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Hearing the Voices of Plants

Plants are often considered to lack vitality compared to humans and animals. This is why an unconscious state is also sometimes referred to as a “vegetative state”. Unlike our perceptions, however, plants can communicate with each other and their surroundings, adapting to any given environment to the utmost. Charles Darwin even insisted in his book, The Power of the Movement in Plants, that plants have both sense and intelligence as the radicles of plants function similarly with the brains of lower animals. The Sungkyun Times (SKT) now introduces the sensitivity and intelligence of plants, communication between trees, and the interaction of plants and humans.

Do plants have sensitivity?

Modularity

Most plants’ characteristic of being imbedded in earth contributed to the development of a special system called modularity designed to resist against dangers to the plants. Modularity means that the bodies of plants are composed of several independent modules and each of them functions differently. It makes plants able to grow even though some parts of the body get attacked. Plants based on modularity construct their own system in order to feel and perceive environmental factors, developing a delicate and sophisticated sensibility. The end part of the root, for instance, can even monitor at least 15 different types of chemical substances simultaneously.

Environmental Perception

Plants have the ability to sense environmental factors like light, noise, and chemical substances. Plants detect the direction of light for photosynthesis, and the root tip gathers the information like gravity, temperature, pressure, humidity, and density of oxygen or carbon dioxide (CO2). The root tip is similar to a data processing center and chooses where to put down the roots based on the data. In the case of a tendril, it intentionally spreads its leaves toward the most favorable environment for better growth.Roots can even recognize noise, reacting differently to various soundwaves. Exposure to the vibration of sound waves stimulates gene expression and germination since plants are more sensitive to the subterranean part. There was a relevant experiment at a grape farm in Montalcino, Italy by the International Laboratory for Plant Neurobiology, and it showed that grapes grown with music for over five years were richer in size, color, and fragrance compared to normal grapes. The interesting part, however, was that positive effects of music were only valid within a specific scope of sound waves between 100 to 500 hertz (Hz).

Plants sense environmental factors based on delicate module systems./ mk.co.kr

Do plants have intelligence?

Roots, the Brains of Plants

Darwin proposed the root-brain hypothesis where by the roots of a plant function in a similar way as the brains of animals. The root tip monitors the input information that each part of the plant sends. All kinds of nutrients and data are delivered ultimately to the root and the stems of plants work like an optical fiber for faster delivery. The root tip which is less than 1mm is where the most important decision making processes are executed and it consumes the majority of the oxygen required. Roots also exchange electronic signals like the neurons of humans. Moreover, root tips are comprised of a module network that activates the communication of plants, and the modularity enhances its durability as it does not collapse even if the main part is compromised. There was an experiment last year by the University of Oxford which shows the intelligence of plants. The experimentation divided the root of a pea into two parts and provided the same amount of nutrients to both parts. The difference between those two was made by giving nutrients regularly to only one part of the root. The other was given nutrients with irregular time intervals. The result was that the root provided with nutrients regularly grew bigger meaning that the plant determined the most favorable circumstances for its growth.

Experiments Proving the Memory of Plants

Plants also have memory in addition to decision-making abilities. Representative experiments are those of the flytrap and mimosa. An experiment on a flytrap was done in 2016 by the Julius Maximilian University of Wurzburg, Germany. A flytrap is an insectivorous plant that captivates the insect by counting how many times it is stimulated. At the first time of stimulation, the leaves do not move. If stimulated again in less than 30 seconds, it starts to close its leaves. It completely closes its leaves from the third time and creates a digestive enzyme from the fourth. Counts on the number of stimulations means plants can memorize the information and it saves a huge amount of energy required in insect hunting. Experiments on a mimosa took place in 2014 by the University of Florence, in Italy. A mimosa folds its leaves inward and droops when touched or shaken. The experiment was based on dropping a flower pot from a height of 15cm, with the floor designed not to give a shock to the plant. The Mimosa folded its leaves when dropped at first in order for defense, but it soon recognized that the floor did not harm it. The mimosa therefore started not to fold its leaves from the second and it was also the same when dropped again after a month. The experiment proved that the mimosa’s memory is based on environmental information.

Wisdom to Avoid Attacks and Strategies to Maximize Benefits

Plants secrete chemical inhibitory substances to protect themselves from insects. Plants also use danger-escaping strategies that attract the natural enemy of the attacker. The lima bean, for example, produces volatile chemical substances to seduce its natural enemy, Phytoseiulus Persimilis, a two-spotted spider mite that attacks the lima bean. Moreover, plants adjust their strategies depending on situations, considering which of them maximizes their benefits. One case is that plants often deceive animals to achieve goals, being opposed to the common belief that plants and animals are symbiotic. It is known that about one-third of orchids delude bees, as can be seen in the case of Ophrys Apifera, which is also known as the ‘bee orchid’. It springs a flower which looks similar to a female bee and attracts a male bee. The bee orchid then returns a male bee with the pollen attached to its body without any compensation.

Can plants talk to each other?

