ISSN:
1573-5036
Keywords:
diffusion
;
diffusion-resistance
;
Frankia
;
oxygen
;
periderm
Source:
Springer Online Journal Archives 1860-2000
Topics:
Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
Notes:
Abstract When excised root nodules ofCoriaria arborea are assayed for nitrogenase activity at various pO2 they show a broad optimum between 20 and 40 kPa O2, with some evidence for adaptation. Continuous flow assays of nodulated root systems of intact plants indicate that Coriaria shows an acetylene induced decline in nitrogenase activity. When root systems were subject to step changes in pO2 nitrogenase activity responded with a steep decline followed by a slower rise in activity both at lower and higher than ambient pO2. Thus Coriaria nodules are able to adapt rapidly to oxygen levels well above and well below ambient. Measurement of nodule diffusion resistance showed that the adaptation is accompanied by rapid increase in resistance at above ambient pO2 and decrease in resistance at below ambient pO2. Plants grown with root systems at pO2 from 5–40 kPa O2 did not differ in growth or nodulation. The anatomy of Coriaria nodules shows they have a dense periderm which encircles the nodule and also closely invests the infected zone. The periderm is both thicker and more heavily suberised in nodules grown at high pO2 than at low pO2. Vacuum infiltration of India ink indicates that oxygen diffusion is entirely through the lenticel and via a small gap adjacent to the stele.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF02232794
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