Acacia stenophylla

Overview

Acacia stenophylla grows along inland Australian waterways and floodplains, including saline clay sites. Existing accounts cover hydroponic NaCl, mixed-sea-salt seedling irrigation and planted-tree field observations; their materials, salt measures and growth endpoints remain distinct. [S1, S2, S3, S4]

Names and classification

Acacia stenophylla A.Cunn. ex Benth. is an evergreen shrub or small tree of inland Australia; habitat records and experimental material are described under the names used by each source. [S1]

Morphology and identification

An evergreen shrub or small tree reaching about 20 m, with pendulous branchlets. [S1]

Distribution, habitat and phenology

WorldWideWattle describes the species along inland Australian waterways and on floodplain heavy clays, and notes that soils can be saline. A long-term planting trial at a salt-drainage site adds measured root-zone salinity and growth observations, but the planted trial is not a wild population. [S1, S2]

Australian accounts give a usual flowering period from March to August, with irregular flowering through the year in some places; pods commonly mature from October to December. [S1]

Salinity in natural habitats

Regional Australian accounts place the species along inland watercourses, floodplains and some saline clay soils. Its occurrence along non-saline waterways shows that saline sites form part of a wider riverine habitat range. [S1]

Salinity studies

Abbas et al. (2017) grew seedlings from five widely separated populations in aerated 25-L half-strength Hoagland solution at 0, 100 and 200 mM NaCl. Plants were 16±2 cm tall at transfer and acclimated without salt for seven days; salinity was stepped to target over two days, and the solution was renewed on day 14. After 28 days of salt exposure, the 200 mM group had terminal stem/root lengths of 13.3±1.22/10.2±1.0 cm and dry masses of 0.32±0.01/0.16±0.006 g; the 100 mM group had terminal stem length 19.1±1.08 cm. Starting measurements immediately before salt treatment were not reported, so terminal size cannot establish net change during exposure. Sahito et al. (2013) grew sand-cultured seedlings from one Karachi tree under mixed-sea-salt irrigation for six weeks (20 saline irrigations), across 0–1.2% sea salt and ECiw 0.60–16.67 dS/m. Trait-specific fitted 50%-reduction values were 8.35–18.52 dS/m (mean 12.51±1.51); the 18.52 dS/m fit exceeds measured maximum ECiw and is extrapolated. Marcar et al. reported planted-tree observations at a salt-drainage site with field ECe about 6–10 dS/m over 61 or 72 months; the abstract reports no growth reduction to 10 dS/m. These hydroponic, irrigation-water and field-soil results describe different systems. [S3]

Sahito et al. (2013) raised greenhouse sand-cultured seedlings from seeds collected in March 2012 from one tree in the Botany Department at the University of Karachi, then irrigated them with mixed sea salt for six weeks (20 saline irrigations). Treatments were 0, 0.15, 0.3, 0.6, 0.9 and 1.2% sea salt, paired with ECiw values of 0.60, 3.51, 5.24, 9.23, 12.81 and 16.67 dS/m. Stem/root length, leaf/phyllode counts and organ fresh/dry mass varied with ECiw. Trait-specific fitted values for 50% reduction ranged from 8.35 to 18.52 dS/m, with a mean of 12.51±1.51 dS/m. The 18.52 dS/m fit exceeds the highest measured ECiw and is an extrapolation, not an observed treatment threshold. [S4]

Marcar et al. observed planted trees at a salt-drainage site for 61 or 72 months and reported ECe of about 6–10 dS/m in the 0–60 cm root zone. Their abstract reports no growth decline in A. stenophylla at ECe up to 10 dS/m. eHALOPH separately lists 6.91 and 60.9 dS/m, but the abstract does not confirm how those values map to this species or its endpoints. [S2, S5]

Reported mechanisms and ecological adaptations

Salinity, alkalinity, and periodic flooding together shape its waterway habitat. Regional accounts describe salt and waterlogging tolerance, while the growth studies do not establish a molecular mechanism for salt adaptation in this species. [S1]

Conclusions and evidence gaps

The hydroponic trial lacks measurements at the start of salt exposure, leaving net growth at 200 mM unresolved. Sahito’s sea-salt treatments are irrigation-water ECiw, while Marcar reports field-soil ECe; neither is interchangeable with the hydroponic NaCl dose. eHALOPH’s 60.9 dS/m remains an unverified database entry. [S1, S2, S3, S4, S5]