Fragrant, smelly, and even fishy! Why do plants have smells?

It is the season of revival again. The air is filled with the scent of soil, grass and flowers. Some curious netizens asked, why do plants have smells? And different plants have different smells, some are fragrant, some are smelly, some are spicy, some are fishy, ​​and there are even plants with a hormone-like smell, such as the heather that is everywhere in Wuhan.

In fact, it is very common for plants to emit odors. Let's talk about it today.

01 Why do plants have smell?

As a kind of synthetic factory in nature, plants synthesize a large number of chemical substances. According to incomplete statistics, plants synthesize and release more than 100,000 low-molecular-weight secondary metabolites, many of which are volatile. This is why we smell the "plant smell".

In fact, the study of plant odor has always been a professional field. Let me introduce it below.

02 How are plant odors sampled?

The main sampling techniques for plant odors include:

1. Collection. There are many methods for collecting plant odors, such as solid phase microextraction, headspace method, capillary adsorbent method, etc. Anyway, the principle is to capture the plant odor molecules.

The above method can capture the smell. However, we know that the captured odor molecules are often in low concentration and dispersed. After all, most of what we see is colorless odor, not this kind of rolling dense substance.

So, after capturing the plant odor, the next step is to concentrate it.

2. Concentration. Regarding concentration, I believe that people who work in biology are familiar with it. For example, the common concentrator we use uses a vacuum method to concentrate excess water.

I have made a simple table of the common concentration technologies currently used as shown below

Anyway, the appropriate concentration method is selected according to different samples. The next step is to analyze the plant odor components.

03 Analysis of plant odor

The most common method for chemical composition analysis is chromatography, also known as chromatography.

Chromatography, also known as chromatography or chromatographic method, is a physical and chemical analysis method. It uses the difference in the interaction forces (distribution, adsorption, ion exchange, etc.) between different solutes (samples) and the stationary phase and mobile phase. When the two phases move relative to each other, each solute undergoes multiple equilibrium between the two phases, so that the solutes are separated from each other.

This is a common chromatograph.

When various substances are injected into the chromatograph, it will then perform corresponding analysis and judgment, and finally give a chromatogram of the substance.

Professionals analyzed and compared the chromatogram results to determine the composition of the plant odors in this set of experiments.

04 Is there a correlation between plant odor and harm to the human body?

The smell of plants is not a basis for judging whether they are harmful to the human body. Through a large number of analytical studies, it can be basically determined that the odor substances of plants mainly include the following components: terpenes, alkanes, alkenes, alcohols, esters, carbonyl and carboxyl substances (Penuelas and Liusia 2003). A simple classification can be made as follows:

1. Odor substances released by flowers and fruits. Mainly aromatic compounds, terpenoid compounds, ester substances and some nitrogen and sulfur compounds.

These compounds often have a certain aroma. For example, aromatic compounds are characterized by the presence of benzene rings (of course there are also examples without benzene rings). The reason for their name is that they have an aromatic smell.

Indole is a compound of pyrrole and benzene in parallel. It is an important component of perfume and has a very good fragrance (of course, it will be unpleasant when indole is too strong).

2. Volatile substances released by nutrient tissues such as rhizomes. The nutrient tissues of many plants, such as rhizomes and leaves, can release volatile substances, which gives the trees themselves a corresponding smell. For example, camphor trees have a camphor smell that can be used to repel insects; pine trees, for example, have a resin smell. The main components of the odors released by these substances are terpenes, fatty acid derivatives such as volatile aldehydes and alcohol compounds.

These smells are part of the tree's composition and are normal substances in the tree's metabolism. Almost all trees have smells, and it would be strange if they didn't have any.

05 What is the function of the smell of plants?

After all this talk, what exactly is the function of the smell of plants?

1. Regulate the growth and development of plants. Plant volatile substances can be used as a cell regulatory signal to affect the growth and development of plants. The most typical one is ethylene. Ethylene is a common volatile substance, and its function is to regulate the maturity of plants. It can break the dormancy of plant seeds, make flowers bloom, and accelerate ripening.

2. Improve plant physiology. In fact, the smell of plants can also have a certain effect on improving plant physiology.

For example, isopentene can help plants resist high temperatures. When the temperature rises, plants secrete isopentene, which can improve the heat resistance of photosynthetic organelles in leaves such as kudzu, thus fighting against heat damage.

3. Plant-animal signal communication. This is easy to understand. For example, when plants bloom, they release fragrance, which attracts many insects to fly over and help the plants spread pollen. When plants mature, they release odors, which can also attract animals to eat them, and then take the seeds of these fruits to various places for sowing.

Of course, some plants also secrete some unpleasant and warning smells, which can be summed up in four words: Keep away from strangers .

At this point, the science popularization is basically over. I believe you have a basic understanding of the smell of plants.

The scents emitted by different plants can affect people's emotions. Some scents can make people feel happy, while others can make people feel anxious. For example, lavender, known as the "king of herbs", has a fresh and elegant aroma and a mild nature. It is recognized as the most sedative, soothing, and hypnotic plant. It can relieve tension, calm the mind, calm the spirit, heal wounds, and remove scars.