PLANT GROWTH REGULATION BY PHOTOCHEMICAL REACTION

参与光合作用的两种主要色素是叶绿素和类胡萝卜素。有人认为，色素生物合成的抑制剂通过诱导叶绿素的光毒中间体积累或对活性氧物种的抗氧化活性恶化而导致植物生长迟缓。抑制剂诱导的植物生长迟缓需要光照。本研究旨在探讨光参与调节色素生物合成的机制以及色素合成抑制剂的作用。主要研究结果如下：1.二苯醚类除草剂等叶绿素合成抑制剂导致原卟啉IX在处理细胞中快速异常积累。已知原卟啉IX是一种高效的光敏剂，在光下产生单线态氧。这种酸性氧诱导膜脂过氧化，导致细胞死亡。2.叶绿素合成的前体β-氨基酮丙酸(ALA)表现出药害作用，并导致原卟啉IX的大量积累。因此，认为积累这种中间体的化学物质可能作为植物生长调节剂。3.光刺激ALA的合成。在植物细胞中，光不仅诱导单线态氧的产生，而且刺激叶绿素的合成。然而，一些植物在黑暗中会诱导丙氨酸和原卟啉IX的积累。这表明植物对叶绿素合成具有物种依赖性的调控机制。4.类胡萝卜素合成中间体及相关化学物质中未发现植物毒性化合物。

The two major pigments involved in photosynthesis are chlorophylls and carotenoids. It has been suggested that inhibitors of the pigments biosynthesis cause growth retardation of plants by inducing accumulation of phototoxic intermediate of chlorophyll or deterioration of anti-oxidative activity to active oxygen species. Light is required for the inhibitor-induced plant growth retardation. This study aimed to investigate a mechanism of light involvement for the regulation of the pigment biosynthesis and the action of the pigment synthesis inhibitors. The results of the study are summarized as follows.1.Chlorophyll synthesis inhibitors such as diphenyl ether-type herbicides caused rapid and abnormal accumulation of protoporphyrin IX in treated cells. Protoporphyrin IX is known to an efficient photosensitizer generating singlet oxygen under light. This acitive oxygen induced peroxidation of membrane lipids leading to cell death.2.delta-Aminolevulinic acid (ALA), precursors of chlorophyll synthesis, showed phytotoxicity and caused huge accumulation of protoporphyrin IX.Therefore, it is considered that chemicals accumulating this intermediate may utilize as plant growth regulators.3.ALA synthesis was stimulated under light irradiation. In plant cells light induces not only singlet oxygen generation but stimulation of chlorophyll synthesis. However, some plant species induce ALA and protoporphyrin IX accumulation in the dark. This suggest that plant has species-dependent regulation mechanism of chlorophyll synthesis.4.No phytotoxic compound was found from intermediate of carotenoids synthesis and related chemicals.