SEEDLING GROWTH-RESPONSE TO ADDED NUTRIENTS DEPENDS ON SEED SIZE IN 3WOODY GENERA

1 We tested whether seedlings of small-seeded species were more relian t on soil nutrients than large-seeded ones by growing 21 species from three woody genera (Eucalyptus, Hakea and Banksia) along a gradient of nutrient availability. 2 At very low nutrient availability, larger se eds produced larger seedlings. This was seen especially among the euca lypts, but the difference was eliminated at optimal soil nutrient leve ls. Hakea species with large seed mass, and all Banksia species, appea red unable to exploit additional soil nutrients for growth, whatever t he level supplied. 3 Larger seeds tended to have proportionately highe r contents of N, P and K and, under nutrient-poor conditions, supplied more of these to their seedlings, although at a diminishing rate. 4 W e suggest that large-seededness could be an adaptation to the high-lig ht, nutrient-impoverished habitats in which these species occur by pro viding the seedling with the mineral nutrients, rather than carbon-bas ed metabolites, needed for maximizing initial root growth. Reaching re liable moisture before summer (drought avoidance) is an alternative st rategy to physiological tolerance of drought.