Promotion of Nitrogen Assimilation by Plant Growth-Promoting Rhizobacteria

*Gabriel Monteiro, Glauco Nogueira, Cândido Neto, Vitor Nascimento and Joze Freitas*

#### **Abstract**

Nitrogen fertilizers are one of the highest expenses in agricultural systems and usually a limitation to the productions of many agricultural crops worldwide. The intensive use of this element in modern agriculture represents a potential environmental threat, one of the many tools for the sustainable use of this resource without losing productivity is the use of plant growth-promoting rhizobacteria, especially nitrogen-fixing bacteria. However, in considering the competitiveness of the market, studies are still needed to determine the most efficient way to use this resource and if the nitrogen mineral fertilization is indeed substitutable. As a result, this study aims to deepen the scientific knowledge of the plant-microbe interactions by addressing their main characteristics and functionalities for plant growth and development and efficiency in the use of nitrogen. For this we reviewed relevant information from scientific works that address these issues.

**Keywords:** biochemistry, nitrogen-fixation, growth, nitrogen fertilizers, nitrogen use efficiency

#### **1. Introduction**

Nitrogen (N) is a key component of most proteins, secondary metabolites and signaling molecules [1]. It is one of the most important macronutrients for plant development and usually one of the most limiting factor to plant production [2].

The use of N-fertilizers has produced a significant increase in food production in recent decades [3], and its consumption has grown from 11.3 Tg N year−1 in 1961 to 107.6 Tg N year−1 in 2013 [4]. However, less than 50% of the added N is effectively absorbed by most cultivated plants [5, 6], and even N effectively converted to biomass, eventually returns to the environment [7]. In the soil, N is available to plants in the form of nitrate (NO3 − ), ammonium (NH4 + ) and organic compounds (usually amino acids), being the NO3, the most abundant [8]. In its ionic form, NO3 − has a negative charge and high water solubility, being susceptible to leaching and runoff [9]. It can also be volatilized by denitrifying microorganisms [10], and lost to the atmosphere in the form of nitrous oxide (N2O, a greenhouse gas 296-fold more potent than a unit of CO2). Leaching of N causes eutrophication of water bodies and contamination of groundwater [11].

N can also be lost to the atmosphere in other forms such as reactive gases (NOx; NH3), aggravating the greenhouse effect [12], and is also related to the acidification of soils through the formation of acid rain, and depletion of exchangeable basic soil cations [13].

To minimize the loss of N in the soil, and consequently the total amount of N necessary for a high-quality production, several strategies have been used. One is the use of urease inhibitors such as N-(n-butyl)-thiophosphoric triamide (NBPT) to delay the hydrolysis of urea, thus reducing losses to the atmosphere and microbial transformations [14]. Increased N use efficiency (NUE) has also been the subject of research, through the selection of genotypes with a higher NUE [15] or through biological nitrogen fixation [16]. Biological nitrogen fixation (BNF) occurs through the conversion of atmospheric N2 to ammonium by free-living or symbiotic diazotrophic bacteria [17]. Plant growth-promoting rhizobacteria (PGPR) can increase the N absorption capacity through BNF [18], phytohormone production [19], stimulate the production and enzymatic assimilation of NH4+ [16], as well as the transport and partition of N [20].

The study of plant nutrition related to the use of BNF as an alternative to increase efficiency and sustainability in the use of N in agriculture is essential, given the complex nature of the interactions between soil, plant, and microorganisms. Therefore, the objective of this review is to deepen the scientific knowledge of these interactions, addressing their main characteristics and functionalities for plant growth and development.

#### **2. Mechanisms of biological nitrogen fixation**

One of the largest N reservoirs is the atmosphere, second only to the lithosphere in absolute amount of N [21]. N makes up about 78% of the atmosphere [22] and is mainly in the form of molecular N (N2). The atoms in the N2 molecule have low-energy orbitals and the bond between the two N molecules is relatively short (1,098 Å) and stable, with a bonding energy of 930 kJ/mol [23]. This set of characteristics gives low reaction potential to the molecule. Alternatively, N2 can be reduced to NH3 naturally by microorganisms through the BNF process. The BNF reaction follows the following stoichiometry:

The BNF process is catalyzed exclusively by an enzyme complex called the nitrogenase complex. The nitrogenase complex is composed of dinitrogenase reductase (Iron-protein) and dinitrogenase (Molybdenum-Iron-protein) (**Figure 1a**). Dinitrogenase-reductase is a dimer of approximately 60 kDa, composed of two identical and symmetrical subunits, which coordinate a redox center 4Fe-4S (**Figure 2**). This enzyme also has sites for the binding of ATP/ADP, one in each subunit, being able to couple the hydrolysis of ATP to fuel the transfer of electrons to the dinitrogenase [26]. Dinitrogenase is a heterotetramer α2β2 with approximately 240 kDa.

Dinitrogenase has two cofactors containing iron (**Figure 1b**), being the group P and the FeMo cofactor [27]. Group P contains a pair of 4Fe-4S centers, which share a sulfur, forming an 8Fe-7S center. The FeMo cofactor is a variation of the iron– sulfur groups, such as the P group, but differs greatly from the other metallic sites within this family. Its structure is composed of [Mo: 7Fe: 9S: C]: Homocitrate [26, 28]. Some microorganisms also have alternative forms of the MoFe cofactor, where Molybdenum (Mo) is replaced by atoms of Vanadium (V) or Iron (Fe) depending on metal availability [29].

In the N2 reduction reaction (Eq. 1), the reduced dinitrogenase reductase couples the hydrolysis of ATP with the transfer of electrons to the dinitrogenase. The oxidized dinitrogenase reductase detaches from the dinitrogenase, only to be reduced again (by ferredoxins or flavodoxins). Again, there is the coupling between

**177**

the case of BNF, is N2 [30].

**Figure 1.**

**Figure 2.**

*Promotion of Nitrogen Assimilation by Plant Growth-Promoting Rhizobacteria*

both enzymes followed by the consumption of ATP to transfer the electrons to the dinitrogenase. This coupling-detaching cycle followed by the electron transfer is repeated until the dinitrogenase is reduced enough to reduce its substrate, which in

*Structure of 4Fe-4S clusters present in nitrogenase complex. (a) The 4Fe-4S binding site between the Dinitrogenase-reductase and Dinitrogenase contains a cubane-like structure where four iron ions and four sulfide ions are placed at the vertices. The Fe centers are typically coordinated by cysteine residuals. Source: [25].*

*Enzymes and cofactors of the nitrogenase complex. (a) The enzyme consists of two symmetrical dinitrogenase reductase molecules (in green), each with a 4Fe-4S redox center and binding sites for ATP, and two identical dinitrogenase heterodimers (in purple and blue), each one with a P group and a FeMo cofactor. (b) The cofactors for the electron transfer. A group P is shown here in its reduced (upper part) and oxidized (middle)* 

*and the cofactor FeMo is showed at the bottom. Source: Taiz et al. [24].*

O2 concentration is expressed by rhizobia-leguminous symbiosis.

