Root nodule

root nodulesnodulesroot nodulatingnodulationnodulateroot nodulationnitrogen-fixing nodulesnod'' genesnoduleroot hair curling
Root nodules are found on the roots of plants, primarily legumes, that form a symbiosis with nitrogen-fixing bacteria.wikipedia
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Rhizobia

rhizobiumrhizobial bacterianitrogen-fixing bacteria
Under nitrogen-limiting conditions, capable plants form a symbiotic relationship with a host-specific strain of bacteria known as rhizobia.
Rhizobia are diazotrophic bacteria that fix nitrogen after becoming established inside the root nodules of legumes (Fabaceae).

Symbiosis

symbioticsymbiontsymbionts
Root nodules are found on the roots of plants, primarily legumes, that form a symbiosis with nitrogen-fixing bacteria.
Examples include diverse microbiomes, rhizobia, nitrogen-fixing bacteria that live in root nodules on legume roots; actinomycete, nitrogen-fixing bacteria such as Frankia, which live in alder root nodules; single-celled algae inside reef-building corals; and bacterial endosymbionts that provide essential nutrients to about 10%–15% of insects.

Legume

pulseslegumesleguminous
Root nodules are found on the roots of plants, primarily legumes, that form a symbiosis with nitrogen-fixing bacteria. Legume crops include beans, peas, and soybeans. Plants that contribute to nitrogen fixation include the legume family – Fabaceae – with taxa such as kudzu, clovers, soybeans, alfalfa, lupines, peanuts, and rooibos.
Legumes are notable in that most of them have symbiotic nitrogen-fixing bacteria in structures called root nodules.

Soybean

soysoybeansGlycine max
Legume crops include beans, peas, and soybeans. Plants that contribute to nitrogen fixation include the legume family – Fabaceae – with taxa such as kudzu, clovers, soybeans, alfalfa, lupines, peanuts, and rooibos.
If rhizobia are present, root nodulation begins by the time the third node appears.

Peanut

groundnutArachis hypogaeagroundnuts
Plants that contribute to nitrogen fixation include the legume family – Fabaceae – with taxa such as kudzu, clovers, soybeans, alfalfa, lupines, peanuts, and rooibos.
Like most other legumes, peanuts harbor symbiotic nitrogen-fixing bacteria in root nodules.

Lupinus

lupinlupinelupins
Plants that contribute to nitrogen fixation include the legume family – Fabaceae – with taxa such as kudzu, clovers, soybeans, alfalfa, lupines, peanuts, and rooibos.
Like other legumes, they can fix nitrogen from the atmosphere into ammonia via a rhizobium–root nodule symbiosis, fertilizing the soil for other plants.

Fabaceae

Leguminosaelegume familylegume
Plants that contribute to nitrogen fixation include the legume family – Fabaceae – with taxa such as kudzu, clovers, soybeans, alfalfa, lupines, peanuts, and rooibos.
Many Fabaceae host bacteria in their roots within structures called root nodules.

Green manure

green fertilizergrass culturesgreen compost
In many traditional and organic farming practices, fields are rotated through various types of crops, which usually includes one consisting mainly or entirely of clover or buckwheat (non-legume family Polygonaceae), which are often referred to as "green manure".
* Leguminous green manures such as clover and vetch contain nitrogen-fixing symbiotic bacteria in root nodules that fix atmospheric nitrogen in a form that plants can use.

Root

adventitious rootsrootsroot system
Root nodules are found on the roots of plants, primarily legumes, that form a symbiosis with nitrogen-fixing bacteria.
Certain plants, namely Fabaceae, form root nodules in order to associate and form a symbiotic relationship with nitrogen-fixing bacteria called rhizobia.

Nitrogen fixation

nitrogen-fixingfix nitrogennitrogen fixing
Root nodules are found on the roots of plants, primarily legumes, that form a symbiosis with nitrogen-fixing bacteria. From this microcolony, the bacteria enter the developing nodule through the infection thread, which grows through the root hair into the basal part of the epidermis cell, and onwards into the root cortex; they are then surrounded by a plant-derived symbiosome membrane and differentiate into bacteroids that fix nitrogen.
They contain symbiotic rhizobia bacteria within nodules in their root systems, producing nitrogen compounds that help the plant to grow and compete with other plants.

Pea

peasPisum sativumgreen peas
Legume crops include beans, peas, and soybeans.
The weevil larvae feed on the root nodules of pea plants, which are essential to the plants' supply of nitrogen, and thus diminish leaf and stem growth.

