Herbicides are widely used to kill weeds and increase crop production all over the world. Nevertheless, some weeds show certain structural modifications in response to herbicide application that ...impart mostly partial or sometimes complete tolerance to these noxious plants. The present study was focused on morpho-anatomical modifications in the root, stem, and leaves of Dactyloctenium aegyptium (L.) Willd. treated with different herbicides and to examine whether it possesses tolerance against herbicides. Two pre- and four post-emergence herbicides were applied to D. aegyptium at the recommended dose in a randomized complete block design (RCBD). Pre-emergence herbicide Bromoxynil enhanced root growth (30%), leaves per plant (3%), and leaf fresh weight (17.2%). Increased stem epidermal thickness (100%) was the most notable feature among anatomical attributes. Post-emergence herbicides generally increased stem epidermal thickness 33-56%), leaf sheath thickness (5%), and root area in roots. Other modifications included increased sclerenchymatous thickness in the stem (133-255%), and epidermal thickness (100-200%) in the leaf blade. These characters assisted D. aegyptium to cope with herbicide toxicity. Collectively, pre-emergence herbicides more effectively controlled D. aegyptium compared with post-emergence herbicides.
Herbicides with new modes of action are badly needed to manage the evolution of resistance of weeds to existing herbicides. Yet no major new mode of action has been introduced to the market place for ...about 20 years. There are probably several reasons for this. New potential products may have remained dormant owing to concerns that glyphosate-resistant (GR) crops have reduced the market for a new herbicide. The capture of a large fraction of the herbicide market by glyphosate with GR crops led to significantly diminished herbicide discovery efforts. Some of the reduced herbicide discovery research was also due to company consolidations and the availability of more generic herbicides. Another problem might be that the best herbicide molecular target sites may have already been discovered. However, target sites that are not utilized, for which there are inhibitors that are highly effective at killing plants, suggests that this is not true. Results of modern methods of target site discovery (e.g. gene knockout methods) are mostly not public, but there is no evidence of good herbicides with new target sites coming from these approaches. In summary, there are several reasons for a long dry period for new herbicide target sites; however, the relative magnitude of each is unclear. The economic stimulus to the herbicide industry caused by the evolution of herbicide-resistant weeds, especially GR weeds, may result in one or more new modes of action becoming available in the not too distant future.
Paraquat, as one of the most widely used herbicides globally, is highly toxic to humans, and chronic exposure and acute ingestion leads to high morbidity and mortality rates. Here, we report ...user-friendly, photo-responsive paraquat-loaded supramolecular vesicles, prepared via one-pot self-assembly of amphiphilic, ternary host-guest complexes between cucurbit8uril, paraquat, and an azobenzene derivative. In this vesicle formulation, paraquat is only released upon UV or sunlight irradiation that converts the azobenzene derivative from its trans- to its cis- form, which in turn dissociates the ternary host-guest complexations and the vesicles. The cytotoxicity evaluation of this vesicle formulation of paraquat on in vitro cell models, in vivo zebrafish models, and mouse models demonstrates an enhanced safety profile. Additionally, the PQ-loaded vesicles' herbicidal activity against a model of invasive weed is nearly identical to that of free paraquat under natural sunlight. This study provides a safe yet effective herbicide formulation.
PP 1/305 (1) Weeds in soybean
Bulletin OEPP,
December 2017, 2017-12-00, 20171201, Volume:
47, Issue:
3
Journal Article
Peer reviewed
Specific scope
This Standard describes the conduct of trials for the evaluation of herbicides in soybean.
Specific approval and amendment
First approved in 2017‐09.
Glyphosate-based herbicides (GlyBH), including Roundup, are the most widely used pesticides worldwide. Their uses have increased exponentially since their introduction on the market. Residue levels ...in food or water, as well as human exposures, are escalating. We have reviewed the toxic effects of GlyBH measured below regulatory limits by evaluating the published literature and regulatory reports. We reveal a coherent body of evidence indicating that GlyBH could be toxic below the regulatory lowest observed adverse effect level for chronic toxic effects. It includes teratogenic, tumorigenic and hepatorenal effects. They could be explained by endocrine disruption and oxidative stress, causing metabolic alterations, depending on dose and exposure time. Some effects were detected in the range of the recommended acceptable daily intake. Toxic effects of commercial formulations can also be explained by GlyBH adjuvants, which have their own toxicity, but also enhance glyphosate toxicity. These challenge the assumption of safety of GlyBH at the levels at which they contaminate food and the environment, albeit these levels may fall below regulatory thresholds. Neurodevelopmental, reproductive, and transgenerational effects of GlyBH must be revisited, since a growing body of knowledge suggests the predominance of endocrine disrupting mechanisms caused by environmentally relevant levels of exposure.
•We have reviewed the toxic effects of glyphosate and its commercial formulations.•Glyphosate-based herbicides cause teratogenic, tumorigenic and hepatorenal effects.•These effects could be explained by endocrine disruption and oxidative stress.•Some effects were detected in the range of the recommended acceptable daily intake.•Current evidence presented raises concerns and indicates the need for further studies.
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