**3. Brazil: a success of BNF in legumes**

Because it deals with large amounts of energy, enough to break the triple bond of the N2 molecule, the nitrogenase complex is not only inactivated by the presence of oxygen (O2) but can have its expression reduced [31]. However, diazotrophic bacteria are able to combine N fixation with their aerobic metabolism in different ways to avoid O2 deactivation [32]. Notably, one of the most advanced means of controlling

Brazil is one of the best examples in the efficient research and use of the BNF in legumes [33]. The use of FBN is interesting from both an economic and an environmental point of view, since once this process is established, nitrogen fertilizers can

*DOI: http://dx.doi.org/10.5772/intechopen.96634*

*Promotion of Nitrogen Assimilation by Plant Growth-Promoting Rhizobacteria DOI: http://dx.doi.org/10.5772/intechopen.96634*

#### **Figure 1.**

*Nitrogen in Agriculture - Physiological, Agricultural and Ecological Aspects*

cations [13].

plant growth and development.

**2. Mechanisms of biological nitrogen fixation**

reaction follows the following stoichiometry:

N can also be lost to the atmosphere in other forms such as reactive gases (NOx; NH3), aggravating the greenhouse effect [12], and is also related to the acidification of soils through the formation of acid rain, and depletion of exchangeable basic soil

To minimize the loss of N in the soil, and consequently the total amount of N necessary for a high-quality production, several strategies have been used. One is the use of urease inhibitors such as N-(n-butyl)-thiophosphoric triamide (NBPT) to delay the hydrolysis of urea, thus reducing losses to the atmosphere and microbial transformations [14]. Increased N use efficiency (NUE) has also been the subject of research, through the selection of genotypes with a higher NUE [15] or through biological nitrogen fixation [16]. Biological nitrogen fixation (BNF) occurs through the conversion of atmospheric N2 to ammonium by free-living or symbiotic diazotrophic bacteria [17]. Plant growth-promoting rhizobacteria (PGPR) can increase the N absorption capacity through BNF [18], phytohormone production [19], stimulate the production and enzymatic assimilation of NH4+ [16], as well as the transport and partition of N [20]. The study of plant nutrition related to the use of BNF as an alternative to increase efficiency and sustainability in the use of N in agriculture is essential, given the complex nature of the interactions between soil, plant, and microorganisms. Therefore, the objective of this review is to deepen the scientific knowledge of these interactions, addressing their main characteristics and functionalities for

One of the largest N reservoirs is the atmosphere, second only to the lithosphere in absolute amount of N [21]. N makes up about 78% of the atmosphere [22] and is mainly in the form of molecular N (N2). The atoms in the N2 molecule have low-energy orbitals and the bond between the two N molecules is relatively short (1,098 Å) and stable, with a bonding energy of 930 kJ/mol [23]. This set of characteristics gives low reaction potential to the molecule. Alternatively, N2 can be reduced to NH3 naturally by microorganisms through the BNF process. The BNF

The BNF process is catalyzed exclusively by an enzyme complex called the nitrogenase complex. The nitrogenase complex is composed of dinitrogenase reductase (Iron-protein) and dinitrogenase (Molybdenum-Iron-protein) (**Figure 1a**). Dinitrogenase-reductase is a dimer of approximately 60 kDa, composed of two identical and symmetrical subunits, which coordinate a redox center 4Fe-4S (**Figure 2**). This enzyme also has sites for the binding of ATP/ADP, one in each subunit, being able to couple the hydrolysis of ATP to fuel the transfer of electrons to the dinitrogenase

Dinitrogenase has two cofactors containing iron (**Figure 1b**), being the group P and the FeMo cofactor [27]. Group P contains a pair of 4Fe-4S centers, which share a sulfur, forming an 8Fe-7S center. The FeMo cofactor is a variation of the iron– sulfur groups, such as the P group, but differs greatly from the other metallic sites within this family. Its structure is composed of [Mo: 7Fe: 9S: C]: Homocitrate [26, 28]. Some microorganisms also have alternative forms of the MoFe cofactor, where Molybdenum (Mo) is replaced by atoms of Vanadium (V) or Iron (Fe) depending

In the N2 reduction reaction (Eq. 1), the reduced dinitrogenase reductase couples the hydrolysis of ATP with the transfer of electrons to the dinitrogenase. The oxidized dinitrogenase reductase detaches from the dinitrogenase, only to be reduced again (by ferredoxins or flavodoxins). Again, there is the coupling between

[26]. Dinitrogenase is a heterotetramer α2β2 with approximately 240 kDa.

**176**

on metal availability [29].

*Enzymes and cofactors of the nitrogenase complex. (a) The enzyme consists of two symmetrical dinitrogenase reductase molecules (in green), each with a 4Fe-4S redox center and binding sites for ATP, and two identical dinitrogenase heterodimers (in purple and blue), each one with a P group and a FeMo cofactor. (b) The cofactors for the electron transfer. A group P is shown here in its reduced (upper part) and oxidized (middle) and the cofactor FeMo is showed at the bottom. Source: Taiz et al. [24].*

#### **Figure 2.**

*Structure of 4Fe-4S clusters present in nitrogenase complex. (a) The 4Fe-4S binding site between the Dinitrogenase-reductase and Dinitrogenase contains a cubane-like structure where four iron ions and four sulfide ions are placed at the vertices. The Fe centers are typically coordinated by cysteine residuals. Source: [25].*

both enzymes followed by the consumption of ATP to transfer the electrons to the dinitrogenase. This coupling-detaching cycle followed by the electron transfer is repeated until the dinitrogenase is reduced enough to reduce its substrate, which in the case of BNF, is N2 [30].

Because it deals with large amounts of energy, enough to break the triple bond of the N2 molecule, the nitrogenase complex is not only inactivated by the presence of oxygen (O2) but can have its expression reduced [31]. However, diazotrophic bacteria are able to combine N fixation with their aerobic metabolism in different ways to avoid O2 deactivation [32]. Notably, one of the most advanced means of controlling O2 concentration is expressed by rhizobia-leguminous symbiosis.

#### **3. Brazil: a success of BNF in legumes**

Brazil is one of the best examples in the efficient research and use of the BNF in legumes [33]. The use of FBN is interesting from both an economic and an environmental point of view, since once this process is established, nitrogen fertilizers can

be dispensed with in whole or in part, thus contributing to enable reforestation and minimize possible environmental impacts resulting of use these supplies [34]. It is estimated an annual economy of more than US\$ 13 billion with the total or partial substitution of nitrogen fertilizers in legumes in Brazil [33].

Rhizobium-leguminous symbiosis is the most important symbiotic system between microorganisms and plants thanks to the efficiency of the N2 fixation process, and one of the justifications is in the amplitude and geographical distribution of the hosts and the economic impact it causes in agriculture, and one of the main sources of N for the biosphere [35]. The leguminosae family comprises almost 20 thousand species, including tree, herbaceous species used as fodder, producers of raw materials or directly in human food [36].

The most successful case here in Brazil according to Hungria et al. [18], is the symbiosis of Bradyrhizobium spp. with soybean (*Glycine max* (L.) Merrill). The main leguminous species produced in Brazil does not require nitrogen-based fertilization, due to the biological nitrogen fixation which supplies the required N for crop development. To get a sense of how important this symbiotic relationship is in Brazil, in the 2018/2019 harvest, over 35 million hectares were sown. According to the National Supply Company [37], soybean production for this same harvest was 115 million tons, resulting in an average productivity of 3,208 kg ha−1, with almost zero N-fertilizer input. On the other hand, the biological nitrogen fixation with other important legumes, such as beans and peanuts, and non-legumes like sugarcane cannot fully supply the demand for N like in soybeans.

