Video Transcript
The image provided shows a cross
section of the stem of a sunflower plant. The vascular bundles can be seen
forming a ring around the central part of the stem, or the pith. Which vascular tissue transports
the majority of water through the plant?
Let’s take a look at the image
provided that shows us a cross section of a stem. We can see the three simple tissues
called the parenchyma, collenchyma, and sclerenchyma. They help provide support and allow
processes like photosynthesis, nutrient storage, and gas exchange to occur. Very clearly visible are the
vascular bundles, one of which has been circled. The vascular bundles are what is of
interest to us in this question.
Each vascular bundle is mainly made
of two kinds of specialized vascular tissues. The xylem is made of big, dead,
hollow cells. The phloem consists of long cells
with a smaller diameter than the xylem cells. The phloem transports substances
like sugars and amino acids either up or down the plant stem. While these sugars and amino acids
are technically dissolved in water so there will be some water involved in phloem
transport, it’s not the phloem’s main function to transport water. That’s the function of the
xylem. The xylem transports water and
minerals from the soil in a one-way flow from the roots through the stem to the
leaves.
We now know that the vascular
tissue that transports water throughout the plant is the xylem.
