Effects of manganese in solution culture on the growth of five deciduous broad-leaved tree species with different successional characters from northern Japan

摘要

The effects of 4 manganese (Mn) concentrations (1, 10, 50 or 100 g m-3 (Mn1, Mn10, Mn50, Mn100)) in solution culture on growth variables were studied for 2- to 3-year-old seedlings of 5 deciduous broadleaved trees with different successional characteristics and shoot development patterns from northern Japan. The 5 species were Betula ermanii, Betula platyphylla var. japonica and Alnus hirsuta (early-successional species with continuous leaf development), Ulmus davidiana var. japonica [U. japonica](mid-successional species with flush and continuous leaf development), and Acer mono [Acer pictum subsp. mono] (late-successional species with a flush type leaf development). In plants grown in the Mn environment for about 45 days, relative growth rate (RGR) decreased with increasing Mn supply. Between the 1 and 100 g(Mn) m-3, RGR decreased by 20% for B. ermanii and B. platyphylla, by 40% for A. hirsuta and A. mono, and by 80% for U. davidiana. Specific leaf area and leaf mass ratio (LMR) of all specieswere little affected by high Mn supply. In U. davidiana, however, there was a 67% decrease in LMR in Mn100 plants. Leaf area ratio (LAR) was higher in early-successional species than in mid- and late-successional ones but differed little among Mn treatments within species, except for U. davidiana where LAR declined substantially with increased Mn supply. While LAR, which represents the relative size of assimilatory apparatus, was little affected, net photosynthetic rate (PN) saturated with radiant energy decreased with increasing Mn supply in all species. Thus PN was adversely affected by high accumulation of Mn in leaves, which resulted in an overall reduction in biomass production. However, the proportional allocation of photosynthates to the assimilatory apparatus was not affected by different Mn toxicity in hardwood tree seedlings.