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Effects of Atmospheric CO2 Enrichment on Subtropical and Tropical Fruit Trees
Schaffer, B., Whiley, A.W. and Searle, C.  1999.  Atmospheric CO2 enrichment, root restriction, photosynthesis, and dry-matter partitioning in subtropical and tropical fruit crops.  HortScience 34: 1033-1037.

What was done
The authors conducted a mini-review of the scientific literature dealing with subtropical and tropical fruit tree responses to atmospheric CO2 enrichment and reported results for several parameters, including photosynthesis and biomass accumulation.

What was learned
Exposure to elevated CO2 concentrations significantly enhanced photosynthesis in leaves of avocado, banana, citrus, mango, and mangosteen fruit trees.  After being exposed to an atmospheric CO2 concentration of 800 ppm for one year, for example, mangosteen leaves displayed photosynthetic rates that were 40 to 60% greater than rates observed in ambiently grown leaves.  In addition, atmospheric CO2 enrichment increased biomass accumulation in each of these species, and in macadamia trees as well.  In most cases elevated CO2 increased total yield and fruit weight.  However, when it did not immediately increase yield in avocado, mango, and macadamia, a preferential allocation of carbon belowground to roots was observed, suggesting that "increasing water and nutrient uptake resulting from increased root mass would eventually increase assimilate partitioning to the aboveground organs," ultimately enhancing yield.

What it means
This mini-review of the scientific literature suggests that future increases in the CO2 content of the air will enhance photosynthetic rates in subtropical and tropical fruit trees.  In addition, it is likely that increasing atmospheric CO2 levels will also increase biomass production and yield in such woody species.

Reviewed 15 November 1999