Photokinesis: Difference between revisions
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'''Photokinesis''' is |
'''Photokinesis''' is a change in velocity of movement of an organism as a result of changes in light intensity.<ref name=Hader>{{cite book|author1=Häder, D.-P.|author2=Lebert, M.|title=Photomovement|url=https://books.google.com/books?id=2nevsljDiCYC&pg=PA305|year= 2001 |publisher=Elsevier |isbn=978-0-08-053886-0 |page=305}}</ref> The behaviour is independent of the direction from which the light is shining. It is described as positive if the velocity of travel is greater in the light than it is in the dark, and negative if it is slower.<ref name=Hemmersbach>{{cite book|author1=Häder, Donat-Peter |author2=Hemmersbach, Ruth |author3=Lebert, Michael |title=Gravity and the Behavior of Unicellular Organisms |url=https://books.google.com/books?id=EQvzwpAWEy0C&pg=PA115 |year=2005 |publisher=Cambridge University Press|isbn=978-0-521-82052-3 |page=115}}</ref> If a group of organisms with a positive photokinesis response is swimming in a partially shaded environment, there will be fewer organisms per unit of volume in the sunlit portion than in the shaded parts.<ref name=Smith>{{cite book|author=Smith, Kendric C. |title=The Science of Photobiology |url=https://books.google.com/books?id=EGfSBwAAQBAJ&pg=PA308 |year=2013 |publisher=Springer Science & Business Media|isbn=978-1-4615-8061-4 |pages=308–309}}</ref> |
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In [[Photosynthesis|photosynthetic]] [[prokaryote]]s, the mechanism for photokinesis appears to be an energetic process. In [[cyanobacteria]], for example, an increase in illumination results in an increase of photophosphorylation which enables an increase in metabolic activity. However the behaviour is also found among [[Eukaryote|eukaryotic]] microorganisms, including those like ''[[Astasia longa]]'' which are not photosynthetic, and in these, the mechanism is not fully understood.<ref name=Hemmersbach/> In ''[[Euglena gracilis]]'', the rate of swimming has been shown to speed up with increased light intensity until the light reached a certain saturation level, beyond which the swimming rate declines.<ref>{{cite journal |author=Wolken, J.J.; Shin, E. |year=1958 |title=Photomotion in ''Euglena gracilis'' * I. Photokinesis II. Phototaxis |journal=The Journal of Protozoology |volume=5 |issue=1 |pages=39–46 |doi=10.1111/j.1550-7408.1958.tb02525.x }}</ref> |
In [[Photosynthesis|photosynthetic]] [[prokaryote]]s, the mechanism for photokinesis appears to be an energetic process. In [[cyanobacteria]], for example, an increase in illumination results in an increase of photophosphorylation which enables an increase in metabolic activity. However the behaviour is also found among [[Eukaryote|eukaryotic]] microorganisms, including those like ''[[Astasia longa]]'' which are not photosynthetic, and in these, the mechanism is not fully understood.<ref name=Hemmersbach/> In ''[[Euglena gracilis]]'', the rate of swimming has been shown to speed up with increased light intensity until the light reached a certain saturation level, beyond which the swimming rate declines.<ref>{{cite journal |author=Wolken, J.J.; Shin, E. |year=1958 |title=Photomotion in ''Euglena gracilis'' * I. Photokinesis II. Phototaxis |journal=The Journal of Protozoology |volume=5 |issue=1 |pages=39–46 |doi=10.1111/j.1550-7408.1958.tb02525.x }}</ref> |
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Revision as of 18:02, 10 July 2020
Photokinesis is a change in velocity of movement of an organism as a result of changes in light intensity.[1] The behaviour is independent of the direction from which the light is shining. It is described as positive if the velocity of travel is greater in the light than it is in the dark, and negative if it is slower.[2] If a group of organisms with a positive photokinesis response is swimming in a partially shaded environment, there will be fewer organisms per unit of volume in the sunlit portion than in the shaded parts.[3]
In photosynthetic prokaryotes, the mechanism for photokinesis appears to be an energetic process. In cyanobacteria, for example, an increase in illumination results in an increase of photophosphorylation which enables an increase in metabolic activity. However the behaviour is also found among eukaryotic microorganisms, including those like Astasia longa which are not photosynthetic, and in these, the mechanism is not fully understood.[2] In Euglena gracilis, the rate of swimming has been shown to speed up with increased light intensity until the light reached a certain saturation level, beyond which the swimming rate declines.[4]
The sea slug Discodoris boholiensis also displays photokinesis; it is nocturnal and moves slowly at night, but much faster if caught in the open during daylight hours.[5]
References
- ^ Häder, D.-P.; Lebert, M. (2001). Photomovement. Elsevier. p. 305. ISBN 978-0-08-053886-0.
- ^ a b Häder, Donat-Peter; Hemmersbach, Ruth; Lebert, Michael (2005). Gravity and the Behavior of Unicellular Organisms. Cambridge University Press. p. 115. ISBN 978-0-521-82052-3.
- ^ Smith, Kendric C. (2013). The Science of Photobiology. Springer Science & Business Media. pp. 308–309. ISBN 978-1-4615-8061-4.
- ^ Wolken, J.J.; Shin, E. (1958). "Photomotion in Euglena gracilis * I. Photokinesis II. Phototaxis". The Journal of Protozoology. 5 (1): 39–46. doi:10.1111/j.1550-7408.1958.tb02525.x.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Bidgrain, P. (2019). "Discodoris boholiensis". Indian Ocean Sea Slugs. Retrieved 10 July 2020.