Plant hormones (or plant growth regulators, or PGRs) are internally-secreted chemicals in plants that are used for regulating the plants' growth. According to a standard definition, plant hormones are signal molecules produced at specific locations, occur in low concentrations, and cause altered processes in target cells at other locations. Divisions Land plants (embryophytes) Non-vascular plants (bryophytes) Marchantiophyta - liverworts Anthocerotophyta - hornworts Bryophyta - mosses Vascular plants (tracheophytes) Lycopodiophyta - clubmosses Equisetophyta - horsetails Pteridophyta - true ferns Psilotophyta - whisk ferns Ophioglossophyta - adderstongues Seed plants (spermatophytes) †Pteridospermatophyta - seed ferns Pinophyta - conifers Cycadophyta - cycads Ginkgophyta - ginkgo Gnetophyta - gnetae Magnoliophyta - flowering plants Adiantum pedatum (a fern...
It is accepted that there are five major classes of plant hormones:
Additional suggested hormone classes: IAA appears to be the most active Auxin in plant growth. ... Zeatin is named after the genera of corn, Zea as it was first discovered in corn. ... Ethylene (or IUPAC name ethene) is the simplest alkene hydrocarbon, consisting of four hydrogen atoms and two carbon atoms connected by a double bond. ... GA452D may be the most common of the Gibberellins. ... Abscisic acid was given its name because it was once thought to be pivotal in leaf abscission. ...
Brassinolid appears to be the most common Brassinosteroid. ... Jasmonates (JAs) are a group of plant hormones. ... Salicylic acid is a colorless, crystalline organic carboxylic acid. ... The polyamines are organic compounds, that have two or more primary amino groups, such as putrescine, spermidine, and spermine, that are growth factors in both eucaryotic and procaryotic cells. ... Florigen is the term used for the hypothesized hormone-like molecules that control and/or trigger flowering in plants. ...
The function of hormones is to serve as a signal to the target cells; the action of hormones is determined by the pattern of secretion and the
regulate metabolic activity of an organ or tissue.
endocrine glands and their hormone products are specialized to serve regulation on the overall organism level, but can in many instances be used in other ways or only on the tissue level.
Growthregulators may also be used to slow growth or "hold" plant material in the greenhouse.
Bonzi is the most widely used growthregulator for horticultural crops and is applied as a foliar spray at the rate of 2 to 90 ppm.
Plants grown under a positive DIF are taller than plants grown at a zero DIF, and plants grown under a zero DIF are taller and have longer internodes than plants grown under a negative DIF.
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