One day your plants will defend themselves.

If plants are humans, you may think that they are pacifists who are uncontested and willing to fight. You are wrong.

 By detecting their environment, plants can manipulate certain factors to meet their needs. Plants have a taste or smell that is used to measure and detect light of different colors, and they also have the ability to feel, and then they use these abilities to respond to different types of attacks.

"Plants have a set of proteins that are similar to proteins in human taste buds," Schultz explained. "They are called receptor-like kinases. There are only a few humans, but a small weed has more than 640 receptor-like kinases."

Plants sense their environment through receptor-like kinases and a variety of sensory molecules that are rarely studied. When diseases or insects attack plants, they release a specific odor. This odor or volatile is used to warn surrounding plants.

The goal of the Schultz study is to take advantage of these unique capabilities. Because only the signals from the affected plants are signaled, they can be detected and treated early before the entire land is infested.

Each attack has a different associated odor.

"When a plant responds to an attack, it emits volatiles into the air, which helps nearby plants react before they are attacked," Schultz said.

How do plants communicate?

"All the evidence suggests that plants know each other's existence, mainly by detecting chemicals that respond to each other," Schultz said. “These chemicals can be transmitted through the air, and some can spread through the soil. That's why plants know that there are similar species nearby.”

Plants respond to attackers, including diseases and insects, releasing chemicals, driving predators or poisoning them.

"All plants respond to insects and diseases by releasing or changing chemical products," Schultz said. “Many of these chemicals are familiar to us because we are already using them.”

Do you know that the caffeine in your afternoon refreshing drink is actually a protective agent for coffee plants against insects?

"Nicotine is a protective agent for tobacco plants," Schultz said. “Many of our drugs, whether entertaining or medicinal, are extracted from plants because they are either active in animals, or toxic to bacteria and other microorganisms, or both.”

What are the stresses that plants can adapt to?

Plants respond to many stresses. Here are three common stresses:

Pest stress

"There are enough insects in the world, and if they breed well enough, they can theoretically eat all the plants since ancient times," Schultz said.

Although an outbreak may occur, this is an exception, not a certain one. Insects only eat about 10% of the global plant, Schultz explained. This is because plants fight back and prevent insects from eating them.

Another method used by plants is to release signals to attract natural enemies of pests to eat attackers.

"These plants control the entire process," Schultz said. “They help their bodyguards discover the pests that cause damage. They tell the friendly insects where they can find their prey or host by releasing the smell.”

Competitive pressure

"If the plant detects that the color of the light it is receiving has passed or is bounced off by something green, the genetic program that is growing taller will be opened," Schultz said.

So it can escape the occlusion of other plants.

Environmental pressure

When subjected to drought stress, the plant closes its stomata. Studies have shown that they pass information on drought to other plants, Schultz said. This may be due to chemical movements in the soil. This clue causes other plants that still feel good about themselves to close their stomata.

Most of us look at a wilting plant and think it is on the verge of death. However, wilting is a plant water saving behavior.

"Different from the symptoms of wilting as a bad state, another way of looking at it is to use it as an adaptive behavior to save water," Schultz said.

What smell is that?

Low concentrations of volatile organic molecules are produced when plants are stressed. Plants emit these odors in response to different attacks.

When plants are trampled, or attacked by disease or insects, the mixture of odors is different, Schultz said.

If the composition that emits the odor of the plant can be identified, the problem can be diagnosed.

"If you can find these differences, you can know which plants are being attacked and which are not." Schultz pointed out.

“A lot of the work in this research was originally funded by the military because they were interested in what plants could report from the battlefield,” Schultz said.

Field application

Schultz's research team has worked with engineers to develop a sensor that reports the specific odour emitted by plants. The sensor will be mounted on a robotic vehicle. As it travels through the field, it is able to detect stressed plants, identify pests, and treat the affected plants. Then it will continue to walk until the next infected plant is found. Once you know which plants are attacked, you can only deal with the plants being attacked and avoid using pesticides to spray the entire field.

The advantage of this technique is that it can be treated before plant damage becomes visible, Schultz said. When you see the damage, it has been significantly damaged economically.

For example, suppose you have a soybean field with a locust. When the locust disease reaches a certain level, it will reduce the soybean yield. When the damage caused by the mites is sufficiently obvious to the naked eye, it has already had a serious impact on the yield. The goal of the sensor is to find the problem before reaching the economic threshold.

“This is a form of precision agriculture,” Schultz said. It treats infected plants in a targeted manner, without treating those plants that are not infected. It saves a lot of money and time, and of course reduces the impact on the environment. ”

Current difficulty

The challenge we face is that the sensor works in an open environment. In order to correctly identify the odor, it must be able to be detected in the open air, while the odor is diluted under open conditions. Another factor is speed, because response time will be crucial, Schultz said.

“We spent a lot of time developing this small device because it was difficult to get it to work very well,” Schultz said. “If we do, we will be the first people to use it in the open air. Most of the research can only be done in the lab.”

The odor emitted by plants is a complex mixture with many different chemicals. This makes detection and identification work more difficult. Researchers are narrowing down the number of molecular species needed to identify plants that are being attacked.

"We are working hard to drop three or four chemicals as a sign of the plant being attacked," Schultz said. “The signs of each situation are different. The first step is to identify the signs of a particular plant when it is subjected to an attack. We will confirm each situation in this way.”