Video Transcript
Which of the following statements
about plants is correct? Plants are fully immobile
organisms, and their direction of growth cannot be changed. Plants have no form of sleep-wake
cycle to respond to dark-light cycles. Plants can respond to stimuli like
light and touch by moving. Or plants communicate between their
own structures using a central nervous system.
All living organisms are capable of
moving and reacting to changes in their internal and external environment. These changes are called
stimuli. Plants are capable of movement in
response to several different types of stimuli, like light intensity, touch, heat,
and gravity. Some plants are incredibly
sensitive to touch, and they can move in response to a touch stimulus via a process
called thigmotropism. For example, when the roots of some
legumes encounter underground rocks in the soil, they are stimulated to change the
direction of their growth away from that obstruction.
Some plants, including legumes,
have photoreceptors that can sense changes in light intensity. During the day, their leaves are
open and upright, but as night approaches and light intensity falls, their leaves
may close up and their stems may droop. When light intensity increases
again as daylight approaches, their leaves will return to their normal upright
position through a sleep-wake cycle sometimes called nyctinasty.
Let’s look at the different
statements given in the question. The first statement says that
plants are fully immobile and their direction of growth cannot be changed. This is incorrect, as we’ve already
seen two of the many examples of how plants can move. The second statement says that
plants have no form of sleep-wake cycle to respond to dark–light cycles. However, as we know, light is one
of the stimuli that plants can respond to, so this is incorrect too.
The third option says that plants
can respond to stimuli like light and touch by moving. This statement is correct; plants
are capable of responding to stimuli or changes in their environment by moving. Let’s just check that the final
option is incorrect before we confirm our answer. The fourth option says that plants
communicate using a central nervous system. Plants generally communicate
between different plant organs through electrical signals and chemicals like plant
hormones, but they do not have a central nervous system. So we can confirm that this option
is incorrect.
Therefore, the accurate statement
is that plants can respond to stimuli like light and touch by moving.
