Understanding Herbicides and Examples
Herbicides are chemical compounds that kill plants or inhibit their normal growth. Herbicides in certain formulations and applications can be described as selective or nonselective herbicides. In agriculture selective herbicides are often used as a substitute for tillage or in combination with tillage and other agronomic practices to be able to control weeds without damaging crops.
Understanding Herbicides
With a non-till or low-till system, scientists have used biotechnology to develop plant varieties with increased tolerance for herbicides. Nonselective herbicides (for example, paraquat) which are poisonous to all plants, are used when needed to fully control plant growth.
Definition of Herbicide
Contact herbicides will kill only those parts of the plant they touch, systemic herbicides are absorbed by leaves or roots and are translocated to other parts of the plant. Preemergence herbicides, mixed into the soil, will kill germinating seeds and small seeds. Postemergence herbicides either inhibit photosynthesis or inhibit growth.
Chemical herbicides were originally inorganic compounds. Herbicides such as ash, salt and a type of bird have been used in agriculture since ancient times. In 1900 a solution of sulfuric acid, iron sulfate, copper nitrate and ammonium and potassium salts which were also known to act as selective herbicides, soon afterwards sodium arsenite solutions became standard herbicides and they were used in large quantities until around 1960. Other inorganic herbicides included ammonium sulfamate, carbon bisulfide, sodium chlorate, sulfuric acid solution and boric containing formulations.
In organic herbicides began to be produced in earnest with dinitrophenol compounds in 1932. A breakthrough occurred in the 1940s with 2,4-D (2,4-dichlorophenoxyacetic acid), a compound similar to plant hormones, which is an herbicide very selective systemic when used in very small quantities. 1,4-D was quickly adopted to control broadleaf weeds in corn, sorgun, small grains and grasslands as well as in other grasses and ornamental grasses.
Phenoxy aliphatic acids and their derivatives are another large group of organic herbicides, which succeed because of their selectivity and ease of translocation. Other groups of organic herbicides include organic arsenic and urea, heterocyclic nitrogen acids, phenol derivatives, triazine and sulfonylureas.
In the 1960s and 197s, a combination of 2,4-D and 2,4,5-T was widely used in Vietnam as a defoliant under the name Agent Orange. Because it has possible health impacts from the use of Orange Agents, the possibility of ecological and health hazards caused by herbicides has resulted in a re-evaluation of many compounds. The use of 2,4,5-T dioxins was banned in the United States in 1984. In 1975, Mexico, at the insistence of the United States government, began spraying marijuana fields with paracels both of which eliminated plants and raised concerns about toxic side effects on cannabis users.
Glyphosate, a compound that was first identified as an herbicide in 1970 and sold starting in the 1970s under the trade name Roundup has been widely used as a herbaceous killer in a broad spectrum because of its toxicity and tendency to decrease relatively quickly in a relatively low environment.
Beginning in the 1990s, the use of plant strains that are resistant to the effects of herbicides has also contributed to their widespread use. However, this use led to the development of so-called super weeds that have developed glyphosate resistance.
Biotechnology in the Formation of New Superior Plant Varieties
In the application of biotechnology in forming superior new plants, many have been developed because human needs are increasing. In addition, the application of plant biotechnology can facilitate a farmer in the process of crop cultivation. Some new superior types of plants made using biotechnology are as follows.
Burbank russet potato is a potato that has a high starch content and is able to produce better fried potatoes and potato chips.
Low nicotine tobacco is a type of tobacco which is considered to reduce the risk of cancer due to smoking.
Golden rice is a grain that is yellow like gold and contains carotenoids.
Flavrsavr tomatoes are tomatoes whose ripe fruit does not rot easily.