<P> The eyespot apparatus ( or stigma ) is a photoreceptive organelle found in the flagellate or ( motile ) cells of green algae and other unicellular photosynthetic organisms such as euglenids . It allows the cells to sense light direction and intensity and respond to it by swimming either towards the light ( positive phototaxis ) or away from the light ( negative phototaxis ) . A related response ( `` photoshock '' or photophobic response ) occurs when cells are briefly exposed to high light intensity , causing the cell to stop , briefly swim backwards , then change swimming direction . Eyespot - mediated light perception helps the cells in finding an environment with optimal light conditions for photosynthesis . Eyespots are the simplest and most common `` eyes '' found in nature , composed of photoreceptors and areas of bright orange - red pigment granules . Signals relayed from the eyespot photoreceptors result in alteration of the beating pattern of the flagella , generating a phototactic response . </P>
<P> The eyespot apparatus ( or stigma ) is a photoreceptive organelle found in the flagellate or ( motile ) cells of green algae and other unicellular photosynthetic organisms such as euglenids . It allows the cells to sense light direction and intensity and respond to it by swimming either towards the light ( positive phototaxis ) or away from the light ( negative phototaxis ) . A related response ( `` photoshock '' or photophobic response ) occurs when cells are briefly exposed to high light intensity , causing the cell to stop , briefly swim backwards , then change swimming direction . Eyespot - mediated light perception helps the cells in finding an environment with optimal light conditions for photosynthesis . Eyespots are the simplest and most common `` eyes '' found in nature , composed of photoreceptors and areas of bright orange - red pigment granules . Signals relayed from the eyespot photoreceptors result in alteration of the beating pattern of the flagella , generating a phototactic response . </P>
what is the function of eye spot in euglena
what is the function of eye spot in euglena
to sense light direction and intensity
to sense light direction and intensity