Trees constantly take in information from the environment through their leaves and root tips, process it and act accordingly. They communicate in the organism and with each other.
Biologists and other scientists have recognized that plants can do a lot more than assumed. You taste, smell, feel, hear and see. Even if trees, bushes and herbs have no sensory organs and no brain, they take signals from the environment, e.g. true about the light or the water with the help of the leaves and the roots. In addition, evidence of the communicative behavior of plants is found worldwide.
The Italian plant neurologist Stefano Mancuso from the University of Florence speaks of the “intelligence of plants”. He argues with other scientists that plants should be viewed in a new way and that they should be valued in science. “The general hierarchy of values banishes plants to the lowest level of living beings,” writes Mancuso. “A whole kingdom, the plant kingdom, is completely underestimated, although our survival and our future on earth depend on it.” (Mancuso, Intelligence of Plants, p. 30)
The cell biologist Frantisek Baluska from the University of Bonn calls it the “command center”, the tip of the roots for the perception of the plant. He researched targeted movement and sensitivity of the root tip, thereby confirming Charles Darwin’s “root brain theory”. The discoverer of evolution compared the root tip with the “brain of one of the lower animals” in his groundbreaking book “The Power of Movement in Plants”. His observations have been confirmed several times, but it was not until 125 years after Darwin that Baluska and a team of scientists from the Universities of Bonn and Florence filmed the movements of the root tip. It is clearly visible that the root tip crawls through the ground like a worm. The tip of the root perceives water or toxins, sends the messages via cells into the root, which then adapts its direction accordingly as it grows.
The roots send messages from the earth to the leaves above. And the leaves send information from the treetop to the roots and other leaves. For example, when the roots don’t find enough water, they tell the leaves to close their openings, the stomata. Otherwise too much water would evaporate from the open stomata.
Trees communicate, they exchange ideas with one another and with other plants in their environment, with mushrooms and with animals. This is how trees inform themselves whether predators such as deer or caterpillars are in the vicinity. The leaves tell each other from cell to cell when they are eaten or when an insect lays its eggs on the leaves. The tree then produces even more chemical substances (such as tannin in oak leaves) that deter predators – or even poison them.
Trees defend themselves successfully
The South African biologist Wouter van Hoven came across the tree as the “serial killer” of kudu antelopes. He investigated why kudus suddenly died en masse on the wildlife ranches in South Africa for no apparent reason. The antelopes appeared perfectly healthy and were externally unharmed. In her rumen, van Hoven found the leaves of acacias, which were the only plants in the region with green leaves during a drought. Van Hoven examined the leaves and trees. He found out that the acacias produced a particularly large amount of plant toxin tannin to protect themselves.
And the trees not only protected themselves from predators. When animals nibbled on their leaves, the leaves secreted ethylene. The volatile chemical notified other acacias, which then produced tannin as a defense. Van Hoven realized: the acacias communicate with each other.
Networked communication in the realm of roots
The Canadian forest scientist Suzanne Simard from the University of British Columbia was the first to demonstrate that trees in a forest are connected to one another via a wood wide web. Using radioactive carbon, Simard demonstrated that trees exchange nutrients and information across the forest through the roots and threads of mycorrhizal fungi. If one tree lacks nutrients, the other trees supply it. Simard was also able to prove that even trees of different species supply themselves: Birch trees supplied Douglas firs with nutrients.
The basis for this behavior is the constant exchange of the trees with fungi, the mycorrhiza. Every tree lives in close association with these fungi, which supply the tree with nutrients from the soil that are difficult to access via a fine network of roots. The tree gives the mushrooms sugar, which the mushrooms cannot produce themselves. The two living beings communicate with each other via the root threads and inform each other about the necessary substances.
When the leaves nibbled, the leaves secreted ethylene. The volatile chemical notified other acacias, which then produced tannin as a defense. Van Hoven realized: the acacias communicate with each other.
Your enemy is my friend
Plants also communicate with animals. With the help of fragrances, they call the predators of their predators. Even herbaceous plants such as wild tobacco can do the trick. Ian Baldwin, Director of the Max Planck Institute for Chemical Ecology in Jena, researches the wild tobacco Nicotiana attenuata and has discovered many possibilities for non-verbal communication in the plant. The tobacco plant uses nicotine against several species of caterpillars. If that is not enough, it lures ants and lizards with fragrances, which eat the insects. However, since the wild tobacco needs the caterpillar’s moths for pollination, the plant also attracts the animals and offers the caterpillars sugary delicacies. If the caterpillars eat too much, they die. Dr. Baldwin speaks of the “razor blade in the apple”. He also found out that Nicotiana attenuata recognizes from the saliva of the caterpillars who is nibbling on the leaf. The tobacco herb can therefore not only send information, but also receive it, understand and implement the message.