Determination of critical levels for selenium toxicity in cowpea beans: characterization of ureide metabolism and ultrastructure changes

Abstract

There are conclusive evidences of selenium (Se) deficiency in Brazilian soils, which can lead Se deficiency in animals and humans. Therefore, is needed to increase Se concentration in edible parts of modern cultivars in order to increase the Se intake by humans. This study aims to evaluate the critical levels of Se toxicity in cowpea plants and its effect of ureide metabolism, ultrastructure changes and cowpea yield under field conditions. Experiments will be conducted in order to characterize physiological and histochemical tissue of plants and evaluate the nitrogen compounds (allantoic acid, allantoin, aminoacids, nitrate and ammonium), sucrose, total sugars in leaves and storage proteins (albumin, globulin, prolamin, and glutelin) in seeds. Selenium concentration and other nutrients will be analyzed in leaves and seeds. In addition, histochemical analysis such as xylem diameter, phloem diameter and scanning electronic microscopy will be use to evaluate ultrastructure changes in leaf tissues. The better understanding regarding the factors involving Se accumulation and its interaction between plant physiology and fertilizer can be an useful and powerfull information in genetic breeding and also on production of better nutritional food. (AU)