Video Transcript
Which type of simple tissue in
plants is being outlined in the following description? The tissue has cells that are oval
or round in shape, surrounded by thin cellulose cell walls, and may contain
chloroplasts.
We are asked to determine which
type of simple tissue has these structural features. So to figure this out, let’s
compare the three simple tissues in plants using a table and define some key terms
along the way. Simple tissues are generally
composed of one type of cell. Or at least the majority of cells
have very similar structures and functions. There are three different types of
simple tissues in plants: parenchyma, collenchyma, and sclerenchyma. The drawings below the table
correspond to the typical shape and structure of cells in each type of simple
tissue.
Parenchyma cells are typically oval
or round in shape, while collenchyma cells usually look like elongated
rectangles. And as you can see, sclerenchyma
cells vary widely in their shape and size. You might notice that parenchyma
cells have the thinnest cell walls of all three tissue types. And these walls are made of
cellulose. Collenchyma cells have thicker cell
walls to provide mechanical support and are reinforced with a substance called
pectin. Sclerenchyma cells have the
thickest cell walls of all three types to structurally support and provide strength
to the plant’s transport vessels, for example. These cell walls are reinforced
with strong substances, such as lignin, to provide them with this strength.
Parenchyma cells also contain
chloroplasts, as one of their many functions is to carry out photosynthesis. Collenchyma cells might also
contain chloroplasts, but they are unlikely to be so many as in a parenchyma
cell. Sclerenchyma cells are technically
nonliving, partly due to the waterproofing lignin in their walls. Therefore, there is no point in
sclerenchyma cells containing chloroplasts as they would not be able to obtain the
water needed for photosynthesis across their walls. Let’s look back to the information
in the question to discover which simple tissue type it is describing.
The question describes the cells’
overall shape as oval or round. This suggests that the cells might
be found in parenchyma tissues rather than the long rectangular cells of
collenchyma. As collenchyma cells vary in their
shape, the cells in the question being round does not necessarily rule out
sclerenchyma. So let’s continue to the other
features. The question also states that the
cell walls of these cells are thin and made of cellulose. This provides further evidence that
they may be found in parenchyma tissues as both collenchyma and sclerenchyma cells
have thicker cell walls that are reinforced with other substances, such as pectin
and lignin.
The question tells us that the
cells in this tissue may contain chloroplasts. We know that these organelles may
be found either in parenchyma or in collenchyma cells, but not in sclerenchyma
cells. Based on this evidence, we can
deduce that these cells are unlikely to be found in collenchyma or in sclerenchyma
tissues, which means that as they meet all the necessary criteria, these cells are
most likely to be found in simple parenchyma tissues.
