Final answer:
When no light is available for photosynthesis, Euglenophyta becomes non-photosynthetic and switches to heterotrophic mode to acquire nutrients from the environment.
Step-by-step explanation:
When no light is available for photosynthesis, Euglenophyta becomes non-photosynthetic and switches to heterotrophic mode to acquire nutrients from its environment. Euglenoids, such as Euglena, have the ability to behave like heterotrophs and take up organic nutrients when light is absent. Without light, their chloroplasts shrink up and temporarily cease functioning.