Studying of nanoparticle structures is gaining
momentum because of their great potential in improving
several fields of science such as agriculture. The water
soluble fraction of the extracellular polysaccharides
(EPS)/matrix of the highly EPS producing cyanobacterium
Nostoc commune have been used as a potent reducing and
capping agent for green synthesis of silver nanoparticles.
The size of these nanoparticles with the EPS coat was found
to be in the range of 15–54 nm as analyzed using
transmission electron micrographs. Interestingly, after
washing the EPS coated silver nanoparticles by ethanol, the
size of nanoparticles reduced to less than 15 nm due to the
formation of silver oxide nanoparticles and removal of the
EPS coat. Silver nanoparticles showed antibacterial
properties against Escherichia coli. The minimum inhibitory
concentration (MIC) was 0.012 mg/ml while the minimum
bactericidal concentration (MBC) was 0.016 mg/ml. The
slight difference between the MIC and MBC suggests that
such silver nanoparticles act as a potent bactericidal agent
against E. coli. Presoaking seeds of crop plants (Sorghum
and broad bean) in five-fold MBC of silver nanoparticles
(0.08 mg/ml) did not adversely affect the germination of
Vicia faba L. and Sorghum bicolor plants. Concomitantly,
such fivefold MBC concentration of silver nanoparticles was
powerful sterilizing agent for seeds and grains against
seed/grain-borne microorganisms. The results showed
gradual depletion of the total colony forming units (CFU) in
seeds and grains sterilized with silver nanoparticles than
those sterilized with chlorine. These results suggest that the
water soluble fraction of the extracellular polysaccharides
(EPS)/matrix of Nostoc commune can be used as a potent
reducing and capping agent for green synthesis of silver
nanoparticles and that silver nanoparticles can be used as a
potent surface sterilizi

Studying of nanoparticle structures is gaining
momentum because of their great potential in improving
several fields of science such as agriculture. The water
soluble fraction of the extracellular polysaccharides
(EPS)/matrix of the highly EPS producing cyanobacterium
Nostoc commune have been used as a potent reducing and
capping agent for green synthesis of silver nanoparticles.
The size of these nanoparticles with the EPS coat was found
to be in the range of 15–54 nm as analyzed using
transmission electron micrographs. Interestingly, after
washing the EPS coated silver nanoparticles by ethanol, the
size of nanoparticles reduced to less than 15 nm due to the
formation of silver oxide nanoparticles and removal of the
EPS coat. Silver nanoparticles showed antibacterial
properties against Escherichia coli. The minimum inhibitory
concentration (MIC) was 0.012 mg/ml while the minimum
bactericidal concentration (MBC) was 0.016 mg/ml. The
slight difference between the MIC and MBC suggests that
such silver nanoparticles act as a potent bactericidal agent
against E. coli. Presoaking seeds of crop plants (Sorghum
and broad bean) in five-fold MBC of silver nanoparticles
(0.08 mg/ml) did not adversely affect the germination of
Vicia faba L. and Sorghum bicolor plants. Concomitantly,
such fivefold MBC concentration of silver nanoparticles was
powerful sterilizing agent for seeds and grains against
seed/grain-borne microorganisms. The results showed
gradual depletion of the total colony forming units (CFU) in
seeds and grains sterilized with silver nanoparticles than
those sterilized with chlorine. These results suggest that the
water soluble fraction of the extracellular polysaccharides
(EPS)/matrix of Nostoc commune can be used as a potent
reducing and capping agent for green synthesis of silver
nanoparticles and that silver nanoparticles can be used as a
potent surface sterilizi

