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Respiratory capacity, nitrogenase activity and structural changes ofFrankia, in symbiosis withAlnus incana, in response to prolonged darkness (1990)

Vikman, Per-Åke ; Lundquist, Per-Olof ; Huss-Danell, Kerstin

Springer

Planta 182 (1990), S. 617-625

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ISSN: 1432-2048

Keywords: Alnus ; Darkness and nitrogenase activity ; Frankia ; Nitrogenase ; Respiration ; Root nodule structure

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Abstract Plants ofAlnus incana (L.) Moench in symbiosis with a local source ofFrankia were exposed to prolonged darkness under controlled climate conditions.Frankia vesicle clusters were prepared from the root nodules, and the condition ofFrankia was measured as respiratory capacity by supplying the preparation with saturating amounts of four different substrates. During darkness, nitrogenase (EC 1.7.99.2) activity decreased in intact plants and in the vesicle-cluster preparations. The respiratory capacity ofFrankia also decreased. After 4 d in darkness most respiration was lost, though all nitrogenase activity was already lost after 3 d. When the dark treatment was ended after 2 d and normal light/dark conditions restored, nitrogenase activity immediately started to recover. The respiratory capacity continued to decrease and no recovery was observed until the third day after the end of the dark treatment. Whole-plant nitrogenase activity slowly increased at a rate similar to the rate of increase observed in untreated plants. Transmission electron micrographs of the root nodules showed that the cytoplasm of infected host cells and the cells ofFrankia were structurally degraded in response to dark treatment, while young vesicles were frequent during recovery. Growth and differentiation ofFrankia cells were apparently important for recovery of the enzyme activities studied.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF02341040

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Lipid composition and nitrogenase activity of symbioticFrankia (Alnus incana) in response to different oxygen concentrations (1994)

Kleemann, Gisela ; Alskog, G. ; Berry, Alison M. ; [et al.]

Springer

Protoplasma 183 (1994), S. 107-115

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ISSN: 1615-6102

Keywords: Alnus incana ; Frankia ; Hopanoids ; Nitrogen fixation ; Oxygen ; Symbiosis ; Vesicle envelope

Source: Springer Online Journal Archives 1860-2000

Topics: Biology

Notes: Summary The role ofFrankia vesicle envelope lipids in regulating oxygen diffusion of symbiotic nitrogen fixation inAlnus incana was examined. Total lipids of symbioticFrankia (vesicle clusters) that had been adapted to oxygen tensions of 5,21, or 40 kPa were analyzed with a normal phase HPLC system. During the oxygen treatment, nitrogenase activity was measured as hydrogen evolution in an open flow-through system. When plants were transferred to low oxygen (5 kPa) or high oxygen (40 kPa), nitrogenase activity dropped initially. Activity recovered in both treatments with a rate comparable to the controls (21 kPa O2). Both lipid content and lipid composition of vesicle clusters were affected by the oxygen treatments. With increasing oxygen tension, the vesicle cluster lipid content increased. This correlated with structural data (fluorescence microscopy and TEM) which showed a thicker vesicle envelope at higher oxygen tension. Three hopanoid lipids, bacteriohopanetetrol (bht) and two isomers of phenylacetyl monoester of bht, made up approximately 80% of the vesicle cluster lipids. With changing oxygen concentrations, the ratio of the two bht esters changed whereas the relative proportion of bht remained fairly constant. Therefore, in theFrankia-Alnus incana symbiosis, adaptation to different ambient oxygen tensions occurs at least partly by increasing the thickness of theFrankia vesicle envelope and by changing its lipid composition.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1007/BF01276818

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