Nitrogen Is One of The Essential Elements Required For The Synthesis of Amino Acids Which
Nitrogen Is One of The Essential Elements Required For The Synthesis of Amino Acids Which
Nitrogen Is One of The Essential Elements Required For The Synthesis of Amino Acids Which
Singhal
Nutrient enrichment of soil by nitrogen fixing symbiotic bacteria present in legumes has
been known for centuries. Scientific demonstration of this symbiosis was stared in 19th
century and it established the fact that bacteria present in nodules on legume roots are
responsible for fixing atmospheric nitrogen (Zsbrau, 1999). Rhizobium spp. are well known
group of bacteria that act as the primary symbiotic fixer of nitrogen. These bacteria infect
the root nodules of leguminous plants, leading to the formation of lumps and nodules where
The bacterium's enzyme system supplies a constant source reduced nitrogen to the host
plant and the plant furnishes nutrients and energy for the activities of the bacterium. This
nitrogenous fertilizer during the growth of leguminous crops (Dilworth and Parker, 1969;
Booling et al., 2007; Hunter et al., 2007). In the present study, strains of Rhizobium were
isolated from the root nodules. Further characterization was done by performing various
biochemical tests and also determine if the rhizobial cells be efficiently immobilized on
Shefali Poonia
Nitrogen is one of the essential elements required for the synthesis of amino acids which, in
turn, are used by the plant to form protein. Plants primarily take nitrogen in the ionic form as
+ -
either ammonium (NH4 ) or nitrate (NO3 ). Leguminous plants are also able to utilize
nitrogen derived from the symbiotic relationship they form with root nodule bacteria.[1].
Legumes play an important role in sustainable management of dry arid regions. Rhizobia are
the gram negative bacteria which have been widely used in agricultural systems for
enhancing the ability of legumes to fix atmospheric nitrogen [2]. These inhabit the root
nodules of most legumes which can provide enough nitrogen for their physiological needs
[1]. Each major legume crop is nodulated by different species of Rhizobium. Intensive
farming practices that accomplish high yields need chemical fertilizers, which are not only
costly but also create environmental problems [3]. The extensive use of chemical fertilizers in
agriculture is currently under debate due to environmental concern and fear for consumers’
health. Consequently, there has recently been a growing level of interest in environment
friendly sustainable agricultural practices and organic farming systems which include the use
Zeenat Wadhwa
With increased concern about the production of adequate amount of food to feed the
constantly increasing human population which is going to touch a mark of 9 billion by 2050
has forced us to reinforce the importance of sustainable increase in crop productivity. One of
the methods for sustainable agricultural includes the use of beneficial microorganisms for
plants as they are able to promote plant growth by growing endophytically on plants, in
symbiotic association with plants or as free-living cells in soil. The requirement for good
agricultural practices is revitalizing the interest in biological nitrogen fixation and Rhizobia-
Legumes are agronomically and ecologically important symbionts that lead to the development of
new plant organ (legume nodule) in response to nitrogen fixing bacteria. In developing countries
like India and other South Asian countries, chickpea is an important source of protein for millions
of people. Other than having high protein content (20-22%), chickpea is rich in fiber, minerals
(phosphorus, calcium, magnesium, iron and zinc) β-carotene and large amount of unsaturated
fatty acids (Gaur, 2010). Besides playing an important role in human diet it also improves soil
fertility by fixing the atmospheric nitrogen (Siddiqi and Mahmood, 2001; Kantar et al., 2007).
Nitrogen fixation in association with compatible Rhizobium strain (Chemining and Vessey,
2006). The genus Mesorhizobium includes species with high geographical dispersion and able to
nodulate a wide variety of legumes, including important crop species, like chickpea. It has been
Rhizobia are one of the most efficient bacterial symbionts of legumes that fix atmospheric
Rhizobia are able to metabolize atmospheric nitrogen and convert it into plant usable form in
specialized structures called nodules where aerobic condition are maintained by leghaemoglobin.
