<P> Plant hormones are signal molecules produced within the plant , and occur in extremely low concentrations . Hormones regulate cellular processes in targeted cells locally and , moved to other locations , in other functional parts of the plant . Hormones also determine the formation of flowers , stems , leaves , the shedding of leaves , and the development and ripening of fruit . Plants , unlike animals , lack glands that produce and secrete hormones . Instead , each cell is capable of producing hormones . Plant hormones shape the plant , affecting seed growth , time of flowering , the sex of flowers , senescence of leaves , and fruits . They affect which tissues grow upward and which grow downward , leaf formation and stem growth , fruit development and ripening , plant longevity , and even plant death . Hormones are vital to plant growth , and , lacking them , plants would be mostly a mass of undifferentiated cells . So they are also known as growth factors or growth hormones . The term ' Phytohormone ' was coined by Went and Thimann and used in the title of their book in 1937 . </P>
chemicals produced in one part of a plant that affect the growth and response of other parts
hormones