Seedling growth response to added nutrients depends on seed size in three woody genera

Authors

  • Per Milberg,

    1. School of Environmental Biology, Curtin University of Technology, GPO Box U1987, Perth, W.A. 6001, Australia
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    • * Present address and correspondence: Department of Biology, Linköping University, S-581 83 Linköping, Sweden (fax 46 13 28 26 11; e-mail permi@ifm.liu.se).

  • María A. Pérez-Fernández,

    1. School of Environmental Biology, Curtin University of Technology, GPO Box U1987, Perth, W.A. 6001, Australia
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  • Byron B. Lamont

    1. School of Environmental Biology, Curtin University of Technology, GPO Box U1987, Perth, W.A. 6001, Australia
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Abstract

1 We tested whether seedlings of small-seeded species were more reliant 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 seeds produced larger seedlings. This was seen especially among the eucalypts, but the difference was eliminated at optimal soil nutrient levels. Hakea species with large seed mass, and all Banksia species, appeared unable to exploit additional soil nutrients for growth, whatever the level supplied.

3 Larger seeds tended to have proportionately higher contents of N, P and K and, under nutrient-poor conditions, supplied more of these to their seedlings, although at a diminishing rate.

4 We suggest that large-seededness could be an adaptation to the high-light, nutrient-impoverished habitats in which these species occur by providing the seedling with the mineral nutrients, rather than carbon-based metabolites, needed for maximizing initial root growth. Reaching reliable moisture before summer (drought avoidance) is an alternative strategy to physiological tolerance of drought.

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