When a plant is moved from one place to another in the house or in your garden, you are usually trying to place it where it will grow more successfully. Maybe the flowers were sparse or the stems were long and lanky or the leaves were becoming crisp. Whatever signs prompted the observant gardener to move it; the plant somehow signaled its need for different conditions and got what it needed.
Scientists think plants know more than we give them credit for and that our interactions with them would benefit from understanding what has been discovered over the past decades.
In a new book, “What a Plant Knows”, scientist Daniel Chamovitz explains how plants see, smell, feel, hear, understand where they are, and remember. To help us understand the new science, Chamovitz compares each sense we think of as being human and animal with the counterpart senses of plants.
For example, plants use a set of genes to determine whether they are located in the light or in the dark. Those same genes are in human and animal DNA and serve the identical purpose – a response to light.
Chamovitz points out that plants have a more difficult survival situation than humans and animals: While we have the mobility to move away from undesirable circumstances, plants have to hold their ground and adapt to whatever comes their way, including changing weather, pests, and encroaching neighbor plants.
In response to their challenging environmental circumstances, over time, plants developed sensory and regulatory systems that they use to change their growth pattern in order to cope.
Plants see how much light they are in and the direction it is coming from. They do not have an animal’s biological eyes but gardeners know that when shaded, plants will move toward the light, even though they often have to lean and become long and lanky.
They also can smell when their fruit is ripe, when a plant nearby is being eaten by an insect and when someone has cut another plant’s stems. One study even found that plants could smell whether they were next to tomatoes or wheat.
Another example of plants’ ability to smell is that an avocado will ripen if put into a bag with a ripe banana and that tomatoes will ripen if put into a bag with an apple. Both apples and bananas emit ethylene gas. Plants’ use of ethylene developed as a way to protect themselves from drought, wounds, and aging.
Plants know when they are being touched, can tell the difference between hot and cold, and vines know when there is a nearby plant or fence to climb. The Venus Flytrap can feel the difference between wind blowing and a frog walking across the hairs that signal it to close. It even knows whether the prey is large enough to bother with, by the number of hairs that are disturbed and how many seconds there were between the triggering of the first and second hair.
Scientists found that plants do not particularly enjoy being touched by us and will stop growing if touched too often.
Despite a hundred years of scientific experiments to try to prove otherwise, Chamovitz concludes that plants cannot tell the difference between Bach and rock music.
They can tell up from down, though. A plant whose pot falls over will continue to grow upward, even if that means completely reversing direction. Plants were sent to outer space to prove that it is gravity that makes roots grow down.
|How Do Plants Know |
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