Form of aluminium for uptake and translocation in buckwheat (Fagopyrum esculentum Moench) |
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Authors: | Jian Feng Ma Syuntaro Hiradate |
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Institution: | (1) Faculty of Agriculture, Kagawa University, Ikenobe 2393, Miki-cho, Kita-gun, Kagawa 761-0795, Japan, JP;(2) Division of Plant Ecology, National Institute of Agro-Environmental Sciences, Tsukuba Norin Danchi, P.O. Box 2, Tsukuba, Ibaraki 305-8604, Japan, JP |
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Abstract: | The forms of Al for uptake by the roots and translocation from the root to the shoot were investigated in a buckwheat (Fagopyrum esculentum Moench, cv. Jianxi) that accumulates Al in its leaves. The Al concentration in the xylem sap was 15-fold higher in the plants
exposed to AlCl3 than in those exposed to an Al-oxalate (1:3) complex, suggesting that the roots take up Al in the ionic form. The Al concentration
in the xylem sap was 4-fold higher than that in the external solution after a 1-h exposure to AlCl3 solution and 10-fold higher after a 2-h exposure. The Al concentration in the xylem sap increased with increasing Al concentration
in the external solution. The Al uptake was not affected by a respiratory inhibitor, hydroxylamine, but significantly inhibited
by the addition of La. These results suggest that Al uptake by the root is a passive process, and La3+ competes for the binding sites for Al3+ on the plasma membrane. The form of Al in the xylem sap was identified by 27Al-nuclear magnetic resonance analysis. The chemical shift of 27Al in the xylem sap was around 10.9 ppm, which is consistent with that of the Al-citrate complex. Furthermore, the dominant
organic acid in the xylem sap was citric acid, indicating that Al was translocated in the form of Al-citrate complex. Because
Al is present as Al-oxalate (1:3) in the root, the present data show that ligand exchange from oxalate to citrate occurs before
Al is released to xylem.
Received: 10 December 1999 / Accepted: 3 February 2000 |
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Keywords: | : Aluminium form Fagopyrum (Al uptake) Root (Al uptake) Translocation (Al) Uptake (Al) Xylem sap |
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