Video Transcript
Flowers are specialized leaves that
are adapted for sexual reproduction. Flower parts are arranged in four
concentric whorls, as shown in the figure. Which structure makes up the outer
whorl only, indicated by label X? (A) Androecium, (B) sepals, (C)
gynoecium, (D) corolla, or (E) perianth.
Flowers are used by plants for
sexual reproduction, and every part of the flower plays an important role in this
process. The organs of a flower are arranged
into concentric circular patterns around the stem, known as whorls, each of which
consists of a different set of organs, which serve a specific purpose. Let’s discuss the location and
function of each of these different whorls so that we can work out which structure
makes up the outermost whorl indicated by label X on the diagram provided by the
question.
The innermost whorl is called the
gynoecium. The gynoecium contains the female
reproductive organs of a flower, which are found within a structure called the
carpel. The carpel includes a stigma, which
is connected by a style to an ovary that contains the female gametes within
ovules. The next whorl outwards,
surrounding the gynoecium, is the androecium. The androecium includes all of the
male reproductive parts of the flower, which are called stamens. Each stamen consists of an anther
that produces the male gametes and a filament to support the anther. As we know that the gynoecium and
the androecium are the innermost whorls, they cannot be structures that make up the
outer whorl labeled with an X. So we can eliminate options (A) and
(C).
Moving outward from the androecium
is a whorl called the corolla. The corolla contains the petals of
the flower, which are often brightly colored and sometimes scented to attract
pollinators. As the petals are also not the
structure that has been labeled with an X, option (D), corolla, can also not be the
correct answer to this question.
Finally, the outermost whorl is
called the calyx. The calyx consists of several
sepals, which protect the developing organs of the flower in the innermost whorls
while the flower is in bud. Sometimes, the calyx and corolla
are collectively referred to as the perianth. As the perianth also includes the
petals of the corolla, it is not the structure that makes up the outer whorl only,
so option (E), perianth, must be incorrect.
Structure X is pointing to just one
of the structures in the calyx whorl. And this question is asking us to
find out which structure makes up this outer whorl. Therefore, the correct answer is
(B), sepals.
