Video Transcript
Which process is not an example of
asexual reproduction in a plant? (A) The growth of a new plant by
tissue culture. (B) The growth of a new plant from
a cutting. (C) The growth of a new plant from
a bulb or tuber. (D) The growth of a new plant from
a seed. Or (E) the growth of a new plant
from a stem runner.
Reproduction can be sexual or
asexual. You’re probably already familiar
with sexual reproduction, as this is how most plants and animals, including humans,
typically reproduce. Sexual reproduction requires the
fusion of a male and female gamete, which typically come from two different
parents. The process of combining genetic
material from two gametes, called fertilization, produces genetically unique
offspring, which increases the genetic variation of sexually reproducing
populations.
Asexual reproduction is found in
organisms belonging to all taxa, from single-celled bacteria to complex,
multicellular animals, such as lizards and snakes. It is faster than sexual
reproduction and only requires one parent. However, asexual reproduction does
not increase genetic variation. Rather, the offspring produced are
clones of the parents and each other. Asexual reproduction can occur
through a variety of methods, some of which are shown here.
The question asks us about asexual
reproduction in a plant. So let’s turn our focus to
vegetative propagation, which is a specific form of regeneration found in plants and
some algae. During vegetative propagation, a
fragment or special structure of a parent plant develops into an entire new
plant. Because it is a form of asexual
reproduction, the new plant will be genetically identical to the parent plant. For example, in the right
conditions, a cutting of a stem or leaf can take root and eventually develop into a
mature individual.
Plant clones can also arise from
runners, which are modified stems that grow sideways, or bulbs and tubers, such as
onions and potatoes. So we can rule out answer choices
(B), (C), and (E) because they are all examples of vegetative propagation.
To study plants in a controlled
environment, scientists often use tissue culture. This technique allows for large
numbers of clones to be grown for experiments that need to control for genetic
differences. Because tissue culture relies on
the same biological mechanisms as vegetative propagation, it is a form of asexual
reproduction. And we can eliminate answer choice
(A).
Seeds are produced when plant sperm
found within grains of pollen fertilize egg cells found in the ovule. The resulting seed is simply a
plant embryo contained within a seed coat. We know that the union of male and
female gametes is a characteristic of sexual reproduction. So the process that is not an
example of asexual reproduction in a plant is choice (D), the growth of a new plant
from a seed.
