Root aeration via aerenchymatous phellem: three‐dimensional micro‐imaging and radial O₂ profiles in Melilotus siculus

Abstract

Summary• Internal root aeration enables waterlogging-tolerant species to grow in anoxic soil. Secondary aerenchyma, in the form of aerenchymatous phellem, is of importance to root aeration in some dicotyledonous species. Little is known about this type of aerenchyma in comparison with primary aerenchyma.• Micro-computed tomography was employed to visualize, in three dimensions, the microstructure of the aerenchymatous phellem in roots of Melilotus siculus. Tissue porosity and respiration were also measured for phellem and stelar tissues. A multiscale, three-dimensional, diffusion-respiration model compared the predicted O 2 profiles in roots with those measured using O 2 microelectrodes.• Micro-computed tomography confirmed the measured high porosity of aerenchymatous phellem (44-54%) and the low porosity of stele (2-5%) A network of connected gas spaces existed in the phellem, but not within the stele. O 2 partial pressures were high in the phellem, but fell below the detection limit in the thicker upper part of the stele, consistent with the poorly connected low porosity and high respiratory demand.• The presented model integrates and validates micro-computed tomography with measured radial O 2 profiles for roots with aerenchymatous phellem, confirming the existence of nearanoxic conditions at the centre of the stele in the basal parts of the root, coupled with only hypoxic conditions towards the apex.

Void space inside the developing seed of Brassica napus and the modelling of its function

“…Diffusion model equations (Ho et al ., 2011; Verboven et al ., 2012) were discretized over the finite volume grid to yield a linear system of algebraic equations on the unknown concentrations at the nodes. The linear equation system was solved by the conjugate gradient method available in Matlab (The Mathworks, Natick, MA, USA).…”

Role of Abscisic Acid in Flood-Induced Secondary Aerenchyma Formation in Soybean (Glycine max) Hypocotyls

“…Under flooded conditions, the phellogen also develops a homologous tissue, secondary aerenchyma, in the stems, roots, and root nodules in some plant species. Examples include some Fabaceae plants such as Sesbania aculeata (Scott and Wager, 1888), Sesbania rostrata (Saraswati et al, 1992;Shiba and Daimon, 2003), Neptunia oleracea (Metcalfe, 1931), Melilotus siculus (Teakle et al, 2011;Verboven et al, 2012), and Viminaria juncea (Walker et al, 1983). In addition, this phenomenon is observed in Onagraceae, e.g., Ludwigia spp.…”

A Microscale Model for Combined CO2 Diffusion and Photosynthesis in Leaves

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