الفهرس 
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Abstract
The thesis includes three main parts. The first part deals with an investigation of the effect of habitat factors on the composition of Ipomoea carnea. The second part was aimed at studying seasonal fluctuations in mineral composition and metabolic contents of leaves and stems of the plant. The third part includes identification of allelochemical compounds present in soil rhizosphere and different plant organs. Studies on the effect of soil rhizosphere and water extract of the tiller system of the plant on growth, anatomy and some metabolic contents of Echinochloa colona also carried out.
1-Ecological studies
The species concerned , Ipomoea carnea , inhabits various habitats ranging from hydric to xeric habitat. Two different habitats namely : (a) canal banks habitat, at Benha and (b) saline habitat at Kafr El-Shiekh were chosen. The climatic factors were summarized . Soil texture, calcium carbonate content, cations namely, Na+, K+, 01.12+, Fe,3+ Mg2+, P3+ and zinc were determined. The pH of the soil was found to be 7.35 and 8.00 in the former and latter habitat respectively. The electrical conductivity for samples collected from canal banks habitat was less than 1mm hos/cm and more than 1mm hos/cm in samples collected from latter habitat indicating that there was no development for alkalinity or salinity in the soil supporting Ipomoea carnea in canal banks habitat and saline nature of the soil supporting the plant in the latter habitat. Effect of habitats on anatomical features of different organs ( root, stem, petiole and leaf) showed noticeable variations in different organs in the plants of the two habitats. It revealed thicker of phellogen layer, bigger diameter of bundle, bigger vascular bundle area and bigger percentage of calcium oxalate , in contrast to smaller diameter of root and smaller area of
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Summary
xylem vessels and increase in number of vascular bundle in plants of saline habitat. In stems, there was smaller diameter, smaller number of parenchyma cells in pith, smaller number of cortical layers as well as higher percentage of calcium oxalate content. In leaves, the study indicates that the maximum length and width of mesophyll , bigger length and diameter of xylem vessels, bigger number of xylem cells in each xylem vessel as well as bigger number of channals in phloem and bigger number of calcium oxalate was attained in plants of saline habitat. The data of plant analysis showed noticeable variations in the plants of the two habitats. Analysis of the ash content revealed higher values of sodium, potassium, calcium and magnesium in leaves and stems of plants of saline habitat. On contrast, the higher values of iron, cupper and zinc were attained in leaves and stems of plants of canal banks. The study of the effect of habitats on metabolic products was achieved by means of studying the carbohydrate fractions, nitrogen components, proteins and fatty acids in leaves and stems of plants of the two habitats. The results obtained revealed that:
The total carbohydrates, direct reducing sugars as well as polysaccharides content varied in response to habitat conditions. The data of total nitrogen, soluble nitrogen and insoluble nitrogen of the leaves and stems showed variations among different parts and habitats. Concerning the amino acids, the results revealed the presence of glycine, alanine isoleucine, valine, threonine, aspartic acid, leucine, serine, proline, methonine, a-amino, cystein, phenyl alanine, glutamic acid, histidine, tyrosine and lysine. The data also indicate variations in the total concentration as well as among the different parts and habitats. With respect to proteins, the SDS-electrophoresis revealed the presence of 9 band in plants of saline habitat and 7 band in plants of canal banks.
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Summary
Analysis of the fatty acids revealed the presence of 12 fatty acids in plants of the two habitats. 2-Physiolouical studies
The second part of the thesis deals with seasonal fluctuations of mineral composition of ash content, carbohydrates, nitrogen components protein bands as well as fluctuation of fatty acids and photosynthetic pigments.
The composition of ash contents of leaves and stems of Ipomoea carnea showed variations in different seasons. Concerning changes in carbohydrate contents results obtained indicated changes in carbohydrate fractions during the different seasons in the two plant organs. Total carbohydrate content showed higher concentration in summer; being 28.7% and 31.1% in leaves and stems of the plant respectively. The total sugar content reached its highest level 4.3% in summer in leaves and 3.9% in spring in the stems. The direct reducing sugars recorded in leaves were higher than those for the stems. It showed negative correlation with polysaccharide contents in leaves and stems. The increase in total reducing sugars in leaves and stems is associated with a decrease in polysaccharide content. The values of nitrogen fraction showed seasonal changes in the two plant organs, with higher values attained in summer.
The SDS-PAG electrophoretic pattern of proteins of leaves revealed differences in the number of bands as well as molecular weight and relative percentage of individual band in different seasons. The higher number of protein bands was recorded in early and late spring, being 11 and 14 bands ( vegetative growth) compared to 7 bands in the rest of the studied seasons.
Gas liquid chromatography of the fatty acid methyl esters of the leaves of Ipomoea carnea revealed the presence of caprilic acid, capric acid, myristic acid, palmitic acid, palmitoleic acid, stearic acid, oleic acid,
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Summary
linoleic acid arahidic acid, eicosamonoenoic acid, benhnic acid and erucic acid, in leaves of plants collected during summer, autumn, winter and early spring. The essential oleic and erucic acids were not detected in leaves of the plants collected during the late spring. The variations in total, concentration as well as the seasonal changes in concentration of individual fatty acid and the presence of the essential oleic and erucic fatty acids may indicate that synthesized fatty acids may be readily converted to glycerides.
Photosynthetic pigments namely chlorophyll ”a”, chlorophyll ”b” and carotenoids were determined during different seasons. The results obtained showed fluctuations during different seasons. The highest values of photosynthetic pigments were attained in summer season. It revealed positive correlation with Mg2+ content and with few exceptions with total carbohydrate and total nitrogen content. 3-Allelopathic studies
The third part of the thesis deals with the identification of allelochemical compounds present in different plant organs and rhizosphere soil. The results revealed the presence of tannins and glycoalkaloids in all investigated organs and soils. The effect of rhizosphere soil supporting Ipomoea carnea as well as the effect of water extract of the shoot system of the plant was studied by using Echinochloa colona grains. The root and tiller lengths, mineral uptake , anatomical and ultra structure changes were determined.