Water in trees

The Quick Study by Missy Holbrook and Maciej Zwieniecki (Physics Today, January 2008, page 76 ), on the physics of transporting water to the tops of trees, invites an immediate agricultural query: Since, as the article describes, the extreme amounts of water that plants require are due to the low concentration of carbon dioxide in the atmosphere, why have we not developed enclosed growing systems with dramatically higher CO₂ concentrations?

For example, capturing coal-plant CO₂ effluent for use in adjacent growth enclosures—which requires almost no net energy consumption—would simultaneously reduce emissions and water consumption and provide abundant supplies of CO₂ for crops. Of course, that might require genetic reconfiguration of plants that have adapted to the low current CO₂ concentrations, but unlike other genetic modifications, those plants could pose no threat other than economic to normal crops, since they would not be viable in the outside world.

Furthermore, one can imagine enhanced growth rates, since the plants would need to expend considerably less of their vital resources on water transport.

Coal plant emissions and water supplies are matters of the utmost concern. In the American Southwest, for example, some 90% of water consumption goes to agriculture. Unfortunately, there seems to be no forum in which the necessary synergy might develop among energy companies, agribusinesses, and environmentalists.