Seed and sowing- Methods to Break the Dormancy
Methods to Break the Dormancy:
1. Scarification: The dormancy due to hard seed coat or impermeable seed coats can be broken by scarification of seed coats. It should be done in such a way that the embryo is not injured.
a. Chilling (Pre-chilling): The seeds are placed in contact with the moist substratum at a temperature of 5 to 10°C for 7 days for germination. E.g. Cabbage, Cauliflower, and Sunflower.
b. Pre-dying: Seeds should be dried at a temperature not exceeding 40°C with free circulation for a period of 7 days before they are placed for germination. E.g. Maize, Lettuce.
c. Pre-washing:In some seeds, germination is affected by naturally occurring substances which act as inhibitors which can be removed by soaking & washing the seeds in the water before placing for germination. E.g.: Sugar beet.
d. Pre-soaking: Some seeds fail to germinate due to hard seed coat. Such seeds should be soaked in warm water for some period so as to enhance the process of imbibitions. E.g. Chillar, Subabul.
e. Rubbing or puncturing seed coat: Some seeds are subjected to mechanical scarification either by rubbing them against rough surface or puncturing the seed coat with pointed needle. E.g.: Coriander, Castor.
f. Application of pressure to seeds: Germination of Medic ago sativa is found to be increased when a hydraulic pressure of 2000 atmosphere at 18°C is applied. It may be due to increase in permeability of seed coat to water and O2.
2) Stratification: In some seeds after ripening, low temperature and moisture conditions require in artificial stratification. Seed layer altered with layers of moist sand or appropriate material to store at low temperature. E.g.: Mustard & Groundnut.
3) Exposure of seeds to light: It also helps to break the dormancy & increase the germination.
4) Chemical treatments:
a. Potassium nitrate treatment (KNO3): The material used for placing the seeds for germination i.e. substratum, may be moistened with 2% solution of KNO3 (2g KNO3 + 100ml of water). E.g. rice, tomato, chilies.
b. Gibberellic acid treatment: The substratum used for germination may be moistened with 500 ppm solution of GA i.e. 500 mg in 1000ml water. E.g. Wheat, Oat.
c. Thio-urea treatment: Potato tubers are dipped in thio-urea solution (1%) for one hour when fresh harvested produce is to be used as seed material.