الفهرس 
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Abstract
The medicinal plants are referred to plants that are used for
their therapeutic or medicinal values. It seems necessary to do
research related to the correlation between medicinal plants and salt
stress for the increasing need of medicinal plants.
Common purslane (Portulaca oleracea L.), which is a
member of Portulacaceae, is widespread as a weed and has been
ranked the eight most common plants in the world. Purslane is one
of the most used medicinal plants, being a common, herbaceous
succulent annual plant. It grows in many geographically different
areas worldwide and is well adapted to extreme drought and heat,
and to saline and nutrient-deficient conditions.
Salinity still remains one of the world’s most serious
environmental problems. Salt stress induced by salinity in general
could be regarded as one of the major environmental factors that
exert considerable alterations on plant growth and metabolism. Soil
salinity is a major abiotic stress that affects seed germination and
limits seedling growth worldwide. Seed germination, seedling
growth and vigour vegetative growth, flowering and fruit set are
adversely affected by high salt concentration, ultimately causing
diminished economic yield. To survive the environmental stresses,
plants respond and adapt through physiological, developmental and
biochemical changes, including activation of antioxidative
enzymatic system and accumulation of some metabolites.
So, the aim of the present study is to evaluate the response of
the medicinal plant namely, P. oleracea L. that collected from
different soil types in relation to environmental stress in an attempt
to improve their production and maintain their sustainable use. The
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objectives used to achieve such aim are: 1) Surveying the
distribution of Portulaca oleracea L. in different habitats of
Fayoum depression. This will be achieved by successive field trips
covering the different habitats in Fayoum depression and collection
of representative specimens. 2) Environmental sittings of the
studied habitats. This will include soil chemical and soil physical
analysis. 3) characterization of the collected specimens through
monitoring of molecular markers and the changes in the level of
antioxidant as a role in salinity tolerance of P. oleracea L.
Therefore, the work could be divided into two parts:
Part one:
The experiments of this part were carried out mainly to study
the effect of different soil types (saline, healthy and reclaimed soils)
on the response of some antioxidant enzymes (catalase, peroxidase
and superoxide dismutase) and the contents of some metabolites
namely, total protein, total fatty acids, choline, glycine betaine, free
proline and total carbohydrates in the leaves of P.oleracea L.
collected from these different soil types. The results obtained could
be summarized as follows:
1- The studied antioxidant enzymes in the leaves of
P.oleracea collected from saline soil exihibited a highly significant
increase in comparison to that collected from healthy and reclaimed
ones which act as a defensive team to protect cells from oxidative
damage and responsible for scavenging ROS.
2- A highly significant increase of the contents of these
metabolites was exhibited in the leaves of P.oleracea collected
from saline soil in comparison to healthy and reclaimed ones which
may help in osmotic adjustment, protection of cellular
Summary and Conclusion
109
macromolecules, maintenance of cellular PH, detoxification of the
cells and scavenging of free radicals.
Part two:
Is concerned with the effect of different concentrations of
salinity on germination, the response of some antioxidant enzymes
(catalase, peroxidase and superoxide dismutase) and the contents
of some metabolites in seedlings. The results obtained could be
summarized as follows:
1- Salinization induced a considerable reduction in seed
germination of the test plants. Generally the germination percentage
at saline soil exhibited slight decrease in comparison to control
while the germination percentage showed a highly significant
decrease at healthy and reclaimed ones.
2- Considerable increment of the contents of peroxidase in
the test plants was induced by salinity stress, which play a role in
removal of H2O2 from chloroplasts and cytosol.
3- Significant decrease of the contents of catalase of the test
plants was induced by salinity stress. Generally, the protective
action of catalase in response to salinity is limited because of its
relatively poor affinity towards its substrate and its sensitivity to
light.
4- Increasing salinity levels exhibited a highly significant
increase in the contents of superoxide dismutase of the test plants
which may help in catalyzing the breakdown of superoxide anion to
oxygen and hydrogen peroxide.
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110
5- The expression of catalase isozyme reduced, resulting in
accumulation of H2O2 which acts as a systemic molecule in
regulating stress tolerant gene expression.
6- The expression of peroxidase increased with salinity
stress, which may help in depletion of excess H2O2.
7- The expression of superoxide dismutase increased with
salinity stress which may help in catalyzing the breakdown of
superoxide anion to oxygen and hydrogen peroxide.
8- The biosynthesis of total carbohydrates exhibited a highly
significant increase under salinity stress which may help in
regulating and osmosis adjustment in current stress.
9- Increasing salinity levels exhibited a highly significant
increase in the contents of total protein of the test plants where the
plant diverted most of the synthesized protein from a state of
growth to a state of osmoregulation (survival).
10- A highly significant increase of the contents of proline of
the studied plants was induced by salinity stress which acts as a
reducer component of osmosis pressure in response to salt stress.
11- Remarkable increase of the biosynthesis of fatty acids of
the studied plant was induced by salinity stress which modifies fatty
acid composition, and is considered to be important for the salt
tolerance of plants.
12- A highly significant increase of the contents of choline
and glycine betaine of the studied plants was induced by salinity
stress which may help in osmotic adjustment, protection of cellular
macromolecules, maintenance of cellular PH, detoxification of the
cells and scavenging of free radicals.