12.1. Do Plants Breathe?

Well, the answer to this question is not quite so direct. Yes, plants require O₂ for respiration to occur and they also give out CO₂. Hence, plants have systems in place that ensure the availability of O₂. Plants, unlike animals, have no specialised organs for gaseous exchange but they have stomata and lenticels for this purpose.

Plants do breathe, but their breathing process differs from that of animals. They need oxygen (O₂) for respiration and release carbon dioxide (CO₂) as a byproduct. Unlike animals that have lungs to exchange gases, plants use stomata—tiny openings on leaves—and lenticels—small openings on stems—for gas exchange. This allows them to take in oxygen for respiration and release carbon dioxide.

Think of the stomata as tiny doors that plants use to let in air and let out gas. Just like how we open a window for fresh air, plants have these openings that help them 'breathe' and release gases.

There are several reasons why plants can get along without respiratory organs. First, each plant part takes care of its own gas-exchange needs. There is very little transport of gases from one plant part to another. Second, plants do not present great demands for gas exchange. Roots, stems and leaves respire at rates far lower than animals do.

Plants do not require specialized respiratory organs because each part of the plant (roots, stems, leaves) manages its own gas exchange effectively. The need for gas exchange is significantly lower in plants compared to animals. While animals have high demands for oxygen, each part of a plant can function independently regarding gas exchange, reducing the need for specialized structures.

Imagine a small town where each household has its own water supply. Each house can take care of its water needs independently, just like each plant part can handle its gas exchange without needing a central 'water supply' system like lungs.

Only during photosynthesis are large volumes of gases exchanged and, each leaf is well adapted to take care of its own needs during these periods. When cells photosynthesize, availability of O₂ is not a problem in these cells since O₂ is released within the cell.

During photosynthesis, plants exchange significant amounts of gases. Leaves are specially adapted for this process, which produces oxygen as a byproduct—meaning that during this time, there is no shortage of oxygen. Cells that perform photosynthesis can create and use their own oxygen, addressing their needs effectively.

Consider a factory that produces more widgets than it needs—for its own operation. The excess produced can be used right away instead of going to waste. Similarly, plants produce oxygen during photosynthesis, which helps them breathe.

The distance that gases must diffuse even in large, bulky plants is not great. Each living cell in a plant is located quite close to the surface of the plant. In stems, the ‘living’ cells are organised in thin layers inside and beneath the bark. They also have openings called lenticels.

In plants, gas diffusion does not occur over long distances, as plant cells are usually close to the surface that is exposed to air. In thick stems, living cells are organized in layers right beneath the bark, which allows for efficient gas exchange through lenticels—openings that permit gas entry and exit.

Think of a multi-story building where people live on the upper floors, but the main entrances are on the ground floor. They don’t need to travel far to enter or exit the building. Similarly, plant cells are situated near the surface, allowing them to 'breathe' without needing extensive internal transport.

The complete combustion of glucose, which produces CO₂ and H₂O as end products, yields energy most of which is given out as heat. If this energy is to be useful to the cell, it should be able to utilise it to synthesise other molecules that the cell requires.

When glucose is fully broken down, it produces carbon dioxide and water, along with energy. However, most of this energy is released as heat. For the energy to be useful for cellular activities, it must be captured and used for synthesizing other necessary molecules instead of being wasted.

Consider a car engine burning fuel. Much of the energy generated heats up the engine, but to be practical, some energy is converted to move the car. Similarly, plants need to channel the energy from glucose breakdown into useful processes within their cells.

During the process of respiration, oxygen is utilised, and carbon dioxide, water and energy are released as products. The combustion reaction requires oxygen. But some cells live where oxygen may or may not be available.

Respiration is the process of breaking down glucose to produce energy, water, and carbon dioxide, relying on oxygen as a vital component. However, there are diverse environments where certain cells can survive either with or without oxygen, indicating that plants, like many other organisms, can adapt to varying oxygen availability.

It’s like how some fish can live in both freshwater and saltwater. Plants, in a way, are versatile, as they can adapt to environments with different oxygen levels to ensure survival.

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