Studying of nanoparticle structures is gaining
momentum because of their great potential in improving
several fields of science such as agriculture. The water
soluble fraction of the extracellular polysaccharides
(EPS)/matrix of the highly EPS producing cyanobacterium
Nostoc commune have been used as a potent reducing and
capping agent for green synthesis of silver nanoparticles.
The size of these nanoparticles with the EPS coat was found
to be in the range of 15–54 nm as analyzed using
transmission electron micrographs. Interestingly, after
washing the EPS coated silver nanoparticles by ethanol, the
size of nanoparticles reduced to less than 15 nm due to the
formation of silver oxide nanoparticles and removal of the
EPS coat. Silver nanoparticles showed antibacterial
properties against Escherichia coli. The minimum inhibitory
concentration (MIC) was 0.012 mg/ml while the minimum
bactericidal concentration (MBC) was 0.016 mg/ml. The
slight difference between the MIC and MBC suggests that
such silver nanoparticles act as a potent bactericidal agent
against E. coli. Presoaking seeds of crop plants (Sorghum
and broad bean) in five-fold MBC of silver nanoparticles
(0.08 mg/ml) did not adversely affect the germination of
Vicia faba L. and Sorghum bicolor plants. Concomitantly,
such fivefold MBC concentration of silver nanoparticles was
powerful sterilizing agent for seeds and grains against
seed/grain-borne microorganisms. The results showed
gradual depletion of the total colony forming units (CFU) in
seeds and grains sterilized with silver nanoparticles than
those sterilized with chlorine. These results suggest that the
water soluble fraction of the extracellular polysaccharides
(EPS)/matrix of Nostoc commune can be used as a potent
reducing and capping agent for green synthesis of silver
nanoparticles and that silver nanoparticles can be used as a
potent surface sterilizi

The objective of this study is to explore the
response of an activated Rhizobium tibeticum inoculum
with a mixture of hesperetin (H) and apigenin (A) to
improve the growth, nodulation, and nitrogen fixation of
fenugreek (Trigonella foenum graecum L.) grown under
nickel (Ni) stress. Three different sets of fenugreek seed
treatments were conducted, in order to investigate the
activated R. tibeticum pre-incubation effects on nodulation,
nitrogen fixation and growth of fenugreek under Ni stress.
Group (I): uninoculated seeds with R. tibeticum, group (II):
inoculated seeds with uninduced R. tibeticum group (III):
inoculated seeds with induced R. tibeticum. The present
study revealed that Ni induced deleterious effects on rhizobial
growth, nod gene expression, nodulation, phenylalanine
ammonia-lyase (PAL) and glutamine synthetase
activities, total flavonoids content and nitrogen fixation,
while the inoculation with an activated R. tibeticum significantly
improved these values compared with plants
inoculated with uninduced R. tibeticum. PAL activity of
roots plants inoculated with induced R. tibeticum and
grown hydroponically at 75 and 100 mg L-1 Ni and was
significantly increased compared with plants receiving
uninduced R. tibeticum. The total number and fresh mass
of nodules, nitrogenase activity of plants inoculated with
induced cells grown in soil treated up to 200 mg kg-1 Ni
were significantly increased compared with plants inoculated
with uninduced cells. Plants inoculated with induced
R. tibeticum dispalyed a significant increase in the dry
mass compared with those treated with uninduced R.tibeticum. Activation of R. tibeticum inoculum with a
mixture of hesperetin and apigenin has been proven to be
practically important in enhancing nodule formation,
nitrogen fixation and growth of fenugreek grown in Ni
contaminated soils.

The objective of this study is to explore the
response of an activated Rhizobium tibeticum inoculum
with a mixture of hesperetin (H) and apigenin (A) to
improve the growth, nodulation, and nitrogen fixation of
fenugreek (Trigonella foenum graecum L.) grown under
nickel (Ni) stress. Three different sets of fenugreek seed
treatments were conducted, in order to investigate the
activated R. tibeticum pre-incubation effects on nodulation,
nitrogen fixation and growth of fenugreek under Ni stress.
Group (I): uninoculated seeds with R. tibeticum, group (II):
inoculated seeds with uninduced R. tibeticum group (III):
inoculated seeds with induced R. tibeticum. The present
study revealed that Ni induced deleterious effects on rhizobial
growth, nod gene expression, nodulation, phenylalanine
ammonia-lyase (PAL) and glutamine synthetase
activities, total flavonoids content and nitrogen fixation,
while the inoculation with an activated R. tibeticum significantly
improved these values compared with plants
inoculated with uninduced R. tibeticum. PAL activity of
roots plants inoculated with induced R. tibeticum and
grown hydroponically at 75 and 100 mg L-1 Ni and was
significantly increased compared with plants receiving
uninduced R. tibeticum. The total number and fresh mass
of nodules, nitrogenase activity of plants inoculated with
induced cells grown in soil treated up to 200 mg kg-1 Ni
were significantly increased compared with plants inoculated
with uninduced cells. Plants inoculated with induced
R. tibeticum dispalyed a significant increase in the dry
mass compared with those treated with uninduced R.tibeticum. Activation of R. tibeticum inoculum with a
mixture of hesperetin and apigenin has been proven to be
practically important in enhancing nodule formation,
nitrogen fixation and growth of fenugreek grown in Ni
contaminated soils.

