Plant hormones are produced naturally by plants and are essential for regulating their own growth. They act by controlling or modifying plant growth processes, such as formation of leaves and flowers, elongation of stems, development and ripening of fruit.
Ethylene has continued to be among the best known examples of plant growth regulators. It is a gaseous plant hormone playing a key regulatory role in ripening of many types of fruits, including banana, apple, pear and melons. It can be produced naturally by ripening fruit or from synthetic sources such as ethephon.
Another major class of plant growth regulators are auxins and related compounds. The earliest study on auxins was intended for the initiation and acceleration of the rooting of cuttings. The natural auxin, indole-3-acetic acid, was identified in 1930s. Later on, synthetic auxins such as indolebutyric acid and naphthylacetic acid were developed. Synthetic auxins have a wide range of applications including the prevention of fruit drop in apples.
Third plant growth regulator called forchlorfenuron. It is a synthetic plant growth regulator under the group called phenylurea type cytokinin, which can induce cell division and cell differentiation. Forchlorfenuron is known to increase size and yield of fruits such as grapes, kiwifruits and watermelon. Proper use of forchlorfenuron (i.e. following the good agricultural practice (GAP)) will result in minimal residue in food and hence low food safety risk.
Source:Center for safety food.