Cytokinins
These plant hormones (CKs) are responsible for
aiding in cellular divisions and maintaining
plant metabolic activity. It is found within plants
wherever there is a site that is actively growing,
such as at leaf tips. Commercially, CKs are used
when propagating with tissue culture. As they
are involved in the action of setting fruit, they are
also utilized as a fruit growth regulator. Unlike
both ethylene and abscisic acid, CKs prevent
senescence in leaves.
Ethylene
Ethylene may be the most well-known of the plant
hormones; it is the only gaseous plant hormone that
is produced (it’s a hydrocarbon). It is responsible
for the ripening of fruits, both naturally and
intentionally. In cases where crops, particularly
fruits like bananas, are picked or shipped before
maturation, they are usually artificially ripened via
natural or synthetic ethylene compounds.
A synthetic form of ethylene known as Ethephon is
used widely in commercial nurseries and plantations.
This hormone is used on much of the world’s
pineapple, rice, coffee, cotton, and other staple crops
to achieve uniform and quicker ripening. It is also the
most common component of most commercial PGRs,
especially for plant seedlings. It is additionally used
for leaf and fruit abscission, where a controlled leaf or
fruit drop is desired for commercial purposes.
“
OTHER IDENTIFIED
PLANT HORMONES
INCLUDE
JASMONATES
(SUCH AS METHYL
JASMONATE),
SALICYLATES,
BRASSINOLIDES, AND
STRIGOLACTONES.”
Abscisic Acid
Abscisic acid (ABA) inhibits cellular growth, unlike
CKs which promote it. It functions to assist with
plant processes such as seed dormancy and takes
the controls of a leaf’s stomates during the process
of wilting. Abscisic acid is the outlier of the
commercial plant hormone world. There are
no synthetic compounds available, and
its high cost, coupled with its lack of
a commercial purpose, mean that this
is the only plant hormone not used
artificially at one time or another
in commercial plantations,
greenhouses, or nurseries.
grow cycle
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