A Parasite on a Fungus
Deep in the leaf litter of Chile's temperate rainforests, a pale, leafless stalk emerges, bearing a single, unusual flower. This is Arachnitis uniflora, a plant that lives a life of deception. Lacking chlorophyll, it cannot perform photosynthesis. It is a mycoheterotroph, a type of parasite that steals its food from fungi. Specifically, it targets arbuscular mycorrhizal fungi from the Glomeraceae family. These fungi form symbiotic relationships with the roots of surrounding photosynthetic trees, such as the southern beeches of the genus Nothofagus. Arachnitis taps into this network, siphoning off carbon and nutrients that the fungus has acquired from its tree partner.
The plant spends almost its entire life underground. Its name, Arachnitis, derives from its root system—a cluster of tuberous, branching rhizomes that resembles a spider or a web. These whitish tubers, typically 4 to 17 in number, are small, measuring only 5 to 10 millimeters long. From this subterranean network, a single, unbranched stem, from 6 to 40 centimeters tall, ascends. The stem, which can be whitish, yellowish, or purple, supports a solitary flower—the reason for its species name, uniflora. The flower has six tepals (petal-like structures). Five are long and thin, while the sixth, the median outer tepal, is broad, concave, and marked with 11 to 13 violet nerves.