Herbicide interactions

Sbrana I, Di Sibio A, Lomi A, Scarcelli V (1993) C-mitosis and numerical chromosome aberration analyses in human-lymphocytes - 10 known or suspected spindle poisons. Mutat Res 287 57-70 Senesi N, Loffredo E, Padovano G (1990) Effects of humic acid-herbicide interactions on the growth of Pisum sativum in nutrient solution. Plant Soil 127 41-47... 

Interactions between surfactants and herbicides in spray solutions are known to occur (57), and those studied either have no effect or are detrimental to herbicide activity. No definite evidence exists that surfactant-herbicide interactions in solution cause enhanced activity of herbicides. 

Herbicides that inhibit photosynthetic electron flow prevent reduction of plastoquinone by the photosystem II acceptor complex. The properties of the photosystem II herbicide receptor proteins have been investigated by binding and displacement studies with radiolabeled herbicides. The herbicide receptor proteins have been identified with herbicide-derived photoaffinity labels. Herbicides, similar in their mode of action to 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) bind to a 34 kDa protein, whereas phenolic herbicides bind to the 43-51 kDa photosystem II reaction center proteins. At these receptor proteins, plastoquinone/herbicide interactions and plastoquinone binding sites have been studied, the latter by means of a plastoquinone-deriv-ed photoaffinity label. For the 34 kDa herbicide binding protein, whose amino acid sequence is known, herbicide and plastoquinone binding are discussed at the molecular level. 

In the host establishment of plant pathogens for experimental purposes the incubation period frequently exceeds 24 h. In this case the period of host tissue wetness will approximate the actual incubation time. It is desirable for a bioherbicide to infect plant tissue with minimum dew requirements because (a) the period of host tissue wetness will vary considerably under natural field conditions, and (b) the unpredictable frequency of dew occurrence in nature. If the experimental dew period in a dew chamber is brief, the actual period of host tissue wetness may not correlate with the actual incubation time. This may be dependent on host species as well as interaction of the host species with the physical parameters of the dew chamber. A lengthy dew period may be sufficient to induce runoff and displace propagules from the host. A lengthy dew period may also give misleading results with host-pathogen-chemical herbicide interactions. 

Eq. 1 allowed the plotting of rates of enrichment of resistance, with different scenarios of selection pressure, seed bank size, fitness, and initial mutation frequency (Fig. 1A). The values that could be plugged into the equation to generate the scenarios were based on a very limited data-base, mostly from corollary systems, such as heavy-metal tolerance. We knew too little about weed-herbicide interactions at that time to make precise estimates. With the experience of hindsight, we can see where the model was clearly correct, and where it needed modification. 

The basic idea was to monitor the loss of trans-membrane proton gradient, which happens due to Dl protein-herbicide interaction, and to use it for herbicide detection. 

Development of the Sensor Unit, Based on Potentiometric Detection of Protein-Herbicide Interaction... 

In order to find and manipulate the genes that code for resistance to herbicides, it is essential that we understand the mechanisms of action of herbicides in plant cells. It is fortunate that most herbicides interact with enzymes and other proteins in metabolic pathways specific to plants, such as amino acid synthesis and photosynthesis. Therefore, they are generally non-toxic to animals, and genetic engineering for these traits is specific for plants. 

Combining this yeast gene replacement strains system with kinetics values from purified plastidic proteins together provide a convenient tool to study herbicide interaction with the enzyme and a powerfiil screening system for new inhibitors. 

The dose response relationship between seven commonly used herbicides and four luminescence-based bacterial biosensors was characterised. As herbicide concentration increased the light emitted by the test organism declined in a concentration dependent manner. These dose responses were used to compare the predicted vs. observed response of a biosensor in the presence of multiple contaminants. For the majority of herbicide interactions, the relationship was not additive but primarily antagonistic and sometimes synergistic. These biosensors provide a sensitive test and are able to screen a large volume and wide range of samples with relative rapidity and ease of interpretation. In this study biosensor technology has been successfully applied to interpret the interactive effects of herbicides in freshwater environments [12]. 

In the sequence of carotene desaturation are two targets for herbicide interaction the step from phytoene to -carotene and the step from -carotene to lycopene. It is assumed that two individual desaturase systems work in sequence. 

Although it has been known for over 30 years that electron transport inhibitor herbicides interact with PSII, our concept of the structural organization of this photosystem, and the exact site of interaction, has advanced greatly during the last few years. 

ALS shows a high degree of primary sequence homology with pyruvate carboxylase and pyruvate oxidase the ubiquinone cofactors of pyruvate oxidase inhibit ALS, and it has been proposed that the ubiquinone-binding site of the ancestral enzyme also is the site of both SMM and imidazolinone binding. Recent evidence suggests, however, that these two types of herbicide interact differently with ALS (a) imidazolinones cause a rapid decrease in the levels of extractable ALS activity in maize, whereas SMM does not and can protect the ALS activity from this in vivo effect of imidazolinones and (b) not all imidazolinone-tolerant cell lines are insensitive to sulfonylureas. Sulfonylureas and imidazolinones do not, however, show synergistic inhibition of maize ALS in vitro. ... 

Adverse interactions between herbicides and other herbicides or nonherbicide chemicals on higher plants have been well documented. The continuous discovery and development of new herbicides dictates the need for continuing studies of the potential interactions of herbicide mixtures. A better understanding of herbicide interactions will facilitate the efficient use of mixtures of old and new herbicides in future crop production. 

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