الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Five submerged hydrophytes flourished in north east Nile Delta have been chosen to be the subject of this study. These are Ceratophyllum demersum, Myriophullum spicatum, Potamogeton crispus, P. nodosus and P. pectinatus .They were growing at three different hydric habitats (kafr Demira irrigating canal, El Gammalia with agricultural chemicals and contaminants and Manzala Lake with both organic and inorganic pollutants.
The physiological aspects of submerged hydrophytes can be summarized as follows:
Chlorophyll a , chlorophyll b and total chlorophylls content in leaves of Potamogeton pectinatus is highest value in winter season if compared with other submerged hydrophytes. On the other hand, chlorophyll a content in Ceratophyllum demersum leaf showed the lowest value.
Comparing the data in table 7 showed that membrane stability index of Ceratophyllum demersum is the highest values if compared with all submerged hydrophytes in winter season. Moreover Potamogeton pectinatus recorded the highest values of membrane stability index (MSI) in summer season. On the other hand, the changes in membrane leakage follow the flowing order: Potamogeton pectinatus > Potamogeton crispus >Potamogeton nodosus > Myriophullum spicatum> Ceratophyllum demersum in winter season. On the other hand, Potamogeton crispus showed the highest membrane leakage if comport with other submerged hydrophytes.
The data presented in table 8 clear that relative water content in leaves of submerged hydrophytes follows the following pattern: Potamogeton nodosus > Potamogeton pectinatus > Myriophullum spicatum> Potamogeton crispus >Ceratophyllum demersum in winter season . In addition in summer season relative water content of Myriophullum spicatum recorded the highest value in all submerged hydrophytes while Potamogeton nodosus showed the lowest one the changes in saturation water deficit in leaves of submerged in winter season. The changes in SWD showed opposite trend in comparing with the changes relative water content.
The seasonal changes in heavy metal concentrations in both root and shoot within winter and summer seasons. The concentration of each measured heavy metal depended on the plant species as well as the season. The pattern of changes in heavy metal detected in both root and shoot behave similar changes with different magnitude, where all elements increase in summer season than winter one. The changes in heavy metal in concentration behave the following order: CrZn >Fe >Pb >Cd.