Root aeration via aerenchymatous phellem: three-dimensional micro-imaging and radial O2 profiles in Melilotus siculus.
• 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 near-anoxic conditions at the centre of the stele in the basal parts of the root, coupled with only hypoxic conditions towards the apex.
BIOSYST-MeBioS, Faculty of Bioscience Engineering, Katholieke Universiteit Leuven, Leuven, Belgium. pieter.verboven@biw.kuleuven.be
Pieter
P
Verboven
Ole
O
Pedersen
Els
E
Herremans
Quang Tri
QT
Ho
Bart M
BM
Nicolaï
Timothy David
TD
Colmer
Natasha
N
Teakle
D000332:Aerobiosis / Q000187:drug effects; D000388:Air; D019069:Cell Respiration / Q000187:drug effects; D004058:Diffusion / Q000187:drug effects; D018546:Hypocotyl / Q000033:anatomy & histology / Q000254:growth & development; D021621:Imaging, Three-Dimensional / Q000379:methods*; D029903:Melilotus / Q000033:anatomy & histology* / Q000187:drug effects / Q000254:growth & development / Q000502:physiology*; D008954:Models, Biological; D010100:Oxygen / Q000494:pharmacology*; D010101:Oxygen Consumption / Q000187:drug effects; D010313:Partial Pressure; D018517:Plant Roots / Q000033:anatomy & histology* / Q000187:drug effects / Q000502:physiology*; D058526:Plant Vascular Bundle / Q000187:drug effects / Q000502:physiology; D016062:Porosity / Q000187:drug effects; D014057:Tomography, X-Ray Computed
D010100:Oxygen