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Monocot and Dicot Plants
Flowering plants known as Angiosperms are the most diverse group of land plants in the
planet. The angiosperms spread across the world, with at least 260,000 living species
classified into 453 families. Traditionally, flowering plants have been divided into two
major groups or classes on the basis of the number of cotyledons present in the seed.
These two groups are the monocots and dicots. A cotyledon is the central portion of a seed
embryo to which the epicotyl and radicle are attached. Plants that are monocots have one
cotyledon and dicots have two cotyledons. To gain a better understanding of the various
features of monocots and dicots, we will now study two plants, one a monocot and the other
a dicot. To do the experiment we will require;
An Orchid plant that is a Monocot and A hibiscus plant that is a Dicot.
Procedure
Ensure that both the plant you have taken have roots, leaves and flowers.
Study the leaves of both the plants carefully by observing their venation. If the leaves
have parallel venation then the plant is a monocot and if the leaves have reticulate
venation, the plant is a dicot. In our case, the venation of the orchid leaf is parallel
so it is a monocot, and the venation of the hibiscus leaf is reticulate, so it is a dicot.
There is another characteristic that helps differentiate a monocot and a dicot. If the
leaves have a stalk then the plant is a dicot and if the leaves have no stalk, the plant
is a monocot. When the leaf has no stalk we call it sessile, meaning the leaf is attached
directly by its base without a stalk. In an orchid plant the leaf is sessile so it is
a monocot. The leaves of a hibiscus have a stalk so it is a dicot.
If you now take a look at the roots of both the plants and study the root system, you
will see that roots differ in a monocot and a dicot. The monocot plant has just a bunch
of roots. This type of root system is known as the adventitious root. A dicot plants has
a tap root system. We can see that the orchid plant has an aerial root system. Aerial roots
are almost always adventitious. So for the orchid plant there's another vote for being
a monocot. The Hibiscus has a taproot system as seen in other dicot plants.
Let us now move on to the stem. If you carefully observe the stem of both the plants, you will
see that the orchid has a weak stem, where as the hibiscus has a strong stem. Monocots
normally have a weak stem and dicots have both weak and strong stems. Looking at our
plants, the weak stem makes the orchid a monocot and the strong stem makes the hibiscus a dicot.
Let’s now carefully observe different parts of the orchid and hibiscus flowers.
If you count the number of petals and sepals, you will find that the monocot flowers tend
to have number of parts that is divisible by three and the dicot flowers have number
of parts that is divisible by four or five. In orchids there are three petals and three
sepals. One of the petals is modified to form a labellum or lip. Overall an orchid satisfies
the condition for a monocot plant. The hibiscus has five petals and five sepals like a typical
dicot plant. From these observations we can conclude that
the Orchid is a Monocot and the hibiscus is a Dicot plant.