This paper evaluated the frequency, magnitude and dose/concentration range of hormesis in four species: The aquatic plant Lemna minor, the micro-alga Pseudokirchneriella subcapitata and the two terrestrial plants Tripleurospermum inodorum and Stellaria media exposed to nine herbicides and one fungicide and binary mixtures thereof. In total 687 dose-response curves were included in the database. The study showed that both the frequency and the magnitude of the hormetic response depended on the endpoint being measured. Dry weight at harvest showed a higher frequency and a larger hormetic response compared to relative growth rates. Evaluating hormesis for relative growth rates for all species showed that 25% to 76% of the curves for each species had treatments above 105% of the control. Fitting the data with a dose-response model including a parameter for hormesis showed that the average growth increase ranged from 9+/-1% to 16+/-16% of the control growth rate, while if measured on a dry weight basis the response increase was 38+/-13% and 43+/-23% for the two terrestrial species. Hormesis was found in >70% of the curves with the herbicides glyphosate and metsulfuron-methyl, and in >50% of the curves for acifluorfen and terbuthylazine. The concentration ranges of the hormetic part of the dose-response curves corresponded well with literature values.

In the present study, a range of benzoxazinoid compounds and phenolic acids, all known to be allelochemicals of rye, were identified and quantified in 13 rye cultivars grown at three different localities. Plant samples were collected in the spring at the time when an autumn-sown rye cover crop would be incorporated into the soil. Significant variations in content among shoots and roots were seen for all of the secondary metabolites, with non-methoxy-substituted benzoxazinoids (BX) dominating the shoots, whereas comparable levels were found in the concentrations of BX and methoxy-substituted benzoxazinoids (MBX) in the roots. This distribution of compounds may indicate different biosynthetic pathways and/or different mechanisms of action of these compounds. Concentrations not only depended on plant part, but also on the geographical location-with differences in contents of up to a factor of 5. These differences can probably be attributed to differences in growing conditions. The variation among cultivars was similar to that among geographical localities, with differences within localities of up to a factor of 7 in the shoots and a factor of 14 in the roots. In roots, the contents of the four phenolic acids and the benzoxazinoid 6-methoxybenzoxazolin-2-one (MBOA) were correlated. In shoots, the contents of the two benzoic acids were correlated with each other, whereas the two cinnamic acids were correlated with MBOA and several other benzoxazinoids. The lack of correlation between MBOA and all other benzoxazinoids in the roots of rye might indicate that a hitherto unknown synthetic pathway exists for MBOA. The genes responsible for the synthesis of some of the benzoxazinoids have never been identified, and further gene expression studies are required to assess the observed correlation between the concentration of these compounds and other benzoxazinoids for which the responsible genes are known. The present study revealed a potential for breeding rye cultivars with a high content of biologically active secondary metabolites. However, growing conditions significantly influenced the level of these compounds.

No abstract

No abstract

No abstract

No abstract

IWMPRAISE is the first EU Framework Research project focusing solely on weed management. Thirty-eight partners in eight European countries are working together on developing integrated weed management strategies for agricultural and horticultural crops. Per Kudsk, the coordinator of IWMPRAISE, and the work package leaders present the project, the on-going studies and some of the early outputs. Weeds are ubiquitous and cause substantial yield losses across all arable and horticultural systems. Currently, the reliance on herbicides is very high in conventional farming systems and in many European countries herbicides are the single most used group of pesticides (https://appsso.eurostat.ec.europa.eu/nui/show.do?dataset=aei_fm_salpest09&lang=en). There are several reasons for the high herbicide use, such as lack of threshold-based spraying decisions and lack of any single sufficiently effective, readily applicable, cost-effective non-chemical method. Nonetheless, two factors are driving an immediate need to change weed control practices in conventional farming: the rapidly increasing problem of herbicide resistance, exacerbated by the fact that no new herbicide sites of action have been marketed since the early 1980s, and the expectation that many of the currently used herbicides will be withdrawn from the EU market as they do not meet the human and environmental toxicity criteria set out in EU Regulation 1109/2009. In addition to these two immediate concerns, it has also been shown that herbicides have partly been responsible for recent declines in farmland biodiversity and hence a negative impact on the associated ecosystem services. The over-reliance on chemical control of weeds has highlighted the need for Integrated Weed Management (IWM) strategies that combine non-chemical management options that reduce either weed density or competition with the crop.

No abstract