Thin sectioning, freeze fracturing, energy dispersive x-ray analysis, and chemical analysis in the study of inclusions in seed protein bodies: almond, Brazil nut, and quandong

Abstract

Protein bodies from almond (Prunus dulcis), Brazil nut (Bertholletia excelsa), and quandong (Santalum acuminatum) have been studied in thin sections of fixed and embedded tissue, in freeze-fracture replicas of unfixed tissue, by chemical analysis of tissue for P, K, Mg, and Ca, and by energy dispersive x-ray (EDX) analysis of both sections of glutaraldehyde-fixed tissue and freeze-dried tissue powders. The protein bodies in all three species contained globoid crystals, protein crystalloids, and proteinaceous matrix regions. Results of EDX analyses were consistent with globoid crystals being rich in phytin. Variation in both the structure and the elemental composition of globoids was common. In almond some globoids were lobed rather than spherical, and large globoid crystals often contained considerable calcium whereas small globoid crystals contained little if any calcium. The globoid crystals of Brazil nut often contained barium in addition to P, K, Ca, and Mg. Protein crystalloids of Brazil nut were compound crystals. Protein bodies of quandong seed, which is largely endosperm rather than embryo, were unexceptional.