Video Transcript
The picture below shows a wilted
plant. What can be assumed about the cells
of this plant? (A) The stems of the plant have
broken and can no longer support the weight of the leaves. (B) Many cells within the plant
have died and are no longer multiplying. (C) Many cells within the plant
have lost water and are no longer turgid. Or (D) the plant has taken in too
much water and its cells have plasmolyzed.
To answer this question, we need to
understand how a plant can become wilted, like the one in this picture. To do this, let’s start by taking a
look at a typical plant cell when there’s plenty of water available to the
plant. When water availability is high
outside the plant cell, water molecules move from an area of high water potential
outside the cell to an area of comparatively lower water potential inside the
cell. Once in the cell, most water is
stored in a structure called the vacuole, which swells as it fills with water. This exerts turgor pressure upon
the cell membrane of the plant cell, which causes the cell to swell. In this state, the plant cell is
described as turgid.
When water availability is low
outside the cell, water molecules move from an area of high water potential within
the cell’s vacuole to an area of comparatively lower water potential outside the
cell. The reduced volume of water in the
vacuole reduces the turgor pressure exerted upon the cell membrane, so it pulls away
from the cell wall. This causes the cell to reduce in
size and appear shrunken and wrinkled. In this state, the cell is
described as plasmolyzed. When there are many plasmolyzed
cells in plant tissues, the tissues are described as flaccid. This causes the whole plant to
wilt. It’s important to note that wilting
is usually reversible and if a plant is provided with more water, its cells can
become turgid again and vice versa.
Now, let’s review our answer
choices to see which is correctly describing what we can assume about the cells of a
wilted plant. Answer choice (A) states that the
stems have broken, which we can see is clearly not the case. Furthermore, this question asks us
what we can assume about the cells of a plant specifically, not about the stem or
leaves. Therefore, we can eliminate option
(A). Option (B) tells us that many of
the cells have died and are no longer multiplying. However, we know that wilting is
reversible and does not necessarily indicate that the cells have died. Therefore, we cannot make this
assumption about the cells of the wilted plant and can eliminate option (B) as
well.
Option (C) states that the cells
have lost water and are no longer turgid. This seems to be correct. We now know that when cells lose
water, they lose turgidity and can become plasmolyzed. This is what causes tissues to
become flaccid when it happens to many cells and eventually causes the plant to
wilt. Before we confirm our answer, let’s
check the final option is incorrect. Option (D) states that the plant
may have taken in too much water, and as a result its cells have plasmolyzed. This is incorrect. We know that plant cells become
plasmolyzed when they lose too much water, and this is what causes wilting. So we can eliminate option (D).
Therefore, we’ve worked out the
correct answer. The assumption we can make about
the cells of the wilted plant is (C), that many cells in the plant have lost water
and are no longer turgid.