AUTUMNAL REDDENING OF LEAVES - SEASONAL-CHANGES IN CONTENTS OF PHENOLIC COMPOUNDS AND SUGAR IN RHUS, EUONYMUS AND ACER LEAVES WITH SPECIAL REFERENCE TO ANTHOCYANIN FORMATION IN AUTUMN

Seasonal variation in sugar, total phenol and flavanol contents was examined in Rhus, Euonymus and Acer [R. succedanea, E. alatus f. ciliato-dentatus, A. buergerianum and A. palmatum var. palmatum] leaves. In all plant leaves, the total phenol and flavanol content per leaf increased rapidly at the early growth stages but thereafter the content was kept rather constant. Later on, sugar content increased to a high level, and the autumnal reddening began. An excessive accumulation of sugar just before the reddening indicated that the accumulation was related to the anthocyanin formation. The incorporation of radioactivity into anthocyanin in autumn leaves from glucose-[U-14C] and phenylalanine-[U-14C] was also observed.