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CO2 Effects on Indole-3-Acetic Acid in Ginkgo biloba Trees
Li, X.-M., He, X.-Y., Zhang, L.-H., Chen, W. and Chen, Q. 2009. Influence of elevated CO2 and O3 on IAA, IAA oxidase and peroxidase in the leaves of ginkgo trees. Biologia Plantarum 53: 339-342.

The Ginkgo biloba tree is considered a "living fossil," because no other trees of its order (Ginkgoales) are known in the fossil record after the Pliocene, which ended about two and a half million years ago. Its other claim to fame is that extracts of its leaves contain certain flavonoid glycosides and terpenoids that have been used pharmaceutically for various purposes.

What was done
The authors grew six-year-old saplings 1.2 to 1.5 meters in height (which were derived from the same maternal plant) individually in pots containing fertile soil out-of-doors in open-top chambers maintained at either 350 or 700 ppm CO2 at the Shenyang Arboretum of the Chinese Academy of Science in Shenyang, Liaoning Province, China, from 1 June to 30 September. In addition to measuring the growth of the trees' terminal shoots over this period, they measured leaf concentrations of the endogenous plant-growth regulator indole-3-acetic acid (IAA) every 20 days.

What was learned
Li et al. report that after 40 days exposure to elevated CO2, the IAA content in the plants' leaves was significantly increased compared with that of plants in the control treatment, and that maximum IAA enhancement was observed 100 days after exposure, when leaf concentrations of IAA were fully 90% greater in the CO2-enriched treatment. Likewise, they state that the growth increment of ginkgo terminal shoots in the high CO2 chambers was increased by 44% from 20 days to 90 days of exposure to the elevated CO2 conditions.

What it means
Botanical relics of the past, as well as plants of the present, clearly love their CO2; and they like it in quantities much greater than what is available to them in the air of today. As humanity burns ever more fossil fuels, therefore, we are providing a welcome benefit to plants of lineages both young and old.

Reviewed 4 November 2009