tree moon

Alolan Exeggutor is one of the sillier pokémon this generation. This guy measures in at 10.9 meters tall, nearly 36 feet! As a result, Alolan Exeggutor hardly fits on the 3DS screen.

Obviously, Alolan Exeggutor is based on a Palm Tree. Different species of palms can grow to different heights: the Quindio wax palm, for example, is the tallest species in the world: it can grow up to 60 meters tall (197 feet). For reference, the tallest Redwood tree in the world is only 114 meters tall (379 feet). Palms can grow half as tall as Redwoods! Here is a picture of some Wax Palms, with a person for scale: 

Despite this, palm trees aren’t really trees. They’re more closely related to grass than to trees. For example, the trunk of a palm tree does not have any bark outside of it, or rings inside of it. A palm tree grows upwards, not outwards, which means it’s not really a tree.

According to the pokédex, when Exeggutor grew taller and taller, it “awakened the power of the sleeping dragon”, and therefore swapped its psychic-typing out for dragon. But, what does that mean? It’s a bit vague for a pokédex entry, but we wouldn’t be the Scientific Pokédex if we didn’t explain this.

For one, Exeggutor might be based on the Dragon Tree, native to Hawaii. This plant has dark red sap called “dragon’s blood”, which is where it gets its name from.

In my opinion, however, simply having dark red sap can hardly be “the power of the sleeping dragon” that Exeggutor was able to harness. Instead, I’d like to talk about one of the coolest superpowers of tall trees: their ability to transport water from their roots up all the way up to their leaves.

Plants have tissue called xylem to transport water from the roots upwards into the leaves. Gravity is trying to pull the water downwards, so sucking it up is quite the feat. In fact, if you had a really long straw, the farthest you could suck up water would be 9.8 meters. This would create a perfect vacuum in the straw, and beyond that you can’t generate enough pressure to fight gravity. Not to mention the water at the top would boil due to the low pressures.

Yet we’ve shown trees that are hundreds of meters tall. In order to suck up water to that height, these trees create pressures below a perfect vacuum: they create negative pressures. That’s right, the inside of a tree has a lower pressure environment than literally outer space. The tops of redwoods can have a pressure as low as -15 atm. For reference, Earth’s atmosphere is 1 atm of pressure, and a perfect vacuum is 0 atm. That’s what I call the power of the sleeping dragon.

The xylem creates this pressure essentially by evaporating water through the leaves at the top. Water leaves the leaves, which pulls up the water molecules underneath it in a process called transpiration. Up to 95% of the water that enters a tree is evaporated in this way to create the astronomical pressure difference. Only 1% is ever used in photosynthesis, and the rest is used for making new cells.

Normally in these conditions, liquid water would instantly evaporate. However, since the water was liquid when it entered the base of the tree, unless it is disturbed it will stay in a delicate, unstable meta-liquid state. Much like when you take water out of a freezer, sometimes it won’t turn to ice until you shake it up. Trees preserve this delicate balance until the water can evaporate through the leaves.

Alolan Exeggutor is a species of palm, which is more closely related to a grass than a tree. As it grows taller, Exeggutor must create pressures lower than the vacuum of space to supply water to the leaves at the top.