Chrysanthemoides monilifera subsp. monilifera (boneseed), a weed of national significance in Australia, threatens indigenous species and crop production through allelopathy. We aimed to identify phenolic compounds produced by boneseed and to assess their phytotoxicity on native species. Phenolic compounds in water and methanol extracts, and in decomposed litter-mediated soil leachate were identified using HPLC, and phytotoxicity of identified phenolics was assessed (repeatedly) through a standard germination bioassay on native Isotoma axillaris. The impact of boneseed litter on native Xerochrysum bracteatum was evaluated using field soil in a greenhouse. Collectively, we found the highest quantity of phenolic compounds in boneseed litter followed by leaf, root and stem. Quantity varied with extraction media. The rank of phenolics concentration in boneseed was in the order of ferulic acid > phloridzin > catechin > p-coumaric acid and they inhibited germination of I. axillaris with the rank of ferulic acid > catechin > phloridzin > p-coumaric acid. Synergistic effects were more severe compared to individual phenolics. The litter-mediated soil leachate (collected after15 days) exhibited strong phytotoxicity to I. axillaris despite the level of phenolic compounds in the decomposed leachate being decreased significantly compared with their initial level. This suggests the presence of other unidentified allelochemicals that individually or synergistically contributed to the phytotoxicity. Further, the dose response phytotoxic impacts exhibited by the boneseed litter-mediated soil to native X. bracteatum in a more naturalistic greenhouse experiment might ensure the potential allelopathy of other chemical compounds in the boneseed invasion. The reduction of leaf relative water content and chlorophyll level in X. bracteatum suggest possible mechanisms underpinning plant growth inhibition caused by boneseed litter allelopathy. The presence of a substantial quantity of free proline in the target species also suggests that the plant was in a stressed condition due to litter allelopathy. These findings are important for better understanding the invasive potential of boneseed and in devising control strategies.

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Phragmites australis is an invasive wetland plant and allelopathy appears to contribute to its invasiveness. We studied dynamics of physicochemical characteristics and phytotoxicity through residue decomposition of Phragmites with and without soil under different conditions and density over time. Physicochemical variables (water-soluble phenolics, dissolved organic carbon, specific ultraviolet absorbance, pH, electrical conductivity, osmotic potential and some anions, namely PO43–, Cl–, NO2–, NO3– and SO42–) of extracts were more consistent and showed normal range in aerobic rather than anaerobic conditions. ‘Residue alone’ and ‘residue with soil’ extracts exhibited significant inhibition on germination and growth of Poa labillardierei and Lactuca sativa initially but reduced over time in aerobic conditions whereas the inhibition increased sharply and remained almost stable in anaerobic conditions (P ≤ 0.001). Regression analyses showed that water-soluble phenolics were a significant predictor of the inhibitory effects on germination and growth of tested species compared with other variables in the extracts. Long-term decomposed residues exhibited significant effects on germination and growth of Melaleuca ericifolia (P ≤ 0.01) depending on residue density in soil. The results demonstrated that decomposition condition and soil incorporation coupled with residue density may play a crucial role over time in dynamics of physicochemical variables and associated phytotoxicity. The study contributes to understanding of the ecological consequences of phytotoxins in residue decomposition, partially explaining the invasion process of Phragmites in wetlands and thereby improving wetland management.

In the urban areas of Bangladesh, service standard of community facilities lacks far behind of any recognized planning standard. Khulna City is an instance of having typical urban problems particularly the crisis of safe water. Approximately 45% population in this area is covered under piped water supply network. In this study an attempt has been made to evaluate the existing water supply system in the Khulna City Corporation (KCC) area regarding water supply installations and their capacity, water consumption pattern, satisfaction level of water supply and water demand-supply analysis. Structured and open-ended interview schedule were used as primary data collection tool. A two stage stratified random sampling was adopted and some statistical conventional techniques were used to analyze the data. The study reveals a wide gap between water supply and demand in KCC area. Again, the study shows that above 90% people use tube well (shallow and deep) water for drinking instead of supplied pipe water. It is shown that most people are not satisfied with quality and quantity of the supplied water for their daily usages. This study suggests to adopt the appropriate policy measures in order to safeguard the interest of the people for water supply, which would eventually improves the living and socio-economic conditions of the people in the study area.