EFFECTS OF FLOODING ON LEAF DYNAMICS AND OTHER SEEDLING RESPONSES IN FLOOD-TOLERANT ALNUS-JAPONICA AND FLOOD-INTOLERANT BETULA-PLATYPHYLLA VAR JAPONICA

Two-year-old seedlings of Alnus japonica Steud. and Betula platyphylla var japonica Hara were flooded from mid-June to early November, to st udy the effects of flooding on seedling survival and growth, morpholog ical changes in stems and roots, leaf emergence, leaf fall, and leaf l ongevity. In A. japonica. growth was not affected by flooding, except for a slight decrease in height growth, but some morphological changes of stems and roots were observed, i.e., stem base hypertrophy, hypert rophied lenticels, formation of adventitious roots and development of new roots. In B. platyphylla var. japonica, growth was severely reduce d by flooding and all seedlings died by the 20th week of flooding, wit hout showing any adaptive morphological changes in stems or roots. Flo oding induced rapid depression of leaf emergence, promoted leaf abscis sion, and reduced leaf longevity in B. platyphylla var. japonica. In c ontrast, in A. japonica, basal leaf senescence was delayed in flooded seedlings, thereby extending leaf longevity compared with unflooded se edlings.