Plant Growth and Development

Photoperiodism


Photoperiod

  • The effect of daily duration of light and dark hours on the growth and development of plants, especially flowering is called photoperiodism.
  • On the basis of photoperiodic response to flowering, plants have been divided into the flowering categories such as, short day plants (SDP), long day plants (LDP), short - long day plants (S-LDP), Long - short day plants (L - SDP), Day neutral (or) inedeterminate plants and Amphiphotoperiodic plants.
  • SDP is also called as long night plants that undergoes dark period (or) scotoperiod If the plant is exposed to even a flash of light before achieving a critical dark period, flowering is inhibited and is called as night break reaction.
  • Photo periodic response is mediated by phytochrome which shows reversible changes in red (660 nm) and far red (730 nm) wavelength.
  • Long day plants require a high ratio of Pfr to Pr for flowering stimulus.
  • Short day plants require a low Pfr to Pr ratio.
  • The chemical inducing flowering has been named as florigen, which is not identified yet.

Watch this video for the topic Photoperiodism Part-1 from 0:20 to 7:55

Watch this video for the topic Photoperiodism Part-2 from 0:10 to 9:52

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