Submitted to: Plant and Soil Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 9/30/1996
Publication Date: N/A
Interpretive Summary: Large areas of land within the U.S. and a significant proportion of the world s arable lands are acidic. In these acid soils, the phytotoxic aluminum ion, Al3+, is solubilized from aluminosilicate clays and is quite toxic to root growth and function. Thus, aluminum (Al) toxicity is the primary factor limiting crop production on these acid soils. Understanding the physiological basis for Al toxicity and the cellular mechanisms that some plant species use to tolerate Al are essential in order to develop crop species that can be cultivated on these acid soils. In this paper, we studied the role of the root exudation of Al-binding compounds in Al tolerance. We found that in Al tolerant genotypes of wheat, the release of the organic acid malate as well as exudation of phosphate play an important role in Al tolerance. Both of these compounds can bind Al in the soil and prevent it from entering the root. These results identify two separate cellular mechanisms of Al exclusion from the root that confer Al tolerance in wheat. Understanding of the genetic and physiological control of these processes will assist scientists in the production of new Al tolerant crop varieties.
Technical Abstract: The goal of this study was to determine if Al-chelators other than malate are released from root apices and are involved in Al-resistance in different wheat genotypes. Also we wanted to establish if root exudates contribute to increases in rhizosphere pH around the root tip. In seedlings of Al-resistant Atlas, we have documented a constitutive phosphate exudation from the root apex. Because phosphate can complex Al and bind protons, it could play an important role in Al resistance, both via complexation of Al3+ and by contributing to the alkalinization of rhizosphere pH observed at the apex of Atlas. This study suggests that in wheat, Al-resistance can be mediated by multiple exclusion mechanisms controlled by different genes.