الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
The twining plants are a widespread group of plants in wetlands. Most of them are nuisance weeds. In the Nile Delta coast, the occurrence of twining plants is represented in four habitats namely salt marsh, sand flat (sand formations), cultivated land and canal bank habitats. The experimental work of this thesis is a comprehensive survey of the response of Swallowwort (C. acutum) to water stress and drought stress during various stages of plant development. Swallowwort (C. acutum) is a problematic invasive perennial twining species, with widespread occurrence in diverse habitats. First, the response of Swallowwort to salt stress and water stress was evaluated at the germination stage. Salinity reduced germination uniformity and germination synchrony and might delay start of germination but accelerates its termination with a consequent shortening of the time spread of germination. The recovery percentage was lower but speed of recovery was higher compared with the corresponding parameters of non-treated seeds. Recovery percentage was slightly improved with the increase in the level of salinity pretreatment.
The adverse effect of lowering water potential of the medium, on germination of C. acutum, induced by PEG was more severe when that of iso-osmotic NaCl, and the relieving effect of SA amendment was more evident under the impact of salinity stress than under water stress. Nevertheless, despite the beneficial role of SA in relieving the adverse effect of stress on germination of C. acutum, it, by itself, exerted a mild impact on non-salinized seeds.
Thereafter, the response of Swallowwort to salt stress up to 160 mM NaCl in combination with the form of N was evaluated during the vegetative stage. . The response of C. acutum to water stress under controlled nutrient supply on sand culture was investigated to assess the effect of water status of the soil on plant use efficiency of water and nutrients. Plants were subjected to water regime (% field capacity) of: 100, 35, 25,
12.5 and 5 for 10 days in a greenhouse. Whereas plant fresh weight was reduced under the impact of water stress, dry weight exhibited its maximum under moderate drought and this was associated with allocation of greater proportions of plant biomass to root and stem at the expense of leaves. The increase in photosynthetic pigments of stressed plants is related to the drought-induced P deprivation. The rates of photosynthesis and transpiration and the stomatal conductance were progressively inhibited under drought stress; but substomatal CO2 concentration showed a minimum at 12.5% field capacity. Soluble sugars and starch were deprived whereas proline was accumulated in the leaves under drought stress. Drought stress affected the uptake and partitioning of minerals within the plant and increased use efficiency of water and minerals, particularly P.