Plant hormones (also known as plant growth regulators (PGRs) and phytohormones) are chemicals that regulate a plant's growth. According to a standard
animal definition,
hormones are signal
molecules produced at specific locations, that occur in very low concentrations, and cause altered processes in target
cells at other locations. Plant hormones on the other hand, are not like animal hormones, they are often not transported to other parts of the plant and production is not limited to specific locations. Plants lack tissues or organs specifically for the production of hormones; unlike animals, plants lack
glands that produce and
secrete hormones to be moved around the body. Plant hormones shape the plant, effecting seed growth, time of flowering, the sex of flowers, its longevity, senescence of leaves and fruits, they affect which tissues grow up and which grow downward, leaf formation and stem growth, fruit development and ripening, and even plant death. Hormones are vital to plant growth and lacking them plants would be mostly a mass of undifferentiated cells.
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