Rhizobium gases form into a solid form via nitrogen

Rhizobium symbiosis is important as plants natural require
nitrogen for its life processes such as protein synthesis, because the plants
cannot fix their own nitrogen from the atmosphere they require nitrogen fixing bacteria
such as Rhizobium bacteria to provide this for them. Legumes have a symbiotic
relationship with these Rhizobium bacteria, these bacteria infect the plant via
their plant root hairs then develop plant root nodules in the plant roots. These
provide nitrogen for the plant, therefor a biological source of nitrogen
instead of being provided for by inorganic fertilisers which can have negative
effects such as ecological, Run off into water sources, or economic, the cost.

From my results we can see that various nitrate
concentration has an effect on the legume plant root nodules, as the nitrate
concentration increases the number of nodules decreases, but the nodule weight

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All organisms require nitrogen as nitrogen is a key factor
to create amino acids which in turn build up to make up proteins in plants and
animals. Whereas 78% of the earth’s atmosphere, living organisms require
nitrogen fixing bacteria to react nitrogen gas with other compounds and turn it
from a gases form into a solid form via nitrogen fixation so living organisms
can use it in solid form and not in a gas state (Barker, 2018).  Rhizobia bacteria are found within root
nodules of leguminous plants, they form a symbiotic relationship the bacteria
fix nitrogen for the legume plant. The Rhizobia bacteria are essential for
farming as nitrogen is essential in plant growth therefore affecting plant crop
yields for farmers who grow legume crops (Lerouge, 2017).

Rhizobia bacteria adjust their population size due to the
plant-root environment, the plant gives out a signal called the flavonoid, and
then in response to this it creates a molecule known as the nod signal (Bothe,
2006). Rhizobia bacteria stay in the soil whilst the plants root hairs curls,
once it grows the Rhizobium bacteria infect them by using these curled root
hair cells. The type of rhizobia bacteria depends of the species of legume
plant. The bacteria will multiply on the legume plant root hairs, an infection
thread enter to the plants allowing the bacteria to supply a source of nitrogen
to the plant. Nodules will then form and surround the rhizobia bacteria,
nodules will become visible on plant roots around a fortnight after the legume
is planted, nodules will start to fix the nitrogen from the atmosphere and
supply the legume plant with solid Nitrogen to be used in protein synthesis

Inorganic and organic fertilisers are used by farmers for
successful plant growth within their crops, application of animal manure
increase the quantities of Nitrogen (N) within the soil (Liu, 2014).

Agriculture would benefit greatly from growing a crop that
allows a nitrogen fixing symbiotic relationship with a bacteria such as the
Rhizobium bacteria. Farmers would benefit from this as it would save greatly on
the expense of buying nitrogen fertiliser as the symbiotic relationship would
provide the crop with all the nitrogen it required to grow. Nitrogen fixing
plants are essential for the world’s agriculture, plants such as Soya beans,
Beans and Rice, fix their own nitrogen which leads to environmental and
economic benefits. The Environmental benefits would stop inorganic fertilisers
from polluting sources of water and disrupting living organisms in the
surrounding areas of the farm. The economic benefits are the low cost of not
buying the inorganic fertilisers that other farmers use for plants which cannot
fix their own nitrogen or have a symbiotic relationship with a nitrogen fixing
bacteria such as the Rhizobium bacteria.

Within this paper a discussion and analysis of results will
be stated, the aim of the paper is to show the affect Rhizobium cultures and
the quantity of nitrogen affects the root growth of alfalfa root cells, this is
important as the data could be used to show how the amount of nitrogen can be
fixed via the root nodules which have been infected by Rhizobium cultures.


Sterilised flasks of Fahraeus’ medium were used to grow the
seeds of alfalfa will be grown in. The medium was nitrogen and carbon free.
Different concentrations of nitrogen’s were added to the medium at the
concentrations of 0mM, 0.1mM, 1mM, 5mM and 10mM at 5 different series within
the flasks. Cultures of Rhizobium bacteria within growth medium were given to
the class.

40 seeds of Alfalfa were washing in 80% concentrated Ethanol
for 10 minutes, this is to sterilise the seeds. The seeds were then rinse with
sterilise distilled water to remove the ethanol from the alfalfa seeds. The
cultures of Rhizobium were centrifuged at a speed of 1000xg for 10 minutes. The
bacteria was then suspended once again in mamitol after the liquid supernant
was removed, the water was at same volume as the liquid supernant. The bacteria
was then centrifuged again.

30 of the seeds were transferred aseptically into the
Rhizobium suspension and incubated for 20 minutes. Then 6 seeds were
transferred aseptically into each flask of medium, also with a minimal volume
of the bacterial suspension. Seeds were ensured to not be covered in water but
still have limited access to water. The flasks were then covered with cotton
wool and foil.


After six weeks of germination of the alfalfa seeds, the
root and hairs were measured and weighed to see how different solution levels
of nitrate affects legume root growth and number of plant root nodules. The
number of nodules per alfalfa plant were counted. The class results show that
plants in solutions with nitrogen under 1mM had many nodules grew on the plant
roots, whereas in solution of 5mM and 10mM had fewer nodules grow on the
alfalfa plant roots.Alfalfa seeds were germinated of six weeks on an agar media
with different nitrate concentrations of nitrate. The alfalfa were kept at a
temperature of 20C. Figure 1 is the data collected from the Alfalfa with error
bars showing a 95% confidence intervals across the mean.