CO2 ASSIMILATION BY PITAHAYA Hylocereus undatus UNDER FIELD CONDITIONS

Abstract

There is no information on CO2 exchange pattern of pitahaya in its habitat; therefore, the CO2 exchange rate (CER) during a 24 hour period, was measured in one year old stems under field conditions. Some microclimatic factors were also measured such as temperature, relative humidity, and wind speed (wired to an automatic weather station) and photosynthetically active radiation (PAR). In stems exposed to 70 % of PAR, the maximum value of CER was half (1.89 mmol CO2 m-2 s-1) of that in stems exposed to 30 % of PAR (3.89 mmol CO2 m-2 s-1). In both cases the photosynthetic mechanism was CAM, with a maximum peak between the 22:35 to 23:54 h at a temperature of 17.6 ºC and 71.8 % of relative humidity. Stems under shaded conditions during the day were able to assimilate CO2 during all 24 hours.