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The Use of Polarography in the Assay of Oxygen Diffusing from Roots in Anaerobic Media
Author(s) -
Armstrong W.
Publication year - 1967
Publication title -
physiologia plantarum
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.351
H-Index - 146
eISSN - 1399-3054
pISSN - 0031-9317
DOI - 10.1111/j.1399-3054.1967.tb07195.x
Subject(s) - oxygen , diffusion , silicone rubber , polarography , botany , chemistry , anaerobic exercise , oxygen transport , aerenchyma , photosynthesis , limiting oxygen concentration , biophysics , horticulture , biology , inorganic chemistry , physiology , physics , organic chemistry , thermodynamics
A “polarographic” technique by which the rate of outward diffusion of oxygen from plant roots may be measured, is described in detail. Oxygen has been found to diffuse from the roots of all of the ten species of bog‐plants so far tested, and the oxygen diffusion rates (ODR) of eight of these species show the existence of interspecific differences. Model roots made from silicone rubber tubing give “polarographs” identical with those obtained around the living roots. Suberization accompanying root maturation is thought to account for a. the association of oxygen diffusion with the apical regions of roots, and b. the lowered diffusion rates associated with winter dormancy. This localisation of root oxygen diffusion may be of survival value in reduced soils. Experiments suggest that aerenchyma can function as an oxygen reservoir in the plant if the stomata were closed for long periods. Calculations of expected ODR based on the internal gas concentrations of a model system give readings very similar to the ODR obtained experimentally using the silicone rubber tubing models. Further calculations, based on reported internal gas concentrations for Menyanthes , rice, Spartina , and Schoenus , also show a close similarity between real and expected values. It is concluded that in these species at least, there is negligible resistance in certain regions of the root to the passage of oxygen from the root intercellular spaces to the surrounding medium. Results have shown that root bases are relatively impermeable to oxygen, and it is suggested that oxygen intake into roots in the basal regions reported by other workers, probably occurs through basally‐borne laterals. One important function of diffusing oxygen from the root is probably the supply of an external source of oxygen to the root meristem.