Acacia rostellifera

Overview

Acacia rostellifera is a shrub of coastal dunes and scrub in Western Australia. In Joseph et al.’s seedling experiment, growth and biomass declined as NaCl was raised stepwise to 300 mM, and the species received a sensitive ranking. [S1, S2, S5]

Names and classification

The accepted name is Acacia rostellifera Benth.; Joseph et al. listed the tested material under this name in their 15-species Acacia screen. [S1, S2, S6]

The experiment used seedlings from the reported seed source, and its conclusions concern that material and treatment. [S2]

Morphology and identification

A Western Australian shrub with the phyllodes and yellow flower heads typical of Acacia, growing on coastal dunes and their lee slopes. Reliable identification requires voucher characters such as mature phyllodes and pods; the abstract linked from the database does not provide enough morphological information to confirm the experimental material. [S1, S5]

Distribution, habitat and phenology

An Australian Wattle/Flora-derived account and a government coastal survey associate the species with dunes and their landward slopes. No verified evidence here places it in salt marsh, salt lake, or soil with measured saline root-zone conditions. Exposure to sea spray, if present, is not equivalent to root-zone salinity. [S1, S5, S6]

Available regional records do not establish a consistent flowering or fruiting season; an observation from one locality or cultivated material does not define phenology across the range. [S6]

Salinity in natural habitats

Reported field habitats are chiefly coastal dunes, leeward slopes and scrub; the available sources do not report root-zone soil salinity for these populations. [S1, S5]

Salinity studies

Seeds were obtained from AustraHort and Nindethana Seed Services in Australia. Seedlings were transplanted to vermiculite:perlite (3:2) and grown for eight weeks before receiving NaCl in Hoagland solution, increased by 50 mM every other day to 300 mM; plants were harvested 48 h after reaching the final concentration, after 13 days of salt exposure. At 300 mM, shoot fresh mass fell from 3.75±0.40 to 1.29±0.75 g and dry mass from 0.86±0.07 to 0.30±0.17 g; root fresh mass fell from 1.55±0.10 to 0.41±0.28 g and dry mass from 0.40±0.07 to 0.11±0.04 g (means±SEM; n=3). Based on combined shoot and root measures, the authors reported fresh- and dry-mass tolerance indices of 0.3 and ranked the species 4 (sensitive). [S2]

Reported mechanisms and ecological adaptations

At 300 mM NaCl, the shoot K⁺/Na⁺ ratio fell from 4.19 to 0.96 and the root ratio from 44.23 to 0.48; Na⁺ content increased in both tissues. The authors noted marked interspecific differences in ion responses and called for further study of ion partitioning under longer exposure. [S2]

Conclusions and evidence gaps

In this short seedling experiment, A. rostellifera was ranked sensitive after stepwise exposure to 300 mM NaCl; its combined fresh- and dry-mass indices were both 0.3. This result applies to the tested treatment. Longer trials with multiple provenances are needed to assess source variation and field performance. [S2]