Ncert Exercises & Solutions

42. Some varieties of wheat are known as spring wheat while others are called winter wheat. Former vaniety 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 maturegrains within a span of a flowering season. Explain, why?

Some annual food plants such as wheat do not flower, unless they experience a low temperature. They remain vegetative during spring (warm period) but grow further to bear flowers and fruits after receiving low temperature (in winter).

The low temperature in winter prevents precocious reproductive development in autumn, thus enabling the plant to reach vegetative maturity before reproductive phase.

Thus, when spring varieties are planted in spring, they flower and bear fruits prion to end of growing season. But, if the winter varieties are planted in spring, they fail to flower and produce mature grains before the end of growing season, as they could not perceive low temperature of winters.

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