What purpose do plants have when they produce toxins?

Recently, I’ve been thinking about toxins in fruits and vegetables that we, consumers, are exposed to.

Potato flower

Well, when the danger occurs, plants can’t run away like animals do in order to survive. Evolutionary, another way of protection was evolved helping plants for generation to increase their survival chances. For example, plants produce certain chemical substances in order to protect themselves from the plant eaters. These substances in various quantities are found in different plant parts: leaves, stems, sprouts and fruits. It is quite usual that some parts of the same plant are edible and others are not. A good example for this is a potato plant. Its fruits are highly poisonous, whereas tubers of this plant can be eaten. However, it would be naïve to think that potato plants retain their poison only in fruits. In order to protect themselves from bugs, insects, worms and other predators, potato plants produce a natural toxin, solanine, which can cause gastrointestinal and neurological disorders in humans. Potato tubers and leaves contain different amounts of it. People, if they eat a rather excessive amount of raw potatoes, can feel weakness and confusion. The toxin causes headaches, diarrhea and cramps. Especially high amounts of solanine contain potato tubers exposed to light. One can recognise such potatoes on their green colour. Good news is that solanine is thermally unstable. In other words, it is degrading when potatoes are boiled, steamed, deep-fried at high temperatures.

When potatoes were first imported to Europe in the sixteenth century, people didn’t know that only tubers can be eaten. A few persons poisoned themselves by eating potato fruits. Afterwards, only flowers of this plant were used, for example, for decoration. Later, people found out which parts of this plant were edible, and soon potato became an important crop in many countries.

Potato plant is one example for natural toxins. It might sound pretty scary, but all plants we eat produce toxic substances. When plants are sprayed with pesticides, they produce less natural toxins. Well, because of a simple reason: pesticides destroy predators, therefore, the plant is not in danger anymore. But to be honest, food, containing pesticides, doesn’t attract me. Most of these industrial chemical substances accumulate in the human body and can cause dangerous diseases. In this case, I prefer natural toxins which taken in small amounts don’t harm me, if I have a balanced diet.

I was always curious, how do the plants know, when to produce toxins? A few days ago, I’ve read an article in the newspaper about tomatoes and their warning signals sent to other tomato plants. Scientists found out that a plant, when attacked by a plant eater, sends chemical compounds to other plants as a warning signal to inform about the danger. Moreover, these volatile compounds are also precursors for the substances that other healthy plats start producing as soon as the warning molecules arrive. In other words, the plants, attacked by the plant eaters, send chemical signals to the healthy plants, so the survivors can produce natural toxins and protect themselves from the plant eaters. Plants seem to have developed a clever form of communication helping each other to survive. They act like social creatures like, we think, only animals do.

I was fascinated when I read this article about the tomato warning signals. I always thought that plants survive according to the principle the weakest will die. Well, it might be too much influence of Darwinism on me. I never thought about plants as organised creatures. Surprise, surprise… I am happy to have an opportunity to change my mind.

What about you?