Alfalfa is another plant species with a high potential for biological nitrogen fixation. As a legume, alfalfa is capable of symbiotically associating with rhizobial bacteria, with N inputs to reaching up to 470 kg of N ha-1 [38]. The main symbiotic alfalfa bacteria belong to the genus Ensifer, having Synorhizobium as a synonym, but previously classified as Rhizobium. Sinorhizobium meliloti and Sinorhizobium mediace are the main symbionts reported in several countries [39]. In Brazil, there are three strains of rhizobia that are used in commercial inoculants for alfalfa, which have been validated for more than two decades and with rare tests conducted with the same [39].

#### **4. Growth promotion by associative and free-living diazotrophic bacteria and stimulating N metabolism**

World production is dominated by the production of four grasses (FAO Stats 2019), namely: Sugarcane (*Saccharum officinarum* L. 1.95 Gt year-1), Maize (*Zea mays* L. 1.15 Gt year-1), Wheat (*Triticum aestivum* L. 0.76 Gt year-1) and Rice (*Oryza sativa* L. 0.75 Gt year-1). Scientific studies have shown that biological nitrogen fixation is not limited only to legumes, with a potentially important group of diazotrophic bacteria capable of forming associations through root colonization and the internal tissues of grasses [40]. These bacterial-grass associations also have different mechanisms of action than legumes, and in addition to fixing N, increase the absorption and assimilation of N by modulating the architecture and development of the root system through the production of phytohormones, such as indole-3-acetic acid [41] and gibberellins [42]. Cases such as diazotrophic bacteria such as those of the genus Azospirillum sp., Herbaspirillum sp. and Glucanobacter sp. are evidence of the influence of PGPR on N metabolism, inducing physiological and morphological changes that are associated with greater NUE.

Grasses are of great interest for the development of biological nitrogen fixation aiming at greater efficiency, in view of its relatively low NUE [43, 44]. The increase

**179**

*Promotion of Nitrogen Assimilation by Plant Growth-Promoting Rhizobacteria*

the accessions according to different concentrations of NO3

the N metabolism, resulting in an increase in growth [16].

bacteria a potential solution for increasing NUE.

the worsening of the greenhouse effect.

sustainable agricultural practice.

**Acknowledgements**

University of Amazonia.

**5. Conclusions**

in NUE is related to several characteristics, Iqbal et al., (2020) working with different cotton genotypes analyzed the biochemical and morphological responses of

ture and efficiency of the enzymes of the assimilation of N were essential for the increase in traction related to NUE. The inoculation of diazotrophic bacteria seems to achieve the same results in different cultures of importance to the global market such as sugarcane (*Saccharum officinarum* L.), corn (*Zea mays* L.), wheat (*Triticum aestivum* L.,) and rice (*Oryza sativa* L.). In sugarcane, the effects vary from the increase in the speed of bud sprouting and the emission of roots in sugarcane stalks used for planting [45], increases in the biomass production of the thatch [46], until the increase in the number of tillers [47]. In maize, inoculation with Azospirillum brasilense increased the transcription of the genes encoding Nitrate reductase (ZmNR), Glutamina sintase (ZmGln1–3), and the intensity of assimilation of the N [48, 49]. In wheat, the inoculation of Azospirillum brasilense was able to modify

Modulation of root architecture induced by PGPR is also a morphological trait

*Nitrogenase N H e ATP NH H ADP Pi* <sup>2</sup> + ++ 8 8 + − →2 3 2 ++ + 16 16 (1)

Since the discovery of the Haber-bosch process in the early 20th century, the levels of N added to the biosphere continue to increase each year and its excessive

Therefore, biological nitrogen fixation process is an essential tool in the current economic, agricultural, and environmental context of many countries, this can be seen through studies and government data that show a reduction in financial expenses in the order of millions, this technological tool. it is a reality in vegetable crops with high potentials in the agricultural network of emerging powers worldwide, in addition to contributing to the reduction of potentially harmful agents for

This technology has been extensively scientifically explored, aiming to expand its possibility in other promising cultures in the agricultural and forestry world, as well as other associative and free-living diazotrophic microorganisms, and their ability to promote plant growth. However, there are still major gaps in knowledge about the diversity and mechanisms of PGPR action and further research is needed to establish the use of these new bacteria as a

To Laboratory of Biodiversity Studies of Upper Plants in Federal Rural

use of this element is a source of numerous environmental problems.

essential to the increase in NUE. The increase in the area explored by the root triggered by the increase in the volume of the roots caused by these bacteria directly influences the interception of nutrients, among them the N. Besides the influence on the morphological characteristics, the PGPR inoculation has an impact on the metabolism activity of the N. The increase in these characteristics makes these

−

and the root architec-

*DOI: http://dx.doi.org/10.5772/intechopen.96634*

*Promotion of Nitrogen Assimilation by Plant Growth-Promoting Rhizobacteria DOI: http://dx.doi.org/10.5772/intechopen.96634*

in NUE is related to several characteristics, Iqbal et al., (2020) working with different cotton genotypes analyzed the biochemical and morphological responses of the accessions according to different concentrations of NO3 − and the root architecture and efficiency of the enzymes of the assimilation of N were essential for the increase in traction related to NUE. The inoculation of diazotrophic bacteria seems to achieve the same results in different cultures of importance to the global market such as sugarcane (*Saccharum officinarum* L.), corn (*Zea mays* L.), wheat (*Triticum aestivum* L.,) and rice (*Oryza sativa* L.). In sugarcane, the effects vary from the increase in the speed of bud sprouting and the emission of roots in sugarcane stalks used for planting [45], increases in the biomass production of the thatch [46], until the increase in the number of tillers [47]. In maize, inoculation with Azospirillum brasilense increased the transcription of the genes encoding Nitrate reductase (ZmNR), Glutamina sintase (ZmGln1–3), and the intensity of assimilation of the N [48, 49]. In wheat, the inoculation of Azospirillum brasilense was able to modify the N metabolism, resulting in an increase in growth [16].

Modulation of root architecture induced by PGPR is also a morphological trait essential to the increase in NUE. The increase in the area explored by the root triggered by the increase in the volume of the roots caused by these bacteria directly influences the interception of nutrients, among them the N. Besides the influence on the morphological characteristics, the PGPR inoculation has an impact on the metabolism activity of the N. The increase in these characteristics makes these bacteria a potential solution for increasing NUE.

$$2N\_2 + 8H^+ + 8e^- + ATP \xrightarrow{N \text{trigonue}} 2NH\_3 + H\_2 + 16ADP + 16Pi \tag{1}$$

#### **5. Conclusions**

*Nitrogen in Agriculture - Physiological, Agricultural and Ecological Aspects*

substitution of nitrogen fertilizers in legumes in Brazil [33].

cane cannot fully supply the demand for N like in soybeans.

