LEAF GAS-EXCHANGE, DRY-MATTER PARTITIONING, AND MINERAL ELEMENT CONCENTRATIONS IN MANGO AS INFLUENCED BY ELEVATED ATMOSPHERIC CARBON-DIOXIDE AND ROOT RESTRICTION

The effects of atmospheric CO2 enrichment and root restriction on net CO2 assimilation (A), dry mass partitioning, and leaf mineral element concentrations in 'Kensington' and 'Tommy Atkins' mango (Mangifera ind ica L.) were investigated. Trees were grown in controlled-environment glasshouse rooms at ambient CO2 concentrations of 350 or 700 mu mol.mo l(-1). At each CO2 concentration, trees were grown in 8-L containers, which restricted root growth, or grown aeroponically in 200-L root mis t chambers, which did not restrict root growth. Trees grown in 350 mu mol.mol(-1) CO2 were more efficient at assimilating CO2 than trees gro wn in 700 mu mol.mol(-1) CO2. However, total plant and organ dry mass was generally higher for plants grown at 700 mu mol.mol(-1) CO2 due to increased A as a result of a greater internal partial pressure of CO2 (Ci) in leaves of plants in the CO2 enriched environment. Root restri ction reduced A resulting in decreased organ and plant dry mass. In ro ot-restricted plants, reduced A and dry matter accumulation offset the increases in these variables resulting from atmospheric CO2 enrichmen t. Atmospheric CO2 enrichment and root restriction did not affect dry mass partitioning. Leaf mineral element concentrations were generally lower for trees grown at the higher ambient CO2 concentration, presuma bly due to a dilution effect from an increased growth rate.