Plants can whisper. Don't you understand? My fault

Without plants, we wouldn't be who we are now. Think about how great they are: provide oxygen, provide organic matter, provide greening, help maintain ecological balance, and don't go on and on, like the people you hate to meet when you go to the movies.

Are you here to see a movie or to chat? Hey! Picture: clickme.net

Huh? Wait, are plants really dumb? Or is it just in a way that we can't hear?

If scientists make a bet, they are likely to think that plants have their own unique way of "speaking". A small review published in the Journal of Integrated Plant Biology (Journal of Integrative Plant Biology) summarizes the achievements of researchers around the world in snooping into "plant language".

Syllables, phrases and sentences? Plants can also have

Don't think that the language of plants is the rustling of the wind against the leaves or the ticking of plantains in the rain. In fact, for plants, "talking" is accomplished by releasing chemicals. This way is essentially different from the way human beings speak, and it is more like some kind of secret "whisper".

What they say has no sound, but it may have a smell-like the familiar smell of pine, camphor ball, lemon, black pepper, etc., which are actually chemicals released by plants, called "biosynthetic volatile organic compounds" (BVOCs) in jargon. These volatile organic compounds are not only the main secondary metabolites of plants, but also the media of signal transmission between plants and plants, plants and other organisms.

"they guess ~ randomly guess ~ not ~ heavy ~ ~ to connect to each other's signal ~ only then can they have a ~ rely on ~ ~" Photo: ransomnaturals.com

Many types of BVOC substances are formed by terpenoids. Isoprene monomer (C5) containing five C atoms is the basic unit of terpenoids, so some scientists compare it to "syllables" in plant "language". These monomers are arranged and combined in different order to form a large number of monoterpenes (C10) and sesquiterpenes (C15), which become "phrases". In the end, BVOC, made from a mixture of different terpenoids, is released by plants, just like the sentences they "speak" to maintain communication among plants.

More miraculously, plants even have "dialects". In the BVOC substances released by plants of different species, the quantity and quality of terpenoids are different. Individuals of the same species communicate more efficiently and encounter fewer pests with their own set of BVOC with the same chemical properties.

Defensive code: be careful, the danger is coming!

How do plants "listen" to their companions? Studies have found that plants can ingest gas compounds such as CO2 and BVOC through stomata, and the intake of BVOC can enter the metabolic pathway of plants.

The BVOC released by pyrethrum (Chrysanthemum cinerariaefolium) during injury can induce adjacent plants to synthesize pyrethroid, and the proportion and concentration of compounds in the released BVOC play a decisive role in the synthesis of pyrethroid.

The gene expression profile analysis of Arabidopsis thaliana also confirmed that the BVOC released by one plant could activate the defense genes of adjacent plants.

These results suggest that in the process of communication between plants, the release of specific components of BVOC provides an important signal of "imminent danger" to neighboring plants.

A piece of pyrethrum. When hurt, they can help each other through communication. Picture: John Logan

Indeed, an important role of communication between plants is to actively defend against possible threats of diseases and insect pests. When a plant encounters diseases and insect pests, it will release BVOC to inform its friends; when they receive the signal, they will start the expression of their disease resistance-related genes, so that they will be fully armed against the enemy's invasion.

This reminds me of the images in plants vs. zombies, where every plant that is about to be in danger is like a pea shooter who prepares its own killer mace to bravely drive away the haunted invaders.

Eavesdropping diners and stale food

In turn, herbivorous insects "eavesdrop" on what plants say. The so-called "radish cabbage, each has his own love", specific herbivorous insects will like to eat a specific small number of plants. Due to the great differences in the proportion of compounds in BVOC released by different plants, herbivorous insects can locate their own delicacies in flowers by sensing these BVOC. Although the air is full of BVOC signals emitted by different plants, they can accurately separate the signals they need from a pile of "noise" according to the proportion of specific compounds, find their targets and try to have a good meal.

"Hey, are you careless? "Picture: pansci.asia

Faced with such a threat of "precision", plants have also established ingenious defenses: when attacked by insects, they immediately change the proportion of compounds in their BVOC, and insects may no longer be interested in the plant as soon as they perceive the "taste" of food. The researchers found that when the larvae of the inchworm moth were fed with European white birch (Betula pendula), some C6 aldehydes of Betula platyphylla reached a peak within 3 minutes after the larvae began to eat the plant.

Compared with the more direct way of insect resistance, plants also have an indirect means of defense. When a plant's leaves are injured, the plant synthesizes and releases another BVOC substance in a short period of time, and secretes a special nectar to attract the natural enemies of the insects that are attacking it. You eat me, I will call to eat you, so that those herbivorous insects do not dare to show off. Cleverness is like a plant, and it also knows the truth of "treating a person in his own way".

"you eat me, and if you eat me, I'll ask it to eat you. Let's see who's careless." Picture: Robert Krulwich/NPR

Standing too far away to hear

In air, different kinds of BVOC have different "lifetimes" because they can react with ozone (O3), hydroxyl (- OH) and nitrate groups (- NO3), and the number of double bonds of BVOC affects the reaction activity. Generally speaking, communication between plants needs to be carried out within a short distance of no more than 1 meter. Due to the influence of oxidants in the air, the effective signal communication distance may be shorter, or higher component concentrations may be required.

In this way, herbivorous insects are more powerful: studies have shown that the reduction or even complete disappearance of BVOC concentrations in ozone-rich air does not eliminate the signals transmitted to insects, indicating that the reaction products of the original BVOC oxidized in the air still have signal value to insects, but more experiments are needed to verify this.

Although the "language" of plants can not be heard directly, this communication plays a vital role in the survival of plants themselves, and cracking them will also help us to better understand nature. When walking in a garden or tree-lined path, you may be able to take a more dynamic look at plants that don't run, don't jump, and don't make a sound-maybe they're chatting happily.

Always happy, no questions... Really?

All the fun is here.

Let me show you more about plants.

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Artemisia annua of Compositae