[Analysis of chlorophyll and photosynthesis of a tomato chlorophyll-deficient mutant induced by EMS.]

We analyzed the growth, leaf chlorophyll content, and photosynthetic parameters of a tomato leaf yellowing mutant (Y55) induced by ethyl methane sulfonate (EMS) from the cultivar "Heinz 1706" (WT). Results showed that the plant height, stem diameter, and fresh mass of Y55 significantly . The contents of chlorophyll a, chlorophyll b, carotenoid, total chlorophyll and the chlorophyll a/b ratio of the mutant were significantly lower than those of WT. The contents of all precursor materials of chlorophyll synthesis, especially porphyrinogen III and those involved in the chlorophyll biosynthesis pathway, were significantly lower in Y55 than those in WT. Moreover, the net photosynthesis (Pn), transpiration rate (Tr), intercellular CO2 concentration (Ci), and conductance to H2O (gs) significantly in Y55. The maximum photosynthetic rate, CO2 saturation and compensation point, and light saturation and compensation point. The Fv/Fm significantly, whereas the Fo significantly in Y55. The photosynthetic electron production and electron transport rates of PSII and PSI also significantly decreased. The total photosynthetic pigment molecules (No) and the minimum average lifetime of photosynthetic pigment molecules in the excited state (τmin) significantly in Y55. All these results suggest that blocking the synthesis of porphyrinogen III ould decrease the chlorophyll content in the mutant Y55. Furthermore, the reduced amount of leaf pigment could affect photosynthesis in leaves and slow down the growth of mutant plants.本试验以测序番茄品种‘Heinz 1706’的甲基磺酸乙酯(EMS)诱变所获得的叶色黄化突变体(Y55)为试材,分析了突变体的植株生长、叶片叶绿素含量及光合参数.结果表明: Y55的株高、茎粗、鲜质量均显著降低;叶绿素 a、叶绿素 b 、类胡萝卜素、总叶绿素含量以及叶绿素 a/b均显著降低,Y55叶绿素合成的前体物质含量均显著低于野生型,尤其是粪卟啉原Ⅲ及其后前体物质;且Y55叶片净光合速率、蒸腾速率、胞间CO2浓度、气孔导度均显著低于野生型,最大光合速率、CO2饱和点与补偿点、光饱和点与补偿点也显著下降;Y55的PSII最大量子效率显著降低,Fo显著升高,PSII与PSI的光合电子产量和电子传递速率显著降低;Y55处于基态的捕光色素分子、捕光色素分子处于最低激发态的平均寿命均显著降低.表明粪卟啉原Ⅲ的合成受阻可能是黄化突变体Y55叶绿素含量下降的主要原因,黄化突变降低了叶片捕光色素分子数量,影响了叶片的光合作用,进而抑制了植株的生长发育.