INFLUENCE OF SEED SIZE AND QUALITY ON SEEDLING DEVELOPMENT UNDER LOW NUTRIENT CONDITIONS IN 5 AUSTRALIAN AND SOUTH-AFRICAN MEMBERS OF THE PROTEACEAE

(1) Seedling development under nutrient-deficient conditions was investigated for five bradysporous members of the Proteaceae to test the hypothesis that large seed size and high embryo nutritional quality reflect the outcome of selection favouring propagules suited for establishment in infertile soils characteristic of those natural environments dominated by members of the Proteaceae. (2) Seeds of Protea lorifolia, Protea cynaroides, Leucadendron laureolum, Hakea sericea and Banksia laricina were germinated and grown on nutrient-deficient sand for 200 days. Every forty days ten seedlings of each species were harvested to determine growth, allocation patterns and nutrient use. Seedling parts were dried, weighed and analysed for N, P, K, Ca and Mg. (3) Seedlings of all Proteaceae species were able to survive prolonged periods of nutrient scarcity irrespective of seed size. (4) Rapid germination of Proteaceae seeds does not appear to be a significant means of increasing seedling fitness. (5) Seed mass was positively correlated with seedling size. (6) No correlation between relative growth rates and seed size was found. (7) Seeds of members of the Proteaceae show selective storage of specific nutrients (N and P) such that seed chemical composition is unbalanced for optimum seedling growth. These elements complement the rich sources of cations Ca,Mg and K found in soils of post-fire environments when maximal recruitment of proteoid species occurs.