The Nutrition of Fruits of Two Proteaceous Shrubs, Grevillea wilsonii and Hakea undulata, From South-Western Australia

Abstract

The accumulation of nutrients by fruits of Grevillea wilsonii was studied throughout their development, and the distribution of nutrients between fruit parts is described for G. wilsonii and Hakea undulata. Fruits of G. wilsonii required 9 weeks from anthesis to maturity, those of H. undulata 25 weeks. Losses of nutrients from the follicle of G. wilsonii during fruit ripening were 87% (P), 67% (Zn) and 28% (N and Cu), and could have provided from 11 to 15% of these nutrients accumulated by mature seeds. Dry matter and K, S, Ca, Mg, Na, Cl, Fe and Mn were not withdrawn from follicles. Seeds of G. wilsonii contained most of the mature fruit's N, P, S, Ca, Mg, Zn, Mn and Cu but less than 35% of its K, Na, Cl and Fe. Seeds of H. undulata contained over 50% of the P, N, S and Zn despite their small contribution to fruit dry matter (2.4%) but only 0.4-3.5% of the fruit's K, Cl and Na. Seeds contained higher levels of all nutrients except Na and Cl than the follicle or capsule. Nutrients were less concentrated in seeds of G. wilsonii than in H. undulata. In G. wilsonii, 46% of the fruits had one aborted seed. The intake of many nutrients into fruit parts of G. wilsonii was out of phase with dry matter acquisition. The K:Ca ratio of seeds of both species was low and the reverse of that found in seeds of other fruits. It was concluded that some Proteaceae have evolved strategies to ensure that plants set a few fruits with at least one viable seed that has high levels of nutrients.