Estudos sobre a alimentação mineral do cafeeiro: VI Efeitos das deficiências de micronutrientes em Coffea arabica L. var. Mundo Novo cultivado em solução nutritiva

Resumo

Young coffee plants (Coffea arabica L., var. Mundo Novo) were grown in nutrient solution purified from micronutrients contaminants by the method of MUNNS & JOHNSON (1960). All plants, except those in the control treatment, wer given all macronutrients and all micronutrients except one which was omitted in order to induce its shortage. Symptoms of deficiency were obtained for all known micronutrients but chlorine. Measurements, observations and chemical analysis of leaves allowed the following main conclusions to be drawn. 1. The relative influence of micronutrients in growth-measured by the fresh weight of the entire plant - was as follows: -Fe -Zn -Cu -Mo -Mn complete = -B = -CI. that is: the omission of iron from the nutrient solution caused the severest reduction in growth; lack of B and Cl had no effect. 2. Symptoms of deficiency of B, Fe, Mn, and Zn were found to be in good agreement with those in the literature. Effects of Cu and Mo shortage, however, had not been described so far: In the case of the Cu-deficient plants, the younger leaves were distorted, having an "S" shape, due probably to lack of growth of the veins; they lost their green color and developed rather large, necrotic patches near the margins. When molybdenum was omitted from the nutrient solution yellow spots develop near the margen of subterminal (fully mature) leaves; they became necrotic; there was a characteristic downward curling of the leaf blade along the mid rib so that the opposite edges touched each other underneath. 3. The levels of micronutrients found in normal and deficient leaves are given in Table 4. It is hoped that those values will serve as a basis of judgement of micronutrient contents found in leaves of field grown plants.