Video Transcript
In a plant stem, which part of the
vascular bundle is responsible for transporting water and minerals from roots to
leaves? (A) Xylem vessels and sieve tubes,
(B) xylem vessels and tracheids, (C) tracheids and sieve tubes, or (D) cambium.
Much like humans, plants need a
vascular system to transport vital molecules, like sugars and water, to all of their
cells. In plants, this vascular system is
primarily composed of vascular bundles. This question asks us about a
specific structure, or structures, found in the vascular bundles of a plant stem
responsible for transporting water and minerals. To work out the correct answer,
let’s take a closer look at a vascular bundle, several of which are displayed in
this diagram of a typical stem, to work out which part is specifically adapted for
this function.
Each vascular bundle is made up of
two main regions: the xylem and the phloem. The xylem and phloem are separated
by a region called the cambium, which contains unspecialized cells called meristem
cells that can extend the xylem and phloem vessels to reach other parts of the plant
as it grows. The phloem is responsible for
transporting solutes, like the sugars that are produced in photosynthesis and amino
acids. The xylem, on the other hand, is
responsible for transporting water and dissolved minerals from the roots up through
the plant stem to all the other parts that require them, like the leaves. This is the structure of interest
to us in this question.
Let’s take a closer look at which
specific parts of the xylem transport water and minerals. Xylem tissue consists primarily of
two types of cell: xylem vessels and xylem fibers. The cells in xylem vessels are
stacked end to end with their end walls broken down to form a hollow, waterproof
tube through which water and any dissolved minerals can be transported. Some parts of the xylem might
include cells called tracheids that can also transport water and dissolved
minerals. Tracheids are structurally similar
to xylem vessels but are tapered, closed, and often longer and thinner. Xylem fibers help to provide
structural support to the xylem vessels, preventing them from collapsing.
This question asks us about the
part of the vascular bundle that transports water and minerals. And we just learned that this is a
responsibility of the xylem, specifically the xylem vessels and tracheids. So, the part of the vascular bundle
that is responsible for transporting water and minerals from roots to leaves is (B),
xylem vessels and tracheids.