**bacteria and stimulating N metabolism**

morphological changes that are associated with greater NUE.

of raw materials or directly in human food [36].

be dispensed with in whole or in part, thus contributing to enable reforestation and minimize possible environmental impacts resulting of use these supplies [34]. It is estimated an annual economy of more than US\$ 13 billion with the total or partial

Rhizobium-leguminous symbiosis is the most important symbiotic system between microorganisms and plants thanks to the efficiency of the N2 fixation process, and one of the justifications is in the amplitude and geographical distribution of the hosts and the economic impact it causes in agriculture, and one of the main sources of N for the biosphere [35]. The leguminosae family comprises almost 20 thousand species, including tree, herbaceous species used as fodder, producers

The most successful case here in Brazil according to Hungria et al. [18], is the symbiosis of Bradyrhizobium spp. with soybean (*Glycine max* (L.) Merrill). The main leguminous species produced in Brazil does not require nitrogen-based fertilization, due to the biological nitrogen fixation which supplies the required N for crop development. To get a sense of how important this symbiotic relationship is in Brazil, in the 2018/2019 harvest, over 35 million hectares were sown. According to the National Supply Company [37], soybean production for this same harvest was 115 million tons, resulting in an average productivity of 3,208 kg ha−1, with almost zero N-fertilizer input. On the other hand, the biological nitrogen fixation with other important legumes, such as beans and peanuts, and non-legumes like sugar-

Alfalfa is another plant species with a high potential for biological nitrogen fixation. As a legume, alfalfa is capable of symbiotically associating with rhizobial bacteria, with N inputs to reaching up to 470 kg of N ha-1 [38]. The main symbiotic alfalfa bacteria belong to the genus Ensifer, having Synorhizobium as a synonym, but previously classified as Rhizobium. Sinorhizobium meliloti and Sinorhizobium mediace are the main symbionts reported in several countries [39]. In Brazil, there are three strains of rhizobia that are used in commercial inoculants for alfalfa, which have been validated for more than two decades and with rare tests conducted

**4. Growth promotion by associative and free-living diazotrophic** 

World production is dominated by the production of four grasses (FAO Stats 2019), namely: Sugarcane (*Saccharum officinarum* L. 1.95 Gt year-1), Maize (*Zea mays* L. 1.15 Gt year-1), Wheat (*Triticum aestivum* L. 0.76 Gt year-1) and Rice (*Oryza sativa* L. 0.75 Gt year-1). Scientific studies have shown that biological nitrogen fixation is not limited only to legumes, with a potentially important group of diazotrophic bacteria capable of forming associations through root colonization and the internal tissues of grasses [40]. These bacterial-grass associations also have different mechanisms of action than legumes, and in addition to fixing N, increase the absorption and assimilation of N by modulating the architecture and development of the root system through the production of phytohormones, such as indole-3-acetic acid [41] and gibberellins [42]. Cases such as diazotrophic bacteria such as those of the genus Azospirillum sp., Herbaspirillum sp. and Glucanobacter sp. are evidence of the influence of PGPR on N metabolism, inducing physiological and

Grasses are of great interest for the development of biological nitrogen fixation aiming at greater efficiency, in view of its relatively low NUE [43, 44]. The increase

**178**

with the same [39].

Since the discovery of the Haber-bosch process in the early 20th century, the levels of N added to the biosphere continue to increase each year and its excessive use of this element is a source of numerous environmental problems.

Therefore, biological nitrogen fixation process is an essential tool in the current economic, agricultural, and environmental context of many countries, this can be seen through studies and government data that show a reduction in financial expenses in the order of millions, this technological tool. it is a reality in vegetable crops with high potentials in the agricultural network of emerging powers worldwide, in addition to contributing to the reduction of potentially harmful agents for the worsening of the greenhouse effect.

This technology has been extensively scientifically explored, aiming to expand its possibility in other promising cultures in the agricultural and forestry world, as well as other associative and free-living diazotrophic microorganisms, and their ability to promote plant growth. However, there are still major gaps in knowledge about the diversity and mechanisms of PGPR action and further research is needed to establish the use of these new bacteria as a sustainable agricultural practice.

#### **Acknowledgements**

To Laboratory of Biodiversity Studies of Upper Plants in Federal Rural University of Amazonia.

## **Appendices and nomenclature**


### **Author details**

Gabriel Monteiro1 , Glauco Nogueira1 \*, Cândido Neto2 , Vitor Nascimento3 and Joze Freitas2

1 Federal Rural University of Amazon (UFRA), Belém, Pará, Brazil

2 Institute of Agrarian Sciences, Federal Rural University of Amazon (UFRA), Belém, Pará, Brazil

3 Rede BIONORTE/UFPA, Belém, Pará, Brazil

\*Address all correspondence to: glauand@yahoo.com.br

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

**181**

*Promotion of Nitrogen Assimilation by Plant Growth-Promoting Rhizobacteria*

resource. Annual Review of Environment and Resources, *34*, 97-125. https://doi.org/10.1146/annurev.

[8] Miller, A. J., Fan, X., Orsel, M., Smith, S. J., & Wells, D. M. (2007). Nitrate transport and signalling. Journal of Experimental Botany, *58*(9), 2297-2306. https://doi.org/10.1093/

[9] Good, A. G., & Beatty, P. H. (2011). Fertilizing nature: A tragedy of excess in the commons. PLoS Biology, *9*(8), 1-9. https://doi.org/10.1371/journal.

[10] Kuypers, M. M. M., Marchant, H. K., & Kartal, B. (2018). The microbial nitrogen-cycling network. Nature Reviews Microbiology, *16*(5), 263-276. https://doi.org/10.1038/nrmicro.2018.9

[11] Sinha, E., Michalak, A. M., & Balaji, V. (2017). Eutrophication will increase during the 21st century as a result of precipitation changes. Science, *357*(6349), 1-5. https://doi.org/10.1126/

[12] Xu, G., Fan, X., & Miller, A. J. (2012). Plant nitrogen assimilation and use efficiency. Annual Review of Plant Biology, *63*, 153-182. https://doi.org/10.1146/ annurev-arplant-042811-105532

[13] Horswill, P., O'Sullivan, O., Phoenix, G. K., Lee, J. A., & Leake, J. R. (2008). Base cation depletion, eutrophication and acidification of species-rich grasslands in response to long-term simulated nitrogen deposition. Environmental Pollution,

*155*(2), 336-349. https://doi. org/10.1016/j.envpol.2007.11.006

[14] Silva, A. G. B., Sequeira, C. H., Sermarini, R. A., & Otto, R. (2017). Urease inhibitor NBPT on ammonia

environ.032108.105046

jxb/erm066

pbio.1001124

science.aan2409

*DOI: http://dx.doi.org/10.5772/intechopen.96634*

[1] Krapp, A. (2015). Plant nitrogen assimilation and its regulation: A complex puzzle with missing pieces. Current Opinion in Plant Biology, *25*, 115-122. https://doi.org/10.1016/j.

[2] Teixeira, E. I., George, M.,

Herreman, T., Brown, H., Fletcher, A., Chakwizira, E., de Ruiter, J., Maley, S., & Noble, A. (2014). The impact of water and nitrogen limitation on maize biomass and resource-use efficiencies for radiation, water and nitrogen. Field Crops Research, *168*, 109-118. https:// doi.org/10.1016/j.fcr.2014.08.002

[3] Gojon, A. (2017). Nitrogen nutrition in plants: Rapid progress and new challenges. Journal of Experimental Botany, *68*(10), 2457-2462. https://doi.

[4] Lu, C., & Tian, H. (2017). Global nitrogen and phosphorus fertilizer use for agriculture production in the past half century: Shifted hot spots and nutrient imbalance. Earth System Science Data, *9*(1), 181-192. https://doi.

org/10.1093/jxb/erx171

org/10.5194/essd-9-181-2017

semcdb.2017.08.034

semcdb.2017.08.027

[5] Kant, S. (2018). Understanding nitrate uptake, signaling and remobilisation for improving plant nitrogen use efficiency. Seminars in Cell and Developmental Biology, *74*, 89-96. https://doi.org/10.1016/j.

