The method by which cells get chemical energy by the consumption of oxygen and the liberating of carbon dioxide is called respiration. In order to carry on respiration, plant cells require oxygen and a means of disposing of carbon dioxide just as animal cells do. In plants, every part such as root, stem executes respiration as plants do not possess any particular organs like animals for the exchange of gases.
This is the main question when we think about plant respiration. As plants do not have any specialized organs like lungs so we can say that plants do not breathe rather they respire. Plants respire with the help of lenticels and stomata (exist in stems and leaves individually) which carry out the function of the gaseous exchange.
Plant respiration happens 24 hours a day, but night respiration is more obvious as the photosynthesis process finishes. During the night, it is very vital that the temperature is much cooler as compared to the day time because plants can undergo stress. Imagine a marathon runner. The runner breathes at higher rates than an individual standing still; so, a runner’s amount of respiration is greater and the temperature of the body rises. The same principle relates to plants, as the temperature at night rises, the respiration rate increases and similar temperature increases. This action would result in flower damage and also in plant poor growth.
In plants, respiration occurs with the help of roots. In soil oxygenated air is already present in spaces between soil particles. This oxygen is then absorbed into the roots with the help of root hair present on the roots. The hairs of the roots are in straight contact with them. In fact, a root hair is a lateral tubular outgrowth of the external epidermal cells of a root. The oxygen present among the soil particles diffuses into the root hairs. From root hairs, oxygen is transported to all the parts of roots for respiration. During the respiration process, oxygen is transformed into carbon dioxide gas which is spread in the opposite direction i.e. out of the roots by the same root hairs which complete the respiration process of roots
In the plants taking herbaceous stem exchange of gases occurs through stomata and the carbon dioxide CO2 formed during the process that gets diffused into the air with the help of stomata only. While in the plants having hard and woody stems the exchange of gases occurs through lenticels. Lenticels are usually loosely packed dead cells which are present as tiny pores on the bark of woody plants. These allow oxygen to pass to the intercellular spaces of the inside of tissues and carbon dioxide (CO2) to be liberated into the atmosphere by the phenomena of diffusion which completes the process of respiration in stems.
In leaves, the exchange of respiratory gases occurs through very small pores called stomata. The stomata are present in big number on the lower side of leaves of the plant. Every stoma has a tiny pore at its center which is enclosed and regulated by two kidney-shaped cells known as guard cells. When the stoma opens the exchange of gases occur between the atmosphere and interior of the leaf by the method of diffusion and that completes the process of respiration in leaves.
There are two kinds of respiration which we categorize on the basis of the absence or presence of oxygen:
The respiration that occurs in the presence of oxygen is named aerobic respiration due to ‘air’ which has oxygen. The aerobic respiration contains utilization of oxygen for the breaking of chemical bonds in glucose to liberate energy in high volumes. It is the central source of energy for plants. Animals and plants that use oxygen for respiration are aerobes. Mostly all the animals have aerobic respiration.