不同生境华东野核桃光合生理特性及叶绿素荧光参数比较

采用LI-6400便携式光合作用系统，于2011年7月下旬的晴朗天气条件下，对浙江省天台山林窗、林缘、林下生境华东野核桃（Juglans cathayensis var. formosana）的光合生理特性及叶绿素荧光参数进行测定，并比较林窗生境中华东野核桃与其伴生植物山胡椒（Lindera glauca）、玉兰（Magnolia denudata）、云锦杜鹃（Rhododendron fortunei）光合日进程的差异. 结果表明：夏季，林窗生境的华东野核桃及主要伴生植物叶片的净光合速率（P_n）日进程均呈“双峰”曲线，有明显的“午休”现象，其“午休”的原因主要是由非气孔限制因素引起的；林下、林缘的P_n日进程均呈“单峰”曲线.林窗生境的华东野核桃与林缘、林下相比，其光补偿点（LCP）低，光饱和点（LSP）高，对光适应的生态幅较宽；并且林窗生境的华东野核桃暗呼吸速率（R_d）低，日均P_n、最大净光合速率（A_max）高，有利于有机物的积累，说明林窗生境适合其生长. 3种生境华东野核桃的PSⅡ最大光化学效率（F_v / F_m）均呈现出“V”型曲线. 林窗生境中华东野核桃的日均P_n均比其他伴生植物高，且差异均极显著（P＜0.01），说明华东野核桃的光合作用能力较强.

Comparison of photosynthetic characteristics and chlorophyll fluorescence parameters of Juglans cathayensis var.formosana in different habitats

The photosynthetic characteristics and chlorophyll fluorescence parameters of Juglans cathayensis var. formosana in canopy gap, forest edge and understory were measured on a sunny day in the late July, 2011, using a portable photosynthesis system （LI-6400）. Diurnal variation of photosynthesis of J. cathayensis var. formosana and its accompanying species including Lindera glauca, Magnolia denudata and Rhododendron fortunei in canopy gap were also measured and compared. The results showed that the diurnal variation of the net photosynthesis rates （Pn） in the leaves of J. cathayensis var. formosana and three main accompanying species in the canopy gap took on double-peak curve with remarkable midday depression, which was mainly due to a non-stomatal limitation. The di- urnal variation of Pn of J. cathayensis var. formosana in the understory and forest edge took on one-peak curve. Light compensation point （LCP） and light saturation point （LSP） of J. cathayensis var. formosana in canopy gap were larger than those of J. cathayensis var. formosana at forest edge and understory, indicating that J. cathayen- sis var. formosana in canopy gap had wider ecological amplitude to light than that in the other habitats. J. cathay- ensis vat. formosana in canopy gap had lower dark respiration rate （Rd）, higher daily average Pn and higher maximal net photosynthesis rates （Amx）, indicating that the canopy gap habitat might be helpful to the accumulation Of organic materials and might be a more suitable habitat for the growth of J. cathayensis var. formosana. The photochemical efficiency（Fv/Fm） of J. cathayensis var. formosana in three kinds of habitats showed curves with ＂V＂ type. The daily aver age Pn in the leaves of J. cathayensis var. formosana was extremely significantly higher than the accompanying spe- cies （P〈0.01）. This indicated that the J. cathayensis vat. formosana had high photosynthesis ability.