effect of age and location of leaf on quantity and quality of Japanese mint oil production

Leaves of debranched Japanese mint (Mentha arvensis L., subsp. haplocalyx Briquet var. piperascens Holmes) were marked to allow subsequent identification for age. Leaves of different age groups were distilled for determination of quantity and quality of oil. Most of the oil and its principal component, menthol, were synthesized during the first 2 weeks of growth, while menthone and the a-pinene percentage composition of the oil declined with age after 2 weeks. A significant decrease in percentage oil content occurred in older leaves indicating that leaf loss through senescence caused less loss of oil than of dry matter. Proportion of young to old leaves had a significant effect on oil composition. This is believed to be the first report on oil composition of leaves from single plants of Japanese mint.