Novel root clusters in the grasstree Kingia australis (Dasypogonaceae) increase the root surface:volume ratio by 70 times

Byron B. Lamont; Andrew Weinert; Helen Duff

doi:10.1071/BT25022

RESEARCH ARTICLE (Open Access)

Next Contents Vol 73(5)

Novel root clusters in the grasstree Kingia australis (Dasypogonaceae) increase the root surface:volume ratio by 70 times

Byron B. Lamont

^A ^§ ^* , Andrew Weinert ^B and Helen Duff ^B

+ Author Affiliations

- Author Affiliations

^A Ecology Discipline, School of Molecular and Life Sciences, Curtin University, PO Box U1987, Perth, WA 6845, Australia.

^B Geographe Community Landcare Nursery, Busselton, WA 6280, Australia.

^* Correspondence to: B.Lamont@curtin.edu.au

^§ The Editors-in Chief wish to acknowledge Byron Lamont’s long-term contribution to the journal. This is his 28th paper to have been published in the (the first occurring 53 years ago!). Ironically, the first paper was also about specialised roots in the SW Australian flora. Byron’s contribution to the journal has also included serving on the editorial board between 1993 and 1996.

Handling Editor: John Morgan

Australian Journal of Botany 73, BT25022 https://doi.org/10.1071/BT25022

Submitted: 24 March 2025 Accepted: 14 July 2025 Published: 4 August 2025

© 2025 The Author(s) (or their employer(s)). Published by CSIRO Publishing. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)

Abstract

Context

Erosion of a riverbank in south-western Australia exposed previously unrecorded clusters of roots/rootlets produced by the grasstree, Kingia australis (Dasypogonaceae).

Aims

Our aim was to prepare an initial report on these roots and consider their possible functions.

Methods

Excavation of root clusters, and quantification of the morphological and histological characteristics, and distribution in the soil.

Results

There were 260 clusters per m³ of soil to a depth of 1.6 m, peaking at a depth of 50−70 cm where nutrients and water were accessible all year. Their length × width averaged 8.4 × 5.5 cm, with 520 roots/rootlets per cluster and 5140 rootlets per litre of rhizosphere soil. Clusters comprised a parent lateral (with aerenchyma), hundreds of secondary roots, 50 × 3 mm, and thousands of rootlets, 10 × 1 mm. Clusters are perennial, new roots occasionally emerging from the previous winter-growing-season cluster. We call these novel clusters kingioid roots. Total root length reached 70 m/litre of rhizosphere soil. All roots are covered in root hairs, with parent lateral hairs 250 μm long increasing to 700 μm for rootlets. They possess a ±150-μm thick mucigel layer. Fineness of the rootlets and the dense root-hair cover result in a 70-time increase in the surface:volume ratio compared with the parent roots. No endogenous fungal hyphae or (cyano) bacteria were evident.

Conclusions

Although perennial, these structures link with seasonal root-cluster types (proteoid/dauciform/capillaroid roots) via the abundance of extremely hairy rootlets and mucigel, implying that the structures enhance water and nutrient uptake rather than storage.

Implications

As these root clusters are distributionally/morphologically/anatomically distinct they deserve more detailed study.

Keywords: Dasypogonaceae, Kingia, mucigel, nutrient uptake, oligotrophic soils, phosphorus, root clusters, root hairs, root surface area, water uptake.

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