SENSING SOIL OXYGEN

Abstract. Under natural conditions where gaseous exchange between soil and atmosphere is restricted by excess water, the concentration of O2 in the rooting zone can become very low while reduced ions and organic compounds that are potentially phytoxic may accumulate. Mechanisms by which shoots and roots detect, and adjust to, this O2‐deficient environment are reviewed. Injury to roots and their inability to function because of insufficient O2 is communicated to the shoot in a variety of ways, so that it adjusts physiologically. Roots may acclimate metabolically to a gradual fall in O2 supply, so that they either improve their tolerance of anoxia, or partially avoid O2‐deficiency by structural changes that aid internal transfer of O2 to the roots from the shoot. Molecular mechanisms regulating such metabolic changes, including environmental cues, are discussed. Copyright © 1990, Wiley Blackwell. All rights reserved