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United States Department of Agriculture

Agricultural Research Service

Title: The Physiology of Aluminum Tolerance in Maize Roots: Evidence That Al-Activated Organic Acid Release Is Not the Only Al Tolerance Mechanism

Authors
item Pineros, Miguel - CORNELL UNIVERSITY
item Shaff, Jon - CORNELL UNIVERSITY
item Kochian, Leon

Submitted to: American Society of Plant Biologists Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: February 2, 2002
Publication Date: March 25, 2002
Citation: PINEROS, M.A., SHAFF, J.E., KOCHIAN, L.V. THE PHYSIOLOGY OF ALUMINUM TOLERANCE IN MAIZE ROOTS: EVIDENCE THAT AL-ACTIVATED ORGANIC ACID RELEASE IS NOT THE ONLY AL TOLERANCE MECHANISM. AMERICAN SOCIETY OF PLANT BIOLOGISTS ANNUAL MEETING. 2002.

Technical Abstract: We have made significant progress in the understanding of the aluminum (Al) tolerance mechanism which involves Al-induced release of Al-binding ligands (primarily organic acids) into the rhizosphere from the root apex. Our recent work identified a cellular mechanism involved in the Al tolerance of maize: Al-induced release of organic acids from the root apex via an Al-gated anion channel [Pineros & Kochian (2001) Plant Physiology. 125: 292-305]. Our present objective was to carry out a comparative study of the physiology of Al-induced citrate release in Al tolerant and sensitive maize lines. Root growth measurements were used to assess the Al tolerance of South American-derived lines that range from moderately (L53 and 11x723) to very (Cateto-Colombia) Al tolerant. Exposure to Al3+ induced a concentration dependent citrate release; no significant differences in exudation rate were observed among the different lines. No clear correlation was observed for malate release. Spatial analysis indicated that the predominant citrate exudation is not confined to the root apex, but could be found as far as 5 cm beyond the root cap, involving both cortex and stelar cells. The use of the patch clamp technique confirmed the presence of the Al-inducible anion channel in protoplasts isolated from either tissue. Comparison of citrate exudation rates between decapped and capped roots indicated the root cap does not play a major role in perceiving the Al signal nor in the exudation process. The lack of differences in citrate tissue content and exudation rates among the different maize lines suggests that, although citrate release constitutes an Al-tolerance mechanism, it is not the only tolerance mechanism operating in maize roots. (Supported by USDA-NRI Grant No. 00-35100-9280.)

Last Modified: 7/23/2014
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