Botanic Talks

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Plantae is a seemingly silent kingdom; yet, it has milliards of secrets to tell. Life on Earth literally depends on plants, which form the bases of food cycles and maintain a balanced atmosphere. However, have you ever wondered how would such a huge kingdom survive and thrive for millions of years without communication? In reality, plants have a social life that scientists have only just begun to understand.

Few decades ago, the idea of plants communication was not widely accepted in the scientific community. Unlike human beings and animals, plants do not depend on sounds or sign language. Alternatively, they use means such as airborne chemicals, soluble compounds exchanged by roots, and underground fungi networks.

Wind-Carried Warnings

When you take in the whiff of freshly mown grass, you are actually smelling a distress call. Plants can call for help and warn their neighbors against nearby dangers through emitting airborne chemicals known as Volatile Organic Compounds (VOCs). Some species can identify the pests attacking them by their saliva, and in response, emit a scent that appeals to their predators; within hours, the predators show up and drive the pests away.

When nearby plants receive these VOCs warnings, they ramp up their own defenses proactively against the hungry pests around. Several studies have demonstrated that VOCs increase the fitness of the receiver plants; they tend to lose less leaves to predators and even produce more new ones. Researchers have been working for some years now to characterize the VOCs chemically and find out how they encode different messages.

Roots Telecommunication

Plants send, receive, and pass on valuable information through their roots. In an in-vitro experiment, researchers grew six garden plants in row and subjected the first one to drought-like conditions. They monitored the microscopic pores on the leaves surfaces, which changes width according to the availability of water; after some minutes, the stressed plant closed its pores, and so did its nearest unstressed neighbor. Within an hour, the remaining four plants closed their pores one after the other, indicating that they, too, received the message to prepare for drought. The experiment was repeated with a control setup where root contact between neighboring plants was blocked; guess what, the pores stayed open.

“Fun-Gi” Connections

Underground botanic chitchats can take more sophisticated forms and involve more parties. Just like human beings, plants have network connections; however, theirs are based on fungi. To us, the mushroom is the most familiar part of a fungus; yet, most of the fungi bodies consist of thin threads known as the mycelium. The mycelium travels underground, connecting the roots of different plants and trees in an area together, allowing them to communicate, among other things.

The relationship between plants and fungi is one of mutual benefits. While plants provide fungi with food in the form of carbohydrates, fungi boost their immune systems, provide them with nutrients, and help them suck up water and exchange substances and information. Trees encode their messages in electrical signals that pass through their roots and spread across fungi networks. Through this strategy, they call for help when they are under attack, feed stricken trees, and sabotage unwelcome plants by spreading toxic chemicals.

Just like our World Wide Web, the mycelium turns out to have its own version of cybercrime. Some plants like the phantom orchid do not have chlorophyll, and hence, fail to produce their own food through photosynthesis; they steal the carbon they need from nearby trees via the mycelia. Other orchid species are more wicked; while they can carry out photosynthesis, they still steal carbon from their neighbors.

Family Ties

Plants can recognize their relatives; some studies suggest that airborne communication is more effective among genetically-matched plants. Moreover, plants adopt a strategy known as “kin selection”, where they compete for resources with strangers and consider the needs of their siblings; the “kin selection” strategy shows best underground. Mother trees use the fungi networks to nurture their saplings. It was also found that plants surrounded by strangers tend to grow more roots to better compete for food, while plants surrounded by relatives grow more restrained roots and share the available resources.

I am sure you might be viewing plants from a different perspective now. Indeed, every creature has its own voice and can speak for itself. It is all about how keen we, humans, are to listen to and consider what nature has to say to us.

*Published in SCIplanet printed magazine, Autumn 2017 Issue.

References

mentalfloss.com
the-scientist.com
bbc.com
theguardian.com
bigthink.com

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