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Explora: Environment
and Resource Anabaena-Azolla for crops and bioenergy

by the enzyme dinitrogenase. Azolla receives the released with the aid of nitrogenase. Later, the nitrogen is
NH from A. azollae. This NH is an essential source of assimilated into plants by amino acids.
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fixed nitrogen for Azolla development and survival. The
nitrogen provided by A. azollae helps the plant become less 5.6.2. Frankia symbiosis
reliant on outside nitrogen sources, including synthetic Certain non-leguminous plant families have modified
fertilizers. A. azollae provides Azolla with a sustainable and lateral roots containing a central vascular system and a
natural source of nitrogen, which is especially beneficial peripheral cortex, which are infected by an actinomycetes
in agricultural systems where Azolla is produced as a called Frankia. This bacterium is associated with a variety
green manure or cover crop to increase soil fertility and of woody, non-legume plants belonging to the families
reduce the need for synthetic nitrogen fertilizers. This Betualceae, Rosaceae, Myricaceae, and Casuarinaceae, etc. 60
rare symbiotic interaction between A. azollae and Azolla
exemplifies the usefulness of symbiotic partnerships that 6. Biofertilizers – a replacement for
fix nitrogen. synthetic fertilizers

5.6. Nitrogen fixation in other symbiotic microbes To achieve maximum yield productivity, chemical
5.6.1. Leguminous plants and Rhizobium species fertilizers are commonly used for rapid growth. While
they can help achieve an immediate increase in yield, they
Prokaryotes are the only organisms capable of performing may later impose negative impacts on the surrounding
biological nitrogen fixation, but plants can live in a environment. To address this problem caused by chemical
mutualistic symbiosis with nitrogen-fixing bacteria fertilizers, a sustainable and environmentally friendly
and, hence, utilize the fixed form of nitrogen. This approach is needed. This has led to the use of biofertilizers,
type of symbiosis takes place in the leguminous plants, which are eco-friendly in nature. 61
specifically within the Fabaceae family. Rhizobia are a
group of bacteria that form specialized structures called The term “biofertilizer” refers to mixtures of living
nodules in leguminous plants. Some species of Rhizobium organisms, primarily microorganisms, that increase
found in the nodules of host plants include Rhizobium nutrient availability through biological activity and
leguminosarum, Rhizobium phaseoli, Rhizobium promote plant growth. These can include active or dormant
trifoli, and Rhizobium meliloti. Figure 3 indicates the microbial cells from effective strains that interact with
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process of nitrogen fixation in leguminous plants. After plants in the rhizosphere to enhance plant nutrient uptake.
photosynthesis, the energy source is provided, and in Common microorganisms used as biofertilizers include
the presence of electron sources such as ferredoxin and nitrogen fixers, plant growth-promoting rhizobacteria,
flavodoxin, the dinitrogen is converted into ammonia phosphate solubilizers, etc. Notable organisms include

Figure 3. Schematic representation of nitrogen fixation in the root nodules of leguminous plants, highlighting the role of nitrogenase and the sequential
reduction of dinitrogen to ammonia
Abbreviations: ADP: Adenosine diphosphate; ATP: Adenosine triphosphate; Fd: Ferredoxin; Fe: Dinitrogenase reductase; Fe-Mo: Dinitrogenase; Fld:
Flavodoxin; Mg: Magnesium; NH: Nihonium; NH : Amine group; NH : Ammonia; N : Atmospheric nitrogen.
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Volume 2 Issue 2 (2025) 6 doi: 10.36922/eer.7975