Sensing soil oxygen

Abstract

Abstract. Under natural conditions where gaseous exchange between soil and atmosphere is restricted by excess water, the concentration of O 2 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 O 2 ‐deficient environment are reviewed. Injury to roots and their inability to function because of insufficient O 2 is communicated to the shoot in a variety of ways, so that it adjusts physiologically. Roots may acclimate metabolically to a gradual fall in O 2 supply, so that they either improve their tolerance of anoxia, or partially avoid O 2 ‐deficiency by structural changes that aid internal transfer of O 2 to the roots from the shoot. Molecular mechanisms regulating such metabolic changes, including environmental cues, are discussed.