Question

Which of the following is enucleate at maturity?
A. Sieve cell
B. Companion cell
C. Cortical cell
D. Palisade cell

Answer 1

Hint: These cells live even after removal of the nucleus after maturity. Companion cells present in association with plasmodesmata, helps in survival of these enucleated cells. Initially they have nucleus but after maturity they lose the nucleus, ribosomes and vacuoles and get important differentiation required for the translocation of food from leaves to other all parts of the plant body.

Complete answer: There are many types of plant cells present in the plant body having different types of function and structure. Various types of cells present in plants are sieve cells, companion cells, cortical cells, etc. These cells have different functions like sieve cells help in transportation of food in plants also help in signalling and coordination among different organs of the plants.
Cells which are enucleated at maturity, undergo degeneration of its nucleus during developmental stages. And companion cells help them to grow and live without nucleus.
So, we have discussed the function of companion cells. Let's consider other cells given in the options.
Next option is cortical cells: These cells are present in-between the surface or epidermis layer and vascular or conducting tissues of stems and roots of the plant. These cells contain different carbohydrates, resins, latex or other essential oils.
Next option is palisade cells: These cells are present on the leaves below the epidermis layer and cuticle of plants. These cells have elongated shape and they resemble spongy mesophyll cells and present below the mesophyll cells.
Next option is sieve cells: These cells are present in string association with companion cells with the help of plasmodesmata.
So, after discussion we can say that our answer is sieve cells as they get enucleated after maturity.

Thus, option ‘A’ is the correct option.

Note: One can think how these sieve cells survive without nucleus. For this answer, sieve cells have nucleus initially but during development of cells, as they convert to conducting cells, they lose their nucleus and companion cells are there to facilitate their survival.