Herbicides and Metabolite Standards
Herbicides are a class of chemicals that kill weeds or harmful plants without affecting the normal growth of crops.
1. Classification of Herbicides
Herbicides can be classified according to their mode of action, conduction, application method, chemical structure, and mechanism of action.
(1) Mode of Action
Herbicides can be divided into selective herbicides and biocidal herbicides according to their mode of action.
Selective herbicides have a selective effect on different plants. Selective herbicides can kill weeds without harming crops, or even kill certain weeds without harming crops and other weeds.
Related Herbicides and Metabolite Standards:
Biocidal herbicides are also called non-selective herbicides. This herbicide has little or no selectivity for different plants. Biocide herbicides are toxic to all plants and do not distinguish between crops and weeds, nor the type of weeds to which they belong.
Related Herbicides and Metabolite Standards:
(2) Conduction
According to the conduction of herbicides in plants, herbicides can be divided into contact herbicides and systemic conduction herbicides.
Contact herbicides only kill the parts of the weeds that are in contact with the herbicide, and play a local killing effect, but cannot or rarely conduct in plants, such as paraquat.
- Systemic Conduction Herbicides
After being absorbed by weeds, systemic conduction herbicides can be transferred to plants through the parts in contact with weeds, which can lead to the death of the whole plant, such as glyphosate.
Some herbicides have both contact killing and systemic conduction, but one mode of action is the primary mode of action.
(3) Application Methods
Herbicides can be divided into stem and leaf treatment agents and soil treatment agents according to their application methods.
The soil treatment agent is directly sprayed on the soil surface in the form of a solution, and is absorbed by the roots, coleoptiles and other parts of weeds to exert a herbicidal effect, such as prometryn.
Related Herbicides and Metabolite Standards:
- Stem and Leaf Treatment Agents
Stem and leaf treatment agents are directly sprayed on the stems and leaves of plants in the form of solutions, such as nicosulfuron.
Certain herbicides, such as atrazine, act as both soil and foliage treatments.
(4) Chemical Structure
According to the chemical structure of herbicides, herbicides can be divided into inorganic herbicides and organic herbicides.
Inorganic herbicides are non-carbohydrate compounds composed of natural mineral sources such as potassium chlorate.
Organic herbicides mainly include phenoxyacetic acids, benzoic acids, amides, dinitroanilines, substituted ureas, carbamates, phenols, diphenyl ethers, sulfonylureas, organophosphorus, imidazoles Linones, heterocycles, etc.
- Phenoxyacetic acid herbicides are selective herbicides. The mechanism of action of these herbicides is to break the balance of plant hormones, make plants grow deformed, and eventually lead to plant death.
Related Herbicides and Metabolite Standards:
- Most benzoic acid herbicides have herbicidal function and plant growth regulating activity. The mechanism of action of benzoic acid herbicides is similar to that of phenoxyacetic acid herbicides.
Related Herbicides and Metabolite Standards:
- Amide herbicides are an important class of selective herbicides. Some varieties of amide herbicides are stem and leaf treatments, such as propanil. More varieties are soil treatments, such as acetochlor and butachlor. This type of herbicide is a special effect product for controlling annual grass weeds.
Related Herbicides and Metabolite Standards:
- Dinitroaniline herbicides are selective contact-killing soil treatments with a wide range of herbicides.
Related Herbicides and Metabolite Standards:
- Substituted urea herbicides are a class of selective herbicides. The mechanism of action of these herbicides is to inhibit the electron transfer process of plant photosynthesis.
Related Herbicides and Metabolite Standards:
- The mechanism of action of carbamate herbicides is to inhibit cell division and elongation, and inhibit the growth of roots and shoots.
Related Herbicides and Metabolite Standards:
- Phenolic herbicides include pentachlorophenol sodium, dinoseb, and the like.
- Most diphenyl ether herbicides are contact herbicides.
- Sulfonylurea herbicides are highly selective and easy to use. The mechanism of action of these herbicides is the inhibition of acetolactate synthase.
Related Herbicides and Metabolite Standards:
- Organophosphorus herbicides (such as glyphosate) have strong systemic conductivity.
- Imidazolinone herbicides have the advantages of wide herbicidal range, strong selectivity and high activity. Its mechanism of action is similar to that of sulfonylurea herbicides.
- Heterocyclic herbicides such as triazepines, pyrimidines, and pyrazoles.
2. The Mechanism of Action of Herbicides
The mechanism of action of herbicides is complex and can be summarized as follows:
(1) Inhibition of photosynthesis: The herbicide enters the plant body, and after reaching the leaves, it can strongly inhibit the photosynthesis, so that the plant cannot get nutrients and die.
(2) Inhibition of respiration: When the herbicide enters the body of the weed, it can disturb or interrupt the respiration, so that the energy released by the respiration cannot be used, and the physiological process of the weed is interrupted and killed.
(3) Inhibiting the synthesis of proteins, nucleic acids, etc.: After herbicides enter the weeds, they can inhibit the synthesis of proteins, nucleic acids, amylase or pantothenic acid, and affect physiological activities.
(4) Destruction of the transport tissue: After the herbicide enters the weed, it hinders the transport of organic matter.
(5) Inhibition of chlorophyll: herbicides have a strong inhibitory effect on the formation of chlorophyll in plants, or have a decomposition effect on the formed chloroplasts.
