GASEOUS EXCHANGE IN PLANTS
Plants get their energy from respiration. Plants have no special organ or system fro exchange of gases. The gaseous exchange in plants occurs in cells, of every part of the plant i.e. roots, stems and leaves etc according to their energy demand. The conducting system (xylem and phloem) of plants transports water and nutrients but plays no role in the transport of gases. The air spaces present between the cells of parenchyma of leaves stem and roots are involved in the gaseous exchange.
Gaseous Exchange in Leaves and Young Stems:
In the leaves and young stems, gaseous exchange occurs through stomata. Some gaseous exchange also occurs through cuticle.
Gaseous Exchange in Woody Stems and Roots:
In woody stem and roots, there are present dead cells beneath the epidermis which form cork tissue. Later on, this tissue becomes porous. The pores are called lenticels. These are involved in gaseous exchange.
Gaseous Exchange in Leaves:
The aquatic parts obtain oxygen for their respiration by diffusion from the dissolved oxygen in water. Whereas the land plants get their oxygen from air directly through their stomata which are more abundant on the lower surface than the upper surface of leaves.
Gaseous Exchange in Roots:
The roots get their oxygen for gaseous exchange through diffusion from the air existing in the space between soil particles.