Some varieties of wheat are known as spring wheat while others are called winter wheat. The former variety is sown and planted in spring and is harvested by the end of the same season. However,winter varieties,if planted in spring,fail to flower or produce mature grains within a span of a flowering season. Explain,why?

(D) Some annual food plants,such as wheat,do not flower unless they experience a low temperature. They remain vegetative during spring (a warm period) but grow further to bear flowers and fruits only after receiving low temperatures (in winter).
The low temperature in winter prevents precocious reproductive development in autumn,thus enabling the plant to reach vegetative maturity before the reproductive phase.
Thus,when spring varieties are planted in spring,they flower and bear fruits prior to the end of the growing season. However,if winter varieties are planted in spring,they fail to flower and produce mature grains before the end of the growing season,as they could not perceive the low temperature of winter. This phenomenon is known as $Vernalization$.