Dormancy: Dormancy is a stage of plant or a part of plant in which its active growth is temporarily inhibited. In other words, the state of temporary ceasation of growth and metabolism of a plant or plant part is called dormancy. Causes of Dormancy of Seeds: 1. Hard seed coat: In many seeds hard seed coat causes dormancy. This hard seed coat is impermeable to water or gases. In some seeds, the seed coat is so hard that it does not break even by the emerging embryo. 2. Dormant embyro: Some apparently healthy seeds remain dormant due to some physiological disturbance. 3. Immature embryo: Some seeds are apparently healthy but do not germinate as they have immature embryo. Actually, development of embryo is not completed in these seeds due to some unknown factors. 4. Germination inhibitors: Many chemical substances have been isolated from seeds which inhibit seed germination. Methods of Breaking Seed Dormancy: 1. Scarification: Dormancy caused by hard seed coat can be broken by this method. In this seed coat is mechanically broken or rendered weak by scratching it to facilitate germination. 2. Pressure: Seeds of some plants are given hydraulic pressure of 2000 atm at 18�C temperature for 5 - 20 minutes to make the seed coat permeable, consequently water starts entering the seed and dormancy is broken. 3. Low temperature: Dormancy of some seeds can be broken by treating them with low temperature. 4. Light: Seeds of some plants germinate in bright light. Exposure of light helps in breaking dormancy in such seeds.