[Comparative study of (45)Ca absorption and translocation in various groups of plants]

Abstract

(45)Ca 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 Ca(2+) 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 (45)Ca 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, (45)Ca migrates very easily in Ascophyllum nodosum, whereas in Laminaria digitata the (45)Ca immobility contrasts with the very high mobility of (32)P. 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.