Plants 2018, 7(2), 47; https://doi.org/10.3390/plants7020047
Developmental Biology and Induction of Phi Thickenings by Abiotic Stress in Roots of the Brassicaceae
School of Environmental and Life Sciences, The University of Newcastle, Callaghan, NSW 2308, Australia
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Received: 25 May 2018 / Revised: 14 June 2018 / Accepted: 17 June 2018 / Published: 19 June 2018
(This article belongs to the Special Issue Plant Cell Wall Dynamics in Plant Growth and Stress Response)
Abstract
Phi thickenings are specialized bands of secondary wall deposited around radial walls of root cortical cells. These structures have been reported in various species from the Brassicaceae, including Brassica oleracea, where previous reports using hydroponics indicated that they can be induced by exposure to salt. Using roots grown on agar plates, we show that both salt and sucrose can induce the formation of phi thickenings in a diverse range of species within the Brassicaceae. Within the genus Brassica, both B. oleracea and B. napus demonstrated the formation of phi thickenings, but in a strongly cultivar-specific manner. Confocal microscopy of phi thickenings showed that they form a complex network of reinforcement surrounding the inner root cortex, and that a delicate, reticulate network of secondary wall deposition can also variously form on the inner face of the cortical cell layer with phi thickenings adjacent to the endodermal layer. Results presented here indicate that phi thickenings can be induced in response to salt and water stress and that wide variation occurs in these responses even within the same species. View Full-TextKeywords:
phi thickening; secondary wall; Brassicaceae roots; Brassica oleracea; Brassica napus; salt stress; water stress
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Supplementary materials
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Externally hosted supplementary file 1
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Description: Figure S1: Computer-generated re-slices through optical stacks collected from roots mounted longitudinally showing berberine-stained lignin (green in overlay) and pontamine-stained cellulose (red in overlay) in B. napus ‘Hyola971CL’ roots. (a) ‘Hyda971CL’ grown on control plates (no NaCl). Casparian strips (Cs) weakly labelled with berberine in the endodermis while xylem (x) strongly labelled in the central vascular tissue. (b) ‘Hyda971CL’ 5 day-old root treated with 80 mM NaCl induced formation of phi thickenings (Φ) in the innermost cortex immediately outside the endodermis containing Casparian strip (Cs). Bar = 100 μm. -
Externally hosted supplementary file 2
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Description: Movie S1: 3D reconstructions of confocal optical stacks of berberine-stained lignin (green) and pontamine-stained cellulose (red) in B. oleracea roots of cultivar ‘Marathon F1’. Control root in the absence of added salt which weakly labelled the Casparian strips in the endodermal layer and strongly labelled the xylem bundles. -
Externally hosted supplementary file 3
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Description: Movie S2: 3D reconstructions of confocal optical stacks of berberine-stained lignin (green) and pontamine-stained cellulose (red) in B. oleracea roots of cultivar ‘Marathon F1’. Root grown in presence of 80 mM NaCl which strongly induced the formation of phi thickenings.
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Aleamotu’a, M.; Tai, Y.-T.; McCurdy, D.W.; Collings, D.A. Developmental Biology and Induction of Phi Thickenings by Abiotic Stress in Roots of the Brassicaceae. Plants 2018, 7, 47.
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