Question

How does respiration take place in the stem of the plant?

Answer 1

In small herbaceous plants, soft stems have several pores, whereas hard stems have loosely packed dead cells for the process of gaseous exchange.

Complete answer: In the case of the stem, air diffuses into the stomata and passes through different parts of the cell for the process of respiration. When stomata open, carbon dioxide is liberated. In the case of woody plants, the trunk has small pores known as lenticels that facilitate gaseous exchange in the trunk. Lenticels are loosely packed dead cells that allow gaseous exchange in plants. They are present in a small area in the bark. Lenticels allow oxygen to pass to the intracellular spaces and carbon dioxide is liberated, therefore completing the process of respiration. Lenticel is an elliptical, small raised pore that develops in the woody stem when cork or bark is formed by replacing epidermis. They appear as circular, oval, or elongated small eruptions in the bark. They are initially formed during the development of periderm in the stem. They appear below the stoma or stomata. Lenticels are also formed on some fruits such as apples and pears. Gaseous exchange is an important step as it helps in the photosynthetic process in plants.

Note: Stomatal opening and closure in a stem facilitates respiration in the stem. In woody stems, lenticels help in respiration. Both the pores facilitate gaseous exchange but these gases are transported to the intracellular spaces by the process of diffusion. They are impermeable to water but permeable to gases.