EFFECTS OF CALCIUM DEFICIENCY ON COFFEA-ARABICA - NUTRIENT CHANGES AND CORRELATION OF CALCIUM LEVELS WITH SOME PHOTOSYNTHETIC PARAMETERS

Calcium deficiency was induced in hydroponically grown 1.5-years-old c offee plants with 12-14 pairs of leaves. Calcium was given in the form of Ca(NO3)(2): 5, 2.5, 0.1, 0.01 and 0 mM. After 71 days of Ca-treatm ent root and shoot as well as total biomass were decreased by severe C a-deficiency. However, a stronger decrease was observed for shoot grow th as revealed by the increase in the root/shoot ratio. New leaves wer e affected showing decreases in the total leaf area and in Leaf Area D uration (LAD). After 91 days of deficiency, leaf protein concentration decreased (by about 45%) in the top leaves while nitrate reductase ac tivity (NRA) and NO3 content showed no significant changes. Total nitr ogen and mineral concentrations (P, K, Ca, Mg and Na) were also determ ined in leaves and roots. With the decrease in calcium concentration i n Ca-deficiency conditions, we observed concomitant increases in the c oncentrations of K+, Mg2+ and Na+ in leaves (maximal changes of 32% fo r K+, 96% for Mg2+ and 438% for Na+) and in roots (108% for K+, 86% fo r Mg2+ and 38% for Na+). Accordingly, the ratio between elements chang ed, including the ratio N/P, showing a non-equilibrium in the balance of nutrients. Significant correlations were obtained between Ca2+ conc entration and some photosynthetic parameters. Ca-deficiency conditions would increase the loss of energy as expressed by the rise in q(E) an d decrease the photochemical efficiency, which confirms the importance of this element in the stabilization of chlorophyll and in the mainte nance of good photochemical efficiency at PS II level.