PHOTOSYNTHETIC GAS EXCHANGE AND WATER RELATIONS DURING DROUGHT IN 'SMOOTH CAYENNE' PINEAPPLE (ANANAS COMOSUS (L.) MERR.) GROWN UNDER AMBIENT AND ELEVATED CO2 AND THREE DAY/NIGHT TEMPERATURES
The effect of water deficits on net CO2 assimilation (A), titratable acidity, and water relations of pineapple, the most important crop species having Crassulacean acid metabolism (CAM), was studied under ambient (350 μmol mol-1) and elevated (700 μmol mol-1) CO2 levels and day/night temperatures of 35/25, 30/25, and 30/20°C. After six months of acclimatization to the above treatments, water was withheld for 70 days. A substantial decrease was noticed after 10 days of drought, particularly at elevated CO2, where stomatal conductance (gs) initially was low but declined more rapidly. Plants grown at elevated CO2 had higher water use efficiency (WUE) than plants grown at ambient CO2, both when well-watered or subjected to drought. The rate of decline of gs and A during drought also varied with the day/night temperature. For plants at 35/25 and 30/25°C, after 40 days of drought, there was an 80 to 90% decrease in the diurnal variation in titratable acids (TA) due to a decline in nocturnal CO2 uptake. However, the diurnal variation in TA for plants at 30/20°C dropped by only about 65% at the end of 70 days of drought at both ambient and elevated CO2. Diurnal variation in TA at the end of the drought period indicated that pineapple continued to re-fix substantial quantities of respiratory CO2. There was a slower rate in the decrease of leaf water content and osmotic potential during drought for plants grown at elevated CO2 than at ambient CO2 resulting in higher predawn leaf water potential and turgor pressure at the end of the drought period. The elevated CO2 levels experimentally engineered to occur would help pineapple, under prolonged drought, to maintain a better water status and higher WUE compared to plants of this species growing at current CO2 levels. Increased temperature due to global warming would not alter this result.
Zhu, J., Bartholomew, D.P. and Goldstein, G. (2005). PHOTOSYNTHETIC GAS EXCHANGE AND WATER RELATIONS DURING DROUGHT IN 'SMOOTH CAYENNE' PINEAPPLE (ANANAS COMOSUS (L.) MERR.) GROWN UNDER AMBIENT AND ELEVATED CO2 AND THREE DAY/NIGHT TEMPERATURES. Acta Hortic. 666, 161-173
Water relations, CO2 enrichment, Crassulacean acid metabolism