Abstract

Changes in growth parameters, 14C0₂ and [U-14C]-sucrose incorporation into the primary metabolic pools and essential oil were investigated in leaves and stems ofCatharanthus roseus L treated with etherel and gibberellic acid (GA). Compared to the control, GA and etherel treatments induced significant phenotypic changes and a decrease in chlorophyll content, carbon assimilation rate, and stomatal conductance. Treatment with etherel led to increased total incorporation of CO₂ into the leaves where as total incorporation from 14C sucrose was decreased. When 14CO₂ was fed, the incorporation into the ethanol soluble fraction, sugars, organic acids, and essential oil was significantly higher in etherel treated leaves than in the control. However, [U-14C] -sucrose feeding led to decreased label incorporation in the ethanol-soluble fraction, sugars, organic acids, and essential oils compared to the control. When 14C0₂ was fed to GA treated leaves, label incorporation in ethanol-insoluble fraction, sugars, and oils was significantly higher than in the control. In contrast, when [U-14C]-sucrose was fed the incorporation in the ethanol soluble fraction, sugars, organic acids, and oil was significantly lower than in the control. Hence the hormone treatment induces a differential utilization of precursors for oil biosynthesis and accumulation and differences in partitioning of label between leaf and stem. Etherel and GA influence the partitioning of primary photosynthetic metabolites and thus modify plant growth and alkaloid accumulation.

Key words: Amino acids, chlorophyll, CO₂ and C-sucrose incorporation, organicacids, primary photosynthetic metabolites, stem, stomatal conductance, sugars, transpiration rate.