Video Transcript
Collenchyma cells have thicker cell
walls than some other simple plant tissues. Which of the following is a major
function of collenchyma tissue? (A) Regulating water loss in
leaves. (B) Regulating water uptake in
roots. (C) Providing defense against
pathogens in the immune response. Or (D) providing support for the
plant, especially in growing areas.
The question asks us about
collenchyma and tells us that it is a type of simple plant tissue. So, let’s start by reviewing the
structure and function of the three simple plant tissues.
Parenchyma cells are thin-walled
and make up most of the soft, fleshy plant parts, such as leaves, stems, and
roots. Most are round or oval, but they
can also be square or rectangular, for example, when found in xylem tissues. Parenchyma cells usually have a
large number of chloroplasts and large vacuoles filled with water, starch, and
minerals. Parenchyma cells are living, and
they have a wide variety of functions. For example, they can store
nutrients and water, carry out photosynthesis, or secrete sap.
The large intercellular spaces
found in some areas of parenchyma tissue also help with gas exchange between the
plant and the atmosphere. Potatoes, which are a type of
tuber, are composed mostly of parenchyma cells whose role is to store starch.
Sclerenchyma cells are lignified
cells of varying shapes with thick, tough cell walls. Young sclerenchyma cells are
living. But mature sclerenchyma cells are
actually dead and have an extremely thick secondary cell wall that surrounds the
lumen. They are found in the cortex of
stems and leaves, the fruit, and in the xylem and phloem tissues.
The main function of sclerenchyma
cells is to provide permanent support for the plant, which is achieved by their very
thick cell walls. Sclerenchyma cells are found in
pears, whose slightly gritty texture comes from the substance lignin.
Collenchyma are elongated cells
with irregular, thick cell walls. The thickness of the cell wall
depends on the mechanical stress that the tissue is subjected to, with higher levels
of stress leading to a thickening of the cell walls. For example, plants grown in windy
conditions will have thicker cell walls than the same species of plant grown without
wind. They are typically found under the
epidermis of leaves and stems, particularly young, growing stems.
Collenchyma cells are strong yet
flexible. This makes them well suited for
their job to provide both structural support and elasticity to growing regions of
the plant. An example of collenchyma is found
in the strings of celery.
Now, let’s return to our answer
options. We can eliminate answers (A) and
(B) because collenchyma tissue is specialized for structural support and resilience,
not water regulation. We can also eliminate answer (C)
because although thick cell walls may provide physical defense against intracellular
pathogens, collenchyma cells are not part of the immune response.
So, the correct answer is (D). The major function of collenchyma
tissue is to provide support for the plant, especially in growing areas.
