In some white caladiums, there is less than a square inch of green space spread over the whole leaf. How do these plants perform the photosynthesis necessary to support the large leaves, the roots, the flowers, and build a corm?
Any free growing (non parasitic) plant will rely on photosynthesis.
Plants do not have to be green though. It says in this article that the white caladium has chlorophyll, but relatively little, or the white color may come from other pigments that reflect other kinds of light.