Video Transcript
The diagram provided outlines the
basic structure of the xylem. What type of simple plant tissue,
comprised of dead cells with thick cell walls, provides structure and support for
the xylem?
To answer this question, let’s look
at the three different types of simple plant tissue: parenchyma tissue, collenchyma
tissue, and sclerenchyma tissue. Parenchyma tissue is made up of
parenchyma cells, which have a thin cell wall made of cellulose and make up most of
the soft tissues found inside the leaves, stem, and roots. The cell wall of parenchyma cells
does not contain any lignin, and water can pass through their cell walls easily. Parenchyma cells are living cells
that carry out a number of functions: photosynthesis, storage of water and
nutrients, secretion of sap, and assistance with aeration for gas exchange with the
atmosphere. As the xylem transports water
through dead cells with thick cell walls, the thin-walled and water-permeable living
parenchyma tissue cells cannot be those providing structure to the xylem.
Collenchyma tissues are composed of
collenchyma cells, which are longer than parenchyma cells and have thicker cell
walls that are reinforced with hemicellulose and pectin. Collenchyma cells are essential to
provide structure, support, elasticity, and flexibility in the growing regions of
plants and are most likely to be found below the epidermis of leaf veins and
stems. Even though they play a role in
structural support, like parenchyma cells, collenchyma cells also tend to be alive
and water permeable. So this cannot be the tissue
providing structure to the xylem.
The final tissue type is
sclerenchyma tissue, which is the toughest of the three simple tissue types in
plants. Mature sclerenchyma cells are
usually dead. And they have thick cell walls
reinforced with both hemicellulose and a substance called lignin, which makes the
cells waterproof. Due to these features, sclerenchyma
tissues function to provide mechanical strength and support, especially in the
vascular tissues of a plant, which are the xylem and phloem, and the cortex of
stems, leaves, and any fruit that is produced.
Therefore, the tissue that’s
comprised of dead cells with thick cell walls that provides structure and support
for the xylem is the sclerenchyma tissue.
