Question

Do all stems have lenticels?

Answer 1

Hint: Lenticels are the tissues which are porous in nature. Their cells contain large intercellular spaces. They are present in the circumference of the organs in which secondary growth has taken place. Its main function is to provide an interface for direct exchange of gases between the environment and the plant.

Complete answer:
Plants have two pathways through which the diffusion of gases mainly takes place, they are stomata and lenticels. Lenticels are present in the bark of the plant. They are involved in the exchange of Oxygen and carbon dioxide. They are present in stems which have already undergone secondary growth. Due to the presence of cambium, secondary growth also occurs in roots. Secondary growth is responsible for increase in circumference or girth of the plant. However, cambium is not responsible for any exchange of gases.
Lenticels are present in the cortex region. So, it may be possible that it is formed by the cambium which is present in the stele. They are present in the woody stem. Wood is formed after secondary growth of a plant. They may be present in fruits like oranges. The word "lenticel" has a literal meaning, which is lens-like. They often appear rough. The bark is usually impermeable to gases but lenticels provide a passage for exchange of gases.

Note:
These openings are present in woody stems. Lenticels can remain permanently open but in contrast stomata don'. Opening and closing of stomata depends on the turgor pressure. The lenticels are the openings which are simply a result of secondary growth in stems and are meant for exchange of gases. They are present in the bark.