6(5)CARBOXYFLUORESCEIN AS A TRACER OF PHLOEM SAP TRANSLOCATION |
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Authors: | Nicole Grignon Bruno Touraine Monique Durand |
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Institution: | 1. Biochimie et Physiologie Végétales, INRA CNRS UA 573, Ecole Nationale Supérieure Agronomique, 34060 Montpellier Cedex, France;2. Biochimie et Physiologie Végétales, INRA CNRS UA 573, Ecole Nationale Supérieure Agronomique, 34060 Montpellier Cedex, France
Physiologie Végétale, USTL, 34060 Montpellier Cedex, France |
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Abstract: | 6(5)carboxyfluorescein (6(5)CF), a polar fluorescein with an apparent pK of 6.3, was introduced, as a pH 6.3 solution, into the apoplast of lamina or petioles of mature soybean leaves. Freehand sections were prepared at various times and immediately observed with a fluorescence microscope. 6(5)CF-associated fluorescence appeared in all sink organs, from shoot apex to roots. It was strictly confined to the phloem regions, even after 4 days. Its transport into young leaves ceased at approximately the time they underwent sink-to-source transition. It was never transported between two leaflets of the same leaf. Its transport was interrupted by phloem destruction. All these transport characteristics were highly reproducible, and were paralleled by those of 14C transport after application of (14C)sucrose to leaf surfaces. In contrast with 6(5)CF, fluorescein was transported between mature leaves, and between leaflets of the same leaf. It was not restricted to phloem, and often appeared in the xylem region. These results indicate that 6(5)CF can be used to monitor phloem sap translocation in real time, in short- and long-term experiments. |
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