Describe the process of respiration in the following parts of a plant: $(a)$ Root. $(b)$ Stem. $(c)$ Leaves.

(N/A) Respiration in roots: Roots take in oxygen from the air present between soil particles via root hairs through diffusion. Oxygen reaches all root cells, and carbon dioxide produced during respiration diffuses out through the same root hairs.
$(b)$ Respiration in stems: In herbaceous plants, oxygen diffuses into the stem through stomata. In woody stems, gas exchange occurs through specialized pores in the bark called lenticels.
$(c)$ Respiration in leaves: Leaves contain tiny pores called stomata. Oxygen from the air diffuses into the leaf through these stomata to reach cells for respiration, while the produced carbon dioxide diffuses out into the air through the same stomata.