Video Transcript
Which of the following is not an adaptation that root hair cells have for their
function? (A) They have thin walls to allow water and minerals to move into the cell. (B) They contain many chloroplasts that photosynthesize and provide glucose for the
root. (C) They are numerous in number to increase water and mineral uptake. Or (D) they have a low water potential inside the root hair vacuole to encourage
water to move into them.
To answer this question, let’s review the information that we need to know about root
hair cells.
Root hair cells are highly specialized cells that are found in the root of the plant
and are involved in absorbing the water and minerals that the plant needs from the
soil. To help them to carry out their role, these cells have several adaptations that make
them different from other plant cells. For example, compared to other plant cells, root hair cells have thin cell walls,
which makes it easier for water molecules to enter the cell. The cells have a long extension to increase their surface area, thereby increasing
the rate of absorption of water and minerals. They are also found in large numbers to increase the surface area further.
Another adaptation that helps root hair cells fulfill their role is the presence of a
vacuole that has a high concentration of solutes and so therefore a low water
potential. If you remember, the vacuole is a fluid-filled sac. Having an increased amount of solutes, like sugar and salts, dissolved in it creates
a low water potential within the vacuole. And so water will move from the soil into the vacuole of the cell through a process
called osmosis.
Root hair cells also contain a lot of mitochondria. As you may remember, mitochondria are the site of cellular respiration. Cellular respiration is the process by which energy is released from nutrients,
mainly glucose. The energy is stored in molecules of ATP until the root hair cells need it, for
example, for active transport of minerals from the soil into the root hair
cells.
However, the organelles that root hair cells do not have that are found in many other
plant cells are chloroplasts. Chloroplasts are the site of photosynthesis, which is the process by which plants use
sunlight energy to convert carbon dioxide and water into sugars, such as glucose,
releasing the waste product oxygen. As root hair cells are found in the soil, there is no need for them to have these
organelles as no light can reach them.
Having reviewed the key facts about the structure of root hair cells, we can return
to the question. The only answer that is not an adaptation of a root hair cell is (B). The adaptation that root hair cells do not have is that they contain many
chloroplasts that photosynthesize and provide glucose for the root.
