Stratification involves the treatment of seed at low temperature $\left(5-10^{\circ} C \right)$ under sufficiently moist conditions to break its dormancy and to induce germination.
Scarification involves any damage or breakage of seed coat by physical methods (eg, use of scalpel, wooden hammer etc) or chemical methods (use of mild acids) to break seed dormany.
Vernalization and Chelation is the chill treatment of plant in its early stages of life history to stimulate or induce early flowering.