Regulation of K+ and NO3− fluxes in roots of sunflower (Helianthus annuus) after changes in light intensity |
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Authors: | Jaume Casadesús Luís Tapia Hans Lambers |
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Institution: | Dept Biologia Vegetal, Univ. de Barcelona, Avgda. Diagonal 645, E-08028 Barcelona, Spain;Dept of Plant Ecology and Evolutionary Biology, Utrecht Univ., P.O. Box 800.84, 3508 TB Utrecht, The Netherlands. |
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Abstract: | Shoot activity has been reported to affect rates of ion uptake by plant roots in other ways than merely through supply of assimilates. To elucidate the mechanisms by which a signal from the upper part of the plant controls the rate of K+ and NO3? uptake by roots, both uptake of K+ and NO3? and secretion into the xylem of young sunflower plants ( Helianthus annuus L.) were measured after changes in light intensity. No close correlation was observed between the uptake of NO3? and that of K+; an increase in light intensity produced a much greater stimulation of NO3? uptake than of K+ uptake. On the other hand, secretion of NO3? into the xylem was tightly coupled to that of K+, and this coupling was strongly disturbed by excision of the root. The results suggest the involvement of the K2-malate shuttle on the regulation by the shoot of K+ and NO3? secretion in the xylem, which is linked to NO3? uptake, while K+ uptake is independent of this regulation mechanism. |
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Keywords: | Helianthus annuus K+ uptake malate-shuttle NO3? uptake root respiration sunflower xylem secretion |
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