Question

The bark of woody plants is dead but the inner layers inside the bark are living. How do these inner layers get oxygen and release carbon dioxide?
A. Lenticels
B. Stomata
C. Pneumatophores
D. Tendrils

Answer 1

The woody plants have bark as their outermost covering of stems. The bark lies outside the vascular cambium and is composed of dead cells. These cells are unable to respire. As the bark does not have stomata, there are pores present on it. These pores are made by lens-like cells.

Complete answer: The general component of the plant through which gaseous exchange occurs is leaves. The leaves consist of pores called stomata. The stem also respires through the same. But in woody plants, the stems are covered by the dead cells that form the bark of the tree. The bark cells are not able to respire and form a hard protective layer around the secondary growths of the vascular cambium.
The inner layers of the bark consist of secondary vascular tissues called secondary phloem. Outer to secondary phloem is the perimeter of the bark. The periderm contains lens-shaped cells that make a porous tissue called the lenticels. The lenticels help in gaseous exchange and water vapor exchange through their pores.
Pneumatophores are the aerial roots found in the Mangrove trees. These hang from the top of the plant towards the ground. These aerial roots are to advance the respiration in plants.
Tendrils are thread-like structures that arise from the stem of a climbing plant. These are tender structures that wind around any nearby structure for growth.
Hence, from the above discussion, we can conclude that the right answer is lenticels, option A.

Note: The periderm development begins just beneath the stomata cells during periderm formation and primary growth of the plant. The raised circular, oval parts of the woody stems have most of the lenticels. These cells have large intercellular spaces. Due to the varying amount of lignin in cell walls of lenticels discoloration may occur as seen in mangoes.