In 2015, the book “The Secret Knowledge of Plants. What do the flowers and trees see, hear and remember ”by author Daniel Chamowitz, was published. This book is written on the basis of numerous research scientists, including Charles Darwin.
Visual system of plants
Of course, no representative of the flora has human eyes, but still they are able to watch us. Plants understand that you approached them, and can distinguish the color of the clothes you wear. If you move the pot to another place or repaint the walls in a different color – they will definitely notice these changes.
No, they may not be able to distinguish a child from an old man, or other small details, but they can see ultraviolet and infrared rays that are not subject to our visual system. Plants understand that if the sun is shining (or the lamp); where the radiation is coming from – left, right or top. If something is blocking the lighting – they also understand it.
Can this be called vision? This is another question. Let’s imagine an absolutely blind person from birth. All his life he lives in the dark, and relies only on tactile and auditory sensations. Then suddenly he begins to distinguish between light and darkness. He can understand when it was a day, and when night has arrived. With these new abilities he can no longer be diagnosed with complete blindness, because he now has new opportunities. In science, this is called the rudimentary form of vision.
But that is not all. Imagine that the same blind person can distinguish the color of objects around him. He understands that the sea is blue and the grass is green. You can agree, it is much better than simply distinguishing white from black. Can this be called the ability to see?
Charles Darwin’s research
First, let’s deal with the structure of our visual system. In simple terms, the system contains cells that absorb light and transmit information to the brain. And how does this work in plants?
After the overwhelming success of his book “On the Origin of Species”, Darwin devoted his time to researching the flora with his son, botanist Francis Darwin.
They were interested in one phenomenon – almost all the plants were bent toward the light. This phenomenon is called phototropism. By the way, it was later established that blue color is responsible for changing the location of the plant toward the light, which is called phototropism. Other colors do not give this effect.
Actually, the experiment itself consisted of a pot with Phalaris seedlings, placed in a dark room. Next, on the other side of the room a lamp was lit, leaving the glow very dim. After some time, the sprouts turned to the light source. And the shoots were bent in a centimeter from the top. This happened every time the position of the light source changed throughout the entire study.
At that moment, it was not entirely clear how the plant sees the light, so Charles and Francis conducted another experiment.
Presumably, the visual system was located at the very top of the plant, and not at a bend.
In the picture below you can see the experiment itself:
A. At the first sprout, the top was left untouched, so that phototropism could be observed visually;
B. The second sprout the top was cut.
C. On the third sprout, a light-tight cap was put on.
D. On the fourth sprout – a transparent cap.
E. And on the last sprout the cap was put on the lower part of the stem of the plant.
As you can see, sprout A arched to the light, as intended by experiment, which shows the phenomenon of phototropism. E and D sprouts also stretched to the light without any obstruction. But the B and C sprouts remained in the same condition, as if “blind”.
In 1880, a scientific work was published in which Darwin described the embryonic form of vision in plants. The main function of the plant’s visual system is to transmit information from the upper part of the stem (where the receptors are located) to the middle part, and thus the plants move towards the light.