In return, Rhizobia utilize the carbon substrates derived from the plant photosynthesis. In
agriculture, perhaps 80% of the biologically fixed nitrogen comes from symbiosis involving
The biological nitrogen fixation because of Rhizobia-legume symbiosis benefits not only the host
crop but also the subsequent crops in that field. Besides this, it may also act as a non-symbiotic
PGPB as in the case of certain non-legume crops such as rice or wheat, which are the best-studied
examples that benefit from Rhizobia as endophytes (Biswas et al., 2000). For all these reasons,
the Rhizobium-legume symbiosis has been widely studied as a model of mutualistic associations
and as a beneficial association for sustainable agriculture. With increasing use of Rhizobium and
other beneficial microbes as bio fertilizers, reduction in the need for chemical fertilizers can be
observed. Therefore, bio fertilization has great importance in decreasing environmental pollution
and deterioration of nature (Vessey, 2006; Erman et al., 2011). The inoculation of seeds with
Rhizobium is known to increase nodulation, N uptake, growth and yield parameters of legume
crops (Erman et al., 2011). Keeping in view the importance of Rhizobia in legume plants, the
present study was undertaken to shed some light on different morpho-physiological and
Mitchell Andrews
The Leguminosae (Fabaceae, the legume family) is comprised of ca. 19,300 species within
750 genera that occur as herbs, shrubs, vines or trees in mainly terrestrial habitats and are
components of most of the world’s vegetation types. Currently, the legume family is divided
the Caesalpinioideae are grouped into four tribes, the Caesalpinieae, Cassieae, Cercideae and
Detarieae comprising ca. 170 genera and 2250 species. The Mimosoideae are grouped into
two tribes, the Ingeae and Mimoseae with ca. 80 genera and 3270 species, while the
Papilionoideae consists of 28 tribes with ca. 480 genera and 13,800 species. However, a new
classification of the legumes has been proposed with six sub-families based on the plastid
matK gene sequences from ca. 20% of all legume species across ca. 90% of all currently
system, the currently recognized Mimosoideae is a distinct clade nested within the re-
Most legume species can fix atmospheric nitrogen (N2) via symbiotic bacteria (general term
“rhizobia”) in root nodules, and this can give them an advantage under low soil nitrogen (N)
conditions if other factors are favourable for growth. Furthermore, N2 fixation by legumes
can be a major input of N into natural and agricultural ecosystems.. Generally, legume
nodules can be classified as indeterminate or determinate in growth. Indeterminate nodules
maintain meristematic tissue, while determinate nodules have a transient meristem. Nodule
type is dependent on host plant, and legume species that can produce both determinate and
indeterminate nodules are rare. All genera examined in the Caesalpinioideae and
Mimosoideae had indeterminate nodules. Within the Papilionoideae, most tribes had
indeterminate nodules, but the Desmodieae, Phaseoleae, Psoraleae and some members of the
determinate nodules. Desmodioid nodules have lenticels, and rhizobia “infected” tissue
within them also contains uninfected cells. Aeschynomenoid nodules do not have lenticels,
have uniform infected tissue and are always associated with lateral or adventitious roots.
The general classification of the Leguminosae follows Lewis et al., 2005 [1], with updates.
separately. The Papilionoideae is split into those that show indeterminate nodules and those
that show determinate nodules. Those that show indeterminate nodules are further split into
the IRLC and all other clades. Nodulating bacteria were classified at the genus level, on the
basis of sequences of the 16S rRNA gene (almost all cases), and/or the 16S–23S DNA
hybridisations, and these results are presented in the tables. Sequences for nif and nod genes
are considered in the text. Rhizobial genus and species names validated in the International
Journal of Systematic and Evolutionary Microbiology were used with one exception:
Burkholderia is being prepared by workers in the field. The term symbiovar (sv.) is used
when describing rhizobial strains within the same species that differ with respect to the
2016 was carried out. Articles were collected by searching the Institute for Scientic
Information (ISI) Web of Science using each legume genus partnered with each of the
and Sinorhizobium as the keywords. Further searches were carried out on the literature
quoted in the selected papers and those listed as quoting the selected papers in the ISI Web of
Science. Only data for plants sampled under field conditions, or for plants grown in soils
taken from the field, or supplied field soil extracts were used. Bacteria isolated from legume
nodules were accepted as rhizobia if they were shown to produce functional (N2 fixing)
nodules on inoculation of their original legume host or a species within the original host
legume genus under axenic conditions. The range of measurements and visual assessments
used as evidence of the occurrence of N2 fixation were accepted. These were acetylene
assumed to be active), increased total plant or shoot dry matter or N content, visually greener
(increased chlorophyll) and increased plant vigour. However, it is acknowledged that in some
cases, greater growth, vigour and/or greenness could have been caused by plant hormone
production by the bacterium. All data obtained for all species are presented with three
exceptions. Representative data are presented for Glycine max, Phaseolus vulgaris and Vigna
Inoculated Rhzobium species often fails to compete with indigenous soil rhizobia and
not enough to increase nodulation as these strains have to complete with native
rhizosphere community for nutrients (Bromfield et al., 1986) and (Singleton and
Tavares, 1986). Therefore, effective inoculants strains have been selected which are
able to compete with the native Rhizobium and thus from a high percentage of
nodulation (Hafeez et al., 1991), (Hafeez et al., 2000) and (Hafeez et al., 2001). There
are different type of legumes from various size and shapes of nodules on their roots.
