Studies of Capsicum annuum seeds: structure, storage reserves, and mineral nutrients

Abstract

Storage reserves of Capsicum annuum (sweet pepper) seeds were studied using light microscopy, histochemical techniques, and electron microscopy. The seed had mainly protein and lipid as storage reserves. Starch was not detected. Thickened endosperm cell walls likely are a store of nonstarch polysaccharide. Protein bodies had protein crystalloids and globoid crystals as inclusions in the proteinaceous matrix. Protein bodies in embryo tissues varied greatly in size both inter- and intra-cellularly, while endosperm protein bodies were similar in size. Energy dispersive X-ray analysis and neutron activation analysis revealed the element content of C. annuum seeds. The presence of P, K, and Mg in all globoid crystals is consistent with their being phytin-rich. The average ratios of Mg:K, based on peak-to-background values for globoid crystals, were lowest in provascular tissues, where most globoid crystals were very small, and were highest in ground meristem tissues, where globoid crystals were large. Fe, Zn, Mn, Ca, S, and Cl were detected in some globoid crystals. In globoid crystals of both the cotyledon and hypocotyl – radicle axis, Fe was always detected in protoderm cells, was occasionally detected in ground meristem cells, and was never detected in provascular cells. Neutron activation analysis results showed that Mg, K, S, and Cu were higher in the embryo than in the endosperm, while Cl, Na, and Ca were higher in the endosperm. Mn had similar concentrations in both tissues. Key words: Capsicum annuum, storage reserves, protein body, globoid crystal, phosphorus, seed.