K+ status and ABA affect both exudation rate and hydraulic conductivity in sunflower roots |
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Authors: | José M. Quintero,José M. Fournier,José Ramos, Manuel Benlloch |
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Affiliation: | J. M. Quintero, J. M. Fournier and M. Benlloch (corresponding author, fax 34‐57‐218569), Dept de Agronomía;;J. Ramos, Dept de Microbiología, Escuela T.S. de Ingenieros Agrónomos y de Montes, Apdo. 3048, E‐14080 Córdoba, Spain. |
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Abstract: | Twenty‐day‐old sunflower plants ( Helianthus annuus L. cv. Sun‐Gro 380) grown in nutrient solutions with different KCl levels were used to study the effects of K+ status of the root and of abcisic acid (ABA) on the exudation rate (Jv), the hydraulic conductivity of the root (Lp), the fluxes of exuded K+ and Na+ (JK and JNa), and the gradient of osmotic pressure between the xylem and the external medium. Jv and Lp increased in direct proportion to the K+ starvation of the root. Also addition of ABA (4 µ M ) at the onset of exudation in the external medium made Jv and Lp rise, and this effect also increased with the degree of K+ starvation. Similarly, K+ starvation and ABA promoted both the flux of exuded Na+ and the accumulation of Na+ in the root. We suggest that ABA acts as a regulating signal for the radial transport of water across the root, and that potassium may be an effector of this mechanism. |
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Keywords: | ABA exudation rate Helianthus annuus hydraulic conductivity potassium sunflower |
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