Source: Chengdu Business Daily
Do plants also have defense systems?
Sichuan experts have confirmed the hypothesis: not only "weapons" but also "distress"
A hypothesis
After the hypothesis of this field of plant research was proposed, an ideal plant population and its corresponding insect taxon have not been successfully found to verify.
One time validation
Sichuan Agricultural University, Zhejiang University, Leiden University in the Netherlands and Neuchâtel University in Switzerland have collaborated on an experiment called verification of the evolution of plants "fangs", confirming that plants do not "slaughter" insects as we think – hundreds of millions of years of evolution have made plants have their own intelligent "armor".
What's the point
"It can form an autonomous defense system in the field to reduce the pests suffered by crops, and there is no need to artificially spray pesticides, which saves time, effort and money, and is more green and environmentally friendly." Lin Tiantian, an associate professor at the College of Forestry of Sichuan Agricultural University, said that perhaps the components of volatile substances can also be found, and through chemical synthesis, they will become new and safe "insect repellents" and "inducers".
Have you ever wondered whether plants that cannot escape are only "ravaged" in vain when they are eaten by insects? As a "low-level" player in the food chain, are plants really so humble?
There has always been a hot hypothesis in the field of plant research: plant-eating insects and their natural enemies are involved in driving the evolution of leaf volatiles to give plants a defensive function.
On August 9, Lin Tiantian, associate professor of the College of Forestry of Sichuan Agricultural University, published a research paper entitled "The Evolution of an Invasive Plant Proves the Defensive Function of Plant Leaf Volatiles" in Contemporary Biology as the first author, confirming that plants do not allow insects to "slaughter" as we think - hundreds of millions of years of evolution have made plants have their own intelligent "armor".
Do plants have defensive functions?
This hypothesis has not been tested
It seems to be beyond the ordinary people's understanding of the "reverse obedience" of the plant.
In the field of plant research, it has not been successful to find an ideal plant population and its corresponding insect population to test this hypothesis, so whether this hypothesis is really true has been highly controversial in the academic community.
"It's obviously unrealistic to rely solely on laboratories to do experiments that require a plant population to evolve for more than 100 years in an environment free of insects and their natural enemies." Lin Tiantian explained.
It just so happens that the research group of Dr. Klaas Vrieling of Leiden University in the Netherlands is studying invasive plants.
A perennial plant native to Eurasia, Qianliguang, was brought to the United States, Canada, Australia, New Zealand and other places by human activities about 150 years ago, becoming a local "invasive plant" and becoming an ideal plant population for this experiment. "In the 'territory' where plants invade, there are no insects and their natural enemies." Lin Tiantian explained that this means that in these more than 150 years, the thousand miles of light "grows wildly" in a "free" environment, and it will also produce insect-resistant substances?
Discoveries of a transnational collaboration:
Plants also have "weapons" and "ask for help"
Since 2015, experiments to verify the evolution of the plant "fangs" have been carried out in cooperation with Sichuan Agricultural University, Zhejiang University, Leiden University in the Netherlands and Neuchâtel University in Switzerland.
"The Leiden University group in the Netherlands mainly collects and breeds plants, and does insect determination in Neuchâtel, Switzerland, because they have insect olfactory analyzers and professional volatiles analyzers." Lin Tiantian said that the experimental team collected more than 20 populations of different distributions in the native environment of Qianliguang, such as the Netherlands and France, and also collected 20 populations in the "invading environment" such as the United States, Canada, Australia and New Zealand. "Put them under the same experimental conditions for comparison and verification."
In the selection of plant-eating insects, the experimental team selected the exclusive eating insect of The Thousand Mile Light- Cinnabar Nocturnal Moth, and the Obligate Parasitic Wasp of the Cinnabar Nocturnal Moth, and at the same time, selected another common-eating insect - kale Nocturnal Moth.
"Clairvoyant leaves produce two volatile substances, one is a constitutive volatile and the other is an inducible volatile." Lin Tiantian said.
Compositional volatiles refer to substances produced by the continuous release of the leaves of the Thousand Mile Light Blade itself, which can be used as a direct defense to avoid being eaten by general-eating insects, which is equivalent to "insect repellent".
The inducible volatiles refer to the rapid secretion of ingredients that can attract insect predators after being eaten by predatory insects, adhering to the strategy of "the enemy of the enemy is a friend", issuing a "distress" signal, summoning the natural enemies of insects to come to "rescue", equivalent to "inducer".
Two control groups were set up for native populations and invasive populations, and the selection preferences of "general eating insects", "specialty insects" and "parasitic bees of specialty eating insects" were tested in the laboratory environment by using insect olfactory testers.
"Simply put, we placed clairvoyant plants from two different populations, native and invasive, in an insect olfactory meter to see which plant each of the three types of insects would prefer." Lin Tiantian said that at the same time, the compositional volatiles and inducible volatiles of two population plants were also collected in the experiment, and the composition and content of different volatile substances were analyzed with detection instruments.
In addition to drawing conclusions in the experimental environment, the team also returned to the natural environment, planting native and invasive populations of clairvoyant light in the test field, placing specialized insect larvae on the leaves, "over time, to measure whether these larvae are parasitized by parasitic wasps, and which clairvoyant population has a higher amount of eggs." Lin Tiantian said.
The study found that the content of constitutive volatiles released by invasive Clairvoyant populations was higher than that of native populations, while the content of induced volatiles released after the invasion of specialty insects was significantly lower. The results of insect olfactory and spawning experiments show that the constitutive volatiles released by invasive populations have a stronger attraction effect on specialty insects and a stronger repellent effect on broad-feeding insects than in native populations. At the same time, induced volatiles released by native populations caused by predatory insect pests have a stronger attraction effect on parasitic wasps than invasive populations. This result is supported by the experiment of natural parasitism rate in the field.
That is to say, in the invading environment of "barbaric growth", because there is no special eating of its own natural enemy insects, the thousand miles of light do not have to laboriously grow "armor" to resist natural enemies, and inducing volatiles have no "place of use" and "degradation" function. However, other insects that "eat omnivorous" may also regard the invading thousand mile light as a "dish on the plate", and the thousand mile light as an "alien guest" should still be careful to use compositional volatiles to make themselves "invisible" and "protected from poison".
Exciting future uses:
Or will let the crops grow their own "armor"
From 2015 to August 2021, the experimental and data analysis work lasted for 6 years. "Because the insects used in the experiment only appear in May and June every year, we have to spend a lot of time collecting insects, doing experiments in the laboratory the previous year, and not doing field experiments until the second year." Lin Tiantian said that most of the time is also doing preliminary preparations, coupled with transnational cooperation, which takes a long time.
The clever behavior of plants has been discovered by humans, and nature cannot be wasted in vain.
"In the future, we may be able to apply other plant materials, such as corn, rice and other crops, to find the regulatory genes of the volatiles of the plant itself, and use gene editing to increase the content of constitutive volatiles and insect-inducible volatiles." Lin Tiantian said that in order to form an autonomous defense system in the field to reduce the pests suffered by crops, there is no need to artificially spray pesticides, which saves time, effort and money, and is more green and environmentally friendly.
Another possibility, perhaps, can be found in the volatile substances, through chemical synthesis, to become a new and safe "insect repellent" and "inducer". "But all of this requires further research by scientists, especially validation by field experiments." Lin Tiantian said.
Chengdu Business Daily-Red Star News reporter Yu Zunsu intern Cheng Jiachi