Respiration does not happens in any one particular part in a plant, but it happens almost every parts of a plant such as roots, stems, leaves, buds, germinating seeds and also in fruits. In plants the rate of respiration is high in actively growing regions of a plant.
1. Respiration through leaves
Respiration happens through leaves and young stem which have porse on them. These porse are called stomata. The exchanges of gases takes place through these stomata. Oxygen and water vapour leave the plant through these stomata while Carbon dioxide enter through them. Each stomata has bean shaped cell which is called guard cells. When ther guard cells are full of water, they swerll and bulge openning the stomata. When the guard cells lose water, they lose their turgidity closing the stomata. When the place by the process of diffusion.
2. Respiration through stems
A tree is covered by the old and mature roots and hard woody stems are covered by bark, which is impervious to gases or water. However, within the layer of the bark, there are very tiny opening called lenticels. These enable the oxygen to reach the intercellular spaces of interior tissue and carbon dioxide to be realeased into the atmosphere. These lenticeles may look like scars on the bark of a tree. Lenticels are also present on many fruits. The lenticels are visible slightly more raised than the generals surface of the stem. At the base of the lenticels are loosely arranged cells that allow the diffused gases to pass through them.
3. Respiration through roots
Respiration also takes place through the roots of the plants. Air is also present in the spaces between the soil particles. The oxygen in this air is absorbed by root hairs present on the roots. From the root hairs, it is supplied to all the parts of the roots. Carbon dioxide released during respiration is diffused out the roots through the same hairs. Plants that grow in salty water have specialized roots. These roots growing out of the surface of water. Plants respire with the help of these roots.