CALCIUM IMPACT ON PHOSPHORUS AND ITS MAIN BIOINDICATORS - RESPONSE INTHE ROOTS AND LEAVES OF TOBACCO

Tobacco plants (Nicotiana tabacum cv Sevilla) were grown under control led conditions and submitted to regular fertilization with macro- and micronutrients. The objectives of the experiment was (i) to determine the effect of the application of high levels of calcium (Ca) [Cal : 2. 5 mM calcium chloride (CaCl2. 2H(2)O) and Ca2:5.0 mM CaCl2. 2H(2)O] on the behavior of phosphorus (P) and its principal bioindicators and (i i) to examine the response to this effect in the roots and leaves of t he plant. The concentration of Ca and the different forms of P (total P, inorganic P, and organic P), acid-phosphatase activity, the levels of carbohydrates, and finally the production of dry matter were analyz ed both in the roots and the leaves. The results indicated that high C a concentrations, the result of high applications of this element in t he culture medium (Ca2), affected the root and leaf performance in rel ation to P, reducing translocation of this element to the leaves, perh aps reflecting the effect of Ca on the foliar accumulation of carbohyd rates, the principal cause of the effect of Ca on P translocation. Fin ally, the inorganic P remained constant in the leaves but varied in th e roots, while significant changes were recorded in the acid-phosphata se activity, organic P and dry-matter yield in both organs.