Internal oxygen transport in cuttings from flood-adapted várzea tree species

Tree species from the Central Amazon inundation areas are subjected to extreme flooding, with trees being partially submerged for up to 10 months. The rapidly advancing floodwater table at the onset of the aquatic phase interrupts the inward diffusion of oxygen from the atmosphere to submerged plant...

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Bibliographic Details
Published in:Tree physiology 2003-10, Vol.23 (15), p.1069-1076
Main Authors: Haase, Karen, De Simone, Oliviero, Junk, Wolfgang J, Schmidt, Wolfgang
Format: Article
Language:English
Subjects:
Adaptation, Physiological - physiology
Microscopy, Electron, Scanning
Oxygen - physiology
Plant Roots - anatomy & histology
Plant Roots - physiology
Salix - physiology
Tabernaemontana - physiology
Trees - physiology
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Summary:Tree species from the Central Amazon inundation areas are subjected to extreme flooding, with trees being partially submerged for up to 10 months. The rapidly advancing floodwater table at the onset of the aquatic phase interrupts the inward diffusion of oxygen from the atmosphere to submerged plant parts. Salix martiana (Leyb.) (Salicaceae) and Tabernaemontana juruana ((Markgr.) Schumann ex J. F. Macbride) (Apocynaceae), tree species typical of Amazon floodplains, respond to low oxygen concentrations by forming adventitious roots capable of longitudinal oxygen transport. Cuttings of these tree species were subjected to simulated flooding and the oxygen concentration of the root cortex was temporally monitored by oxygen microelectrodes that penetrated the roots. Changes in the floodwater table made it possible to localize precisely the entry points of atmospheric oxygen. Under experimental conditions, mathematical description of the transport kinetics revealed that longitudinal transport of O2 in both species was mainly attributable to diffusion. Based on the finding that diffusion was inhibited by a small increase in the floodwater table, we conclude that internal oxygen transport during a rising water table is only attainable when adventitious roots are continuously and rapidly developed, as is the case in S. martiana. In T. juruana, slow growth of adventitious roots and low root porosity suggest that other adaptations are required to overcome long flooding periods.
ISSN:0829-318X
1758-4469
DOI:10.1093/treephys/23.15.1069