Introductory Crop Physiology (1+1)

Phytohormones

• Plant hormones or plant growth regulators area organic substances produced by higher plants that alter growth patterns and/or maintenance of the plant.
• Thimann (1948) proposed the term phytohormone as these hormones are synthesized in plants.
• 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.