Abstract
The influence of Al exposure on long-distance Ca2+ translocation from specific root zones (root apex or mature root) to the shoot was studied in intact seedlings of winter wheat (Triticum aestivum L.) cultivars (Al-tolerant Atlas 66 and Al-sensitive Scout 66). Seedlings were grown in 100 [mu]M CaCl2 solution (pH 4.5) for 3 d. Subsequently, a divided chamber technique using 45Ca2+-labeled solutions (100 [mu]M CaCl2 with or without 5 or 20 [mu]M AlCl3, pH 4.5) was used to study Ca2+ translocation from either the terminal 5 to 10 mm of the root or a 10-mm region of intact root approximately 50 mm behind the root apex. The Al concentrations used, which were toxic to Scout 66, caused a significant inhibition of Ca2+ translocation from the apical region of Scout 66 roots. The same Al exposures had a much smaller effect on root apical Ca2+ translocation in Atlas 66. When a 10-mm region of the mature root was exposed to 45Ca2+, smaller genotypic differences in the Al effects effects on Ca2+ translocation were observed, because the degree of Al-induced inhibition of Ca2+ translocation was less than that at the root apex. Exposure of the root apex to Al inhibited root elongation by 70 to 99% in Scout 66 but had a lesser effect (less than 40% inhibition) in Atlas 66. When a mature root region was exposed to Al, root elongation was not significantly affected in either cultivar. These results demonstrate that genotypic differences in Al-induced inhibition of Ca2+ translocation and root growth are localized primarily in the root apex. The pattern of Ca2+ translocation within the intact root was mainly basipetal, with most of the absorbed Ca2+ translocated toward the shoot. A small amount of acropetal Ca2+ translocation from the mature root regions to the apex was also observed, which accounted for less than 5% of the total Ca2+ translocation within the entire root. Because Ca2+ translocation toward the root apex is limited, most of the Ca2+ needed for normal cellular function in the apex must be absorbed from the external solution. Thus, continuous Al disruption of Ca2+ absorption into cells of the root apex could alter Ca2+ nutrition and homeostasis in these cells and could play a pivotal role in the mechanisms of Al toxicity in Al-sensitive wheat cultivars.
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Selected References
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- Huang J. W., Shaff J. E., Grunes D. L., Kochian L. V. Aluminum effects on calcium fluxes at the root apex of aluminum-tolerant and aluminum-sensitive wheat cultivars. Plant Physiol. 1992 Jan;98(1):230–237. doi: 10.1104/pp.98.1.230. [DOI] [PMC free article] [PubMed] [Google Scholar]
- Sanderson C. J., Wilson D. V. A simple method for coupling proteins to insoluble polysaccharides. Immunology. 1971 Jun;20(6):1061–1065. [PMC free article] [PubMed] [Google Scholar]
- Siegel N., Haug A. Aluminum interaction with calmodulin. Evidence for altered structure and function from optical and enzymatic studies. Biochim Biophys Acta. 1983 Apr 14;744(1):36–45. doi: 10.1016/0167-4838(83)90337-0. [DOI] [PubMed] [Google Scholar]