title: Effects of light on gravitaxis and velocity in Chlamydomonas reinhardtii.
abstract: The effects of light on gravitaxis and velocity in the bi-flagellated green alga Chlamydomonas reinhardtii were investigated using a real time automatic tracking system. Three distinct light effects on gravitaxis and velocity with parallel kinetics were found. Photosynthetically active continuous red light reversibly enhances the swimming velocity and increases or decreases the precision of gravitaxis, depending on its initial level. Blue light flashes induce fast transient increases in velocity immediately after the photophobic response, and transiently decrease or even reverse negative gravitaxis. The calcium dependence of this response, its fluence-response curve and its spectral characteristics strongly suggest the participation of chlamy-rhodopsin in this effect. The third response, a prolonged activation of velocity and gravitaxis, is also induced by blue light flashes, which can be observed even in calcium-free medium.
authors.affiliation: Moscow State University, Biol. Dept., Moscow, Russia.
authors.forename: O
authors.initials: O
authors.lastname: Sineshchekov
authors.forename: M
authors.initials: M
authors.lastname: Lebert
authors.forename: D P
authors.initials: DP
authors.lastname: Hader
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology / Q000502:physiology; D002696:Chlamydomonas / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects*; D003623:Dark Adaptation; D006112:Gravitation; D018466:Gravity Sensing / Q000187:drug effects / Q000528:radiation effects*; D008027:Light; D009043:Motor Activity / Q000187:drug effects / Q000528:radiation effects*; D009949:Orientation / Q000187:drug effects / Q000528:radiation effects*; D011190:Potassium Cyanide / Q000494:pharmacology; D013550:Swimming
chemical_list: D011190:Potassium Cyanide; D002118:Calcium