Annals of Botany

Suberised barriers support composite water and solute transport in barley roots

Roots possess complex anatomical structures characterised by suberised apoplastic barriers that are deposited in localised cell wall layers. Barley roots lack an exodermis, but form an endodermis that accounts for the majority of the roots’ total suberin content.

Appearance of Casparian bands (CBs) and suberin lamellae (SL) in the endodermis, and presence of suberin in the rhizodermis of barley roots.
Appearance of Casparian bands (CBs) and suberin lamellae (SL) in the endodermis, and presence of suberin in the rhizodermis of barley roots. Freehand cross-sections of seminal roots of 16- to 20-day-old barley plants stained with either berberine–aniline blue (A-D) or lipophilic fluorochrome, Fluorol yellow 088 (E, F and H). At 10 mm from the apex, no CBs appeared in the endodermis (A), whereas, ‘dot-like’ bands, indicated by a faint green fluorescence, appeared at 20 mm from the apex (B; arrowheads). Continuous bands with intense yellowish green fluorescence in the radial walls at 30 (C) and 40 mm (D) from the tip, respectively. Stained SL appeared as a yellow, patchy ring in the endodermis (arrows) at 60 mm (E), but as a complete lamellae ring with bright yellow fluorescence (arrows) at 100 mm from the apex (F). Autofluorescence (G) and greenish yellow fluorescence (H) in the radial and outer tangential walls of the rhizodermis at 100 mm from the apex. Section stained with Toluidine blue O, showing only four cortical cell layers in the cortex (I). Scale bars = 50 µm.

Ranathunge et al. show that the basal zone with greater suberin is shown to have lower water permeability than the apical zone in Hordeum vulgare. A comparison of root and cell water permeabilities suggests a primary cell-to-cell water and nutrient transport system in barley roots in addition to flow via apoplastic pathways. Roots exhibited different permeabilities according to the different solutes used.

Reference

Ranathunge, K., Kim, Y. X., Wassmann, F., Kreszies, T., Zeisler, V., & Schreiber, L. (2017). The composite water and solute transport of barley (Hordeum vulgare) roots: effect of suberized barriers . Annals of Botany, mcw252. https://doi.org/10.1093/aob/mcw252

About the author

Annals of Botany Office

The Annals of Botany Office is based at the University of Oxford.

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