Abies veitchii and Abies mariesii are dominant species at the tree-line in Central Japan. Recently, we observed needle death, probably due to photodamage of the photosynthetic apparatus at the tree-limit during March῍April. A. veitchii survives winter without any needle death due to photodamage at the tree-line. However, there is no conspicuous damage between the two species because this phenomenon is only observed at the tree-limit. In this study, we examined the di#erence in winter

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... tion of PS II between A. veitchii and A. mariesii and observed the following results: In March, (+) Fv/Fm of both species was about *.+, showing the photochemical e$ciency being severely inhibited. (,) The de-epoxidation state, expressed as [(AῌZ)/(VῌAῌZ)], was about *.-/ for both species. (-) Chlorophyll (Chl) content of A. veitchii was much less than that of A. mariesii and Pchlide was found only in A. veitchii. In April, (+) Fv/Fm increased and [(AῌZ)/(VῌAῌZ)] decreased for both species. (,) Chl content of A. veitchii increased by four-fold while Pchlide nearly dissappeared. These results indicate the following: During cold periods, most of Chl of A. veitchii may have been converted to Pchlide which is easily re-converted to Chl in spring, an intermediate of Chl biosynthesis. Winter conversion from Chl to Pchlide in A. veitchii may provide e#ective protection from photodamage of the photosynthetic apparatus. Furthermore, this may explain the higher ability of A. veitchii to prevent photodamage compared to A. mariesii.