Seed Nutrient Reserves of Proteaceae with Special Reference to Protein Bodies and their Inclusions

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Abstract
The storage reserves of seeds of a wide taxonomic range of Proteaceae were examined by chemical analyses for macronutrients, protein and non-protein-N composition, by light microscopy of cotyledonary tissue for morphological and histochemical study of protein bodies and their inclusions, and by X-ray point microanalysis for determining the elemental composition of the various types of inclusions. The 70 species from 30 genera showed higher levels of N, P and Mg but not of Ca and K in seed dry matter in comparison with a similarly sized sample of non-proteaceous species. Small-seeded Proteaceae tended to have seed dry matter significantly more enriched with minerals than large-seeded species. Protein levels ranged from 18 to 89 per cent of embryo dry weight (mean for 32 species 39.5 per cent). Protein and ethanol soluble N fractions of many species were exceptionally rich in arginine. Oil was abundant in most species, starch universally absent. Seven types of protein body inclusions were identified on the basis of size, shape and reaction to toluidine blue. Mineral composition of the inclusions differed significantly, particularly in ratios of Ca to P and of P to S and Mg. All genera and certain species could be distinguished one from another on the basis of distribution and frequency of inclusion types within tissues of the cotyledons and staining patterns of protein bodies to amido black. The taxonomic significance of the data is evaluated.