Effect on light intensity and mineral nutrition on carbohydrate and organic acid content in leaves of young coffee plants

Young coffee plants (Coffea arabica, L., var. Caturra) were grown under different conditions of mineral nutrition (1/8 N-P-K, N-P-K, 3 N-P-K, N 1/2-P-K and N-2P-K) and illumination (directly in the sunlight or shaded) with the aim of studying the effect of light and mineral nutrition on carbohydrate and organic acid content of the leaves. For determining these compounds 14CO2 was used. Sugars were separated after the method of paper chromatography. The results obtained showed that the incorporation of 14C in sugars and organic acids was more intensive in plants grown directly in the sunlight, while in starch 14C was incorporated more intensively in the shaded plants. Carbohydrate content rose parallel to the increase of nitrogen in the nutrient solution. Changingthe rate of phosphorus from 1/2P to two doses exerted highest effect on 14C incorporation in starch and in hemicellulose. (author)