Coexistence of Trees in the Forest

The ‘crown shyness’ phenomenon refers to a situation whereby adjoining trees adjust their growth rate in order to avoid touching the crown of another tree, the part where branches and leaves grow away from the trunk. This is so as not to interrupt each tree, showing that trees have consideration for each other. In addition, trees release energy more from the areas above the ground than from subterranean areas when growing together with relatives. It shows that trees can recognize their relatives since energy investment in roots means intensive competition for nutrients. A danger alarm also shows the coexistence of trees. The maple species emits volatile substances into the air when it senses danger in order to notify the situation to neighboring trees. According to an experiment by Dartmouth College in the United States (US), maple released toxic substances like phenol and tannin when attacked by insects. Those substances, however, were also found in maples which were not in danger but were just near the attacked maple. It means trees which sense volatile substances emitted by the attacked tree produce the toxic ingredient in advance so as to protect themselves. The interesting part is that this communication is also possible between different species like Artemisia Montana and tobacco.

Nutrition Exchange between Trees

A lab study was conducted to investigate whether the roots of Korean red pine seedlings exchange carbon with each other. The experiment in the forest with 80 groups of birch, needle fir, and Japanese cedar was then implemented to prove it. The experimenter put a plastic bag on the trees, injected CO2, and then ran a CO2 counter over the leaves after an hour. It was to verify the hypothesis that trees absorb CO2 through photosynthesis, convert CO2 into sugar, deliver it to the root, and finally send surplus CO2 to other trees’ roots. The reaction of trees could be identified by examining whether the counter made a sound when put close to the leaves. Its noise meant that the tree had sucked up the CO2. The consequence was that the counter on the birch and needle fir reacted while the counter on the Japanese cedar made no sound, meaning that birch and needle fir were connected through a subterranean network while the Japanese cedar was not connected. The surprising fact is that trees can change the amount of nutrient delivery depending on various situations. For example, a birch sends more CO2 to needle firs when needle firs cannot get enough sunlight. When needle firs are growing well and birch have fewer leaves, in contrast, needle firs send CO2 to birch. Trees’ interactions show how they are communicating wisely.

Roles of Mycorrhiza

Mycorrhiza is a symbiosis of a fungus with a plant and is formed by a fungus growing within or on the outside of the plant roots. Fungus lives by infecting roots of trees and its reproductive organ is a mushroom. Mycorrhiza connects trees since carbon exchange occurs when fungus cells and root cells meet. The connection of trees through mycorrhiza creates a mycorrhizal network which consists of nodes and links, and the biggest node is where the interaction is most active. The tree that corresponds to that node is called the mother tree and cares for young trees at the bottom of the forest. Its role is to send surplus carbon to young seedlings through the roots of the mycorrhizal network, and it is known that carbon nutrients increase the survival rate of the seedlings by more than four times. The mother tree can also recognize its kin as can be seen in the experiment of growing a mother tree, a kin seedling and a stranger seedling altogether. The mother tree embraced the kin seedling with a bigger mycorrhiza network and sent more carbon. Moreover, it reduced the root competition and its own growth to allow more room for its young.

Mycorrhiza creates a mycorrhizal network between plant roots that enhances the interaction and carbon exchange./ ted.com

Can plants interact with humans?

Recognition of Plants on Humans

In addition to the interaction between plants, humans and plants can also communicate. Cleve Backster, a specialist for the Central Intelligence Agency (CIA), said plants can recognize humans and even read humans’ minds since the galvanometer connected to plants shows intense reaction when humans puts scissors close to the plants to cut the stem but shows no reaction when a human only pretends to cut the stem just for fun. It is said that a shallot can even distinguish between wind and air movement and when it is physically being touched. When a human touches a shallot, the graph representing the voltage fluctuates intensely and continues until the touch stops. In the case of a breeze of wind, however, a shallot reacts only for a minute and recovers its composure much faster. It means that it can differentiate between different types of stimulation.

Humans’ Efforts to Understand Plants’ Language and Emotions

Based on studies on the vitality of plants, humans have started to accept plants more as companions: like pet plants, and interaction between humans and plants is growing in popularity. The plant whisperer is a new job where a person talks to a plant and it has its significance in that it regards that plants can participate in conversation. B&Q, the biggest British multinational Do-It-Yourself (DIY) company and horticulture business, recently hired plant whisperers from a botanist team including Tim Clapp. Their job was to have conversations with plants depending on their types and upload the result on twitter to give tips to customers. Since all plants have a unique personality, they need different songs and words. Plant whisperers have a conversation with diverse expressions to find out which of them are effective for their growth. Clapp says plants are the same as humans in that they are all different and need proper care depending on their individual characteristics.

The plant whisperer emerged following the current trend of accepting plants as our companions./ mollyyoung.tumblr.com

Plants are no longer silent and static but are becoming as dynamic as humans. They have sense and intelligence, talk with each other, and can even be friends with humans. There is certainly a reason why plants have not become extinct and have survived, and the key has been their vitality and wisdom. The SKT hopes Kingos will try to understand the hidden power of plants and try to look on plants again with warm and affectionate eyes.

이진샘  jeansam0319@naver.com

<저작권자 © THE SUNGKYUN TIMES, 무단 전재 및 재배포 금지>

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