Alders are trees comprising the genus Alnus in the birch family Betulaceae. The genus comprises about 35 species of monoecious trees and shrubs, a few reaching a large size, distributed throughout the north temperate zone with a few species extending into Central America, as well as the northern and southern Andes.
Rosaceae, the rose family, is a medium-sized family of flowering plants that includes 4,828 known species in 91 genera.
Dryas octopetala, the mountain avens, eightpetal mountain-avens, white dryas or white dryad, is an Arctic–alpine flowering plant in the family Rosaceae. It is a small prostrate evergreen subshrub forming large colonies. The specific epithet octopetala derives from Greek octo 'eight' and petalon 'petal', referring to the eight petals of the flower, an unusual number in the Rosaceae, where five is the normal number. However, flowers with up to 16 petals also occur naturally.
Rhizobia are diazotrophic bacteria that fix nitrogen after becoming established inside the root nodules of legumes (Fabaceae). To express genes for nitrogen fixation, rhizobia require a plant host; they cannot independently fix nitrogen. In general, they are gram negative, motile, non-sporulating rods.
The Casuarinaceae are a family of dicotyledonous flowering plants placed in the order Fagales, consisting of four genera and 91 species of trees and shrubs native to eastern Africa, Australia, Southeast Asia, Malesia, Papuasia, and the Pacific Islands. At one time, all species were placed in the genus Casuarina. Lawrence Alexander Sidney Johnson separated out many of those species and renamed them into the new genera of Gymnostoma in 1980 and 1982, Allocasuarina in 1982, and Ceuthostoma in 1988, with some additional formal descriptions of new species in each other genus. At the time, it was somewhat controversial. The monophyly of these genera was later supported in a 2003 phylogenetic study of the family. In the Wettstein system, this family was the only one placed in the order Verticillatae. Likewise, in the Engler, Cronquist, and Kubitzki systems, the Casuarinaceae were the only family placed in the order Casuarinales.
Diazotrophs are bacteria and archaea that fix gaseous nitrogen in the atmosphere into a more usable form such as ammonia.
Root nodules are found on the roots of plants, primarily legumes, that form a symbiosis with nitrogen-fixing bacteria. Under nitrogen-limiting conditions, capable plants form a symbiotic relationship with a host-specific strain of bacteria known as rhizobia. This process has evolved multiple times within the legumes, as well as in other species found within the Rosid clade. Legume crops include beans, peas, and soybeans.
Frankia is a genus of nitrogen-fixing bacteria that live in symbiosis with actinorhizal plants, similar to the Rhizobium bacteria found in the root nodules of legumes in the family Fabaceae. Frankia also initiate the forming of root nodules.
Purshia is a small genus of 5–8 species of flowering plants in the family Rosaceae which are native to western North America.
Chamaebatia, also known as mountain misery, is a genus of two species of aromatic evergreen shrubs endemic to California. Its English common name derives from early settlers' experience with the plant's dense tangle and sticky, strong-smelling resin. They are actinorhizal, non-legumes capable of nitrogen fixation through symbiosis with the actinobacterium, Frankia.
Actinorhizal plants are a group of angiosperms characterized by their ability to form a symbiosis with the nitrogen fixing actinomycetota Frankia. This association leads to the formation of nitrogen-fixing root nodules.
The subfamily Dryadoideae consists of four genera in the family Rosaceae, all of which contain representative species with root nodules that host the nitrogen-fixing bacterium Frankia. They are subshrubs, shrubs, or small trees with a base chromosome number of 9, whose fruits are either an achene or an aggregate of achenes.
The flavans are benzopyran derivatives that use the 2-phenyl-3,4-dihydro-2H-chromene skeleton. They may be found in plants. These compounds include the flavan-3-ols, flavan-4-ols and flavan-3,4-diols (leucoanthocyanidin).
Frankia alni is a Gram-positive species of actinomycete filamentous bacterium that lives in symbiosis with actinorhizal plants in the genus Alnus. It is a nitrogen-fixing bacterium and forms nodules on the roots of alder trees.
Dryas integrifolia is a species of flowering plant in the rose family known by the common names arctic avens, entireleaf mountain-avens, white mountain-avens, northern white mountain avens, and mountain avens. It is native to northern parts of North America, where it occurs from Alaska across Canada to Greenland. It is a common species of the Arctic and it is probably the most common flowering plant on some of the western Arctic islands.
Rhizomarasmius epidryas is one of a group of mushrooms formerly in the genus Marasmius. It grows amongst dwarf shrubs of the genus Dryas in arctic or high mountain environments.
A symbiosome is a specialised compartment in a host cell that houses an endosymbiont in a symbiotic relationship.
Dryas drummondii is a species of flowering plant in the rose family known by the common names yellow mountain-avens, yellow dryas, or yellow dryad. It is native to Alaska, Canada, and the Northern United States. This species is actinorhizal, able to live in symbiosis with nitrogen-fixing bacteria.
