الفهرس 
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Abstract
The present study includes two parts: first, detailed survey of weed flora in the fields of winter crops at El-Dakahlia district. 56 species belonging to 49 genera and 21 families were recorded. The major families include Poaceae, Asteraceaea, Chenopodiaceae, Fabaceae and Brassicaceae. Therophytes (72%), hemicryptophytes (3.7%) are the dominant chorotypes. Floristically, the species are mainly Mediterranean, Irano-Turanian and cosmopolitan elements. The statistical analysis revealed that, there are significant differences between soil factors and the important characters that control the distribution and abundance of weed flora in the cultivated land habitats are soil texture, moisture content, salinity level and pH. Second, investigation of autecological and phytochemical characteristics of two chosen winter weeds namely, Anthemis cotula and Coronopus squamatus. Fresh samples of the plants were examined to detect the morphological characters and life strategy of the plants. Microscopic examination of the cross sections showed the anatomical characteristics of stems. Leaves and root. The chromosomes counts of A. cotula and C. squamatus were 2n=18 and 2n=32in the two plants respectively. Taxonomical, A. cotula belongs to subfamily Asteroideae, tribe Anthemideae, subtribe Anthemidineae while C. squamatus family Barassicaceae and tribe Lepideae. The ecological characteristics of the types of the two plants were investigated (vegetation and edaphic factors). The phytochemical study revealed that, The nutritive values of the two plants were 244.39 and 225.55 Cal./100g, respectively the polyphenols and flavonoids contents were higher in A. cotula (3.92 and 6.65%) that in C. squamatus (1.15 and 2.17%). The shoot system of C. squamatus contained 9 essential amino acids and 8 non-essential amino acids. Blue-coloured volatile oils with mean value of 56 mg/ 100g were obtained from the flowers head of A. cotula. Using GC/MS analysis, Fourteen compounds were detected.