Potassium deficiency increases tropane alkaloid synthesis in Atropa acuminata via arginine and ornithine decar☐ylase levels

Abstract

Total biomass, percentage of tropane alkaloid, total alkaloid per plant, ornithine decar☐ylase activity (ODC), arginine decar☐ylase (ADC) activity and putrescine levels were determined separately in roots, stems and leaves of Atropa acuminata fed with nutrient solution containing varying concentrations of potassium ion. With five-fold more potassium than the control, the total biomass increased, the percentage of alkaloids decreased and there was no effect on total alkaloid produced per plant. With five-fold reduction in potassium compared to the control, the total biomass decreased, the percentage of alkaloids increased while there was no significant effect on the total alkaloid produced per plant. With 100-fold less potassium than the control, the total biomass decreased while both the percentage and total alkaloid produced per plant increased. The increase in total alkaloid produced per plant indicates that the deficit in potassium ion increases the supply of alkaloid precursor with only minimal restriction in plant growth. The increase in ODC and ADC activities which are responsible for putrescine production and the increased putrescine levels support the idea that potassium ion directly influences the enzymes concerned in alkaloid biosynthesis in Atropa acuminata.