The objective of this study is to explore the
response of an activated Rhizobium tibeticum inoculum
with a mixture of hesperetin (H) and apigenin (A) to
improve the growth, nodulation, and nitrogen fixation of
fenugreek (Trigonella foenum graecum L.) grown under
nickel (Ni) stress. Three different sets of fenugreek seed
treatments were conducted, in order to investigate the
activated R. tibeticum pre-incubation effects on nodulation,
nitrogen fixation and growth of fenugreek under Ni stress.
Group (I): uninoculated seeds with R. tibeticum, group (II):
inoculated seeds with uninduced R. tibeticum group (III):
inoculated seeds with induced R. tibeticum. The present
study revealed that Ni induced deleterious effects on rhizobial
growth, nod gene expression, nodulation, phenylalanine
ammonia-lyase (PAL) and glutamine synthetase
activities, total flavonoids content and nitrogen fixation,
while the inoculation with an activated R. tibeticum significantly
improved these values compared with plants
inoculated with uninduced R. tibeticum. PAL activity of
roots plants inoculated with induced R. tibeticum and
grown hydroponically at 75 and 100 mg L-1 Ni and was
significantly increased compared with plants receiving
uninduced R. tibeticum. The total number and fresh mass
of nodules, nitrogenase activity of plants inoculated with
induced cells grown in soil treated up to 200 mg kg-1 Ni
were significantly increased compared with plants inoculated
with uninduced cells. Plants inoculated with induced
R. tibeticum dispalyed a significant increase in the dry
mass compared with those treated with uninduced R.tibeticum. Activation of R. tibeticum inoculum with a
mixture of hesperetin and apigenin has been proven to be
practically important in enhancing nodule formation,
nitrogen fixation and growth of fenugreek grown in Ni
contaminated soils.

The objective of this study is to explore the
response of an activated Rhizobium tibeticum inoculum
with a mixture of hesperetin (H) and apigenin (A) to
improve the growth, nodulation, and nitrogen fixation of
fenugreek (Trigonella foenum graecum L.) grown under
nickel (Ni) stress. Three different sets of fenugreek seed
treatments were conducted, in order to investigate the
activated R. tibeticum pre-incubation effects on nodulation,
nitrogen fixation and growth of fenugreek under Ni stress.
Group (I): uninoculated seeds with R. tibeticum, group (II):
inoculated seeds with uninduced R. tibeticum group (III):
inoculated seeds with induced R. tibeticum. The present
study revealed that Ni induced deleterious effects on rhizobial
growth, nod gene expression, nodulation, phenylalanine
ammonia-lyase (PAL) and glutamine synthetase
activities, total flavonoids content and nitrogen fixation,
while the inoculation with an activated R. tibeticum significantly
improved these values compared with plants
inoculated with uninduced R. tibeticum. PAL activity of
roots plants inoculated with induced R. tibeticum and
grown hydroponically at 75 and 100 mg L-1 Ni and was
significantly increased compared with plants receiving
uninduced R. tibeticum. The total number and fresh mass
of nodules, nitrogenase activity of plants inoculated with
induced cells grown in soil treated up to 200 mg kg-1 Ni
were significantly increased compared with plants inoculated
with uninduced cells. Plants inoculated with induced
R. tibeticum dispalyed a significant increase in the dry
mass compared with those treated with uninduced R.tibeticum. Activation of R. tibeticum inoculum with a
mixture of hesperetin and apigenin has been proven to be
practically important in enhancing nodule formation,
nitrogen fixation and growth of fenugreek grown in Ni
contaminated soils.

