EFFECTS OF BLANCHING TREATMENT ON THE ESSENTIAL OIL AND THE OIL DUCTS OF UDO (ARALIA CORDATA THUNB.)

Udo (Aralia cordata Thunb.) was grown in three controlled environments: (1) in consecutive complete darkness in an underground blanching cellar, (2) using chaff for blanching of the bottom alone and (3) without any blanching treatment. Blanching treatment began with planting and the crops were harvested 20 days after the treatment. Essential oil concentration was highest in the roots. Although essential oil concentration per unit weight in the stem decreased by blanching treatment, essential oil concentration per plant increased because of the succulent growth of the plant by the treatment. The oil ducts of Udo were observed in roots, stems, petioles and leaf blades. Many oil ducts in the roots were observed in the cortex and the phloem. Those in the stem and the petiole were observed in the collenchyma, the cortex and the pith. The influence of light on the number of oil ducts in the cross sections of the central part of the stem and the petiole was not observed. The size of the oil duct increased as the plant was blanched. Consequently, it was demonstrated that the number of oil ducts was not influenced by light, and that the essential oil was obtained even in complete darkness because it was secreted the oil ducts from the roots.