�tude compar�e de l'Absorption et de la r�distribution du 45Ca chez divers groupes de v�g�taux

Abstract

45Ca long-distance transport was studied within various groups of plants (higher plants and marine Algae) in relation to the absorption process at the level of the source organs. The purpose was to determine whether the well-known absence of Ca2+ movement might be attributed to some particularity of the cell absorption. — The results obtained lead to the following conclusions: 1) In higher plants, the translocation of 45Ca applied to the leaf is possible; it occurs through the phloem (heat-girdling). After a darkness-pretreatment, the translocation decreases significantly while the absorption in the leaf does not; this allows us to distinguish between the two processes and to underline the relationship which exists between the long distance transport and the phloem metabolism. The significant decrease of the translocation after a local application of cycloheximide to the stem underlines the dependence of the phloem transport on the protein metabolism. 2) In the case of Algae, 45Ca migrates very easily in Ascophyllum nodosum, whereas in Laminaria digitata the 45Ca immobility contrasts with the very high mobility of 32P. 3) In every case studied (leaf, thallus) the lack of effect on the calcium absorption of the different factors used (low temperature, darkening, metabolic inhibitors: KCN, CCCP, CHM, etc.) is in agreement with a non-metabolic nature of the calcium ion uptake.