cwelling

Currently, I am lying on my couch eating King Cake and watching The Two Towers (extended edition, eh hem). Just now, Merry and Pippin escaped the dinner conversation between the quibbling Uruk hai and orcs, and haunting Fangorn Forest towers in the background. Ah, Fangorn Forest- home to that loveable Treebeard. He’s so funny. Mostly, because he is a tree. A walking, talking, poetry-loving tree, who thinks it’s easier to travel south because “somehow, it feels like going downhill.”

A big part of Treebeard’s strength as a character is just this- he is a tree that can move and walk and talk. In the films, his entrance surprises and delights us when Pippin realizes he is clinging onto the face of a conscious tree. It seems contrary to us that a plant should locomote and exhibit behavior of any type. While I am (sadly) unaware of any actual Ents in existence, I am aware of a few plants that are capable of motion.

Sensitive plant, Mimosa
(0364920.netsolhost.com)

Those cute little sensitive plants that grow in the grass, Venus Fly Traps snapping their prey, fields of sunflowers that begin the day facing the east and end it facing west; moonflowers that close up at dawn and reopen at dusk; the world of plants is surprisingly animated.

Without muscles, ligaments, or tendons, how do they do it? When you touch the leaves of a sensitive plant and they close up in a matter of seconds, what do you think is causing the motion?

In most cases, a change in turgor pressure is the mechanism. Turgor pressure is simply the water pressure within a plant cell. By localized swelling in turgor pressure, the shape of a leaf may be altered. For instance, if the cells of just one side of a leaf swells, the whole structure will become bent (Fig. 1). Conversely, if a bunch of cells expel their water, that area of the plant will collapse.

Figure 1: A.) Even turgor pressure B.) Increased turgor
pressure on top layer forces leaf to bend

The stimuli for these pressure changes vary. Sometimes, sunlight exposure will trigger cell swelling (cwelling, new word? I think so). Other times it is a reaction to sensory hairs called trichomes, or simply pressure setting off an ionic message through the cells like dominos. It varies from species to species.

If we could ever get our hands on an Ent, wouldn’t it be something to see if their physiology operates on a turgor pressure differential system? That Isengard and Soromon were defeated basically by the simple act of water diffusion? 

Why yes, Aragorn. We should go get drinks later.