Auxins are a group of plant growth substances (often called phytohormones or plant hormones), the most common example being indoleacetic acid (IAA), responsible for raising the pH around cells, making the cell wall less rigid and allowing elongation. Auxins are also responsible for phototropism which is the bending toward light sources. Used in high doses, it stimulates the production of ethylene which stops the growth and may cause leaves to fall and can kill the plant.
Auxins include indoleacetic acid , phenylacetic acid , and 4-chloro-indoleacetic acid . Commercially, auxins are used to promote root growth, to promote uniform flowering, and to set fruit and prevent premature fruit drop . Synthetic auxins such as 2, 4-D and 2, 4, 5-T have been used as herbicides, broad-leaved weeds like dandelions are much more susceptible to auxins than narrow-leaved plants like grass and cereal crops.
The defoliant Agent OrangeAgent Orange is the code name for a powerful herbicide and defoliant used widely by the U. military during the Vietnam War. Agent Orange was used from 1961 to 1970 and has caused serious harm to the health of both Vietnamese and Americans, their children was a mix of 2, 4-D and 2, 4, 5-T. 2, 4-D is still in use and is thought to be safe, but 2, 4, 5-T was more or less banned by the EPA in 1979Events January-February January 1 Sino-American relations: United States and the People's Republic of China establish diplomatic relations January 4 State of Ohio agrees to pay $675,000 to families of dead and injured in Kent State University shootings.. The dioxinDioxin is the term used to describe a family of toxic chlorinated organic compounds that cannot travel long distances (because they are heavy compounds of about 350 amu) and bioaccumulate in humans and wildlife due to their fat solubility. The most notori TCDDTCDD is an abbreviation used for Turkish Republic Railways ( T rkiye C umhuriyeti D evlet D emiryollari ) External links . is an unavoidable contaminant produced in the manufacture of 2, 4, 5-T, as a result of the integral dioxin contamination, 2, 4, 5-T has been implicated in leukaemia, miscarriageMiscarriage is the lay term for the natural or accidental termination of a pregnancy at a stage where the fetus is incapable of surviving. The medical term for it is " abortion"; when the abortion is not deliberately induced, it is termed a "spontaneous as, birth defectA birth defect is a physical or mental abnormality present at the time a child is born. Birth defects range from minimal, such as birthmarks, and slightly mobility-impairing, such as amelia of the legs, to very serious, such as cerebral palsy, and incompas, liver damage, and other diseases.
1 Location, Characteristics and Occasions for Synthesis Induction
- Synthesized in shoot and root meristematic tissue
- Synthesized in young leaves
- Synthesized in mature leaves in very small amounts
- IAA peaks during the day
- Synthesized in mature root cells
- Released by meristematic cells when they have enough sugar and Oxygen to support both themselves and any dependent cells and are in good growing conditions
- Released by all cells when they are experiencing conditions which would normally cause a shoot meristematic cell to produce Auxin
- Directly or indirectly induced by high levels of Ethylene
2 Effects
- Stimulates cell elongation
- Stimulates cell division with CK
- Induces xylem and phloem
- Directly stimulates Ethylene synthesis
- IAA inhibits Ethylene formation and transport of precursor
- Induces shoot apical dominance
- Inhibits abscission prior to formation of abscission layer (inhibits senescence of leaves)
- Involved in phototropism, gravitropism, tropism toward moisture
- Induces sugar and mineral accumulation at the site of application
- Flower initiation
- Sex determination
- Induces xylem and phloem
- Induces new root formation by breaking root apical dominance induced by CK
- Inhibits root hair growth and causes them to die back
- (From Theory II) Stimulates the rate of metabolism of cells in the root (who are not at their peak metabolism rates) in response to an increase in the levels sugar and essential gases
Plant hormones
