XVI International Botanical Congess

Seedlings of Hakea sp. (Mt. Coolum P.R. Sharpe 3338, former Hakea gibbosa) produce abundant cluster roots in the organic matter rich top soil of the nutrient poor wallum, suggesting a role of cluster roots for nitrogen acquisition. The pool of soluble soil nitrogen sources in the wallum is dominated by complex organic N, followed by amino acids and ammonium. 15N-labeling studies with organic (glycine) and inorganic (ammonium, nitrate) nitrogen sources showed that cluster roots of Hakea have a greater ability to take up organic nitrogen than ordinary roots of Hakea and other plant species in Australian plant communities. We are currently investigating whether cluster roots may have a similar function to ecto-mycorrhizal associations that can broaden the plants access to complex nitrogen sources including protein and peptide nitrogen.