Abstract:

This research was to examine if rice (Oryza sativa L.), a monocotyledon of angiosperm, was able to synthesize chlorophyll (Chl) in complete darkness. Five-cm-tall etiolated seedlings of rice were used as starting materials and treated with or without various concentrations of glucose and/or δ-aminolevulinic acid (ALA) in the dark. Leaves harvested at the indicated time were determined for their contents of Chl, protoporphyrin Ⅸ(Proto), Mg-protoporphyrin Ⅸ(Mg-Proto) and protochlorophyllide (Pchlide). The mole percentage of porphyrin was calculated. The Chl content in the etiolated rice seedlings slightly increased from about 2.5 μg/g to 7.5 μg/g within 12 d in the dark, but the total Chl of dark-grown rice increased from 0.36 μg/g to 3.6 μg/g. While the mole percentages of Proto, Mg-Proto and Pchlide in the dark-grown seedlings without any treatment were about 65%, 27.5% and 7.5% at the beginning, respectively, those in the light-grown seedlings were about 42.5%, 35% and 22.5%, respectively. The mole percentage of porphyrin of etiolated seedlings resumed its normal ratio within 2 d after treatment with glucose. While the Chl content of etiolated seedlings grown in culture solution with 3% and 6% glucose increased 2.5 and 4.0 folds, respectively, those with 3% and 6% glucose and 1 mmol/L ALA increased 22 and 24 folds, respectively. It is concluded that angiosperm might be able to synthesize a small amount of Chl in complete darkness, that either glucose or ALA could stimulate dark Chl synthesis in angiosperm, and that a combination of glucose and ALA exhibited an additional effect. It is still unknown and remains to be further explored what is the mechanism of the effect of glucose and ALA on the Chl synthesis of rice in the dark. Key words: angiosperm; rice; dark chlorophyll synthesis; glucose; δ-aminolevulinic acid; protoporphyrin Ⅸ; Mg-protoporphyrin Ⅸ; protochlorophyllide

葡萄糖和δ—氨基酮戊酸促进水稻在黑暗中合成叶绿素

杨棋明 蔡慧美 杨佳豪
（中国台北植物研究所，台北11529）

摘要： 本研究检测单子叶被子植物水稻（Oryza sativa L.)在完全黑暗中是否能合成叶绿素。以5cm高的水稻黄化幼苗为研究材料，在黑暗中用不同浓度的葡萄糖和δ-氨基酮戊酸（δ-aminolevulinic acid,ALA)处理之，定时采收叶片检测其叶绿素，原卟啉Ⅸ（Proto),Mg-原卟啉Ⅸg-Proto)及原叶绿酸酯（Pchlide)的含量，并计算它们的卟啉的摩尔百分比。在黑暗中12d，水稻幼苗的叶绿素从2.5μg/g增加到7.5μg/g，但叶绿素总量从0.36μg/g增至3.6μg/g。在黑暗中未经处理的幼苗Proto,Mg-Proto及Pchlide的摩尔百分比分别为65%，27.5%和7.5%；而光照下幼苗相应的摩尔百分比分别为42.5%,35.0%和22.5%。在黑暗中用葡萄糖处理水稻黄化幼苗2d。其卟啉的摩尔百分比即可恢复到正常值（如光照下之相同比例）。在黑暗中以3%和6%的葡萄糖处理水稻黄化幼苗2d，其叶绿素含量分别增加2.5和4.0倍；若同时辅以1mmool/Lδ-氨基酮戊酸，其叶绿素含量分别增加22和24倍，因此，被子植物在黑暗中可以合成叶绿素；葡萄糖或δ-氨基酮戊酸可以促进被子植物在黯部合成叶绿素；葡萄糖和δ-氨基酮戊酸并用有加成作用。葡萄糖或δ-氨基酮戊酸促进水稻在黑暗中合成叶绿素在生理机制有待研究。

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