الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
This work was carried out on Najas marina L. subsp. armata to specify the environmental agents (water and sediment) controlling its distribution in Lake Burullus, Egypt. In addition to assess the impact of pollution with heavy metals on secondary metabolites of N. marina collected from different locations. In order to achieve the aims of this study the following points were applied: 1- Prevailing the vegetation composition of N. marina at the study area. 2- Identify the characteristic aquatic plant groups and their indicator species through the application of multivariate analysis. 3- Evaluate the vegetation – environmental relationships through identifying the environmental variables mainly hydrosoil and water that influence the aquatic vegetation in the study area using statistical methods. 4- Assessment of the water and hydrosoil features in twenty-five sites through measuring some chemical parameters as pH, electric conductivity, chlorides, carbonates, bicarbonates, K+, Na+, Ca++, Mg++, total nitrogen and total dissolved phosphorus. 5- Determination of the secondary active metabolites (phenolics, flavonoids, tannins, and alkaloids) in N. marina plant at four locations. 6- Evaluation of antioxidant activities and antimicrobial potential of different extracts prepared from N. marina plant at four locations. 7- Assessment of the heavy metals impact on the secondary metabolites content in N. marina plant at four locations. This investigation found that: • Analysis of the studied sites revealed that the Najas marina subsp. armata (H. Lindb.) Horn plant was associated with nine associated species at the study area. All recorded associated species were perennials. The vegetation analysis of the study area was classified using multivariate analysis (classification and ordination). The application of TWINSPAN classification on the importance values of ten plant species recorded in 25 sites at the study area (Lake Burullus) led to the recognition of six vegetation clusters: Cluster A, B and C represented Mastroh location which indicated by Arthrocnemum macrostachyum, Juncus acutus and Suaeda vera, respectively. Cluster D represented Al Maksabah location which indicated by the Potamogeton pectinatus and dominated by Phragmites australis. Cluster E represented Deshimi location. N. marina subsp. armata is the indicator species of this cluster. Cluster F represented Abo Amer location. Phragmites australis represents the indicator species in this cluster. The factors affected the distribution of vegetation groups evaluated by Canonical Correspondence Analysis (CCA) ordination. The most important factors affecting vegetation types in Lake Burullus were salinity, total nitrogen and total dissolved phosphorous. The ethanolic extract of total phenolic, total flavonoids, total tannins, total alkaloids and antioxidant scavenging activity in N. marina exhibited higher values than the petroleum ether extract. Also, there is a marked variation in the total phenolic, total flavonoids, total tannins, total alkaloids content and antioxidant scavenging activity between the plant samples at the four locations (Mastroh, Ab Amer, Al Maksabah and Deshimi). The antimicrobial activity of N. marina plants extracts were tested against many microbial pathogens, where the obtained results elucidate that the extracts of N. marina plant, generally, possess activity against only Bacillus subtilis and Bacillus cereus out of the tested microorganisms. The results exposed that the extracts of N. marina from Mastroh location expressed better antimicrobial activity than those of the same plant from the other studied localities. There is a spatial variation in K+, Na+, Ca++, Mg++, TP and TN as well as heavy metals concentration (Co, Cu, Pb, Cd, Cr, Ni, Mn, Zn, Fe, As) in sediment, water and N. marina samples collected from the four studied locations. Mastroh location showed the highest metals concentrations whereas, Deshimi location exhibited the lowest metals concentrations. Bioaccumulation factor of ten elements were varied at the different studied locations