Interspecific variation of photosynthesis and leaf characteristics in canopy trees of five species of Dipterocarpaceae in a tropical rain forest

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Tree Physiology, 24:1187–1192

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Interspecific variation of photosynthesis and leaf characteristics in canopy trees of five species of Dipterocarpaceae in a tropical rain forest

Tanaka Kenzo (1, 2), Tomoaki Ichie (3), Reiji Yoneda (4, 5), Yoshinori Kitahashi (6), Yoko Watanabe (3), Ikuo Ninomiya (4) and Takayoshi Koike (3)

1. The United Graduate School of Agricultural Sciences, Ehime University, Matsuyama, 790-8566, Japan / 2. Corresponding author (mona@agr.ehime-u.ac.jp) / 3. Hokkaido University Forests, FSC, Sapporo, 060-0809, Japan / 4. Faculty of Agriculture, Ehime University, Matsuyama, 790-8566, Japan / 5. Forestry and Forest Products Research Institute, Tsukuba, 305-8687, Japan / 6. Graduate School of Agriculture, Hokkaido University, Sapporo 060-8589, Japan / Received December 17, 2003; accepted March 5, 2004; published online August 2, 2004

Summary

Photosynthetic rate, nitrogen concentration and morphological properties of canopy leaves were studied in 18 trees, comprising five dipterocarp species, in a tropical rain forest in Sarawak, Malaysia. Photosynthetic rate at light saturation (P_max) differed significantly across species, varying from 7 to 18 µmol m^–2 s^–1. Leaf nitrogen concentration and morphological properties, such as leaf blade and palisade layer thickness, leaf mass per area (LMA) and surface area of mesophyll cells per unit leaf area (A_mes/A), also varied significantly across species. Among the relationships with leaf characteristics, P_max had the strongest correlation with leaf mesophyll parameters, such as palisade cell layer thickness (r² = 0.76, P < 0.001) and A_mes/A (r² = 0.73, P < 0.001). Leaf nitrogen concentration and P_max per unit area also had a significant but weaker correlation (r² = 0.46, P < 0.01), whereas P_max had no correlation, or only weakly significant correlations, with leaf blade thickness and LMA. Shorea beccariana Burck, which had the highest P_max of the species studied, also had the thickest palisade layer, with up to five or more layers. We conclude that interspecific variation in photosynthetic capacity in tropical rain forest canopies is influenced more by leaf mesophyll structure than by leaf thickness, LMA or leaf nitrogen concentration.

Keywords: dipterocarp, leaf morphology, Malaysia, nitrogen content, palisade layer, photosynthetic capacity, Sarawak.