Mineral Nutrition of Developing Fruits of the Western Australian Christmas Tree, Nuytsia floribunda (Labill.) R. Br. ex Fenzl

Abstract

The mineral nutrition of developing fruits of the hemiparasite Nuytsia floribunda was studied in natural habitat near Perth, W.A. Nuytsia fruits were similar to those of other higher plants in their mineral nutrition. Changes in the contents of specific nutrients in fruits and their bracts were described. Accumulation of mineral elements in fruits and bracts was synchronized closely with the acquisition of dry matter. Bracts lost 45-75% of their nitrogen, phosphorus, sulfur, zinc and copper, 16-29% of their potassium, magnesium, iron and manganese, but less than 5% of their calcium and sodium during senescence. Mobilization from bracts was estimated to provide 0-35% of the fruit's accumulation of specific nutrients. Analysis of xylem sap showed that asparagine was the main solute for transport of nitrogen. Mature seedsconsisted mainly of a thick layer of endosperm surrounding the embryo and cotyledons. Seeds contained 31% oil, 35% protein, but no storage carbohydrate. Scanning X-ray microprobe analysis on thin sections of endosperm showed that phosphorus, sulfur, calcium, magnesium and iron were associated with protein bodies. Manganese was localized in certain iron-rich protein bodies.