The manganese nutrition of cotton

Abstract

The influence of substrate manganese on the growth and development, distribution and tissue content of different plant constituents, and the IAA oxidase system of cotton (Gossypium hirstum L. variety Deltapine 15) was studied. The plants were grown in nutrient solution with 0.000, 0.005, 0.05, 0.5, 5.0 and 50 ppm substrate manganese. Deficiency symptoms occurred within two weeks with the 0.000 ppm Mn treatment and maximum growth was obtained in 28 days. In those plants apical meristems were dead within 36 days and limited growth was produced from buds at the cotyledonary node. At squaring (28 days) deficiency symptoms became apparent in the 0.005 ppm Mn plants. Symptoms first occurred in young and then progressed to the older leaves. Those plants produced seed cotton. The leaf deficiency symptoms occurred with the appearance of chlorotic spots along the veins, expansion of spots to form chlorotic banding of veins, and development of interveinal chlorosis. Toxic symptoms were necrotic spots and puckering of the leaves. Manganese at 50 ppm was very toxic to cotton. The first leaf of these plants exhibited toxicity symptoms and the apical meristem died within five days. Later, short branches developed from proliferation of tissue of the cotyledonary node. Five ppm substrate manganese was toxic to seedlings but produced no symptoms in subsequent plant growth. Plant height, dry weight, flowers, and bolls per plant decreased when substrate manganese was lowered to 0.005 ppm. The flowering pattern and time of boll set were influenced by treatments. High manganese (5.0 ppm) promoted early boll set and increased fiber weight per plant/ a direct relationship occurred between substrate manganese (0.000 to 0.5 ppm) and seed cotton per boll. Micronaire (fiber fineness) was reduced when substrate manganese was increased or decreased from 0.5 ppm. ...