Phytochromes are active in

Most of the plants are seasonal due to

Phytochrome is:

$A$ group of plants flowered when exposed to a $12$ hour day and $12$ hour night cycle. Another group of the same plants did not flower when exposed to the same day-night cycle but with a brief light interruption during the night. What type of plants are these?

Photoperiod is an important factor which affects

For flowering,the critical dark period should always be exceeded in