Daylength sensitivity

• What is the plant sensitivity to lack of light called?

  • photoperiodism
  • Controlled by pigments called phytochromes (Pr and Pfr)
• What is photoperiodism?

  • Sensitivity to lack of light
  • Due to sensitive light pigment (phytochrome)
  • Ratio of Pr and Pfr changes depending on light levels
  • Affects dormancy of leaf buds, flowering timing and formation of tubers
• how are plants sensitive to day (or dark) length?

  • Have light sensitive phytochrome pigment
  • Exists in two forms- Pr and Pfr
  • Each form absorbs a different type of light and the ratio of Pf to Pfr changes depending on the levels of light
• what is a phytochrome?

  light sensitive pigment that helps plants respond to the lack of light present
• what plant responses are affected by the photoperiod?

  • breaking of dormancy
  • flowering
  • formation of tubers
• why is it stressful to plants when there are lower light levels?

  • less photosynthesis occurs
  • less glucose produced
  • less glucose means less energy for the plant to maintain their leaves, respire and produce chemicals that might protect them from freezing