Abstract |
• Some recent data on O(2) scavenging by root segments showed a two-phase reduction in respiration rate starting at/above 21 kPa O(2) in the respirometer medium. The initial decline was attributed to a down-regulation of respiration, involving enzymes other than cytochrome oxidase, and interpreted as a means of conserving O(2). As this appeared to contradict earlier findings, we sought to clarify the position by mathematical modelling of the respirometer system. • The Fortran-based model accommodated the multicylindrical diffusive and respiratory characteristics of roots and the kinetics of the scavenging process. Output included moving images and data files of respiratory activity and [O(2)] from root centre to respirometer medium. • With respiration at any locus following a mitochondrial cytochrome oxidase O(2) dependence curve (the Michaelis-Menten constant K(m) = 0.0108 kPa; critical O(2) pressure, 1-2 kPa), the declining rate of O(2) consumption proved to be biphasic: an initial, long semi-linear part, reflecting the spread of severe hypoxia within the stele, followed by a short curvilinear fall, reflecting its extension through the pericycle and cortex. • We conclude that the initial respiratory decline in root respiration recently noted in respirometry studies is attributable to the spread of severe hypoxia from the root centre, rather than a conservation of O(2) by controlled down-regulation of respiration based on O(2) sensors.
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Authors | William Armstrong, Peter M Beckett |
Journal | The New phytologist
(New Phytol)
Vol. 190
Issue 2
Pg. 431-41
(Apr 2011)
ISSN: 1469-8137 [Electronic] England |
PMID | 21118258
(Publication Type: Journal Article)
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Copyright | © 2010 The Authors. New Phytologist © 2010 New Phytologist Trust. |
Chemical References |
- Pyruvates
- Electron Transport Complex IV
- Oxygen
|
Topics |
- Cell Hypoxia
- Cell Respiration
- Electron Transport Complex IV
(metabolism)
- Models, Biological
- Organ Specificity
- Oxygen
(metabolism)
- Oxygen Consumption
- Peas
(cytology, enzymology, metabolism)
- Plant Roots
(anatomy & histology, cytology, metabolism)
- Pressure
- Pyruvates
(metabolism)
- Temperature
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