EFFET DES CONCENTRATIONS EN MANGANÈSE DU SOL SUR LA CROISSANCE DU MANIOC (MANIHOT ESCULENTA CRANTZ) AU GABON

Abstract

Manganese is an essential micronutrient for the plants. At the lowest concentrations in plants, manganese stimulates various physiological mechanisms and it’s getting toxic at the high doses. This is the case for example in Gabon where Mn phytotoxicity was reported. The present work was undertaken to study the effect of manganese on cassava’s (Manihot esculenta CRANTZ) growth. Cassava microcuttings were planted and grown in a greenhouse on three enriched manganese soils (25 % Mn, 50 % Mn and 75 % Mn). The effect of manganese on cultivated cassava was evaluated by measuring at plant morphological indices and comparing them with the controls during 90 days. The results showed that manganese induced no symptom of toxicity on all cultivated plants during the experiment period. However, this element induced either a delay or an inhibition of the tuberization in the treatments with Mn at 50 and 75 %. It also reduced the number of leaves per plant and dry matter of plants. Nevertheless, inductions of foliar growth have been observed at the beginning of study, with exposed plants in the treatments with Mn at 25 and 50 %.