Efeito do fósforo na captação de minerais e pigmentação de Azolla caroliniana Willd. (Azollaceae)

Abstract

Mineral bioaccumulation, N2 fixation and pigment accumulation of A. caroliniana were established under nutritional stress. Cultures were conduced in polystyrene flasks using phosphate gradient between 10-7 and 10-3 mol.L-1 . Minerals (P, S, B, and Sn) were quantified by induced coupled plasma and total nitrogen by Kjeldhal methodology. Nitrogenase activity was determined by the reaction of acetylene reduction and pigments were photometrically determined in acidified methanolic extracts. Macronutrients uptake (N, P, S) were shown to be related to phosphorus supplements and micronutrient absorption (B and Sn) was independent of phosphorous supplements. Mineral selectivity showed that A. caroliniana can act as biofertilizer. Phosphorus concentration below 10-5 mol.L-1 decreased the ratio chlorophylls/anthocyanins causing reddening of the plant. This behaviour of A. caroliniana could be used for biomonitoring environmental phosphorus availability.