When plants breathe

Plants, taxonomically grouped in the kingdom Plantae , are a diverse group of autotrophic organisms. What does this mean? That they are capable of producing substances that are essential for the maintenance of their metabolism, from water, minerals and solar energy that they obtain from the environment that surrounds them. This process is known as photosynthesis and thanks to photosynthetic autotrophic organisms, vast trophic chains are sustained.

Although plants depend mostly on solar energy, to a lesser extent they require energy obtained through respiration. 

When do plants breathe during the day or at night?

We will start directly by clearing up the mystery about when plants breathe . Like other living organisms, plants always breathe . Yes always. This means that they breathe both day and night . Now, how is the process of plant respiration defined? It can be broadly defined as the mechanism by which plants incorporate oxygen into plant tissues and release carbon dioxide and water vapor into the atmosphere. In this way, respiration is the opposite process to the photosynthesis process , since in the latter, plants incorporate carbon dioxide from the atmosphere and expel oxygen, thanks to the energy provided by sunlight. Therefore,Photosynthesis, being a process that requires light, only occurs during the day, while respiration always occurs.

As we have seen, both photosynthesis and plant respiration involve the same components: water, carbon dioxide and oxygen, only they do it in different ways, as a substrate or as a product. Another fundamental difference is that respiration occurs in all plant cells, since they all have mitochondria, these are organelles specialized in cellular respiration . While in contrast, photosynthesis occurs only in cells that present chloroplasts, which are organelles responsible for carrying out photosynthesis. Another difference lies in the different metabolic pathways that are used for both processes.

Where do plants breathe?

Now that we know when plants breathe, we can delve even further into what respiration looks like in plants . In principle, plants breathe thanks to structures called stomata. Stomata are small holes formed by occlusive cells of the epidermis that delimit a pore called ostiole, this leads to a substomatic chamber in which gases are stored. Thus, stomata allow gas exchange that occurs during photosynthesis and respiration of plants . Commonly located on the underside of leaves and stemsgreens of all plants and even some mosses can also have stomata. The truth is that stomata are so tiny that they can measure between 0.006 to 0.035 millimeters depending on the plant species.

As we have mentioned, stomata make possible the exchange of gases that occurs both in respiration and in photosynthesis. In addition to this, stomata are the main route by which the plant loses water in the form of water vapor, through the process called plant transpiration. Eventually the stomata can be closed to prevent excessive water loss, this mainly occurs in environments that are very dry or where water is scarce. Likewise, the opening or closing of the stomata can be influenced by other environmental factors, such as the concentration of carbon dioxide and the light that falls on the plant. In this way, the stomata can be closed or opened depending on the physiological needs of the plant.

A special case is plants with CAM metabolism (crassulaceae acid metabolism), which absorb carbon dioxide during the night. Then, in the presence of sunlight, the photosynthesis process is triggered with carbon dioxide that was fixed during the night. This mechanism is an adaptive strategy that allows plants to keep their stomata closed during the day to avoid excessive loss of water through perspiration. In contrast, plants with this type of metabolism absorb carbon dioxide at night while other plants release carbon dioxide from the respiration process at night. If you want to know plant species with CAM metabolism, we recommend reading the article onPlants that produce oxygen at night .

Do plant roots breathe?

While photosynthesis occurs in green leaves and stems, respiration occurs in leaves, stems, and roots too! . Among the many functions that roots carry out , such as anchoring, absorption of nutrients and water and more, one of them is respiration.

In the case of roots, respiration does not take place through the stomata, but rather through the lenticels . These are small lenticular-shaped openings, hence their name, that allow the gaseous exchange of the roots and lignified stems , since in the latter, the lenticels are located on the bark. Also, lenticels may be present on some fruits. like apple and pear, and in tubers, like potato. In particular, lenticels are easier to see than stomata, because they are larger and raised. Some lenticels have particular shapes that are useful, for example, to identify tree species.

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