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Title: Interactive intoxicating and ameliorating effects of tannic acid, aluminum (Al3+), copper (Cu2+), and selenate (SeO42-) in wheat roots. A descriptive and mathematical assessment

Author
item Kinraide, Thomas
item HAGERMAN, ANN - Miami University - Ohio

Submitted to: Physiologia Plantarum
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2009
Publication Date: 3/2/2010
Citation: Kinraide, T.B., Hagerman, A.E. 2010. Interactive intoxicating and ameliorating effects of tannic acid, aluminum (Al3+), copper (Cu2+), and selenate (SeO42-) in wheat roots. A descriptive and mathematical assessment. Physiologia Plantarum. 139:68-79.

Interpretive Summary: Plant productivity and persistence in many soils are limited by the availability of nutrients and the abundance of toxicants. This is particularly true in the case of agricultural and ecological systems receiving minimal management and originating on former forested lands that are acidic. In Appalachia, and in many other parts of the world, these include silvopastoral systems, conventional pastures, and conservation sites on reclaimed areas. In nearly all cases, site quality is improved as organic matter increases. Nutrients are better retained and become more accessible and toxicants become less accessible. Tannins are a major component of the organic matter, both soluble and particulate, in most systems. The present study is an attempt to elucidate the interactions among tannins, mineral nutrients, and mineral toxicants. The study demonstrated that tannins strongly detoxify several mineral toxicants, such as aluminum, copper, and selenium in experimental solutions and these findings indicate a similar role in natural systems, which can be further studied. Tannins are produced more abundantly by some plants than others, and the study of tannins are aimed at the development of management strategies to promote the on-site production of tannins without possible adverse accompanying effects.

Technical Abstract: Tannic acids and tannins are polyphenolic compounds produced by plants and are important components of soil and water organic matter. Tannic acids and tannins form complexes with proteins, metals, and soil particulate matter and perform several physiological and ecological functions. The tannic acid used in our study was a mixture of galloyl glucoses, gallic acid, and a lower molecular weight component. TA inhibited root elongation in wheat seedlings at concentrations > 4 mg L-1; but TA alleviated the toxicity of Al3+, Cu2+, and SeO42-; and Al3+ and SeO4-' alleviated the toxicity of TA. The interactions of Al3+ and TA (each toxic but each alleviating the toxicity of the other) were stoichiometric. Growth was affected as though 1 kg TA bound 2.76 mol Al so strongly that if (mol Al)/(kg TA) < 2.76, then free Al ˜ 0, and if (mol Al)/(kg TA) > 2.76, then free TA ˜ 0. This stoichiometry may imply that one mole of galloyl ester binds 0.5 mol Al. Using this binding scheme, growth was modeled successfully on the basis of free TA and free Al. These and other interactions among TA, Al3+, Cu2+, SeO4-', Ca2+, Na+, and H+ were quantified with a comprehensive nonlinear equation.