Seasonal photosynthesis in young plants of Agave tequilana

Studies of the effects of the environment on the photosynthesis of young plants of Agave tequilana are scarce, although these plants occupy one third of the cultivated surface in the State of Jalisco, Mexico. The effect of the seasonal variation on irradiance, air temperature and relative humidity and plant water status in the photosynthesis of young plants of A. tequilana was studied during 2001 and 2002. The experimental design was randomized complete blocks and the different dates of measurements of photosynthesis, from January 2001 to November 2002, were considered as the treatments. Net CO2 uptake occurred during both dry (January to May) and wet months (July to October) of the year, and the higher values of daily net CO2 uptake coincided with cool daytime/nighttirne air temperature and the highest values of irradiance. Night uptake of CO2 was accompanied by positive CO2 assimilation during the day. Both showed a greater relationship with temperature than with relative humidity. The succulence of the photosynthetic tissue, and both the night and the day net CO2 uptake were determinant to maintain carbon gain in A. tequilana throughout the year, particularly during the dry season.