Changes of leaf morphological, anatomical structure and carbon isotope ratio with the height of the Wangtian tree (Parashorea chinensis) in Xishuangbanna, China.

Leaf morphological and anatomical structure and carbon isotope ratio (delta13C) change with increasing tree height. To determine how tree height affects leaf characteristics, we measured the leaf area, specific leaf mass (ratio of leaf mass to leaf area [LMA]), thickness of the total leaf, cuticle, epidermis, palisade and sponge mesophyll, stomata traits and delta13C at different heights of Parashorea chinensis with methods of light and scanning electron microscopy (SEM) and isotope-ratio mass spectrometry. The correlation and stepwise regression between tree height and leaf structure traits were carried out with SPSS software. The results showed that leaf structures and delta13C differed significantly along the tree height gradient. The leaf area, thickness of sponge mesophyll and size of stomata decreased with increasing height, whereas the thickness of lamina, palisade mesophyll, epidermis, and cuticle, ratios of palisade to spongy thickness, density of stomata and vascular bundles, LMA and delta13C increased with tree height. Tree height showed a significant relationship with all leaf indices and the most significant relationship was with epidermis thickness, leaf area, cuticle thickness, delta13C. The delta13C value showed a significantly positive relationship with LMA (R = 0.934). Our results supported the hypothesis that the leaf structures exhibited more xeromorphic characteristics with the increasing gradient of tree height.