Abstract
AbstractThe effects of caffeine, ionophores and calcium flux blockers on the step‐up photophobic response, phototactic orientation and the intracellularly recorded, light‐induced electrical action potential were studied in the ciliate, Stentor coeruleus. Caffeine alters the absorption and CD spectra and enhances the fluorescence of the photoreceptor pigment, stentorin. Independent of its effects on the spectroscopic properties of the photoreceptor pigment, caffeine shortens the photophobic response time by enhancing the Ca2+ conductivity of membranes, while Ca2+ flux blockers (LaCI3 or ruthenium red) prolong it; both effects cancel each other. Evidence is presented that phototactic orientation is brought about by repetitive photophobic responses, since a change in the phobic response time results in a decreased accuracy of phototaxis.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
