What is the primary function of
structural support materials in plants? (A) To increase the rate at which
materials pass through the plant. (B) To allow flexibility and
movement for the plant. (C) To maintain the shape of the
plant and the plant cells. Or (D) to control which substances
enter and leave plant cells.
Unlike many animals like you and I,
plants do not have a skeleton to support them and so require other support
mechanisms in order to function effectively. This support comes in two forms:
structural support and physiological support.
Physiological support is given to
plant cells and, as a result, the plant as a whole by water exerting turgor pressure
on cell membranes. This is a temporary measure, as
dehydrated plants lose the support of water in their tissues and become wilted. Structural support describes the
permanent deposition of strong polymers into cell walls, which remains even after
the plant has died. For example, polymers like lignin
can be deposited into the cell walls of xylem vessels, keeping them rigid and
upright to increase the efficiency of water transport.
Some structural support polymers
like lignin have other functions, like making the cell impermeable to water. But their main role is to maintain
cell shape to keep the plant strong. So what is the primary function of
structural support in plants?
The deposition of tough substances
into certain cell walls actually limits their flexibility by making these tissues
rigid and strong, so we can eliminate option (B).
The deposition of polymers like
lignin into plant cell walls does function to make a cell impermeable to water,
thereby increasing the efficiency of water transport. However, this is one specific
example and does not describe the primary function of structural support in
general. So options (A) and (D) are
Instead, the primary function of
these structural support mechanisms in plants is to maintain the shape of the plant
cells and, as a result, the plant as a whole. So the primary function of
structural support materials in plants, and the correct answer to this question, is
(C): to maintain the shape of the plant and the plant cells.