biomedicalephemera:

Rafflesia arnoldii - Rafflesia or Corpse Flower (colloquially “stink plant” or “meat plant”)

So, like a lot of people, I already knew the Rafflesia (specifically Rafflesia arnoldii) for its record of being the largest single flower in the world, and because it’s one of the “carrion flowers” that apparently attracts seed-spreaders by its terrible stench. But this thing is way more than just big and smelly - it’s managed to make me actually find it repulsive, and I’m someone who loves “gross” things!

To start, this plant is an obligate parasite, also known as a holoparasite - it has no way to create “real” roots of its own, and grows by sucking the nutrients directly from its host plant. This can be any vine from the Vitaceae family, which are abundant in Indonesia, Malaysia, and the surrounding area, where the Rafflesia live. Coincidentally, some members of the Vitaceae family are opportunistic parasites, themselves.

When a seed from the Rafflesia is deposited near or upon a suitable vine by a tree shrew or other animal (not much is known about seed dispersal yet), it doesn’t grow a taproot upon germination, like most plants. No, this fun flower grows what are known as haustoria - fungus-like probing appendages, that penetrate the host plant, and dig into the thick xylem and phloem of the vine.

The tip of each haustorium narrows as it grows between cells, and widens once it’s entrenched in an area. The parts of the haustoria not working on expanding and lengthening absorb the water and nutrients that are sucked up by the roots of the host vine. This creates an effective river of nutrients flowing up to the Rafflesia flower, which is the only part of the plant that we see. Have you ever noticed that Rafflesia don’t have any leaves? That’s because the organic compounds created by photosynthesis are sucked up through the vine, so the plant doesn’t need any!

I think I would be more settled with this plant if it didn’t effectively create a “zombie vine”. Some botanists have reported coming across old Rafflesia flowers that had so thoroughly entrenched themselves into the host plant, that the host plant didn’t even have any living tissue beyond the entrance point of the haustoria. Vines that once scaled huge trees were killed off, down to about 2-3 feet up the tree, and the haustoria of the Rafflesia had even penetrated the roots of the host. One Filipino naturalist even described it as “effectively killing [the host], but keeping [the host plant] alive enough to parasitise nutrients from … ‘piloting’ the plant from the inside.”

Choix de Plants Rares ou Nouvelles dans le Jardin Botanique de Buitenzorg. F.A.W. Miquel, 1864. (via Scientific Illustration, from venusmilk)