Insights into the differences in leaf functional traits of heterophyllous Syringa oblata under different light intensities

Many plants exhibit heterophylly; the spatially and temporally remarkable ontogenetic differences in leaf morphology may play an adaptative role in their success under diverse habitats. Thus, this study aimed to gain insights into differences in leaf functional traits of heterophyllous Syringa oblata Lindl., which has been widely used as an ornamental tree around the world under different light intensities in East China. No significant differences existed in specific leaf area （SLA） between lanceolate- and heart-shaped leaves. Differ- ences in the investment per unit of light capture surface area deployed between lanceolate- and heart-shaped leaves may benot obvious. This may be attributing to the fact that single leaf wet and dry weight of heart-shaped leaves were significantly higher than those of lanceolate leaves but leaf length and leaf thickness of heart-shaped leaves were significantly lower than those of lanceolate leaves. The SLA of shade trees was sig- nificantly higher than that of sun trees. The investment per unit of light capture surface of shade trees was lower than that of sun trees, making it possible to increase light capture and use efficiency in low-light environments. The phenotypic plas- ticity of most leaf functional traits of lanceoiate leaves was higher than those of heart-shaped leaves because the former is the juvenile and the latter is the adult leaf shape during the process of phylogenetic development of S. oblate. The higher range of phenotypic plasticity of leaf thickness and leaf moisture for sun trees may be beneficial to obtain a more efficient control of water loss and nutrient deprivation in high- light environments, and the lower range of phenotypic plas- ticity of single leaf wet and dry weight, and SLA for shade trees may gain an advantage to increase resource （especially light） capture and use efficiency in low-light environments. In brief, the successfully ecological strategy of plants is to find an optimal mode for the trade-off between various functional traits to obtain more living resources and achieve more fitness advantage as much as possible in the multivariate environment.