Give the natural and artificial overcoming of seed dormancy



Natural overcoming of seed dormancy:
(a) Weakening of tough and impermeable seed coats by microbial action.
(b) Rupturing or weakening of seed coats by mechanical abrasions.
© Action of digestive enzymes present in alimentary canals of birds and other animals which happen to feed on their fruits.
(d) Leaching of inhibitors present in the seed coat.
(e) Inactivation or oxidation of inhibitors by heat, cold and light.
Artificial overcoming of seed dormancy : .
(a) Rupturing of seed coats or sacrification by abrasion
through machine threshing, filing, chipping vigorous shaking, etc.
(b) Treatment with hot water or fat solvents for dissolution of surface inhibitors, waxes, etc.
© Treatment with concentrated sulphuric acid for a short period followed by through washing to remove all traces of the mineral acid.
(d) Stratification or subjecting the moist seeds in the presence of oxygen to periods of low or high temperature.
(e) Counteracting the effect of growth inhibitors by soaking the seeds in potassium nitrate, ethylene chlorohydrin, thiourea, gibberellins, etc. Exposure to high concentration of oxygen has similar effect.