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Plant Physiol. 1993 Nov;103(3):685-693.

Aluminum Tolerance in Wheat (Triticum aestivum L.) (I. Uptake and Distribution of Aluminum in Root Apices).

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  • 1Division of Plant Industry, Commonwealth Scientific and Industrial Research Organization, GPO Box 1600, Canberra ACT 2601, Australia (E.D., S.C., V.C.J., P.J.R.).


We investigated the uptake and distribution of Al in root apices of near-isogenic wheat (Triticum aestivum L.) lines differing in Al tolerance at a single locus (Alt1: aluminum tolerance). Seedlings were grown in nutrient solution that contained 100 [mu]M Al, and the roots were subsequently stained with hematoxylin, a compound that binds Al in vitro to form a colored complex. Root apices of Al-sensitive genotypes stained after short exposures to Al (10 min and 1 h), whereas apices of Al-tolerant seedlings showed less intense staining after equivalent exposures. Differential staining preceded differences observed in either root elongation or total Al concentrations of root apices (terminal 2-3 mm of root). After 4 h of exposure to 100 [mu]M Al in nutrient solution, Al-sensitive genotypes accumulated more total Al in root apices than Al-tolerant genotypes, and the differences became more marked with time. Analysis of freeze-dried root apices by x-ray microanalysis showed that Al entered root apices of Al-sensitive plants and accumulated in the epidermal layer and in the cortical layer immediately below the epidermis. Long-term exposure of sensitive apices to Al (24 h) resulted in a distribution of Al coinciding with the absence of K. Quantitation of Al in the cortical layer showed that sensitive apices accumulated 5- to 10-fold more Al than tolerant apices exposed to Al solutions for equivalent times. These data are consistent with the hypothesis that Alt1 encodes a mechanism that excludes Al from root apices.

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