Video Transcript
Which of the following correctly
compares the positioning of mimosa leaflets during the day and at night? (A) During the day, they close up;
at night, they are held horizontally. Or (B) during the day, they are
held horizontally; at night, they close up.
The mimosa plant has amazing
capabilities that allow its leaves to respond to stimuli, such as touch and
light. What are these responses and how do
they serve the plant?
Each of the leaves of a mimosa
plant are composed of many small leaflets, some of which we can see in this
diagram. Generally, mimosa leaflets are held
open in a horizontal position, most likely so that they can gather as much light as
possible during the daytime. When the leaves of the plant are
touched or the plants are exposed to low levels of light, the leaflets tend to close
up and are held vertically.
This plant exhibits a type of
movement called nyctinasty, which means the movement of leaves in response to light
and dark cycles. This type of movement provides the
plant with an evolutionary advantage, as its leaves can look more wilted and less
appetizing to herbivores when the plant is unable to photosynthesize, such as at
night.
Now we know the correct answer to
this question. The answer that correctly compares
the positioning of the mimosa leaflets during the day and at night is (B). During the day, they are held
horizontally; at night, they close up.
