2016-3-1 UPDATE

Bow down, animals!
The curious behavior of moving plants

We tend to believe that animals are active and move around, while plants are always passive…
But is that image really true?
Actually, plants sometime behave even more actively than animals.

There is a plant of the pea family called Mimosa pudica, which means “bashful Mimosa.” In English, it is known by many popular names, including “sensitive plant” and “touch-me-not.” These intriguing appellations come from the fact that the leaves close up if you touch them even slightly. It’s Japanese name ojigisou means “bowing weed,” because the branch bows down as well. If you leave it alone, it will soon return to its original shape. It’s all very strange.
The peculiar behavior of this plant has interested people since ancient times, and even the discoverer of evolution, Charles Darwin himself did some research on it.
The general image is that that animals move around as they like, while plants stay put in one place. But things aren’t quite that simple after all. Sometimes plants move as well.

Bengal alfalfa is another plant in the pea family. Its leaves are divided in three, and the two smaller leaves that grow at the base of the larger leaf display a very interesting motion. If you observe them closely, you’ll find that they move rhythmically according to the movements of the sun! One might even call them natural photometers.

In the common rue of the citrus family, the stamens perform a curious dance. Normally, they line up well-mannered around the short and stout pistil in the middle of the yellow flower, but when the pollination season arrives, first one of the stamens moves its body to touch the pistil. Then another one does exactly the same thing. Now, the extraordinary thing is that the stamens do their touching in odd-numbered order: 1, 3, 5, etc. When the odd-numbered stamens have finished, it’s the turn of the even-numbered ones to go through the same motion. What weird sort of evolutionary process could have resulted in such a quaint pattern?

There are snakes that can spit their venom towards a foe several meters away, but they are no match for a species of bitter melon that grows around the Mediterranean. If you inadvertently happen to touch one of its small, cucumber-like fruits when it’s ripe, it comes right off the flower stalk and gushes out a sticky, seed-filled liquid with tremendous power – the liquid reportedly sprays over everything within a range of 4.5 meters!

So if you thought that plants were quiet and only reacted passively to their surroundings, well, that wasn’t exactly true. On the contrary, many of them have evolved astonishing mechanisms to stay alive and multiply their offspring.