page_title: Photomorphogenesis
section_title: Seedling development
hierarchical_section_title: Photomorphogenesis / Developmental stages affected / Seedling development
caption_attribution_description: Ipomea seed growng
context_page_description: In developmental biology, photomorphogenesis is light-mediated development, where plant growth patterns respond to the light spectrum. This is a completely separate process from photosynthesis where light is used as a source of energy. Phytochromes, cryptochromes, and phototropins are photochromic sensory receptors that restrict the photomorphogenic effect of light to the UV-A, UV-B, blue, and red portions of the electromagnetic spectrum.
  The photomorphogenesis of plants is often studied by using tightly frequency-controlled light sources to grow the plants. There are at least three stages of plant development where photomorphogenesis occurs: seed germination, seedling development, and the switch from the vegetative to the flowering stage.
  Most research on photomorphogenesis comes from plants, it occurs in several kingdoms: Fungi, Monera, Protista, and Plantae.
context_section_description: In the absence of light, plants develop an etiolated growth pattern. Etiolation of the seedling causes it to become elongated, which may facilitate it emerging from the soil.
  A seedling that emerges in darkness follows a developmental program known as skotomorphogenesis (dark development), which is characterized by etiolation. Upon exposure to light, the seedling switches rapidly to photomorphogenesis (light development).
  
  There are differences when comparing dark-grown (etiolated) and light-grown (de-etiolated) seedlings
   
  Etiolated characteristics:
  Distinct apical hook (dicot) or coleoptile (monocot)
  No leaf growth
  No chlorophyll
  Rapid stem elongation
  Limited radial expansion of stem
  Limited root elongation
  Limited production of lateral roots
  De-etiolated characteristics:
  Apical hook opens or coleoptile splits open
  Leaf growth promoted
  Chlorophyll produced
  Stem elongation suppressed
  Radial expansion of stem
  Root elongation promoted
  Lateral root development accelerated
  The developmental changes characteristic of photomorphogenesis shown by de-etiolated seedlings, are induced by light.
caption: A dicot seedling emerging from the ground displays an apical hook (in the hypocotyl in this case), a response to dark conditions
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