Managing artificially drained low-gradient agricultural headwaters for enhanced ecosystem functions.

Large tracts of lowlands have been drained to expand extensive agriculture into areas that were historically categorized as wasteland. This expansion in agriculture necessarily coincided with changes in ecosystem structure, biodiversity, and nutrient cycling. These changes have impacted not only the landscapes in which they occurred, but also larger water bodies receiving runoff from drained land. New approaches must append current efforts toward land conservation and restoration, as the continuing impacts to receiving waters is an issue of major environmental concern. One of these approaches is agricultural drainage management. This article reviews how this approach differs from traditional conservation efforts, the specific practices of drainage management and the current state of knowledge on the ecology of drainage ditches. A bottom-up approach is utilized, examining the effects of stochastic hydrology and anthropogenic disturbance on primary production and diversity of primary producers, with special regard given to how management can affect establishment of macrophytes and how macrophytes in agricultural landscapes alter their environment in ways that can serve to mitigate non-point source pollution and promote biodiversity in receiving waters.

Comparative mutagenic effects of structurally similar flavonoids quercetin and taxifolin on tester strains Salmonella typhimurium TA102 and Escherichia coli WP-2 uvrA.

Quercetin (QT) and Taxifolin (TF) are structurally similar plant polyphenols. Both have been reported to have therapeutic potential as anti-cancer drugs and antioxidants. Mutagenic effects of QT and TF were evaluated using Salmonella typhimurium TA102 and Escherichia coli WP-2 uvrA tester strains. Either in the presence or absence of S9 mix, QT was mutagenic to TA102 and WP2 uvrA. However, the mutagenicity of QT was significantly enhanced in the presence of S9 mix. Likewise, in the presence of Iron (Fe2+) and NADPH generating system (NGS) and absence of S9 mix, QT induced significantly high mutations in both TA102 and WP-2 uvrA. Mutagenicity of QT decreased in both strains in the presence of Iron (Fe2+) or NGS alone. TF was not mutagenic in the presence or absence of S9 mix in both TA102 and WP-2 uvrA 2, regardless of the presence of iron or NGS. Incorporation of antioxidants (ascorbate, superoxide dismutase (SOD), catalase (CAT)) and/or iron chelators (desferroxamine (DF) and ethylenediamine-tetraacetate (EDTA)) in the test systems markedly decreased QT-induced mutations in both tester strains. These results suggest that QT but not TF, could induce mutations in the presence or absence of rat liver S9 or Iron (Fe2+) and NGS in both tester strains by redox cycling and Fenton reactions to produce oxygen free radicals. Our results indicate that a minor structural variation between the two plant polyphenols could elicit a marked difference in their genotoxicities. These results provide a basis for further study into the potential use of QT in combination with iron supplements.