PowerPoint Presentation: Welcome- PowerPoint Presentation: Seed dormancy BOT-367 Principles of seed technology PowerPoint Presentation: Content- Introduction- Types of seed dormancy- Causes of seed dormancy- Methods of seed dormancy- Principles of quality seed- PowerPoint Presentation: Seed dormancy- Def- Failure of fully developed & mature viable seed to germinate under favorable conditions of moisture & temperature. - This condition called as resting stage, period or dormancy. - This seed called as dormant seed. PowerPoint Presentation: In some seeds – germination is obstructed for sometimes after attaining maturity even If optimum conditions which is moisture, temperature and oxygen are available. Dormancy helpful for the seed to survive under adverse conditions or climate. Quiescence- The inhibition of growth due to non-availability of favorable environmental conditions. PowerPoint Presentation: Types of dormancy- Primary dormancy- Due to internal causes even favorable environmental conditions are available for germination. Secondary dormancy- They germinate immediately after present the favorable conditions, but the dormancy is induced in the seeds if there is kept under certain conditions. Eg . Mustard seed – is kept in higher concentration with CO2 due to respiration. PowerPoint Presentation: Special dormancy- Some species are germinated , but the primary roots fail to develop that’s why epicotyls is stopped. Organic dormancy- Seed remains hard after the expiry of germination period and don’t germinate, when the moisture reduced below 4%. PowerPoint Presentation: Causes of dormancy- 1) Impermeability of seed coat to water- Seed coat become hard (family- Leguminosae , Solanaceae , Malvaceae , Convolvulaceae , Chenopodiaceae .) the seed contain external waxy coating made up off Lignin, Suberin or Cutin which is impermeable to water. - These seed remain dormant until seed coat is removed by microbial activity of alteration of temperature. PowerPoint Presentation: 2) Impermeability of seed coat to oxygen- Germination is inhibit due to impermeability of the seed coat to oxygen. Eg . Fruit of Oats and Xanthium- These contains two seed (upper & lower) lower is germinate under soil and upper seed doesn’t germinate until seed coat is punctured or removed by the high concentration of oxygen. PowerPoint Presentation: 3) Growth of embryo- Mustard & Amaranthus - seed are easily permeable in oxygen and water, but the seed coat doesn’t rupture. 4) Immaturity of embryo- The development of other parts of seed completed except embryo. 5) Temperature requirement- Apple , Peach require low temperature to germinate further more require high temperature to germinate. PowerPoint Presentation: 6) Light requirement- Carrot, tobacco require absolute requirement of light, while Datura exposure to light is inhibitory for germination. 7) Germination Inhibitors- Tomato fail to germinate due to presences cirulic acid found in the sap of fruits. These chemical present the husk in Rice and Oats seed . PowerPoint Presentation: Methods of breaking dormancy- Mechanical treatment of seeds- The dormancy can be removed by mechanically to weakening the seed coat called as Scarification. Filing (using sand) Chipping (using knife) Piercing (using needle) Chilling (using temperature) Pre-drying (using temperature) Pre-washing (using water) Pre-soaking (using warm water) PowerPoint Presentation: 2) Chemical treatment- Seed are dipped in mineral acid (HCL, H 2 SO 4 ) or organic solvent (Alcohol, Acetone) to cause degrading of seed coat and dissolving of waxy coating. 3) Use of growth regulator- Germination can be influence by using growth hormones (GA3, IBA, IAA, NAA, 2,4-D) PowerPoint Presentation: Advantages of Dormancy- Seed survive in adverse conditions. Seed stored till next season, transport to another place without loosing its viability. Seed use in research such as gene pool. Some seed kept in cold condition to get best price when there is off season. Due to dormancy species are saved from wipeout in case of natural calamity. Seed germinate itself. PowerPoint Presentation: Dis-advantages of Dormancy- The seed can not sown immediately after maturity, will have to wait for the expiry of dormant period. Seed remain naked during dormant period they get shabby look. Germination of the seeds is poor and growth of buds is slow and irregular even under favorable condition. Noxious weed seed lie dormant for many years in soil and thus growing year after year becomes eradication impossible. PowerPoint Presentation: Thank you….!