Studies on the Chemical Regulation of Alkaloid Biosynthesis in Tobacco Plants

Part I. Inhibition of Nicotine Biosynthesis by Helminthosporol and Helminthosporic Acid

Abstract

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.