Question

Which structure or compartment is part of the symplast?

(A) the interior of a vessel element

(B) the interior of a sieve tube

(C) the cell wall of a mesophyll cell

(D) an extracellular air space

Short answer

(A) The option “the interior of a vessel element” is false.

(B) The option “the interior of a sieve tube” is true.

(C) The option “the cell wall of a mesophyll cell” is false.

(D) The option “an extracellular air space” is false.

Step-by-step solution

Symplast

Symplast is the inner region of the plasma membrane that facilitates the movement of water and solute via diffusion. They possess more than a single nucleus. The primary function of this is to facilitate the movement of minerals, amino acids, and sugars.

Explanation of option ‘(A)’

The interior of a vessel element is not a part of the symplast. The symplast is semipermeable, and hence it facilitates the easy diffusion of selected ions and molecules into and out of the cell. However, the vessel element is not semipermeable.

Thus, the interior of a vessel element is not a part of the symplast.

Therefore, the given option is false.

Explanation of option ‘(B)’

The interior of a sieve tube is a part of the symplast. This sieve tube helps in continuously transporting the cytoplasmic contents. The symplast is elongated interconnected perforations that form the sieve tubes.

Thus, the interior of a sieve tube is not a part of the symplast.

Therefore, the given option is true.

Explanation of option ‘(C)’

The cell wall of mesophyll cells is not a part of the symplast because they are ground cells that are found on the epidermal regions of the cells. The cell wall of the mesophyll cells are apoplast, and hence they lack cytoplasm in them.

Thus, the interior of a sieve tube is not a part of the symplast.

Therefore, the given option is false.

Explanation of option ‘(D)’

The extracellular air spaces are not a part of the symplast because they facilitate the movement of water and ions through the apoplastic pathway. Such kind of pathway occurs only in cells that do not have cytoplasm.

Thus, the extracellular air spaces are not a part of the symplast.

Therefore, the given option is false.