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This study aimed to develop new prediction models that include sediment properties (pH, organic matter, and silt and clay concentrations) for estimating the potential uptake of heavy metals (HMs) by the invasive grass Vossia cuspidata. Plant and sediment samples were collected from the microsites that represent the natural distribution of the species in two Nile islands in Cairo, Egypt. The results show that the root was the main accumulating organ for the analyzed HMs (Fe, Mn, Zn, Cu, Ni, and Pb). The mean concentrations of Fe and Mn and the maximum concentrations of Cu, Ni, and Pb were phytotoxic. The values of the bioconcentration factor were >1, while the translocation factor was >1 for Zn and Cu in rhizome and stem, Mn in leaf, and Ni and Pb in stem and leaf. There were no significant differences between the measured and the predicted HM concentrations in all organs of the species. This indicates the excellent robustness of the developed regression models. Sixteen equations (out of 24) had high R2 values. Thus, V. cuspidata could be considered a biomonitor for HM pollution, and the developed equations will benefit the prediction of HM uptake by the species in the River Nile ecosystem.

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Egyptian Journal of Botany http://ejbo.journals.ekb.eg/ A QUATIC plants are of real interest for their nutritive value. The present study aimed at investigating the forage potentiality of the aquatic macrophyte Vossia cuspidata (Roxb.) Griff (Poaceae). Two islands in the River Nile system in Greater Cairo, Egypt were selected for sampling the leaf laminae from V. cuspidata in eighteen quadrates (0.5x 0.5m each) during February (winter), and August (summer) of 2017. The chemical analyses revealed that there were no significant differences between the contents of summer and winter leaves in their percentages of moisture, dry matter, ash, nitrogen-free extract, neutral detergent fibers, acid detergent fibers, acid detergent lignin, cellulose, and hemicellulose. The leaves were characterized by a high percentage of dry matter (DM, ≈ 92%), low moisture content (7.94-7.27% DM), high crude fibers (24.1-38.2%DM), moderate crude protein (7.2=19.2%), and low lipids content (1.7-2.0% DM). The plant is rich in many important elements (K, Ca, P, Cu, and Zn). The ratio of Ca/P (= 2.43) is within the adequate range for animal forage. The other parameters of the nutritive values of the leaves and their importance to animal feeding were discussed. The leaves of V. cuspidata are recommended as good forage for beef cattle and lactating cows.

Invasive plant species are major drivers of biodiversity losses, particularly on islands that are vulnerable to invasion and extinction. The objective of this study was to document the vegetation structure and changes over time in two Nile Islands due to invasion by Vossia cuspidata (Hippo grass). One-hundred and one stands were assigned in three sites along the River Nile in Cairo, Egypt. Fifty-one associated species were recorded, belonging to 28 families. Annuals (Thereophytes) were the main life form in the area (51%) followed by helophytes (29%). Twelve vegetation groups were identified, representing the main communities in the studied stands. V. cuspidata was the dominant species and its maximum cover was recorded during the summer season. The lowest values for species diversity were recorded in open water, while the highest values were recorded in water edges and slopes of the riverbanks. There was up to 70% reduction in the cover of native species in the study area due to the invasion by V. cuspidata. Many native species were either disappeared or poorly recorded in the studied sites. Stem height and the cover of V. cuspidata in aquatic and riparian habitats lead to severe negative impacts on the growth and the diversity of native flora in the River Nile. Consequently, conservation of the native flora through removing the invasive species should be a future priority along the River ecosystem.