Although many more differences have been even found within the same species of
legumes. Hence, nodules are collected when plants are in flowering stage and one can
make out an effective nodule which is large in size and red in colour. Such nodules
made by following usual techniques. Yeast Extract Manitol Agar (YEMA) is the
special medium used to get the Rhizobium growth. Following tests are performed in
the laboratory.
This cross inoculation groups as a new concept that is separate Rhizobium species
nodulating soya bean cannot infect groundnut plants and vice versa. The cross
inoculation groups have naterbigul compartment and no exceptions are found from
the published information so far it is not known what are the colonies grown on a
medium may not be only of Rhizobium they can be even of Agrobacterium for
definite conclusion one has to inoculates seeds of particular sequence and wait for
formation of nodules on such plants isolated colonies are of Rhizobium for this
purpose one has to see that inoculated plants form effective nodules on roots. For
Besides, there are several tests of nodule formation on roots of legume conducted, of
which following are most important reasons for existence of cross inoculation groups
in the nature.
Sharma (2007)
nutrients from soil which rescue the lower amount of nutrients in soil. On the other
hand lower consumption of nutrients from soil which rescue the higher amount of
nutrients in soil.
Jain (2008)
co-inoculants with and without different sources of organic increased the available
nutrients and balance sheet of nutrients in soil and economic viability of chickpea.
acids. NPK is most important elements in controlling the normal growth and yield of
crops including Pigeon pea. Generally the crops need recommended doses of 25kg P:
50 kg/ha and to get the 1.2 a tonnes/ha yield, the crop plant required 8.5, 8.0 and
He observed that Rhizobium spp. are gram-negative soil bacteria that have a
the maintenance of soil fertility. For this reason and taking into consideration the
importance of legumes in animal and human consumption, some attention has been
given to the effects that heavy metals exert on Rhizobium isolates as free-living
[1] J.C. Cleyet-Marel, R. Di Boniot and D.P. Beck. Chickpea and its root-nodule bacteria:
implications of their relationships for legume inoculation and biological nitrogen fixation. In:
Saxena, M.C. (ed.), present status and future prospects of chickpea crop production and
japonicum in Thailand by primer-based technology and direct DNA extraction. Plant and
Soil, 204:127-134. 1998 [3] D. Rigby and D. Caceres. Organic farming and the sustainability
of agricultural systems. Agricultural Systems, 68:21-40.2001 [4] J.Y. Lee and S.H. Song
isolated from wild chickpea collected from high altitudes in Erzurum. Turkish Journal of
Dilworth MJ, Parker CA (1969). Devolopment of the nitrogen fixing system in legumes. J.
Hunter WJ, Kuykendall LD, Manter DK (2007). Rhizobium selenireducens sp. nov.: A
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conditions and in arid climate. Microbiol. Mol. Biol. Rev. 63: 968-989.
Rhizobium strains for commercial use, Vol. (3) No. (2) December, 2010(132-136)
Shefali Poonia, Department of Botany, D.N. College, Meerut, U.P, INDIA, International Journal of
Engineering and Management Research Vol. 1, Issue-1, November-2011 ISSN No.: 2250-0758
Zeenat Wadhwa1, Vivek Srivastava2, Raj Rani1, Tanvi1, Kanchan Makkar1 and Sumit