الفهرس 
Ecological studiesOnly 14 pages are availabe for public view
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Abstract
This study attempts to overview the ecophysiology and molecular biology of plant tolerance mechanisms in response to most important abiotic stress factors. This study was carried out at two regions of the north western and eastern coast of Egypt included: Wadi El Maktala of Sedi Brani of North Western and El Bardawil Lake of eastern coast (north Sinai). The selected representative plants include xerophytes and halophytes naturally growing under different habitat conditions of two concerned regions.
Climatic data was collected from metrological stations of El Arish that represent El Bardawil lake area and El Sallum that represent Sedi Brrani. The data indicated that the highest temperature was on August and the highest relative humidity was at July and August in both regions. Amount of rainfall was the highest in El Arish compared with El Sallum whereas wind velocity has the opposite trend.
Texture of the soil associated with the studied species of both regions was sand (Aridosol) according to World Soil Taxonomy. The soil moisture was increased during wet season compared with dry one for most soil samples except for the soil associated with D. tortuosa and J. acutus. Slight variation of saturation point was found between seasons at different depths except for the soil associated with J. acutus.
Electrical conductivity was very high at El Bardawil lake area, while it was very low at Sedi Brrani. Soil reaction was weakly alkaline in both regions. Calcium followed by magnesium cations and chloride anions were the dominant in the soil samples of Sedi Brrani. Whereas, the soil samples around El Bardawil lake area was characterized by high concentrations of both cations and anions.
It is evident from the obtained results that creating a favorable water potential gradient is the most challenging factor in the adjustment of the different species to various stress conditions. In this respect, the behavior of xerophytes and halophytes showed different mechanisms in heir adjustment which show in both Tables (104 and 105).
The DNA-RAPD technique was used for identification of finger print of the studied species under stress by 8 successive primers. The results indicated that the percentage of polymorphism between the studied species of most primers were 100% in which the primer OPI-15 has the highest amplified fragments. The primer OPQ-18 exhibits the lowest percentage of polymorphism (85%).
Protein pattern gel electrophoresis study revealed the appearance of most proteins that have specific low molecular weights, which are unique for each plant. These patterns reflect variations of behavior and adaptation of these species under stress conditions. Also, the result demonstrated that only leaves of D. tortuosa and J. acutus have specific unique high molecular weights proteins during dry season. Also, the data showed that there is a presence of three isoforms of POD enzyme in leaves and roots of studied species during both seasons. In which, the isozyme No. (1) is the dominant in some sample species and the isozyme No. (2), (3) are specific for roots of D. tortuosa during dry season. As regard to PPO, there is one isoform that appeared in all the studied leaves and roots of species during both seasons.