Plant Growth Regulators

Plant growth regulators are hormone-like chemicals that occur naturally in plants, and play a central role in their growth and development. Five major classes of plant growth regulators have been identified as plant hormones, but scientists believe that there are more waiting to be discovered. The five growth hormones include auxins, gibberellins, cytokinins, abscisic acid, and ethylene. Collectively, they regulate many facets of plant growth and development including seed germination, root growth, stem elongation, leaf expansion, flowering, seed development, fruit ripening, and dropping of leaves and fruits. Each of these processes is directly relevant to agriculture; what is harvested for food, feed, or fibers is the result of one of these developmental events. For example, cereal grains are the seed, potatoes are the highly specialized stem, spinach is the leaf, and cotton comes from the highly developed cell walls of the ovule, a part of the maternal reproductive structure. The more we understand these processes, the better chance we will have of developing a strategy for crop Improvement. With the advent of biotechnological techniques, it is now distinctly possible to manipulate the natural regulatory mechanisms to produce improved crop varieties with desirable genetic traits.