Author(s):

Nitin Sharma, Kuldeep Singh and Gururaj Mathapati

Abstract: Light is an important external stimulus that acts both as an information stimulus and energy source. Plant employs two contrasting developmental programs to succeed under prevailing light conditions: skotomorphogenesis and photomorphogenesis. Skotomorphogenesis is characterized by the closed cotyledon, elongation of hypocotyl and apical hook formation for rapid growth of young seedlings utilizing energy reserve present in seed. On the other hand, photomorphogenesis is the process where light signals prevent the speedy elongation of hypocotyl, expand the cotyledons, and encourage greening to allow light harvesting and autotrophic growth. Also, seasonal changes in photoperiod (light duration) promotes switch from vegetative to reproductive growth by inducing flowering. To monitor changes in light direction, quality, quantity and duration, plants have evolved various photoreceptors to modulate plant growth and development.

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