Norio Yasumatsu

Studies on the Chemical Regulation of Alkaloid Biosynthesis in Tobacco Plants: Part II. Inhibition of Alkaloid Biosynthesis by Exogenous Auxins

Effect of auxin treatment upon the alkaloid content of Nicotiana was examined using hydroponically grown plants. Nicotine content of Nicotiana tabacum was reduced by the addition of 3-indoleacetic acid or 2, 4-dichlorophenoxyacetic acid to nutrient solution, an the incorporation of nitrate-15N into nicotine was decreased by the addition of 2, 4-dichloro-phenoxyacetic acid. Contents of nicotine, nornicotine, anabasine and anatabine in Nicotiana glutinosa were decreased by 2, 4-dichlorophenoxyacetic acid added to the nutrient solution. Foliar applications of eleven kinds of synthetic auxins were effective in reducing nicotine content of Nicotiana tabacum and the effectiveness of the compounds seemed to be concerned with their auxin activities. Foliar application of auxin tended to increase the dry weight of stems whereas decreased that of roots, and, moreover, higher content of soluble sugars and lower content of starch in leaves were observed by the treatment. A possibility of a practical application of au...

Studies on the Chemical Regulation of Alkaloid Biosynthesis in Tobacco Plants: Part I. Inhibition of Nicotine Biosynthesis by Helminthosporol and Helminthosporic Acid

Effects of helminthosporol and helminthosporic acid (H-acid) on nicotine biosynthesis in Nicotiana were examined. By the addition of these compounds into nutrient solution, nicotine formation in decapitated and intact plants of Nicotiana tabacum was decreased. In sterile culture of excised roots of Nicotiana rustica, H-acid reduced the yield of nicotine exerting no effect on growth rate. Incorporation of l-glutamic acid-U-14C and dl-ornithine-2-14C into nicotine in the roots was decreased by the addition of H-acid, and that of nicotinic acid-3H(G) was not influenced. Since H-acid did not enhance destruction of nicotine-3H exogenously added, it is probable that the decrease of nicotine yield by the acid in the root culture is due to reduction in the production rate of the alkaloid.