[6] Plett, D. C., Holtham, L. R., Okamoto, M., & Garnett, T. P. (2018). Nitrate uptake and its regulation in relation to improving nitrogen use efficiency in cereals. Seminars in Cell and Developmental Biology, *74*, 97-104. https://doi.org/10.1016/j.

[7] Robertson, G. P., & Vitousek, P. M. (2009). Nitrogen in agriculture: Balancing the cost of an essential

**References**

pbi.2015.05.010

*Promotion of Nitrogen Assimilation by Plant Growth-Promoting Rhizobacteria DOI: http://dx.doi.org/10.5772/intechopen.96634*

#### **References**

*Nitrogen in Agriculture - Physiological, Agricultural and Ecological Aspects*

**Appendices and nomenclature**

CONAB National Supply Company NUE Nitrogen use efficiency

BNF Biologic nitrogen fixation

NBPT N-(n-butyl)-thiophosphoric triamide PGPR Plant growth-promoting rhizobacteria

**180**

**Author details**

Gabriel Monteiro1

Belém, Pará, Brazil

and Joze Freitas2

, Glauco Nogueira1

3 Rede BIONORTE/UFPA, Belém, Pará, Brazil

provided the original work is properly cited.

\*Address all correspondence to: glauand@yahoo.com.br

1 Federal Rural University of Amazon (UFRA), Belém, Pará, Brazil

2 Institute of Agrarian Sciences, Federal Rural University of Amazon (UFRA),

© 2021 The Author(s). Licensee IntechOpen. This chapter is distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/ by/3.0), which permits unrestricted use, distribution, and reproduction in any medium,

\*, Cândido Neto2

, Vitor Nascimento3

[1] Krapp, A. (2015). Plant nitrogen assimilation and its regulation: A complex puzzle with missing pieces. Current Opinion in Plant Biology, *25*, 115-122. https://doi.org/10.1016/j. pbi.2015.05.010

[2] Teixeira, E. I., George, M., Herreman, T., Brown, H., Fletcher, A., Chakwizira, E., de Ruiter, J., Maley, S., & Noble, A. (2014). The impact of water and nitrogen limitation on maize biomass and resource-use efficiencies for radiation, water and nitrogen. Field Crops Research, *168*, 109-118. https:// doi.org/10.1016/j.fcr.2014.08.002

[3] Gojon, A. (2017). Nitrogen nutrition in plants: Rapid progress and new challenges. Journal of Experimental Botany, *68*(10), 2457-2462. https://doi. org/10.1093/jxb/erx171

[4] Lu, C., & Tian, H. (2017). Global nitrogen and phosphorus fertilizer use for agriculture production in the past half century: Shifted hot spots and nutrient imbalance. Earth System Science Data, *9*(1), 181-192. https://doi. org/10.5194/essd-9-181-2017

[5] Kant, S. (2018). Understanding nitrate uptake, signaling and remobilisation for improving plant nitrogen use efficiency. Seminars in Cell and Developmental Biology, *74*, 89-96. https://doi.org/10.1016/j. semcdb.2017.08.034

[6] Plett, D. C., Holtham, L. R., Okamoto, M., & Garnett, T. P. (2018). Nitrate uptake and its regulation in relation to improving nitrogen use efficiency in cereals. Seminars in Cell and Developmental Biology, *74*, 97-104. https://doi.org/10.1016/j. semcdb.2017.08.027

[7] Robertson, G. P., & Vitousek, P. M. (2009). Nitrogen in agriculture: Balancing the cost of an essential

resource. Annual Review of Environment and Resources, *34*, 97-125. https://doi.org/10.1146/annurev. environ.032108.105046

[8] Miller, A. J., Fan, X., Orsel, M., Smith, S. J., & Wells, D. M. (2007). Nitrate transport and signalling. Journal of Experimental Botany, *58*(9), 2297-2306. https://doi.org/10.1093/ jxb/erm066

[9] Good, A. G., & Beatty, P. H. (2011). Fertilizing nature: A tragedy of excess in the commons. PLoS Biology, *9*(8), 1-9. https://doi.org/10.1371/journal. pbio.1001124

[10] Kuypers, M. M. M., Marchant, H. K., & Kartal, B. (2018). The microbial nitrogen-cycling network. Nature Reviews Microbiology, *16*(5), 263-276. https://doi.org/10.1038/nrmicro.2018.9

[11] Sinha, E., Michalak, A. M., & Balaji, V. (2017). Eutrophication will increase during the 21st century as a result of precipitation changes. Science, *357*(6349), 1-5. https://doi.org/10.1126/ science.aan2409

[12] Xu, G., Fan, X., & Miller, A. J. (2012). Plant nitrogen assimilation and use efficiency. Annual Review of Plant Biology, *63*, 153-182. https://doi.org/10.1146/ annurev-arplant-042811-105532

[13] Horswill, P., O'Sullivan, O., Phoenix, G. K., Lee, J. A., & Leake, J. R. (2008). Base cation depletion, eutrophication and acidification of species-rich grasslands in response to long-term simulated nitrogen deposition. Environmental Pollution, *155*(2), 336-349. https://doi. org/10.1016/j.envpol.2007.11.006

[14] Silva, A. G. B., Sequeira, C. H., Sermarini, R. A., & Otto, R. (2017). Urease inhibitor NBPT on ammonia volatilization and crop productivity: A meta-analysis. Agronomy Journal, *109*(1), 1-13. https://doi.org/10.2134/ agronj2016.04.0200

[15] Iqbal, A., Qiang, D., Alamzeb, M., Xiangru, W., Huiping, G., Hengheng, Z., Nianchang, P., Xiling, Z., & Meizhen, S. (2020). Untangling the molecular mechanisms and functions of nitrate to improve nitrogen use efficiency. Journal of the Science of Food and Agriculture, *100*(3), 904-914. https://doi.org/10.1002/jsfa.10085

[16] Silveira, A. P. D. da, Sala, V. M. R., Cardoso, E. J. B. N., Labanca, E. G., & Cipriano, M. A. P. (2016). Nitrogen metabolism and growth of wheat plant under diazotrophic endophytic bacteria inoculation. Applied Soil Ecology, *107*, 313-319. https://doi.org/10.1016/j. apsoil.2016.07.005

[17] Franche, C., Lindström, K., & Elmerich, C. (2009). Nitrogen-fixing bacteria associated with leguminous and non-leguminous plants. Plant and Soil, *321*(1-2), 35-59. https://doi.org/10.1007/ s11104-008-9833-8

[18] Hungria, M., Franchini, J. C., Campo, R. J., Crispino, C. C., Moraes, J. Z., Sibaldelli, R. N. R., Mendes, I. C., & Arihara, J. (2006). *Nitrogen nutrition of soybean in Brazil: Contributions of biological N 2 fixation and N fertilizer to grain yield*.

[19] Glick, B. R. (2012). Plant Growth-Promoting Bacteria : Mechanisms and Applications. *2012*.

