Plant Hormones Lesson 2 PDF

 Plant behaviors you are used to seeing, such as the ripening of fruit, the growth of shoots upward and roots downward, the growth of plants toward the light, the dropping of leaves in the fall, and the growth and flowering of plants at times of the year are all controlled b...

 Plant behaviors you are used to seeing, such as the ripening of fruit, the growth of shoots upward and roots downward, the growth of plants toward the light, the dropping of leaves in the fall, and the growth and flowering of plants at times of the year are all controlled by PLANT  Plant cells communicate with each other via chemical messengers called hormones, chemical signals produced by cells that act on target cells to control their growth or development. Plant hormones are among the most important biochemicals affecting plant growth and yield production under different conditions, including stress.  Auxins stimulate the elongation of cells in the plant stem and phototropism (the growth of plants toward light). If a plant receives equal light on all sides, its stem grows straight. If light is AUXIN uneven, then Auxin moves toward the darker side of the plant. This may seem backward, but when the shady side of the stem grows, the stem in its crookedness, actually bends toward the light. This action keeps the leaves toward the light so photosynthesis can continue. AUXIN  Gibberellins promote both cell division and cell elongation, causing shoots to elongate so that plants can grow taller, and leaves can grow bigger. GIBBERELLINS (Gibberellic acid) They speed the elongation of dwarf varieties to normal sizes and promote flowering, stem and root elongation, and growth of fruit. Gibberellins can be used to: end seed dormancy. promote flowering. increase fruit size. CYTOKINI N Cytokinin are plant hormones that cause increased cell division by stimulating the process of mitosis, promote leaf expansion, and slow down the aging of leaves. They are made naturally by plants but have been synthesized by humans. Increased mitosis results in plant growth and the formation of  ABSCISIC ACID (ABA) Abscisic acid inhibits cell growth and can help prevent water loss by triggering stomata to close; promotes dormancy in seeds and ETHYLENE Ethylene gas is a plant hormone that regulates plant growth, development and response to environmental stress. It is produced from leaves, roots, stems, flowers and fruits, and it plays a major role in FRUIT RIPENING, FLOWERING AND ABSCISSION (the BRASSINOSTEROID (BR) Brassinosteroid controls many aspects of plant growth and development. They’re extremely powerful and can affect the concentrations of other plant hormones, promoting or inhibiting plant growth depending on the stage of development. They can counteract the effects of abscisic acid, acting to promote flowering, seed germination, and the opening of stomata. Regulate a wide range of physiological processes including plant growth, development and immunity.