Effect of temperature, CO2, and water stress on leaf gas exchange and biomass accumulation of pineapple

The effects of temperature, CO2, and water stress on leaf CO2 exchange rate (CER), titratable acidity (TA), plant biomass, and C-13 isotopic composition of pineapple were studied. Plants were grown for up to 8 months in controlled environment chambers at light/dark temperatures of 35/25, 30/25, and 30/20 degrees C at ambient (350 mu L L-1) and elevated (700 mu L L-1) CO2 levels. Leaf CER and TA were measured at ambient and elevated CO2 concentrations. CO2 dark fixation, TA, water use efficiency (WUE), and biomass accumulation were higher in the 35/25 and 30/20 degrees C regimes than in the 30/25 degrees C regime. CO2 fixation and leaf WUE in the light approximately doubled as a result of exposure to elevated CO2. The effects of elevated CO2 on CO2 dark fixation and leaf WUE were more variable, but generally fixation was higher with elevated CO2. Plants in the 35/25 and 30/20 degrees C environments were enriched in C-13 relative to those grown at 30/25 degrees C, reflecting their higher CAM activity. Under severe water stress, diurnal CO2 fixation, transpiration and leaf TA decreased as leaf relative water content declined. With water stress, fixation of CO2 in the dark was lowest at a high dark-period temperature. A high temperature in the light period increased leaf water loss.