[20] Mantelin, S., Desbrosses, G., Larcher, M., Tranbarger, T. J., Cleyet-Marel, J. C., & Touraine, B. (2006). Nitrate-dependent control of root architecture and N nutrition are altered by a plant growth-promoting Phyllobacterium sp. Planta, *223*(3), 591-603. https://doi.org/10.1007/ s00425-005-0106-y

[21] Stevenson, F. J. (2015). *Origin and Distribution of Nitrogen in Soil* (Issue 22, pp. 1-42). https://doi.org/10.2134/ agronmonogr22.c1

[22] Williams, D. R. (2016). Earth Fact Sheet. NASA Fact Sheets, 1. https:// nssdc.gsfc.nasa.gov/planetary/ factsheet/earthfact.html

[23] Fernandes, M. S., & Pereyra Rossiello, R. O. (1995). Mineral Nitrogen in Plant Physiology and Plant Nutrition. Critical Reviews in Plant Sciences, *14*(2), 111-148. https://doi. org/10.1080/07352689509701924

[24] Taiz, L., Zeiger, E., Møller, I. M., & Murphy, A. (2017). *Fisiologia e desenvolvimento vegetal*. Artmed Editora.

[25] Cammack, R. (2012). Iron–sulfur proteins. The Biochemist, *34*(5), 14-17. https://doi.org/10.1042/BIO03405014

[26] Einsle, O., & Rees, D. C. (2020). Structural Enzymology of Nitrogenase Enzymes. Chemical Reviews, *120*(12), 4969-5004. https://doi.org/10.1021/acs. chemrev.0c00067

[27] Morrison, C. N., Hoy, J. A., Zhang, L., Einsle, O., & Rees, D. C. (2015). Substrate Pathways in the nitrogenase MoFe protein by experimental identification of small molecule binding sites. Biochemistry, *54*(11), 2052-2060. https://doi.org/10.1021/bi501313k

[28] Einsle, O. (2014). Nitrogenase FeMo cofactor: An atomic structure in three simple steps. Journal of Biological Inorganic Chemistry, *19*(6), 737-745. https://doi.org/10.1007/ s00775-014-1116-7

[29] Eady, R. R. (1996). Structurefunction relationships of alternative nitrogenases. Chemical Reviews, *96*(7), 3013-3030. https://doi.org/10.1021/ cr950057h

[30] Rees, D. C., Akif Tezcan, F., Haynes, C. A., Walton, M. Y., Andrade, S.,

**183**

s10533-004-0370-0

*Promotion of Nitrogen Assimilation by Plant Growth-Promoting Rhizobacteria*

[36] Cantarella, H. (2007). Nitrogênio. Fertilidade Do Solo, *2*, 375-470.

 Levantamento. https://www. conab.gov.br/info-agro/safras/graos/

[38] Ormeño-Orrillo, E., Hungria, M., & Martinez-Romero, E. (2013). Dinitrogen-fixing prokaryotes. In *The Prokaryotes: Prokaryotic Physiology and Biochemistry* (Vol. 9783642301414, pp. 427-451). Springer-Verlag Berlin Heidelberg. https://doi. org/10.1007/978-3-642-30141-4\_72

[39] de Soares, L.H. B, Michel, D. C., & Zilli, J. É. (2020). Fixação biológica do nitrogênio. In Ministério da Agricultura, Pecuária e Abastecimento (Ed.), *Alfafa: do cultivo aos múltiplos usos* (p. 173).

[40] Rosenblueth, M., Ormeño-Orrillo, E., López-López, A., Rogel, M. A., Reyes-Hernández, B. J., Martínez-Romero, J. C., Reddy, P. M., & Martínez-Romero, E. (2018). Nitrogen fixation in cereals. *Frontiers in Microbiology*, *9*(AUG), 1-13. https://doi.

org/10.3389/fmicb.2018.01794

[41] Spaepen, S., Vanderleyden, J., & Remans, R. (2007). Indole-3-acetic acid in microbial and microorganismplant signaling. FEMS Microbiology Reviews, *31*(4), 425-448. https://doi. org/10.1111/j.1574-6976.2007.00072.x

[42] Bottini, R., Cassán, F., & Piccoli, P. (2004). Gibberellin production by bacteria and its involvement in plant growth promotion and yield increase. Applied Microbiology and Biotechnology, *65*(5), 497-503. https:// doi.org/10.1007/s00253-004-1696-1

[43] Herrera, J. M., Rubio, G., Häner, L. L., Delgado, J. A., Lucho-Constantino, C. A., Islas-Valdez, S., & Pellet, D.

[37] CONAB. (2019). *Boletim da Safra de Grãos*. Acompanhamento Da Safra 2018/19 Brasileira de Grãos

boletim-da-safra-de-graos


MAPA/AECS.

*DOI: http://dx.doi.org/10.5772/intechopen.96634*

Einsle, O., & Howard, J. B. (2005). Structural basis of biological nitrogen fixation. *Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences*, 363(1829), 971-984. https://doi.org/10.1098/

[31] Gallon, J. R. (1981). The oxygen sensitivity of nitrogenase: a problem for biochemists and microorganisms. Trends in Biochemical Sciences, *6*(C), 19-23. https://doi. org/10.1016/0968-0004(81)90008-6

[32] Goldberg, I., Nadler, V., & Hochman, A. (1987). Mechanism of nitrogenase switch-off by oxygen. Journal of Bacteriology, *169*(2), 874-879. https://doi.org/10.1128/

[33] Auras, N. É., Zilli, J. É., Soares, L. H. de B., & Fontana, J. (2018). Recomendação de uso de estirpes fixadoras de nitrogênio em leguminosas de importância agronômica e florestal. Embrapa Agrobiologia-Documentos (INFOTECA-E).https://www.infoteca.

infoteca/bitstream/doc/1099443/1/

[34] Barbieri, A.; Carneiro, M.A.C.; Moreira, F.M.S.; Siqueira, J.O. (1998). Nodulação em leguminosas florestais em viveiros no sul de minas gerais. CERNE,

v.4, n.1, p.145-153. https://www.

[35] Galloway, J. N., Dentener, F. J., Capone, D. G., Boyer, E. W., Howarth, R. W., Seitzinger, S. P., Asner, G. P., Cleveland, C. C., Green, P. A., Holland, E. A., Karl, D. M., Michaels, A. F., Porter, J. H., Townsend, A. R., & Vöosmarty, C. J. (2004). Nitrogen Cycles: Past, Present, and Future. Biogeochemistry, *70*(2), 153-226. https://doi.org/10.1007/

researchgate.net/publication/242531593

jb.169.2.874-879.1987

cnptia.embrapa.br/

recomendacaodeus odeestirpesfixadoras.pdf

rsta.2004.1539

*Promotion of Nitrogen Assimilation by Plant Growth-Promoting Rhizobacteria DOI: http://dx.doi.org/10.5772/intechopen.96634*

Einsle, O., & Howard, J. B. (2005). Structural basis of biological nitrogen fixation. *Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences*, 363(1829), 971-984. https://doi.org/10.1098/ rsta.2004.1539

*Nitrogen in Agriculture - Physiological, Agricultural and Ecological Aspects*

[21] Stevenson, F. J. (2015). *Origin and Distribution of Nitrogen in Soil* (Issue 22, pp. 1-42). https://doi.org/10.2134/

[22] Williams, D. R. (2016). Earth Fact Sheet. NASA Fact Sheets, 1. https:// nssdc.gsfc.nasa.gov/planetary/ factsheet/earthfact.html

[23] Fernandes, M. S., & Pereyra Rossiello, R. O. (1995). Mineral Nitrogen in Plant Physiology and Plant Nutrition. Critical Reviews in Plant Sciences, *14*(2), 111-148. https://doi. org/10.1080/07352689509701924

[24] Taiz, L., Zeiger, E., Møller, I. M., & Murphy, A. (2017). *Fisiologia e desenvolvimento vegetal*. Artmed Editora.

