal growth of plant.