A scientist has taken a cross section from a conifer. He notices a small nucleus contained within a lignified cell wall. This cell is MOST likely:

Question

Quizplus · Accepted Answer

The presence of a small nucleus within a lignified cell wall suggests that the cell is still developing and has not fully differentiated. Tracheid cells, which are involved in water transport, lose their nucleus and other organelles as they mature and lignify, so it is unlikely that this is a mature tracheid cell (choice A). Similarly, sieve elements, which are involved in sugar transport, also lack a nucleus and mature cytoplasmic components, so it is unlikely that this is a mature sieve element cell (choice C). It is more likely that this is an immature tracheid (choice B) or sieve element cell (choice D) that still has a nucleus and is still developing. Therefore, the best choice is B. Choice E can be eliminated because it includes mature cells, which lack a nucleus.

A Scientist Has Taken a Cross Section from a Conifer