I've seen it a number of times, but for some reason I took the time to think about it on this occasion. A vining plant was taking over a chain link fence in our yard, and at the growing ends I noticed they were “reaching” for a tree branch on the yard side of the fence. “How do they know where to grow” I wondered out loud. The vines were obviously growing toward the tree branch to find more support for continued invasion.
How do plants know where to send their new growth to grab the safest hold? A Venus Fly Trap needs to have two of the hairs on its leaves touched by a bug in order to shut, so it remembers that the first one has been touched. But this only lasts about 20 seconds, and then it forgets.
Can plants “smell”? If you put a ripe and an unripe fruit together in the same bag, the unripe one will ripen faster. This happens because the ripe one releases a ripening pheromone into the air, and the green fruit smells it and then starts ripening itself. In a very recent study we learned that plants also communicate through signals passed from root to root. In this case the “talking” plant had been stressed by drought, and it “told” its neighboring plants to prepare for a lack of water. When first formed, a pea tendril is almost straight, and while growing it slowly waves around in a process called circumnutation. When it encounters a foothold, the end of the tendril wraps around it, securing a support. In this way the pea vine winches the entire vine upwards. Darwin, one of the great plant researchers, proposed what has become known as the “root-brain” hypothesis. Darwin proposed that the tip of the root, the part that we call the meristem, acts like the brain does in lower animals, receiving sensory input and directing movement.
Many of us as gardeners or growers of houseplants talk to, or sing to our plants. I like to give them a “petting” when watering sometimes. There is much we understand about our plants that can't be explained by scientists, but one thing is for sure – our plants do “see, hear, smell and think”. We don't need an explanation to appreciate them.
