Responses of strawberry to doubled CO2 concentration and phosphorus deficiency .2. Gas exchange and water consumption

One-year-old strawberry (Fragaria x ananassa Duch. cv. 'Elsanta') plants grown in controlled environmental chambers were supplied with a P-sufficient (0.5 mmol P l(-1)) or P-deficient (0.05 mmol P l(-1)) Hoagland nutrient solution and acclimatized by an ambient CO2 (340 +/- 20 ppm) or doubled CO2 (680 +/- 20 ppm) concentration fdr one month. P deficiency stunted the plants in leaf growth and development, especially in new leaf number, single leaf area and leaf dry weight, but increased specific leaf weight of both new and old leaves. Plants at doubled CO2 concentration increased by 10-62 %, 42-51 %, and 22-22 % in the number of new leaves, leaf dry weight, and single leaf area, respectively, as compared with those at ambient CO2 level. Chlorophyll content was decreased by both doubled CO2 concentration and P deficiency, especially in old leaves. Furthermore, P deficiency reduced leaf transpiration, stomatal conductance, net photosynthesis, and dark respiration, especially in new leaves. Doubled CO2 concentration, however, limited leaf transpiration, stomatal conductance, and dark respiration, but increased by 17-46 % in net photosynthetic rate of new and old leaves. Water use efficiency decreased by 24-27 % and 40-42 % in P-deficient plants at ambient and doubled CO concentrations, while increased by 30-31 % and 44-46 % in virtue of doubled CO2 concentration at P-deficient and P-sufficient conditions, respectively. By comparison, daily water consumption of the plants reduced by 38-41 % due to P deficiency, whereas it increased by 12-17 % as a result of doubled CO2 concentration. Consequently, daily water use CO2. efficient was tripled by P deficiency, while reduced by 11 % owing to doubled CO2 concentration.