How to treat seeds and overcoming dormancy

                                                                                         

Dormancy is a period of rest in the life cycle of plants during which growth is suspended. Dormancy seeds fail to germinate in a favorable environment condition (favorable temperature and water supply). However, such seeds will germinate under similar conditions after a storage period of time up to several months.


         causes of seed dormancy

• These related to morphology and physiology of the seed
• In legumes, the seed coat or testa may be impermeable to water. For example, germination of white clover may require the breaking of the seed coat, where concentrated acids are usually used.
• Immunity of the embryo due to prematurely harvested seeds, for example, poor germination of sugar beets.
• Presence of germination inhibitors in the seed coat or testa. This is solved by washing the inhibitors by soaking the seeds before planting. The inhibitors are water-soluble.                                                                                                                                                                                     Breaking seed dormancy                                                                                                                 Some of the common methods of seed treatment and overcoming dormancy are mentioned below:
• Boiling water treatment, It is generally used for the seeds having a very hard seed coat, for example, Acacia auriculiformis, Acacia mangium. The seeds are kept in boiling water for about two minutes after that they are kept in cold water for one or two days before sowing.                                      
• Hot water treatment, This method is generally used for the seeds having hard shell, for example, Albizia, cassia, Leucaena leucocephala. After boiling the water, it is allowed to cool for ten minutes. The seeds are soaked for one or two days till they get swelled.                                         
• Coldwater treatment, This method is used in most of the species to get uniform germination. The seeds are soaked at room temperature for a period ranging from two to four eighty hours depending on the species. The seeds, which float on the top of the water , are discarded for example Acacia, Albizia, and poplars.                                                                                              
• Wet and dry method, It is generally used for teak.  This process is repeated eighty or ten times after that seeds are sown in the nursery beds.                                                                                                   
• Acid scarification, Some species, which have very hard seed coats, require ten to sixty minutes soaking in concentrated sulphuric acid followed by one or two days soaking in cold water to break dormancy, for example, Albizia falcataria, Elaeocarpus ganitrus.                                                                                                                                                                                             
• Mechanical scarification, For large quantities filling seeds with sharp gravel-stones in a rotatory drum having abrasive disks on the inner side, is very useful for example Acacia catechu, A- nilotica, Albizia spp.                                                                                                                                                                              
• Stratification,  Dormancy can be overcome by keeping the seeds at low temperature, usually between one centigrade to fifteen centigrade, with abundant aeration and moisture for periods varying from thirty to one hundred and twenty days. After stratification seeds should be sown without delay.                                                                                                                                                   
• The light requirement, Dormancy in few seeds may be due to exclusion of light by seed coats for example lettuce, red light and far red are involved through the phytochrome in the stimulation of germination. Red light stimulates growth but far-red inhibits germination. Exposure to a single shot of light is enough to resume germination. The light requirement is also found to be coupled with thermal requirements.