XVI International Botanical Congess

We evaluated the effects of seasonal variation in temperature, irradiation and soil moisture content on the photosynthesis rates of O. ficus-indica and S. queretaroensis. The lowest values of net CO2 uptake were recorded during the summer rainy season, and the highest during autumn and winter. The peak values were due to a prolonged period of CO2 assimilation caused by decreased cloudiness, and high rates of nocturnal CO2 assimilation due to moderate day/night air temperatures. In spring, when drought is exacerbated, daily net CO2 uptake was negative for both species. Stem photosynthesis allowed both species to obtain carbon during the fall and winter, when soil water reached low values.