SULPHUR NUTRITION OF COTTON

Abstract

Cotton plants were grown on nutrient solns. low in S. The leaves were chlorotic with symptoms resembling N deficiency, stem elongation was retarded, leaf size reduced, and old leaves deteriorated. Vegetative growth and fruit increased proportionately with S supply, i.e., there was no differential effect of S on the 2 growth activities. With S deficiency, the concns. of reducing sugars and sucrose in the leaves, and sometimes in the stems, were characteristically too low for measurement by the usual analytical procedures. Starch in all tissues was reduced only moderately if at all, and hemicellulose not at all. Nitrate and soluble organic N accumulated in high concns.; the increase in the latter was in the same order as the reductions in sugars. Protein N was greatly reduced by S deficiency in the tops of young plants and in the leaves of plants 65 days old. In the stems more protein was found in low-S than in high-S plants. Although S deficiency greatly decreased the amt. of protein in the leaves, the % of S in this protein was higher. The discussion of the data is in a large part on the basis of the reactions of cotton to S deficiency in comparison with the results of others who worked with tomato, soybean, sunflower, and mustard. A table summarizing the salient results with the 5 plants is presented. There were noteworthy differences in the reactions of the plants. In cotton, S deficiency resulted in extra accumulations of P, Ca and Mg. The accumulations of Fe and K were changed little. Little tangible symptomatic or biochemical evidence could be found of proteolysis and the re-use of S. The biochemical difficulty of demonstrating S re-use is indicated.