Biology of the Frankia-Alnus maritima subsp. maritima symbiosis

Kratsch, Heidi

doi:10.31274/rtd-180813-17298

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“…As we have documented hypoxia in the soils of this obligate wetland shrub (Kratsch 2004), we hypothesized that A. maritima ssp. maritima has adapted to low root‐zone O 2 concentrations by way of physiological and structural adjustments within its nodules.…”

Section: Introductionmentioning

confidence: 99%

Oxygen concentration affects nodule anatomy and nitrogenase activity of Alnus maritima

Kratsch

Graves

2005

Plant Cell & Environment

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Alnus maritima is a shrub that associates with N 2 -fixing Frankia in the wetlands in which it is native. Despite low concentrations in waterlogged soils, O 2 is critical to the maintenance of this symbiosis, and Frankia -infected nodules exist on roots of plants in native stands. The objective of the present study was to determine how root-zone O 2 concentration influences N 2 fixation and the anatomy of nodules on A. maritima . Root zones of plants inoculated with soil from native stands were exposed to eight O 2 concentrations. Nitrogenase activity increased with increasing O 2 concentration. Photosynthetic rate, plant dry mass, leaf N content, and nodule fresh mass were maximal in plants maintained with 15-25% O 2 in the root zone. Nodule counts were maximal on roots maintained at 10% and above 25% O 2 , and nodules that developed at £ £ £ £ 2% O 2 were < < < < 2 mm in diameter and single-lobed. Mean total area of air spaces within nodules decreased, and mean area per space increased, with increasing O 2 concentration. Seasonal and O 2 -dependent nodule pigmentation was observed. Our data illustrate that O 2 is critical to the development of functional symbioses, and that nodules of this species, which are submersed in nature, possess mechanisms for responding to their low-O 2 environment.

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Section: Introductionmentioning

confidence: 99%