**4.4 Treatments with growth regulators and other chemicals**

*Treatments with growth regulators and other Chemicals;* the presence of germination inhibitors may cause endogenous dormancy. Low-dose growth regulators (Gibberellins, Cytokinins, and Ethylene) may be used to break seed dormancy. Gibberellins and kinetics are the most extensively utilized growth regulators; for example, presoaking seed treatment with GA3 at a concentration of 100 ppm has been employed to break seed dormancy in sorghum seeds. Potassium nitrate (0.2 percent) and thio – urea (0.5 to 3 percent) is commonly used to break seed dormancy in oat (Avena sativa), barley (Hordeum vulgare), and tomato (Solanum lycopersicum) (Solanum Lycopersicum) [30].

Several methods have been devised for breaking the dormancy of seeds and for shortening the period of dormancy so that they may germinate promptly. Whenever dormancy results of any of the causes inherent in the seed coats it can be interrupted by scarification. For example, machine thrashed legumes seeds usually show a higher percentage of germination than those that have been harvested by hand. Strong mineral acids have been used successfully to interrupt seed dormancy caused by resistant or impermeable seed coats. Soaking the seeds in certain chemicals like potassium nitrate, ethylene, chlorohydrine, thiourea or in certain plant hormones is known to break dormancy. After ripening of many seeds occurs more rapidly when they are kept at low temperatures than when stored at higher temperatures. Temperatures from 5–10°C for two or three months are effective with seeds of conifers. Under natural conditions, seed dormancy is gradually overcome by processes such as weakening of the seed coat by the digestive juices in the alimentary canal of fruit-eating birds and other animals, or in still due to the action of microbes or due to mechanical abrasions. Dormancy of seeds is also broken by subjecting the seeds alternately to relatively low and high temperatures. Light is also considered as means of breaking dormancy of seeds. Seeds of sweet clover (Melilotus alba) and alfalfa (Medicago sativa) showed greatly improved germination after being subjected to hydraulic pressures of 2000 atmphere at 18°C. The following are some general approaches for breaking seed dormancy [31–33]:

