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Plants in the local flora with nitrogen-fixing symbionts

Symbiotic Nitrogen Fixation & Legume Nodule Formation

Ferns  

Azollaceae,  Azolla filiculoides (other hydrophytes are known to have extra-cellular symbionts, bacteria and archaea). Azolla hosts the cyanobacterium Anabaena azollae.

Angiosperms 

Eudicots – Superrosids

            Order Fabales – Fabaceae (most).  Rhizobium bacteria

            Order Cucurbitales – Datiscaceae,  Datisca glomerata.  Frankia bacteria

            Order Fagales – Betulaceae,  Alnus rhombifolia.  Frankia bacteria

            Order Rosales – Rosaceae,  Cercocarpus betuloides var. betuloides.   Frankia bacteria
                                    – Rhamnaceae,  Ceanothus cuneatus var. cuneatus, Ceanothus oliganthus var. sorediatus.   Frankia bacteria

Associative Nitrogen Fixation

Some grasses such including Digitaria spp. are known to have an Azospirillum association. We have no information on this grass/bacterial relationship at Jasper Ridge.

"Azospirillum are able to form close associations with several members of the Poaceae (grasses), including agronomically important cereal crops, such as rice, wheat, corn, oats, and barley. These bacteria fix appreciable amounts of nitrogen within the rhizosphere of the host plants. Efficiencies of 52 mg N2 g-1 malate have been reported (Stephan et al. 1979). The level of nitrogen fixation is determined by several factors, including soil temperature (Azospirillum species thrive in more temperate and/or tropical environments), the ability of the host plant to provide a rhizosphere environment low in oxygen pressure, the availability of host photosynthates for the bacteria, the competitiveness of the bacteria, and the efficiency of nitrogenase (Vlassak & Reynders, 1979)" -- Biological Nitrogen Fixation (www.nature.com)

References