The effects of four manganese (Mn) concentrations (1, 10, 50, and 100 g m-3 = Mn1, Mn10, Mn50, Mn100) in solution culture on growth variables were studied for seedlings of five deciduous broad-leaved trees with different successional characteristics and shoot development patterns in northern Japan. The five species were: Betula ermanii, Betula platyphylla var. japonica, and Alnus hirsuta (early-successional species with continuous leaf development), Ulmus davidiana var. japonica (mid-successional species with flush and continuous leaf development), and Acer mono (late-successional species with a flush type leaf development). In plants grown in the Mn environment for about 45 d, 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 (SLA) and leaf mass ratio (LMR) of all species were 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. and M. Kitao, T. T. Lei, T. Koike.
The effects of NaCl stress on the growth and photosynthetic characters of Ulmus pumila L. seedlings were investigated under sand culture condition. With increasing NaCl concentration, main stem height, branch number, leaf number, and leaf area declined, while Na+ content and the Na+/K+ ratio in both expanded and expanding leaves increased. Na+ content was significantly higher in expanded leaves than in those just expanding. Chlorophyll (Chl) a and Chl b contents declined as NaCl concentration increased. The net photosynthetic rate, intercellular CO2 concentration, stomatal conductance, and transpiration rate also declined, but stomatal limitation value increased as NaCl concentration increased. Both the maximal quantum yield of PSII photochemistry and the effective quantum yield of PSII photochemistry declined as NaCl concentration rose. These results suggest that the accumulation of Na+ in already expanded leaves might reduce damage to the expanding leaves and help U. pumila endure high salinity. The reduced photosynthesis in response to salt stress was mainly caused by stomatal limitation., Z. T. Feng, Y. Q. Deng, H. Fan, Q. J. Sun, N. Sui, B. S. Wang., and Obsahuje bibliografii