The herbicide glyphosate has been on the market for nearly 50 years in the 20th century and has grown to become the largest herbicide in sales in the world and the most widely used herbicide in the world.
Glyphosate in the broad sense is the general name for various glyphosate salts, and glyphosate in the narrow sense refers to glyphosate acid.
Let’s get to know glyphosate!
Product Information
Glyphosate, whose chemical name is N-(phosphomethyl)glycine and whose chemical formula is C3H8NO5P, is an organophosphate herbicide and a systemic conductive broad-spectrum herbicide. It was developed by Monsanto Company of the United States in the early 1970s and is now acquired by Bayer Company of Germany.
Product Name: Glyphosate
CAS NO.: 1071-83-6
Chemical Name: N-(phosphomethyl)glycine
Molecular Formula: C3H8NO5P
Molecular Weight: 169.073
Melting Point: 230°C
Boiling point: 465.8°C
Density: 1.74 g/cm3
Water solubility: Slightly soluble
Solubility: 1.2 g/100 mL
Structural formula:
When used, it is usually made into isopropylamine salt or sodium salt. Glyphosate salt is easier to dissolve in water. Its isopropylamine salt is the active ingredient of the famous herbicide brand "Roundup".
Transport Conduction
After glyphosate is absorbed through the plant cuticle and stomata, it is converted into water-soluble salts in the plant body. Its main mode of transportation is to transport the photosynthetic products from the phloem to the vigorously growing parts.
By dissolving the waxy layer on the surface of weeds' leaves, branches and stems, the drug's effect quickly enters the plant's transmission system and takes effect. It can kill the entire plant including roots, thereby preventing regeneration caused by roots, causing weeds to wither and die, thus achieving the effect of eliminating weeds and roots.
Mechanism of action
Glyphosate is a chronic broad-spectrum biocidal herbicide that mainly inhibits enolpyruvyl shikimate phosphate synthase (EPSPS) in plants. Thereby inhibiting the conversion of shikimic acid into phenylalanine, tyrosine and tryptophan, interfering with protein synthesis and causing plant death.
It has an inhibitory effect on 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS). This enzyme catalyzes the conversion of shikimate-3-phosphate and enolpyruvyl phosphate to 5-enolpyruvylshikimate-3-phosphate (EPSP). Therefore, glyphosate interferes with the enzymatic reaction of this biosynthesis, leading to the accumulation of shikimic acid in the organism. In addition, glyphosate can also inhibit the activity of other plant enzymes.
EPSP synthases from different organisms have high homology.
Glyphosate mainly blocks the biosynthesis of aromatic amino acids, affecting plant cell division, chlorophyll synthesis, transpiration, respiration, protein and other metabolic processes, ultimately leading to plant chlorosis, yellowing, wilting and death.
Aromatic amino acids participate in the metabolism of some alkaloids, coumarins, flavonoids, lignin, indole derivatives, phenolic substances, etc. in plants.
1. EPSPS normal mechanism
PEP first forms a transition state with the enzyme, then forms a ketal tetrahedron with S3P, and finally generates EPSP.
2. Glyphosate inhibition mechanism
Glyphosate forms a ternary complex with EPSP synthase and EPSP, thereby blocking the catalytic effect of EPSP synthase.
Glyphosate competes to inhibit the binding site of the substrate PEP on EPSPS. Inhibits the activity of 5-enolpyruvoylshikimate-3-phosphate-synthase (EPSPS). This leads to a large accumulation of shikimic acid content. The accumulation of shikimic acid is an important indicator of the impact of glyphosate on crop physiological mechanisms.
3. Shikimate pathway
The shikimic acid metabolic pathway is a pathway used by plants and microorganisms to synthesize three aromatic amino acids: phenylalanine, tyrosine, and tryptophan. The intermediate metabolite shikimic acid can also be used to synthesize vitamins, adipic acid and other compounds.
4. Aromatic amino acids
Aromatic amino acids refer to amino acids with a benzene ring structure in their molecular structure.
Degradation products
1. Mammals
Glyphosate targets and blocks a plant metabolic pathway not found in animals - the shikimate pathway. Glyphosate is rapidly excreted by mammals after oral ingestion and does not bioaccumulate.
2. Green plants
The main metabolite in plants is aminomethylphosphonic acid. Soil strongly adsorbs glyphosate and quickly combines with iron, aluminum and other metal ions in the soil and loses its activity.
3. Soil and water
The main degradant in soil and water is also aminomethylphosphonic acid.
Weeding objects
Glyphosate is absorbed through stems and leaves and then transmitted to all parts of the plant. It can control plants from more than 40 families including monocotyledons and dicotyledons, annuals and perennials, herbs and shrubs. It is very effective against perennial root weeds and is widely used for weeds in rubber, mulberry, tea, orchards, sugarcane fields, farmland fallow areas, and fieldside weeds. For annual weeds such as barnyard foxtail, wheatgrass, goosegrass, crabgrass, cocklebur, pigweed, chickweed, pigweed, etc.
Glyphosate has a killing effect only after it comes into contact with green tissue, and it sprays evenly and directionally on the stems and leaves of weeds.
Product Features
After glyphosate enters the soil, it quickly combines with metal ions such as iron and aluminum and loses its activity. It has no adverse effects on seeds and soil microorganisms hidden in the soil.
Plants that have had their stems and leaves cut off should wait until the weeds regenerate to have enough new leaves before applying pesticides.
Instructions
The current normal dosage for weeding is 200g/barrel (15l) sprayed on one acre of land, which is 75 times liquid spray.
The retail price of 200g/bottle of 41% glyphosate isopropylamine salt water (dissolvable agent) on the market is mostly 7-10 yuan, and may be higher or lower in some areas.
Generally, for broadleaf weeds in the early germination or flowering stage, and grasses at the late jointing stage or early heading stage, spray 20-30 kg of water per acre.
When controlling perennial weeds, divide the dosage into two times and apply them 5 days apart to improve the control effect.
Precautions
1. Clean soft water should be used when diluting pesticides. Adding muddy or dirty water will reduce the effectiveness of the pesticide.
2. Please do not mow, graze or plow the ground within 3 to 5 days after application.
3. Glyphosate is acidic, so plastic containers should be used whenever possible when storing and using it.
4. When using, you can add an appropriate amount of surfactants such as washing powder and diesel to improve the weeding effect.
5. Adding gibberellin after glyphosate weeding can increase the weeding effect. Compared with the same dose of glyphosate treated with a single dose, the crop color will be more yellow, the wilting will be more severe, and the death time can be shortened.
Source: AgroPages