[25] Cammack, R. (2012). Iron–sulfur proteins. The Biochemist, *34*(5), 14-17. https://doi.org/10.1042/BIO03405014

[26] Einsle, O., & Rees, D. C. (2020). Structural Enzymology of Nitrogenase Enzymes. Chemical Reviews, *120*(12), 4969-5004. https://doi.org/10.1021/acs.

[27] Morrison, C. N., Hoy, J. A., Zhang, L., Einsle, O., & Rees, D. C. (2015). Substrate Pathways in the nitrogenase

identification of small molecule binding sites. Biochemistry, *54*(11), 2052-2060. https://doi.org/10.1021/bi501313k

MoFe protein by experimental

[28] Einsle, O. (2014). Nitrogenase FeMo cofactor: An atomic structure in three simple steps. Journal of Biological Inorganic Chemistry, *19*(6), 737-745. https://doi.org/10.1007/

[29] Eady, R. R. (1996). Structurefunction relationships of alternative nitrogenases. Chemical Reviews, *96*(7), 3013-3030. https://doi.org/10.1021/

[30] Rees, D. C., Akif Tezcan, F., Haynes, C. A., Walton, M. Y., Andrade, S.,

chemrev.0c00067

s00775-014-1116-7

cr950057h

agronmonogr22.c1

volatilization and crop productivity: A meta-analysis. Agronomy Journal, *109*(1), 1-13. https://doi.org/10.2134/

[15] Iqbal, A., Qiang, D., Alamzeb, M., Xiangru, W., Huiping, G., Hengheng, Z., Nianchang, P., Xiling, Z., & Meizhen, S. (2020). Untangling the molecular mechanisms and functions of nitrate to improve nitrogen use efficiency. Journal of the Science of Food and Agriculture, *100*(3), 904-914. https://doi.org/10.1002/jsfa.10085

[16] Silveira, A. P. D. da, Sala, V. M. R., Cardoso, E. J. B. N., Labanca, E. G., & Cipriano, M. A. P. (2016). Nitrogen metabolism and growth of wheat plant under diazotrophic endophytic bacteria inoculation. Applied Soil Ecology, *107*, 313-319. https://doi.org/10.1016/j.

[17] Franche, C., Lindström, K., & Elmerich, C. (2009). Nitrogen-fixing bacteria associated with leguminous and non-leguminous plants. Plant and Soil, *321*(1-2), 35-59. https://doi.org/10.1007/

[18] Hungria, M., Franchini, J. C., Campo, R. J., Crispino, C. C., Moraes, J. Z., Sibaldelli, R. N. R., Mendes, I. C., & Arihara, J. (2006). *Nitrogen nutrition of soybean in Brazil: Contributions of biological N 2 fixation and N fertilizer to* 

[19] Glick, B. R. (2012). Plant Growth-Promoting Bacteria : Mechanisms and

[20] Mantelin, S., Desbrosses, G., Larcher, M., Tranbarger, T. J., Cleyet-Marel, J. C., & Touraine, B. (2006). Nitrate-dependent control of root architecture and N nutrition are altered by a plant growth-promoting Phyllobacterium sp. Planta, *223*(3), 591-603. https://doi.org/10.1007/

agronj2016.04.0200

apsoil.2016.07.005

s11104-008-9833-8

*grain yield*.

Applications. *2012*.

s00425-005-0106-y

**182**

[31] Gallon, J. R. (1981). The oxygen sensitivity of nitrogenase: a problem for biochemists and microorganisms. Trends in Biochemical Sciences, *6*(C), 19-23. https://doi. org/10.1016/0968-0004(81)90008-6

[32] Goldberg, I., Nadler, V., & Hochman, A. (1987). Mechanism of nitrogenase switch-off by oxygen. Journal of Bacteriology, *169*(2), 874-879. https://doi.org/10.1128/ jb.169.2.874-879.1987

[33] Auras, N. É., Zilli, J. É., Soares, L. H. de B., & Fontana, J. (2018). Recomendação de uso de estirpes fixadoras de nitrogênio em leguminosas de importância agronômica e florestal. Embrapa Agrobiologia-Documentos (INFOTECA-E).https://www.infoteca. cnptia.embrapa.br/ infoteca/bitstream/doc/1099443/1/ recomendacaodeus odeestirpesfixadoras.pdf

[34] Barbieri, A.; Carneiro, M.A.C.; Moreira, F.M.S.; Siqueira, J.O. (1998). Nodulação em leguminosas florestais em viveiros no sul de minas gerais. CERNE, v.4, n.1, p.145-153. https://www. researchgate.net/publication/242531593

[35] Galloway, J. N., Dentener, F. J., Capone, D. G., Boyer, E. W., Howarth, R. W., Seitzinger, S. P., Asner, G. P., Cleveland, C. C., Green, P. A., Holland, E. A., Karl, D. M., Michaels, A. F., Porter, J. H., Townsend, A. R., & Vöosmarty, C. J. (2004). Nitrogen Cycles: Past, Present, and Future. Biogeochemistry, *70*(2), 153-226. https://doi.org/10.1007/ s10533-004-0370-0

[36] Cantarella, H. (2007). Nitrogênio. Fertilidade Do Solo, *2*, 375-470.

[37] CONAB. (2019). *Boletim da Safra de Grãos*. Acompanhamento Da Safra 2018/19 Brasileira de Grãos - 12o Levantamento. https://www. conab.gov.br/info-agro/safras/graos/ boletim-da-safra-de-graos

[38] Ormeño-Orrillo, E., Hungria, M., & Martinez-Romero, E. (2013). Dinitrogen-fixing prokaryotes. In *The Prokaryotes: Prokaryotic Physiology and Biochemistry* (Vol. 9783642301414, pp. 427-451). Springer-Verlag Berlin Heidelberg. https://doi. org/10.1007/978-3-642-30141-4\_72

[39] de Soares, L.H. B, Michel, D. C., & Zilli, J. É. (2020). Fixação biológica do nitrogênio. In Ministério da Agricultura, Pecuária e Abastecimento (Ed.), *Alfafa: do cultivo aos múltiplos usos* (p. 173). MAPA/AECS.

[40] Rosenblueth, M., Ormeño-Orrillo, E., López-López, A., Rogel, M. A., Reyes-Hernández, B. J., Martínez-Romero, J. C., Reddy, P. M., & Martínez-Romero, E. (2018). Nitrogen fixation in cereals. *Frontiers in Microbiology*, *9*(AUG), 1-13. https://doi. org/10.3389/fmicb.2018.01794

[41] Spaepen, S., Vanderleyden, J., & Remans, R. (2007). Indole-3-acetic acid in microbial and microorganismplant signaling. FEMS Microbiology Reviews, *31*(4), 425-448. https://doi. org/10.1111/j.1574-6976.2007.00072.x

[42] Bottini, R., Cassán, F., & Piccoli, P. (2004). Gibberellin production by bacteria and its involvement in plant growth promotion and yield increase. Applied Microbiology and Biotechnology, *65*(5), 497-503. https:// doi.org/10.1007/s00253-004-1696-1

[43] Herrera, J. M., Rubio, G., Häner, L. L., Delgado, J. A., Lucho-Constantino, C. A., Islas-Valdez, S., & Pellet, D.