The nitrogen cycle of Earth is one of the most critical yet poorly understood biogeochemical
cycles. Current estimates of global N2 fixation are approximately 240 Tg N y−1 with a marine
contribution of 100–190 Tg N y−1. Of this, a single non-heterocystous genus, Trichodesmium
sp. contributes approximately100 Tg N y−1 (Capone pers. comm.). Geochemical evidence
suggests that, on a global scale, nitrogen fixation does not always keep pace with denitrification
on time scales of centuries to millenia (Falkowski and Raven, 1997), yet it remains unclear
what process (es) limits nitrogen fixation in the oceans. More importantly, given the
potential for heterocystous cyanobacteria to outcompete organisms such as Trichodesmium, itis unclear why the apparent tempo of evolution of marine diazotrophic cyanobacteria is so
slow. Diazotrophic cyanobacteria have effectively become the “gate keepers” of oceanic productivity,
yet despite the rapid radiation of eukaryotic oxygenic photoautotrophs throughout
the Phanaerozoic eon marine cyanobacteria seem like living fossils (Berman-Frank et al.,
2003). Finally, some Questions needs answering, Are there N2-fixing picoplankton? What
limits the growth of N2-fixing microorganisms in the open ocean? Is N2 fixation associated
with zooplankton?

The nitrogen cycle of Earth is one of the most critical yet poorly understood biogeochemical
cycles. Current estimates of global N2 fixation are approximately 240 Tg N y−1 with a marine
contribution of 100–190 Tg N y−1. Of this, a single non-heterocystous genus, Trichodesmium
sp. contributes approximately100 Tg N y−1 (Capone pers. comm.). Geochemical evidence
suggests that, on a global scale, nitrogen fixation does not always keep pace with denitrification
on time scales of centuries to millenia (Falkowski and Raven, 1997), yet it remains unclear
what process (es) limits nitrogen fixation in the oceans. More importantly, given the
potential for heterocystous cyanobacteria to outcompete organisms such as Trichodesmium, itis unclear why the apparent tempo of evolution of marine diazotrophic cyanobacteria is so
slow. Diazotrophic cyanobacteria have effectively become the “gate keepers” of oceanic productivity,
yet despite the rapid radiation of eukaryotic oxygenic photoautotrophs throughout
the Phanaerozoic eon marine cyanobacteria seem like living fossils (Berman-Frank et al.,
2003). Finally, some Questions needs answering, Are there N2-fixing picoplankton? What
limits the growth of N2-fixing microorganisms in the open ocean? Is N2 fixation associated
with zooplankton?

Impact of harsh environmental conditions play an essential role in the control of legume-rhizobia
interactions. They can arrest the growth, multiplication and survival of rhizobia in soil
rhizosphere. The harsh environmental conditions may also have depressive effect on the
steps involved in legume-Rhizobium symbiosis such as molecular signaling, infection process,
nodule development and function, resulting in low nitrogen fixation and crop yield. Selection
of hosts and their nitrogen-fixing endosymbionts that are tolerant to a broad range of
environmental stresses is important for agriculture system. Understanding the key molecular
factors and steps in rhizobia-legume interaction is of crucial importance for the development
of Rhizobium strains and legume cultivars with high N2-fixation potential. Prevelence
and aboundance of rhizobia species vary in their tolerance to major environment factors;
consequently, the selection of resistant strains is an important option. Better N2 fixation can
be achieved by selecting tolerance or resistance rhizobia from soil subjected to environmental
stress. The selection and characterization of harsh conditions-tolerant strains with efficient
symbiotic performance may be a strategy to improve Rhizobium-legume symbiosis and
crop yield in adverse environments. Environmental stress severely affected on various metabolic
activities of legumes including, nod gene expression, photosynthesis, synthesis of proteins,
enzymes and carbohydrates. Therefore, understanding the environmental stress–
rhizobia–legume interactions is urgently required for growing legumes under harsh environmental
stress. Research into these areas is currently underway in several research groups
throughout the world and it is anticipated that this research will provide beneficial outcomes
resulting in improved sustainability and productivity in agricultural systems