马占相思（Acacia mangium）是一种具有较高经济价值和生态效益的热带速生树种。为了研究其光合作用对一天内光强、温度等环境因子变化的响应，揭示其迅速生长的生理生态机制，在叶片水平上测量了马占相思在24 h内的净光合速率(Pn)、蒸腾速率、气孔导度(Gs)、胞间CO2浓度(Ci)、每日固定碳的总量、夜间消耗碳的总量以及日间光合系统Ⅱ光化学效率(Fv/Fm)的变化。结果显示：其净光合速率在正午降低了14.5%；其较高的蒸腾速率和气孔导度有助于保持叶片日间较高的碳固定速率；光合系统Ⅱ对于高光强和高温有较强的忍受度；每日固定碳的总量为502 mmol CO2·m-2，夜间碳的损失为54 mmol CO2·m-2。研究结果在一定程度上揭示了马占相思在热带高光强和高温条件下迅速生长的生理机制。
Acacia mangium is a fast growing tropical tree species with significant economic and ecological values. The diurnal variations of photosynthesis and daily-integrated photosynthetic CO2 assimilation over whole photoperiods of A. mangium phyllode were investigated. The results showed that the photosynthetic CO2 uptake of A. mangium phyllode exhibited a 14.5% decrease during midday. The PSII of the A. mangium phyllode was tolerant to high Photosynthetic photon flux density (PPFD) levels and high temperatures. The integrated daily carbon gain and nocturnal carbon loss of A. mangium phyllode was 502 mmol CO2·m-2·day-1 and 54 mmol CO2·m-2·day-1, respectively. All of these physiological traits allow A. mangium to take advantage of the high PPFD environment in the tropics and help this plant to realize rapid growth.
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