Differences in investment and functioning of cluster roots account for different distributions of Banksia attenuata and B. sessilis, with contrasting life history

Abstract

Aims Banksia attenuata is a resprouting species growing in deep sand, while B. sessilis is a fire-killed species occurring in shallow sand over laterite or limestone. We aimed to discover the ecophysiological basis for their different distributions by exploring their investment in deep non-cluster roots and shallow cluster roots, and their cluster-root functioning.Methods Deep-pot (1 m), shallow-pot (400 mm), hydroponic experiments and phosphorus (P)-extraction experiment were carried out. Biomass allocation, clusterroot exudation, plant P and leaf manganese (Mn) concentrations were measured.Results Banksia attenuata allocated more biomass to deep roots and less biomass to cluster roots than B. sessilis did in deep pots. The two Banksias released similar Revised version without track changes Click here to access/download;Revised version without track changes;Banksia manuscript 20190126 revision clean.docx carboxylates in all experiments, with similar carboxylate-exudation rates in hydroponics. The carboxylate amount per unit cluster root of B. sessilis grown in shallow pots was greater than that of B. attenuata, and B, sessilis acquired more P than B. attenuata did in limestone substrate. Conclusions Greater investment in deep roots for water uptake accounts for the presence of B. attenuata in deep sand, and vice versa for the absence of B. sessilis. A larger investment in cluster roots, which released greater amounts of carboxylates, likely accounts for B. sessilis occurring over limestone. Trade-offs in investment and cluster-root functioning support the species' distribution patterns and life histories.Leaf Mn concentration was a good proxy for the plant capacity to acquire P.

Root positioning and trait shifts in Hibbertia racemosa as dependent on its neighbour's nutrient‐acquisition strategy

“…This is likely because the non‐cluster roots of B . attenuata roots also release carboxylates (Roelofs, Rengel, Cawthray, Dixon, & Lambers, 2001; Shi, Strack, Albornoz, Han, & Lambers, 2020), solubilizing soil nutrients. We also highlight H .…”

Xylomelum occidentale (Proteaceae) accesses relatively mobile soil organic phosphorus without releasing carboxylates

“…This connection between carboxylate release and high leaf [Mn] was confirmed in a glasshouse trial comprising 100 chickpea accessions (Pang et al., 2018). Therefore, a high [Mn] in leaves of Banksia species was expected, because their cluster roots exude large amounts of carboxylates (Denton, Veneklaas, Freimoser, & Lambers, 2007; Shi, Strack, Albornoz, Han, & Lambers, 2019) that mobilize P as well as Mn. Therefore, its low leaf [Mn] suggests that X. occidentale either does not exude significant amounts of carboxylates into its rhizosphere to mobilize P, or that the carboxylates were quickly consumed by soil microbes (D'Angioli, Viani, Lambers, Sawaya, & Oliveira, 2017).…”

Specialized roots of Velloziaceae weather quartzite rock while mobilizing phosphorus using carboxylates

“…Vellozioid roots are highly efficient at P acquisition, since they can solubilize P from the rock in a matrix comprising predominantly Si (>96% of the content). This is a far more extreme situation than the strategies of plants with cluster or dauciform roots that grow in soil (Shane & Lambers, ) or on rock surfaces (Shi, Strack, Albornoz, Han, & Lambers, ). These Velloziaceae, due to their physical and chemical actions inside the rocks, act in the process of weathering in campos rupestres .…”