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Episode 205 – Parasitic Plants

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Listen to Episode 205 on PodBean, YouTube, Spotify, or wherever you listen to your favorite podcasts!

Not all plants rely on the sun. Some steal the nutrition they need from other photosynthesizers. This episode, we explore the diversity and evolution of Parasitic Plants.

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Plants Parasitizing Plants

Parasitic plants are species that get some or all of their nutrition from other living plants. Over 4,000 species are known to live this way. Depending on the species, they might be full-time or part-time parasites, they might be parasites of other plants’ roots or stems, and some must be at least partially parasitic in order to complete their life cycle.

Hemiparasites are partial parasites, obtaining only some of their nutrition from hosts.
Left: Common mistletoe (Viscum album) is a stem parasite on trees. Image by Pascal Volk, CC BY-SA 4.0
Right: Prairie-fire (Castilleja) is a root parasite on grasses and forbs. Image by KimonBerlin, CC BY-SA 2.0

Parasitic plants all share a feature called a haustorium, which penetrates the host’s tissues and connects the parasite to the host’s vascular system. Several parasitic plants cause stunted growth, low reproduction, or even high mortality in their hosts, including some especially damaging agricultural pests.

Holoparasites obtain all of their carbon from plant hosts. These parasites often lack chlorophyll, as they’re doing none of their own photosynthesis.
Left: Stinking corpse lily (Rafflesia) is a parasite of grapevines. These parasites lack stems, leaves, and roots, and they grow the world’s largest flowers. Image by Maizal Chaniago, CC BY-SA 4.0
Right: Dodder (Cuscuta) is a vine that is also a stem parasite. Image by Mikenorton, CC BY-SA 4.0

Parasitic lifestyles in plants have evolved several times independently across various flowering plant lineages since the Cretaceous Period. The haustorium has even evolved convergently several times. Since the haustorium is the only obvious anatomical structure of parasitic plants, and since it is often very small and hidden within the plants’ tissues, there are no confirmed fossils of parasitic plants, although there are reports of fossil pollen from modern parasitic plant families.

Cross-section of the parasitic organ (haustorium) of mistletoe invading the tissue of a linden tree. Image by Yuliya Krasylenko, CC BY-SA 4.0

Learn More

Impacts of parasitic plants on natural communities (technical, open access)
Parasitic angiosperms: How often and how many? (technical, paywall)
A living bridge between two enemies: haustorium structure and evolution across parasitic flowering plants (technical, paywall)

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