SCREENING OF PLANT GROWTH REGULATORS FROM INTERMEDIATES OF PLANT PIGMENT BIOSYNTHESIS

叶绿素和类胡萝卜素的生物合成途径是植物特有的。近年来，有研究表明，叶绿素前体如原卟啉IX通过光动力作用表现出植物毒性。本研究旨在从色素生物合成途径的中间体和生物合成调节剂中筛选出可用于除草的新植物生长调节剂。主要研究结果如下：1.研究了叶绿素前体、中间体和叶绿素途径调节剂对几种植物生长的影响。在测试的天然化合物中，d-氨基乙酰丙酸（ALA），叶绿素的所有四吡咯中间体的前体，当它们被外源施加到植物时是最除草的。浓度为10 μ M <-4>~ 10 μ <-3>M的ALA溶液会引起植物白化，并杀死许多植物物种。乙酰丙酸、二氧庚酸和gabaculine在较高浓度下也表现出植物毒性，如失绿。2.从ALA的作用方式研究中发现，大量积累叶绿素中间产物。原卟啉IX是最常见的卟啉积累。这是已知的光敏剂在光下产生单线态氧。因此，积累该中间体的化学物质可能成为有效的生长调节剂。3.为了刺激植物中ALA的合成，研究了植物中ALA合成的调节。结果表明，ALA的合成受光照和该途径产物的反馈抑制作用的调控; 4.建立了水稻田一年生杂草稗草水培苗的生长调节剂生物测定体系

Chlorophylls and carotenoids biosynthetic pathways are peculiar to plants. Recently, it was reported that chlorophyll precursor such as protoporphyrin IX showed phytotoxic activity by its photodynamic action. This study aimed to screen new plant growth regulators available for herbicidal use from intermediates of the pigments biosynthetic pathways and modulators of the biosynthesis. The results of the study are summarized as follows.1.Effect of chlorophyll precursors, intermediates, and modulators of chlorophyll pathway on growth of several plant species were surveyed. Among the natural compounds tested, d-aminolevulinic acid (ALA), precursors of all the terapyrrole intermediates of the chlorophyll are most herbicidal when they were exogenously applied to the plants. ALA solution sprayd at 10^<-4> to 10^<-3> M caused bleaching and killed many plant species. Levulinate, dioxoheptanoic acid and gabaculine also showed phytotoxic activity such as chlorosis at higher concentrations.2.From the mode of action study of ALA,huge accumulation of chlorophyll intermediates was identified. Protoporphyrin IX was the prevalent porphyrin accumulating. This known to photosensitizer generating singlet oxygen under light. Therefore, chemicals that accumulate this intermediate may become effective growth regulator.3.To stimulate ALA synthesis in plants, regulation of ALA synthesis in plants was investigated. It was shown that ALA synthesis was regulated by light and feedback inhibition of the products of the pathway.4.Bioassay system of plant growth regulators using hydroponically grown barnyardgrass seedlings, most troublesome annual weed in rice paddy, was established