Influence of etherel and gibberellic acid on carbon metabolism, growth, and essential oil accumulation in spearmint (Mentha spicata)

Changes in growth parameters and (CO2)-C-14 and [U-C-14]-sucrose incorporat ion into the primary metabolic pools and essential oil were investigated in leaves and stems of M. spicata 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, CO2 exchange rat e, and stomatal conductance. Treatment with etherel led to increased total incorporation of (CO2)-C-14 into the leaves wheras total incorporation from C-14 sucrose was decreased. When (CO2)-C-14 was fed, the incorporation int o the ethanol soluble fraction, sugars, organic acids, and essential oil wa s significantly higher in etherel treated leaves than in the control. Howev er, [U-C-14]-sucrose feeding led to decreased label incorporation in the et hanol-soluble fraction, sugars, organic acids, and essential oils compared to the control. When (CO2)-C-14 was fed to GA treated leaves, label incorpo ration in ethanol-insoluble fraction, sugars, and oils was significantly hi gher than in the control. In contrast, when [U-C-14]-sucrose was fed the in corporation in the ethanol soluble fraction, sugars, organic acids, and oil was significantly lower than in the control. Hence the hormone treatment i nduces a differential utilization of precursors for oil biosynthesis and ac cumulation and differences in partitioning oflabei between leaf and stem. E therel and GA influence the partitioning of primary photosynthetic metaboli tes and thus modify plant growth and essential oil accumulation.