What
do you understand by photoperiodism and vernalisation? Describe their
significance.
What do you understand by photoperiodism and vernalisation? Describe their significance.
Photoperiodism
refers to the response of plants with respect to the duration of
light (i.e., period of day and night). On the basis of its response
to the duration of light, a plant is classified as a short-day plant,
a long-day plant, or a day-neutral plant. Short-day plants flower
when they are exposed to light for a period less than the critical
day-length (for example: Chrysanthemum). Long-day plants
flower when they are exposed to light for a period more than the
critical day-length (for example: radish). When no marked correlation
is observed between the duration of exposure to light and the
flowering response, plants are termed as day-neutral plants (for
example: tomato).
It is
hypothesised that the hormonal substance responsible for flowering is
formed in the leaves, subsequently migrating to the shoot apices and
modifying them into flowering apices. Photoperiodism helps in
studying the response of flowering in various crop plants with
respect to the duration of exposure to light.
Vernalisation
is the cold-induced flowering in plants. In some plants (such as the
winter varieties of wheat and rye and biennials such as carrot and
cabbage), exposure to low temperature is necessary for flowering to
be induced. The winter varieties of rye and wheat are planted in
autumn. They remain in the seedling stage during winters and flower
during summers. However, when these varieties are sown in spring,
they fail to flower. Similar response is seen in cabbage and radish.
Photoperiodism refers to the response of plants with respect to the duration of light (i.e., period of day and night). On the basis of its response to the duration of light, a plant is classified as a short-day plant, a long-day plant, or a day-neutral plant. Short-day plants flower when they are exposed to light for a period less than the critical day-length (for example: Chrysanthemum). Long-day plants flower when they are exposed to light for a period more than the critical day-length (for example: radish). When no marked correlation is observed between the duration of exposure to light and the flowering response, plants are termed as day-neutral plants (for example: tomato).
It is hypothesised that the hormonal substance responsible for flowering is formed in the leaves, subsequently migrating to the shoot apices and modifying them into flowering apices. Photoperiodism helps in studying the response of flowering in various crop plants with respect to the duration of exposure to light.
Vernalisation is the cold-induced flowering in plants. In some plants (such as the winter varieties of wheat and rye and biennials such as carrot and cabbage), exposure to low temperature is necessary for flowering to be induced. The winter varieties of rye and wheat are planted in autumn. They remain in the seedling stage during winters and flower during summers. However, when these varieties are sown in spring, they fail to flower. Similar response is seen in cabbage and radish.
