Question

_______ are the opening in the bark of the woody stem.
A. Stomata
B. Lenticels
C. Epiblema
D. None of these

Answer 1

Hint: The bark of the woody stem is the result of secondary growth of xylem and phloem of the plant’s vascular system. The plants need to respire and photosynthesis to meet their daily requirements. Various gases are required and produced as waste during these processes. Thus, the plant needs to expel them through pores. The cells involved are lenticular shaped or lens-shaped cells.

Step by step answer:In plants, various life processes occur like photosynthesis and respiration. During these processes, various gases like carbon dioxide and oxygen are required. Also, these gases are released as waste products in the plants. Now, these waste products or waste gases need to be expelled out of the plant body to inhibit any toxic effect.In softer plants, the gaseous exchange occurs through stomata. Stomata are pores or openings present generally over the surface of leaves and stems. These are specialized cells guarded by guard cells that assist their opening and closing. In woody stems, the stomata cannot perform gaseous exchange as secondary growth occurs. The woody appearance is due to modifications of xylem and phloem. Thus a woody stem requires specialized cells for gaseous exchange. These cells are lens-shaped or have a lenticular appearance. These are large cells having intercellular spaces and are called lenticels. The lenticels make a porous tissue on the bark of the plant and help in the gaseous exchange of carbon dioxide and oxygen. Epiblema is a moth species that has no role in plant gaseous exchange.
Therefore, the correct answer is option B.

Note: The lenticel formation occurs just beneath the stomatal cell layer during primary growth. During the occurrence of the first layer of periderm, the lenticels completely replace the stomata cells. The lenticels are characterized by raised oval structures present externally over the bark of the tree.