Elaeagnaceae

Russian olive family
Frankia nodulates approximately two hundred species in the following orders (families in parentheses): Cucurbitales (Coriariaceae and Datiscaceae), Fagales (Betulaceae, Casuarinaceae, and Myricaceae), Rosales (Rhamnaceae, Elaeagnaceae and Rosaceae).
The Elaeagnaceae often harbor nitrogen-fixing actinomycetes of the genus Frankia in root nodules, making them useful for soil reclamation.

Faboideae

legumePapilionaceaePapilionoideae
The flowers are classically pea-shaped, and root nodulation is very common.

Frankia

FrankiaceaeFrankia sp.Frankia'' sp. Eu11b
Root nodules that occur on non-legume genera like Parasponia in association with Rhizobium bacteria, and those that arise from symbiotic interactions with Actinobacteria Frankia in some plant genera such as Alnus, vary significantly from those formed in the legume-rhizobia symbiosis.
Frankia also initiate the forming of root nodules.

Soil

soilsdirtsoil moisture
When the plant dies, the fixed nitrogen is released, making it available to other plants and this helps to fertilize the soil.
It is estimated that such symbiotic bacteria in the root nodules of legumes add 45 to 250 pounds of nitrogen per acre per year, which may be sufficient for the crop.

Rosaceae

rose familyrosaceousroses
Frankia nodulates approximately two hundred species in the following orders (families in parentheses): Cucurbitales (Coriariaceae and Datiscaceae), Fagales (Betulaceae, Casuarinaceae, and Myricaceae), Rosales (Rhamnaceae, Elaeagnaceae and Rosaceae). For instance, of 122 genera in the Rosaceae, only 4 genera are capable of fixing nitrogen.

Alder

Alnusalder treealder trees
Root nodules that occur on non-legume genera like Parasponia in association with Rhizobium bacteria, and those that arise from symbiotic interactions with Actinobacteria Frankia in some plant genera such as Alnus, vary significantly from those formed in the legume-rhizobia symbiosis.
This bacterium is found in root nodules, which may be as large as a human fist, with many small lobes, and light brown in colour.

Leghemoglobin

leghaemoglobinleghaemoglobins
Legume nodules harbor an iron containing protein called leghaemoglobin, closely related to animal myoglobin, to facilitate the diffusion of oxygen gas used in respiration.
Leghemoglobin (also leghaemoglobin or legoglobin) is an oxygen carrier and hemoprotein found in the nitrogen-fixing root nodules of leguminous plants.

Trevoa

Along with some related plants in the family Rhamnaceae, they fix nitrogen via root nodules which contain Frankia bacteria.

Flavonoid

flavonoidsflavanoidbioflavonoid
Legumes release organic compounds as secondary metabolites called flavonoids from their roots, which attract the rhizobia to them and which also activate nod genes in the bacteria to produce nod factors and intitiate nodule formation.
Rhizobia living in soil are able to sense the flavonoids and this triggers the secretion of Nod factors, which in turn are recognized by the host plant and can lead to root hair deformation and several cellular responses such as ion fluxes and the formation of a root nodule.

Symbiosome

bacteroidsBacteroid
From this microcolony, the bacteria enter the developing nodule through the infection thread, which grows through the root hair into the basal part of the epidermis cell, and onwards into the root cortex; they are then surrounded by a plant-derived symbiosome membrane and differentiate into bacteroids that fix nitrogen.
In 1989 the concept was applied to the similar structure found in the nitrogen-fixing root nodules of certain plants.

Nod factor

Nod factors.Nod signalling factorsnodulation factor
Legumes release organic compounds as secondary metabolites called flavonoids from their roots, which attract the rhizobia to them and which also activate nod genes in the bacteria to produce nod factors and intitiate nodule formation.
Nod factors (nodulation factors or NF), are signaling molecules produced by soil bacteria known as rhizobia during the initiation of nodules on the root of legumes.

Bradyrhizobium

Photorhizobiumnod'' genesP. carboxydohydrogena
Legumes release organic compounds as secondary metabolites called flavonoids from their roots, which attract the rhizobia to them and which also activate nod genes in the bacteria to produce nod factors and intitiate nodule formation.
Nodules are growths on the roots of leguminous plants where the bacteria reside.

Purshia

bitterbrushcliffroseCowania
The roots have root nodules that host the nitrogen-fixing bacterium Frankia.