(2016). Emerging and established technologies to increase nitrogen use efficiency of cereals. Agronomy, *6*(2), 11-18. https://doi.org/10.3390/ agronomy6020025

[44] Tilman, D., Cassman, K. G., Matson, P. A., Naylor, R., & Polasky, S. (2002). Agricultural sustainability and intensive production practices. Nature, *418*(6898), 671-677. https://doi. org/10.1038/nature01014

[45] Landell M.G. de A, Campana, M. P., Figueiredo, P., Xavier, M. A., Anjos, I. A. dos, Dinardo-Miranda, L. L., Scarpari, M. S., Garcia, J. C., Bidóia, M. A. P., & Silva, D. N. da. (2012). Sistema de multiplicação de cana-de-açúcar com uso de mudas pré-brotadas (MPB), oriundas de gemas individualizadas. *Ribeirão Preto: Instituto Agronômico de Campinas*, *17*.

[46] Gírio LA da S, Dias, F. L. F., Reis, V. M., Urquiaga, S., Schultz, N., Bolonhezi, D., & Mutton, M. A. (2015). Plant growth-promoting bacteria and nitrogen fertilization effect on the initial growth of sugarcane from pre-sprouted seedlings. Pesquisa Agropecuaria Brasileira, *50*(1), 33-43. https://doi. org/10.1590/s0100-204x2015000100004

[47] Oliveira, A. R. De, & Simões, W. L. (2016). Cultivares de cana-de-açúcar inoculadas com bactérias. Energia Na Agricultura, *31*, 154-161.

[48] da Fonseca Breda, F. A., da Silva, T. F. R., dos Santos, S. G., Alves, G. C., & Reis, V. M. (2019). Modulation of nitrogen metabolism of maize plants inoculated with Azospirillum brasilense and Herbaspirillum seropedicae. Archives of Microbiology, *201*(4), 547-558. https://doi.org/10.1007/ s00203-018-1594-z

[49] Pereira-Defilippi, L., Pereira, E. M., Silva, F. M., & Moro, G. V. (2017). Expressed sequence tags related

to nitrogen metabolism in maize inoculated with Azospirillum brasilense. Genetics and Molecular Research, *16*(2), 1-14. https://doi.org/10.4238/ gmr16029682

**185**

**Chapter 12**

**Abstract**

organic matter and soil particles.

Mycorrhiza

**1. Introduction**

Mycorrhizal Fungi and

Sustainable Agriculture

*Soibam Helena Devi, Ingudam Bhupenchandra,* 

*Soibam Sinyorita, S.K. Chongtham and E. Lamalakshmi Devi*

The 20thcentury witnessed an augmentation in agricultural production, mainly

through the progress and use of pesticides, fertilizers containing nitrogen and phosphorus, and developments in plant breeding and genetic skills. In the naturally existing ecology, rhizospheric soils have innumerable biological living beings to favor the plant development, nutrient assimilation, stress tolerance, disease deterrence, carbon seizing and others. These organisms include mycorrhizal fungi, bacteria, actinomycetes, etc. which solubilize nutrients and assist the plants in up taking by roots. Amongst them, arbuscular mycorrhizal (AM) fungi have key importance in natural ecosystem, but high rate of chemical fertilizer in agricultural fields is diminishing its importance. The majority of the terrestrial plants form association with Vesicular Arbuscular Mycorrhiza (VAM) or Arbuscular Mycorrhizal fungi (AMF). This symbiosis confers benefits directly to the host plant's growth and development through the acquisition of Phosphorus (P) and other mineral nutrients from the soil by the AMF. They may also enhance the protection of plants against pathogens and increases the plant diversity. This is achieved by the growth of AMF mycelium within the host root (intra radical) and out into the soil (extra radical) beyond. Proper management of Arbuscular Mycorrhizal fungi has the potential to improve the profitability and sustainability of agricultural systems. AM fungi are especially important for sustainable farming systems because AM fungi are efficient when nutrient availability is low and when nutrients are bound to

**Keywords:** Actinomycetes, Bacteria, Mycorrhizal fungi, Vesicular Arbuscular

The productivity of agriculture has increased steadily since the middle of the last century in temperate regions and, more recently, in tropical areas [1] mainly due to improved varieties, machinery, fertilizers, and pesticides. However, recently agricultural yields have plateaued [2], largely because of land degradation often associated with unsustainable farming practices [3, 4]. To meet future demand, food production must rise significantly through this century, utilizing less cultivable land in a sustainable manner [5]. Many factors have contributed to making this increase in crop production essential, including population increases worldwide, food shortages in developing countries, the importance of agricultural products

#### **Chapter 12**

*Nitrogen in Agriculture - Physiological, Agricultural and Ecological Aspects*

to nitrogen metabolism in maize

gmr16029682

inoculated with Azospirillum brasilense. Genetics and Molecular Research, *16*(2), 1-14. https://doi.org/10.4238/

(2016). Emerging and established technologies to increase nitrogen use efficiency of cereals. Agronomy, *6*(2), 11-18. https://doi.org/10.3390/

[44] Tilman, D., Cassman, K. G., Matson, P. A., Naylor, R., & Polasky, S. (2002). Agricultural sustainability and intensive production practices. Nature, *418*(6898), 671-677. https://doi.

[45] Landell M.G. de A, Campana, M. P., Figueiredo, P., Xavier, M. A., Anjos, I. A. dos, Dinardo-Miranda, L. L., Scarpari, M. S., Garcia, J. C., Bidóia, M. A. P., & Silva, D. N. da. (2012). Sistema de multiplicação de cana-de-açúcar com uso de mudas pré-brotadas (MPB), oriundas de gemas individualizadas. *Ribeirão Preto: Instituto Agronômico de* 

[46] Gírio LA da S, Dias, F. L. F., Reis, V. M., Urquiaga, S., Schultz, N.,

Bolonhezi, D., & Mutton, M. A. (2015). Plant growth-promoting bacteria and nitrogen fertilization effect on the initial growth of sugarcane from pre-sprouted seedlings. Pesquisa Agropecuaria Brasileira, *50*(1), 33-43. https://doi. org/10.1590/s0100-204x2015000100004

[47] Oliveira, A. R. De, & Simões, W. L. (2016). Cultivares de cana-de-açúcar inoculadas com bactérias. Energia Na

[48] da Fonseca Breda, F. A., da Silva, T. F. R., dos Santos, S. G., Alves, G. C., & Reis, V. M. (2019). Modulation of nitrogen metabolism of maize plants inoculated with Azospirillum brasilense and Herbaspirillum seropedicae. Archives of Microbiology, *201*(4), 547-558. https://doi.org/10.1007/

[49] Pereira-Defilippi, L., Pereira, E. M., Silva, F. M., & Moro, G. V. (2017). Expressed sequence tags related

Agricultura, *31*, 154-161.

s00203-018-1594-z

org/10.1038/nature01014

*Campinas*, *17*.

agronomy6020025

**184**
