Video Transcript
Plants can be classified depending
on whether they have clearly defined leaves, roots, and stems or not. Which of the following plants does
not have clearly defined leaves, roots, or stems? (A) Rosebush, (B) mint plant, (C)
moss, or (D) mango tree.
This question is asking about some
features of plants: leaves, roots, and stems. So let’s review some key facts
about plants and how they can be classified.
A plant is a multicellular organism
that can make its own food by a process called photosynthesis. “Multicellular” means it is made up
of more than one cell, multi- meaning many. Now we have reminded ourselves of
what a plant is, what about the structures mentioned in the question?
Starting at the bottom of the
plant, roots are the part of a plant that are usually found underground. They anchor the plant in the ground
and absorb water and minerals from the ground. Plants also use their roots to
store food, for example, yams and potatoes. Stems are a part of a plant’s shoot
system, and they provide structural support to the plant, usually keeping the plant
upright above the ground. Some plants, like trees and bushes,
have specialized woody stems, which are stronger and can provide more support to the
plant. Leaves tend to be green because all
plants have cells which contain chloroplasts.
The chloroplasts contain
chlorophyll, which is a green pigment that absorbs sunlight energy for
photosynthesis. Photo- means light, and synthesis
means to make. So they use light to make their own
food. But what happens to all this food
made in the leaves and how does some of it get to the roots to be stored for
later?
In some types of plants called
vascular plants, there is a system of transport vessels, which are tubelike
structures. One type of vessel carries the food
made in the leaves to wherever it is needed in the plant. Vascular plants also have another
type of vessel to carry water and minerals. The water is carried from the
roots, where it is absorbed, to the leaves, where some of it is used in
photosynthesis.
Nonvascular plants do not have
vessels and do not grow as tall as vascular plants, because it is harder to get the
food and water around the plant. Because they do not have vessels to
carry water around the plant, they are more at risk of drying out. Nonvascular plants are therefore
often aquatic or live in damp areas. Transport vessels are an important
structure in leaves, roots, and stems. The lack of vessels means
nonvascular plants do not have true leaves, roots, and stems.
Having reviewed some key facts
about plant structure and classification, we can now return to the question. It asks for a plant which does not
have clearly defined leaves, roots, or stems. We have already mentioned that
trees and bushes have woody stems. So we can rule out options (A) and
(D).
This leaves a mint plant and a
moss. Mint plants are herbaceous plants
with green stems and fresh-tasting leaves. So this is not the correct
answer. Mosses are nonvascular plants
growing close to the ground. They have green, flat structures
resembling leaves, which absorb water and nutrients. These are attached to a central
stalk, and they have hairlike structures, not roots, to anchor them in place. This means that mosses do not have
true leaves, roots, or stems.
Therefore, the correct answer is
(C). The plant that does not have
clearly defined leaves, roots, or stems is the moss.
