By Robert C. Balling Jr., Ph.D.
Arizona State University

Last issue, we saluted two research teams for their innovative approach to proving carbon dioxide's benefits to plants. This issue, we have another one to add to the list—with a study that marks the first we've covered to take place aboard a space station.

It's true we already know that wheat grows faster, larger, more water-use efficient, and more resistant to stress when grown in fields or chambers with elevated atmospheric CO₂ concentrations. Earthbound experiments have proven that time and time again.

Now, the Journal of Plant Physiology brings us great news about CO₂, wheat, and plant stresses that is literally out of this world.

A team of scientists from Utah State University grew super dwarf wheat onboard the Mir space station. Some plants were grown in this microgravity environment with atmospheric carbon dioxide concentrations as high as 7,000 parts per million, or ppm (compared with a natural level 370 ppm on Earth and a commercial greenhouse level of 1,000 ppm); they forced both water-deficit and waterlogged conditions.

As the wheat accumulated harmful levels of various acids in the leaf tissues, Nan and colleagues sought to discover why. Water stress—whether from too much or not enough H₂O—was the answer. They determined that the extremely high CO₂ levels did not influence tissue acid levels at all.

The Utah State team may not get as excited about this development as we would—after all, their focus was water stress and light levels, not the physiological effects of atmospheric carbon dioxide. Nonetheless, this experiment from Mir is notable for failing to show evidence of any harmful effects of very high atmospheric carbon dioxide concentrations.

Reference:

Nan, R., J.G. Carman, and F.B. Salisbury, 2002. Water stress, CO₂ and photoperiod influence hormone levels in wheat. Journal of Plant Physiology, on-line early release.