A study on the effects of light conditions on the longevity and characteristics of Daphniphyllum macropodum leaves

The aim of this study was to investigate the effects of light conditions on the longevity and characteristics of Daphniphyllum macropodum leaves by determining the number of leaves, leaf area, shoot length, leaf thickness, leaf mass per area (LMA), and chlorophyll content (SPAD value) of D. macropodum leaves from three individual trees growing under different light intensities. Measurements were made each month from February to November 2014. Shoots growing under weak light intensity had a larger number of leaves, broader leaf area, and longer leaf longevity. Under this condition, self-shading is unavoidable as the leaves overlap each other. The trees appear to increase their light-receiving capacity by enhancing shoot growth in the intemodes, which broadens the interval between the leaves and reduces self-shading. By contrast, D. macropodum plants growing with sufficient light had thicker leaves and higher LMA and SPAD values, which reflected a strategy for increasing the photosynthesis rate. Leaf longevity in this case was relatively short. A strategy of early shedding of the old leaves (after reabsorption of nutrients) and forming new leaves rather than retaining the old leaves is more beneficial in terms of photosynthetic productivity. These large differences in leaf longevity and characteristics can be seen as an adaptation to differences in light intensity.