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Available online xxxKeywords: Ecology Halophyte Mesembryanthemum crystallinum Relative growth rate Nile delta Conservation a b s t r a c t Ice plant (Mesembryanthemum crystallinum L.) is an important stress-tolerant halophyte distributed in saline areas along the Mediterranean coast of the Nile delta, Egypt. Plant communities dominated by M. crystallinum were studied in different habitats. The application of TWINSPAN classification based on 77 species recorded in 50 stands, led to the recognition of four vegetative groups, which are categorized under three communities. The first is salt marsh community co-dominated by M. crystallinum and Senecio glaucus L. The second is sand dune community dominated by Hordium murinum L. The third is sand flat community dominated by M. crystallinum. Electrical conductivity (EC), sodium ion concentration, Sodium Absorption Ratio (SAR) and sand fraction are the main controlling factors in the distribution of the different vegetative community. The distribution of M. crystallinum community was influenced by calcium carbonate, pH, E.C. and calcium.Various growth parameters including root, shoot and total fresh weight, diameter, leaf area, number of flowers and fruits were measured at two-week interval in the three habitats (sand dune, sand flat and salt marsh). The sand dune and salt marsh habitats, which are threatened by anthropogenic activities, were optimizing growth, flowering and fruiting of M. crystallinum.

Land reclamation causes weedy species to replace wild plant species. The present study characterizes the community of Brassica tournefortii Gouan in reclaimed areas of the Nile Delta of Egypt to determine its ecological amplitude, soil factors controlling its distribution, and its allelopathic control. The plant communities dominated by B. tournefortii were investigated in 60 sites. The importance value of each species based on cover and density was determined. Data were treated by multivariate analyses. Soils representing each community were analyzed. The allelopathic effects of Conyza bonariensis (L.) Cronquist, Trianthema portulacastrum L., and Pulicaria undulata (L.) C.A.Mey. and their mixtures on germination and seedling growth of B. tournefortii were investigated. Total phenolics, tannins, alkaloids, flavonoids, and saponins were estimated. The applications of TWINSPAN classification based on 140 species led to recognition of 4 vegetation clusters; 3 were dominated by B. tournefortii and 1 was codominated by Malva parviflora L. and Senecio glaucus L. Canonical correspondence analysis demonstrated that CaCO 3 , soil texture, and water holding capacity contributed significantly to the distribution of species. The water extracts of T. portulacastrum, C. bonariensis, and P. undulata could be applied at a concentration of 10 g/L for the management of this weed.

People rely on the synthetic chemical pesticides in most of the agricultural practices, which have a serious problem on human health and ecosystem. Essential oil (EO), derived from wild plants, offers a new opportunity to explore eco‐friendly green biocides. This study aimed to characterize the chemical constituents of EO from Egyptian ecospecies of Cleome droserifolia (Forssk.) Delile and evaluate its antioxidant and allelopathic potential. The EO was extracted from aerial parts by hydrodistillation and analyzed by GC/MS. To assess the allelopathic potential, EO concentrations from 50 to 200 μL L−1 were tested on Trifolium repens and three weeds. Antioxidant activity was determined using DPPH. Hydrodistillation yielded 0.64 % of dark yellow oil, which comprises 35 compounds, in which sesquiterpene was a major class and represented by 61.97 % of the total essential oil. Moreover, the dominant sesquiterpenes are cis‐nerolidol, α‐cadinol, δ‐cadinene, and γ‐muurolene. The speed of germination index, shoot and root length of clover and weeds were reduced in a concentration‐dependent manner. The IC50 values of C. droserifolia EO on germination of T. repens, Cuscuta trifolii, Melilotus indicus, and Chenopodium murale were 181.6, 183.5, 159.0, and 157.5 μL L−1, respectively. From the obtained data, we concluded that C. droserifolia EO could provide a hope to produce environment‐friendly bioherbicide as well as a natural resource of antioxidants.

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Aromatic plants attract the attention of many researchers worldwide due to their worthy applications in agriculture, human prosperity, and the environment. Essential oil (EO) could be exploited as effective alternatives to synthetic compounds as it has several biological activities including allelopathy. The EO from the aerial parts of Rhynchosia minima was extracted by hydrodistillation and investigated by gas chromatography/mass spectrometry (GC/MS). Different concentrations (50, 100, 150 and 200 lL L À1 ) of the EO were prepared for investigation of their allelopathic potential on two weeds; Dactyloctenium aegyptium and Rumex dentatus. Twenty-eight compounds, mainly sesquiterpenes (69.13%) were determined. The major compounds are a-eudesmol, 2-allyl-5-tertbutylhydroquinone, caryophyllene oxide, trans-caryophyllene, and s-cadinol. The EO from the R. minima showed a significant inhibition of D. aegyptium and R. dentatus germination, while the seedling growth was stimulated. Therefore, it is not recommended to treat these noxious weeds with the EO of R. minima before the germination. In contrast, the apparent stimulatory effect on the seedling growth offers further studies to use the EO of R. minima to enhance the fitness of different economic crops. However, characterization of green bio-herbicides such as EO (allelochemicals) from wild plants raises a new opportunity for the incorporation of new technology of bio-control against the noxious weeds.

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