Vernalization is chilling or cold treatment of the young plants or seeds to induce flowering. It is a process of shortening of the juvenile or vegetative phase and fastening the flowering by a process of cold treatment. It was first reported by a Russion worker, Lysenko (1928) while working on cold requiring biennial plants. Common examples of plants requiring vernalization are winter rye, winter wheat, winter barley, pea, Chrysanthemum etc.
Cryobiology is the study of life at low temperature, usually at liquid nitrogen (ie$ -196^{\circ}C$) and preservation of organisms in liquid by chemical methods.
Photoperiodism is the effect of photoperiods or daily duration of light hours (and dark periods) on the growth and development mainly flowering in plants. It was first studied by Garner and Allard (1920) on Maryland Mammoth variety of tobacco.