One-flowered Cancer-root (Orobanche uniflora), also known as One-flowered Broomrape, is now flowering in fens — wetlands similar to bogs, but less acidic and more mineral-rich. Covered with glandular hairs, its flower looks like it’s made of crystallized sugar. One plant produces up to five flowering stalks, each of which bears a single, fragrant, white-to-lavender flower.
One-flowered Cancer-root has no chlorophyll in the scale-like leaves that grow on its underground stem, and thus is incapable of making its own food. This parasitic plant is classified as a holoparasite – entirely dependent upon other host plants for its nutritional needs. A One-flowered Cancer-root seedling must find a suitable host plant (often sedums, saxifrages and asters) within a few days of germinating or die. The search for a host by One-flowered Cancer-root is guided by chemicals released by the growing roots of the host species. Once a host plant is located, the One-flowered Cancer-root’s root hairs exude an adhesive substance that attaches its roots to those of the host plant. Enzymes break down the cell walls of the host, and a tuber-like connection (haustorium) forms between the vascular tissue of the two plants, allowing the movement of water, minerals and carbohydrates to flow in one direction, from host to parasite. (Thanks to Shiela and Steve Swett for photo op.)
Flowering plants have a variety of ways to obtain food. Most have chlorophyll and thus are capable of photosynthesizing their own nutrients. A majority of these plants (90%) are also associated with mycorrhizal fungi – fungi which attach to the roots of other plants, often trees, with which most have a symbiotic relationship (both benefit). The plant receives minerals and water from the fungi, and the fungi feed on carbohydrates and other nutrients the plant produces.
Flowering plants with no chlorophyll cannot make their own food and must rely completely on other organisms for their nutrients. Some of these parasitic plants get their nutrients directly from the roots of another plant (Beechdrops) and others (Indian Pipe and Pinesap) receive food indirectly from fungi which get their nutrients from a photosynthetic plant. In these situations, the mycorrhizal relationship between the non-photosynthetic plant and the fungi is not mutualistic, as only the chlorophyll-lacking plant benefits. (Photo: Indian Pipe, Monotropa uniflora (one flower per stalk) and (insert) Pinesap, Monotropa hypopitys (many flowers per stalk).