There is more to plants than may immediately meet the eye, says this botanist gleefully.
Most people have probably seen photos or paintings of fields full of sunflowers all seemingly facing the same direction toward the sun. As the sun moves from east to west during the day, the flowers appear to move so they are always facing the sun.
A closer look reveals that the minor movement of each individual flower in the field is random and not in a straight line. Rather the flowers appear to make small movements up and down, round and round, side to side etc. This movement is called “circumnutation” and observant people have known about it for a long time.
In a recent study, sunflowers were grown in a dense row and their motions were observed over 10 days. The results were used to create a computer model showing that, as the flowers twisted and turned, they ultimately grew in a position that ensured every flower would get as much sunlight as possible. They grew in a zigzag pattern, so each flower received the maximum amount of sunlight and once they did, the movement decreased.
It is well known that many plants go through similar movements, but no one thought until now that they were navigating to identify the best growth strategy, although it makes perfect sense.
Another example of plants responding to other plants around them in their search for light is a phenomenon called “canopy or crown shyness.”
Many years ago, we were taken on a walk through a forest in a Borneo jungle when we were stopped and asked to look up. We all gasped as we saw that not one of the many tree canopies was touching another one. Each was separated from its neighbours by a narrow space of sky, all were angular in outline and fitted together like an intricate puzzle.
It is thought that the trees somehow sense the proximity of the neighbouring trees and can adjust their growth accordingly so that all the trees can maximize their exposure to the available light at the top of the canopy.
Too often plants are dismissed as unfeeling green organisms. However, not only do they produce the oxygen that we need to breathe and the ultimate source of most of our food, but they are sentient beings and deserve our respect.
