Nutrient Reserves in Seeds of Selected Proteaceous Species From South-Western Australia.

Abstract

Seed reserves of eight species of Proteaceae from south-western Australia were examined by chemical analysis, microscopy and scanning X-ray microanalysis. Cotyledons were the principal reserve organs of all species. Seeds had 30-500 times the level of P, 8-100 times the level of N, Cu and Zn and, on most species, higher levels of Mg, K, Mn and S than leaves or woody parts of fruits. Levels of Ca, Fe, Na and Cl in leaves and fruit parts were the same as or higher than those in seeds. The K:Ca ratios of seeds were very low (1:2). Seeds had only 1-16% of total fruit dry matter but contained 83-98% of a fruit's P, 43-78% of its N and much of its Zn, Mn and Cu. Seeds had no more than 3% of a fruit's Na or Cl. Oil (14-31%) and protein (15-64%) were major organic reserves of seeds; starch was absent. Protein bodies occurred at high density throughout the parenchyma of cotyledons of all species, and in epidermal and provascular tissues of some species. Globoids occurred in some protein bodies; crystalloids were absent. Globoid-containing protein bodies were confined to central mesophyll layers of cotyledons of Hakea spp. and Grevillea annulifera, to subepidermal parenchyma of Banksia spp. and Xylomelum angustifolium, but occurred in most cotyledonary tissues of Grevillea leucopteris; X-ray microanalysis of cotyledon tissues suggested that the globoids were rich in P, Ca, S and Mg, and in some species also in Fe, Zn and K. The species of Proteaceae investigated were considered to be very effective in channelling essential nutrients to their seeds.