الفهرس 
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Abstract
Soil salinity is one of the major environmental stresses affecting
crop productivity. Effects of salinity on plants vary widely depending on
the developmental stage of the plant as well as types and concentrations
of salts. Salinity soil becomes the biggest challengers for human life;
about 40% of the world land is threatened with salinization over the
world. Multi approaches were urgently needed to get ride of salinity, like
selective a new salinity resistant plant grains, continuous reclamation of
salt-affected soils, chemical treatments of plants and inoculation of the
plants with bio-fertilizer salt-tolerant microorganisms. The present work
carried out at Sakha Agricultural Research Station, Kafr El- Sheikh.
Therefore, the aim of the present study was to isolate nitrogen
fixing cyanobacteria from salty soils and using them to increase rice
productivity in saline soil and getting rid of soil salinity. Also studying
the role of inoculation with different cyanobacterial inoculants Nostoc
calcicola, Anabaena variabilis and Nostoc linkia on rice growth
parameters in soil at different concentrations of salinity. Growth
parameters had been recorded after 40 days.
Twenty nine samples were collected from the upper surface layer
of the soil (0-15 cm) from different sites at Kafr El-Sheikh Governorate;
to sort and isolate some of the most common cyanobacteria isolates
inhabited these rice soils. The 13 isolated cyanobacteria isolates were
identified morphologically and physiologically. The propagated
cyanobacteria isolates were also tested for their biomass accumulation,
nitrogen content and their biochemical composition, i.e., carbohydrates,
polysaccharides, Protein, lipids, and pigments content.
The obtained results can be summarized as in the following:
5.1. Soil analysis:
Soils were collected from different salty sites in (Baltim, Elhamoul,
El ryaad and Seidy-Salem) at Kafr El-Sheikh. Soil had different
characteristics such as EC, pH, CO3
- -, HCO3
-, Cl -, SO4 - -, Mg++, K+, Na+
and Ca++. Cyanobacteria were isolated from soil showed highly adaption
and bear salinity from 4 to 73 dS.m-1.
5.2. Identification of the cyanobacteria isolates:
Four nitrogen fixing cyanobacteria were isolated and identified as
three isolates were used in study Nostoc calcicola {Baltim ,site (1),
Seidy salem, site (6, 7, 8, 13), El hamoul, Site (9)} Anabaena variabilis
{(El hamoul, Site (2, 4), El ryad, Site (11)}, Nostoc linkia {(El ryad,
Site (3), Seidy salem, Site (10)}, the fourth one was toxic isolate which
was identified as Nodularia herveyana (Baltim, Site (12).
5.3. Biomass production by the isolated cyanobacteria strains:
All the cyanobacterial isolates grow under the continuous
illuminated conditions when they cultured for different periods of 1, 2, 3,
4, 5 and 6 weeks under light intensity of 5000 lux and ambient
temperature of 28-32oC on BG11 medium. The data indicated that the
highest biomass of 0.949 g.L-1 was recorded by N. calcicola after 5
weeks, followed by N. linkia, which produced 0.680 g.L-1 in the same
period. While A. variabilis, recorded high dry weight 0.675 g.L-1 in the
fourth weeks.
5.4. Pigments Determination:
There was ahighly significant difference between chlorophyll a
content of all tested cyanobacteria strains. Results revealed that the
highest Chlorophyll a content due to N. Calcicola, and Anabaena
variabilis, then Nostoc linkia respectively. Aside chloropylls as the
primary photosynthetic pigment, microalgae also form various accessory or secondary pigment, such as phycobiliproteins and awide range of
carotenoids. Carotenoid and Phycopilin Pigments, the highest contents
were due to Nostoc calcicola.
5.5. Nitrogen content:
All the isolated cyanobacteria strains had the ability to produce
nitrogen. By increasing the incubation period from 1 to 6 weeks the
nitrogen activity increased. The highest nitrogen content was recorded by
Nostoc calcicola, followed by Anabaena variabilis, then Nostoc linkia.
5.6. Total carbohydrate content:
All the tested isolated cyanobacteria strains on at periods of 1 to 6
weeks led to increase the total carbohydrate contents along with
increasing the time of incubation respectively, except in case of Nostoc
calcicola, which start decreasing in fifth week, also N. calcicola showed
the highest total carbohydrate contents of 29.7% followed by 23.107%,
17.837% recorded by Nostoc linkia and A. variabillis respectively.
5.7. Exopolysaccharides content:
Results confirmed that the presence of EPS in the isolated
cyanobacteria isolates and showed a highly significant difference between
all tested cyanobacteria isolates. Exopolysaccharides content of
cyanobacteria isolates increase by increasing the incubation periods.
Results revealed that the highest ESP content of 0.198 mg. ml-1 due to N.
calcicola in the sixth week followed by Anabaena variabilis, which give
0.183 mg. ml-1 in the fifth week followed by Nostoc linkia, which give
ESP content of 0.090 mg. ml-1 in the fifth weeks.
5.8. Total protein contents:
The highest TPC, 25.850 mg. g -1 had recorded by Nostoc calcicla,
followed by Anabaena variabilis, which gave 17.687 mg. g -1, in the fifth
week followed by Nostoc linkia, which gave biomass of 17.190 mg. g -1
in the fifth weeks.
5.9. Effect of filtration of cyanobacterial growth on rice seedlings:
Salinity had a highly significant decrease of root length and shoot
length of rice seeds. The root length and shoot length (cm) of rice
seedlings showed a highly significant reduce with rising salinity
concentrations (5, 10, 15, 20, 25 ds. m-1), incase of control (without
inculant) and also with inoculation with different cyanobacteria inoculant.
Otherwise, inoculation showed a highly significant increase in root length
rice seeds compared with un-inoculated.
5.10. Pots experiment:
The aim of this experiment was to study the role of inoculation
with different cyanobacterial inoculant Nostoc calcicola, Anabaena
variabilis and Nostoc linkia on rice growth parameters in soil at different
concentrations of salinity. Growth parameters had been recorded after 40
days. The shoot and root length (cm) were highly significant reduced with
rising salinity concentrations. Otherwise, inoculation showed a highly
significant increase in shoot and root length compared with un-inoculated
soils. In addition, inoculation with cyanobacterial isolates (Nostoc
calcicola, Anabaena variabilis, and Nostoc linkia).
A significant positive effect of inoculation with the tested cyanobacterial
isolates in EC was detected. Inoculation decreased the EC of soils
compared with (un-inoculated control). It is concluded that: -
1- Cyanobacterial isolates under studying are more efficient in salty
soils they had the ability to fix nitrogen.
2- The isolates can biosynthesize and secrete a great diversity of
primary and secondary metabolites such as polysaccharides,
pigments and carbohydrates which are valuable substances with
potential applications in the food, pharmaceutical and cosmetics
industries.