Recommended
More Related Content
What's hot
What's hot (20)
Similar to Phytochrome
Similar to Phytochrome (20)
More from Halala Rahman
Recently uploaded
Recently uploaded (20)
Phytochrome
- 1. University of Salahaddin College of Education Biology department 1 Halala Rahman Qadir M.Sc. Plant physiology 10/29/2015
- 2. The objectives are: ļ¶Definition of phytochrome 2 ļ¶Role of phytochrome ļ¶Founding of phytochrome 10/29/2015
- 3. Definition of transpiration Phytochrome: is a photoreceptor, a pigment that plants, and some bacteria and fungi, use to detect light. It is sensitive to light in the red and far-red region of the visible spectrum. Biochemically, phytochrome is a protein with a bilin chromophore. The Pigment That Controls Growth and Flowering In Many Plants 10/29/2015 3
- 4. 10/29/2015 4
- 5. Role of phytochrome 1. Many flowering plants use it to regulate the time of flowering based on the length of day and night (photoperiodism) and to set circadian rhythms. 2. It also regulates other responses including the germination of seeds(photoblasty), elongation of seedlings, the size, shape and number of leaves, the synthesis of chlorophyll, and the straightening of the epicotyl or hypocotyl hook of dicot seedlings. 3. It is found in the leaves of most plants. 10/29/2015 5
- 6. Founding of phytochrome Phytochrome has been found in most plants including all higher plants; very similar molecules have been found in several bacteria. A fragment of a bacterial phytochrome now has a solved three-dimensional protein structure. 10/29/2015 6
- 7. 10/29/2015 7
- 8. 10/29/2015 8
- 9. characteristics of phytochrome-mediated responses ļ¶ The action spectrum of the light needed for these responses shows a peak in the red at about 660 nm. ļ¶ These responses can be reversed by an application of far- red light (peak at 730 nm) soon after the red treatment. ļ¶ Sensitive spectrophotometers can measure a decrease in absorbance at 660 nm and in increase in absorbance at 730 nm when sensitive plant tissues are exposed to red (660 nm) light. ļ¶ The change in absorbance is caused by the conversion of a the photoreceptor from one structural form to another. The red-absorbing form changes to the far-red absorbing form when it absorbs red light (660 nm) and back again when it absorb far-red light (730 nm) 10/29/2015 9
- 10. The phytochrome molecule is the photoreceptor for red light responses. It exists in two forms, Pr and Pfr: ļ¶ The Pr form: ā¢ Absorbs at a peak of 666 nm ā¢ Is the form synthesized in dark-grown seedlings. ā¢ When Pr absorbs red light, it is converted to the Pfr form. 10/29/2015 10
- 11. ļ¶The Pfr form: ā¢ Absorbs at a peak of 730 nm ā¢ The Pfr form is the active form that initiates biological responses ā¢ When Pfr absorbs far red light, it is converted to the Pr form ā¢ Pfr can also spontaneously revert to the Pr form in the dark over time = dark reversion; Pfr is also susceptible to proteinases. ā¢ Pfr absorbs some red light, so in red light, there is a balance of 85% Pfr and 15% Pr ā¢ Pr absorbs very little far red light, so in far red light, there is a balance of 97% Pr to 3% Pfr 10/29/2015 11
- 12. 10/29/2015 12