Q. Do all plants need sunlight?
A. Plants do need sunlight or other light sources to power the chemical reactions of photosynthesis and make food for themselves. But some plants rely on others to make food for them and can survive without sunlight.
Parasitic plants take nutrients directly from other plants. For example, the many species of the genus Cuscuta, commonly called dodder or witch’s hair, use structures called haustoria to pierce the stems of other plants.
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Once contact has been made, the dodder's own roots disappear, and its thin vines, with only vestigial leaves, grow using the host plant's resources. The dodder’s targets range from crops like alfalfa and potatoes to flowers like chrysanthemums and petunias.
What have historically been called saprophytic plants get nutrients from decaying plant materials, without need of sunlight or chlorophyll. They are believed to do this by acting as parasites of the fungi that do the actual work of decomposition (and thus are more properly called mycotrophic plants).
There is at least one plant that scientists believe can use both of these means to get nutrition. Researchers have found that Erythrorchis cassythoides, a climbing orchid common in Eastern Australia, can take nutrients directly from other plants and from surrounding fungi.
