| Co-Investigator(Kenkyū-buntansha) |
SASSA Takeshi Yamagata Univ., Dept. Agriculture, Professor, 農学部, 教授 (80023456)
NATSUME Masahiro Nagoya Univ., Dept. Agriculture, Research Associate, 農学部, 助手 (10201683)
SAKAGAMI Youji Nagoya Univ., Dept. Agriculture, Associate Professor, 農学部, 助教授 (80107408)
FUTATSUYA Fumio Nippon Kayaku Co., Ltd., Agrochemicals Division, Group Manager, 農薬研究所, 主任研究員
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| Research Abstract |
Based on our success in the previous isolation of 4-chloroindole--acetic acid and its methyl ester from immature seeds of Pisum sativum, we synthesized all ten regioisomers of dichloro-derivatives of indole--acetic acid, and measured their auxin activity. Among them, -dichloroindole--acetic acid (5, 6-Cl_2-IAA) showed the strongest auxin activity, and this activity was stronger than all the known natural and synthetic auxins. It induced many lateral roots in mung bean seedlings, and resisted peroxi-dase-catalyzed decomposition. In contrast, 5, 7-dichloroindole--acetic acid (5, 7-Cl_2-IAA) showed much weaker auxin activity than the other dichloro-indole derivatives. Interestingly, when wheat and rice seeds were germinated with 5, 7-Cl_2-IAA their roots curled markedly upwards. This negative geotropism is clearly an antiauxin activity. To eliminate its weak auxinlike activity, we changed the side chain of AA from acetyl to isobutyryl group, which is known to change auxin activity of 2, 4
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-D to antiauxin of PCIB. alpha-(5, 7-Dichloroindole-3-)isobutyric acid (5, 7-Cl_2-IIBA) thus synthesized showed to inhibit auxin-mediated elongation of avena coleoptiles. Its activity is stronger than that of alpha-(pchlorophenoxy)isobutyric acid and is comparable to that of 2, 3, 5-triiodobenzoic acid, which are typical antiauxins.
5, 6-Cl_2-IAA induced tropane alkaloid production in root cultures of a Duboisia hybrid at 0.01mg/L, which was comparable to 0.5mg/L IAA. By using 5, 6-Cl_2-IAA, the alkaloids were detected not only in the root tissue but also in the medium. An in vitro bioassay system for floral bud formation was established using Nicotiana tabacum explants excised from floral stalks cultured on modified Murashige-Skoog medium containing excess auxin (IAA) and antiauxin (5, 7-Cl_2-IIBA). In this system, 5, 7-Cl_2-IIBA was very effective : leaf exudate from short day-treated plants stimulated floral bud formation. Moreover, the buds produced grew into large, well-developed ones with shapes similar to those of the natural floral buds of intact tobacco plants. Less
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