Plant hormones (also known as phytohormones) are chemicals that regulate plant growth, which, in the UK, are termed 'plant growth substances'.

Plant hormones are signal molecules produced within the plant, and occur in extremely low concentrations. Hormones regulate cellular processes in targeted cells locally and, when moved to other locations, in other locations 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 called as growth factors or growth hormones^{[citation needed]}.

Larry Dunn (born June 19, 1953) is a keyboardist, musical director and one of the founding members of the music group Earth, Wind, & Fire. Dunn, along with other members of Earth, Wind & Fire were inducted into the Rock & Roll Hall of Fame in 2000.

Born Lorenzo Dunn, he attended East High School in Denver. During most of the Earth, Wind & Fire years, Larry produced, performed, composed and arranged for side-projects like Dee Dee Bridgewater, Caldera, Ramsey Lewis, Ronnie Laws, Stanley Turrentine, Sylvia St. James, Lenny White with Twennynine, and many more.

Dunn has also toured with Al McKay and his L.A. All Stars. He is, together with ex-EWF keyboardist Morris Pleasure and ex-EWF guitarist Sheldon Reynolds, one of the founding members of the band Devoted Spirits. The first Devoted Spirits album, Devoted Spirits: A Tribute to Earth Wind and Fire, contains their cover versions of classic EWF songs as well as some new material. A second Devoted Spirits album, called The Answer, is due to be released. Dunn and his wife Luisa are owners of Source Productions, and are involved in music for TV, film and commercials in addition to working with various other musicians.