Dryadoideae
Encyclopedia
The Dryadoideae subfamily of the Rosaceae
consists of four genera, all of which share root nodule
s that host the nitrogen-fixing
bacterium Frankia
. They are sub-shrubs, shrubs, or small trees with a base chromosome number of 9, whose fruits are either an achene
or an aggregate
of achenes.
Rosaceae
Rosaceae are a medium-sized family of flowering plants, including about 2830 species in 95 genera. The name is derived from the type genus Rosa. Among the largest genera are Alchemilla , Sorbus , Crataegus , Cotoneaster , and Rubus...
consists of four genera, all of which share root nodule
Root nodule
Root nodules occur on the roots of plants that associate with symbiotic nitrogen-fixing bacteria. Under nitrogen-limiting conditions, capable plants form a symbiotic relationship with a host-specific strain of bacteria known as rhizobia...
s that host the nitrogen-fixing
Nitrogen fixation
Nitrogen fixation is the natural process, either biological or abiotic, by which nitrogen in the atmosphere is converted into ammonia . This process is essential for life because fixed nitrogen is required to biosynthesize the basic building blocks of life, e.g., nucleotides for DNA and RNA and...
bacterium Frankia
Frankia
Frankia is a genus of nitrogen fixing, filamentous bacteria that live in symbiosis with actinorhizal plants, similar to the Rhizobia bacteria that are found in the root nodules of legumes in the Fabaceae family. Bacteria of this genus also form root nodules.The genus Frankia was originally named by...
. They are sub-shrubs, shrubs, or small trees with a base chromosome number of 9, whose fruits are either an achene
Achene
An achene is a type of simple dry fruit produced by many species of flowering plants. Achenes are monocarpellate and indehiscent...
or an aggregate
Compound fruit
A compound fruit is one that develops from several ovaries in either a single flower or multiple flowers. In contrast, a simple fruit develops from one ovary.image:Longitudinal section of raspberry flower.gif...
of achenes.