Application of chlorophyll fluorescence to evaluate Mn tolerance of deciduous broad-leaved tree seedlings native to northern Japan

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Tree Physiology, 18:135–140

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Application of chlorophyll fluorescence to evaluate Mn tolerance of deciduous broad-leaved tree seedlings native to northern Japan

M. Kitao (1), T. T. Lei (1, 2) and T. Koike (1, 3)

1. Forestry and Forest Products Research Institute, Hokkaido Research Center, Sapporo 062, Japan / 2. Biology Department, Virginia Polytechnic Institute and State University, Blacksburg, VA 24061, USA / 3. Forest Science Research, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183, Japan / Received February 20, 1997

Summary

We used chlorophyll fluorescence to examine photosynthetic responses to excess Mn accumulation in leaves of four tree species differing in successional traits. Betula ermanii Cham. (Be) and Alnus hirsuta Turcz. (Ah) were studied as representatives of early-successional species. Ulmus davidiana Planch. var. japonica (Rehder) Nakai (Ud) was selected as a mid-successional species, and Acer mono Maxim. var. glabrum (Lév. et Van't.) Hara (Am) was chosen as a late-successional species. In Be, Ah and Am, high foliar concentrations of Mn had little effect on maximum photochemical efficiency of photosystem II (PSII), as indicated by the values of dark-adapted F_v/F_m, whereas a significant decrease was observed in Ud. Photochemical quenching (qP) and the excitation capture efficiency of open PSII (F'_v/F'_m) decreased with increasing leaf Mn concentration at photosynthetic steady state after a 15-min exposure to 430 μmol m^–2 s^–1 PPFD. Compared with early-successional species, these decreases were greater in mid- and late-successional species leading to lower effective quantum efficiencies of PSII (ΔF/F'_m = qP × F'_v/F'_m = (F'_m – F)/F'_m). To determine the extent of photoinhibition, F_v/F_m of the illuminated leaves was remeasured after a 15-min dark period. Compared with the dark-adapted F_v/F_m, we observed a significant decrease in F_v/F_m in Am leaves containing high concentrations of Mn. These chlorophyll fluorescence studies indicate that the early-successional species Be and Ah have a higher tolerance to excessive accumulations of Mn in leaves than the mid- and late-successional species Ud and Am.

Keywords: deciduous broad-leaved trees, Mn toxicity, photochemical quenching, photoinhibition, photosynthesis, photosystem II.