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The plant produces fruits in the form of hairy legumes each with one seed inside. The flower and leafing pattern is similar to Amorpha fruticosa , however, A. canescens typically only grows to be 1 meter (3 ft 3 in) high and prefers drier habitats whereas A. fruticosa can grow to be 5 or 6 meters (16 or 20 ft) high and lives in wetter areas.
The nitrogen-fixing clade consists of four orders of flowering plants: Cucurbitales, Fabales, Fagales and Rosales. [a] This subgroup of the rosids encompasses 28 families of trees, shrubs, vines and herbaceous perennials and annuals. The roots of many of the species host bacteria that fix nitrogen into compounds the plants can use. [4] [5]
[7] Parasponia, a tropical genus in the Cannabaceae is also able to interact with rhizobia and form nitrogen-fixing nodules. As related plants are actinorhizal, it is believed that the plant "switched partner" in its evolution. [8] The ability to fix nitrogen is far from universally present in these families.
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. Actinorhizal plants are distributed within three clades, [1] and are characterized by nitrogen fixation. [2]
The rosids are members of a large clade (monophyletic group) of flowering plants, containing about 70,000 species, [2] more than a quarter of all angiosperms. [3] The clade is divided into 16 to 20 orders, depending upon circumscription and classification. These orders, in turn, together comprise about 140 families. [4]
Rhizobia are diazotrophic bacteria that fix nitrogen after becoming established inside the root nodules of legumes . To express genes for nitrogen fixation, rhizobia require a plant host; they cannot independently fix nitrogen. [1] In general, they are gram negative, motile, non-sporulating rods.
Plants cannot use atmospheric nitrogen; they must use a combined or fixed form of the element. After photosynthesis, nitrogen fixation (or uptake) is the most important process for the growth and development of plants. [12] The levels of ureide nitrogen in a plant correlate with the amount of fixed nitrogen the plant takes up. [13]
The Azolla plant undergoes photosynthesis and provides fixed carbon for the Anabaena to use as an energy source for dinitrogenases in the heterocyst cells. [8] In return, the heterocysts are able to provide the vegetative cells and the Azolla plant with fixed nitrogen in the form of ammonia which supports growth of both organisms.