EVALUATION OF STOMATAL AND NON-STOMATAL LIMITATION IN PHOTOSYNTHETIC INDUCTION RESPONSE OF LEAVES GROWN UNDER DIFFERENT LIHT AND WATER ENVIRONMENTS

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To evaluate the stomatal and non-stomatal limitation in photosynthetic induction response for leaves developed under different light and water availabilities, the project used three approaches :(1) Experiment using phytotron and hybrid popular species: Seedlings of the popular species were grown under two light levels (a high-light and a low-light) x two water levels (well-watered and dehydrated) conditions. Although light regimes affected photosynthetic induction efficiency considerably, water availability showed no significant influence. Since stomata of the hybrid species exhibited little response to light change, the induction limitation on leaf carbon gain could be considered as mainly to be due to the biochemical components.(2)Photosynthetic induction response, dynamic photosynthesis and chlorophyll fluorescence response were examined in natural environment for five alpine grassland species on Qinghai-Tibet plateau. The five grasslands species showed no significant difference in induction response and dynamic photosynthetic carbon gain under different soil water availability and vapor pressure deficit during about two weeks.(3)Modeling approach is used to evaluate the effects of stomatal patchiness on photosynthetic induction response and dynamic photosynthesis under different air temperatures. The model consists of two major components : a stomatal component and a biochemical component. Using the improved model, we found that patchiness decreased photosynthetic CO_2 uptake through the decrease of stomatal conductance during the induction response. Induction response showed a more rapid increase in a model leaf experiences an increase of light following a short shade-fleck under a higher temperature.