Differences in leaf mass per area, photosynthetic pigments and δ13C by orientation and crown position in five greening tree species
HE Chun-Xia, LI Ji-Yue, ZHANG Yan-Xiang, ZHENG Quan-Shui, XIE Bo, DING Yi-Ting
Chin J Plan Ecolo. 2010, 34 (2):
Related Articles |
Aims Light, temperature and humidity conditions differ among individual leaves and may influence leaf mor-phology, anatomy, stomatal conductance, chlorophyll content and distribution and leaf photosynthetic processes. Our objective was to determine the influence of local microenvironment on structure and biophysical characteristics of leaves through research on changes of leaf morphology and biophysical indices along the lateral distribution of leaves within tree crowns and with orientation differences.
Methods We selected five tree species with wide crowns (Sophora japonica, Platanus orientalis, Ginkgo biloba, Ficus microcarpa and F. lacor) and measured leaf photosynthetic pigments (including chlorophyll a, chlorophyll b and carotenoids), leaf mass per area (LMA) and carbon isotope ratio (δ13C) along the horizontal distance from the sample point to the tree trunk and with different orientations in each tree species. Pigment content was measured by colorimetry, LMA as the ratio of leaf dry mass to fresh area and δ13C with a mass spectrograph.
Important findings Leaf δ13C and LMA increased and photosynthetic pigment decreased with horizontal distance from the sample point to the trunk. Leaf δ13C and LMA also differed by orientation, with southward leaves having the highest values, followed by westward leaves, and eastward leaves having the lowest values. Photosynthetic pigments had a more complex relation with orientation, although chlorophyll a, chlorophyll b, total chlorophyll content, chlorophyll a to b ratio and carotenoids were the highest in eastward leaves. These results suggest that southward, westward and leaves on the outside of the crown have increased LMA, reduced stomatal aperture and photosynthetic pigment content and, as a result, decreased photosynthesis and increased δ13C values in response to stronger irradiance, higher temperature and lower humidity. Therefore, local microenvironmental differences within an individual tree greatly influence leaf morphological and biophysical characteristics.