A few members asked us to post the presentation about asexual reproduction, so here it is.
Unlike humans, plants can reproduce sexually and asexually.
The advantages of asexual reproduction are that it is faster, less
energy-consuming, and that it produces clones of the original plant - identical
at a genomic level. However, it fails to increase diversity, and any
susceptibility to disease that the original plant had will be passed on to its
clones.
The simplest method of asexual reproduction is through
cuttings. Cut a branch off of a plant (usually an herb) that is still soft and
not woody yet, remove the lower leaves, and plant it in moist soil, adding
rooting hormone if desired. That branch has the potential to develop into an
identical plant. This normally happens in nature when branches of a plant are
broken and fall down into soil; if the branches fall into an ideal environment
with the right orientation, they can continue growing and form a new plant.
Layering is a similar technique, where part of the branch of
the plant is buried beneath the soil or comes in contact with the soil. The
submerged part of the branch will grow roots, and soon enough that branch will
be able to obtain its own water and nutrients independent of the original
plant; the branch can be severed and will develop into a mature clone.
A plant’s amazing ability to regrow from almost any part is
due to the fact that the shoots and roots of most plants exhibit indeterminate
growth, meaning that they grow continually, and even when separated from the
original plant, can still grow to form a new plant.
Some plants send out stolons or runners, aerial stems that
contain plantlets (miniature plants) capable of growing roots and developing
into mature clones. Examples are strawberries and spider plants.
Rhizomes are the underground equivalent of stolons. Ginger
and bamboo use rhizomes to expand, explaining why many people who grow bamboo
for the first time have trouble keeping its growth under control.
Suckers are almost the same as rhizomes, except that they
are much shorter (usually within a foot of the
mother plant). A new plant
arises with its roots intertwined with its parent’s roots. It’s a great way to
get lots of clones of a plant fast. Examples are aloe vera, snake plant, and
banana palm.
Certain succulents produce plantlets at the tips of their
leaves, each of which is able to form a new plant. A prominent example is the
Mother of Thousands plant.
Plants with bulbs or tubers can divide their respective
systems to generate clones. Daffodils, tulips and garlic all have bulbs while
potatoes have tubers.
More advanced techniques include grafting and tissue
cultures. We won’t go too much in detail for these, but grafting involves
joining two different plants together to obtain the best of their qualities;
the bottom ‘rootstock’ provides a strong root system while the top ‘scion’
grafted to the rootstock has the growing and fruiting capabilities. The
rootstock is cut and the scion is attached to the cut part, where the vascular
systems combine to become one. It’s the fastest way to produce cultivars of fruit
trees with the desired properties.
With tissue culture, you need small pieces of leaf from the
plant you want to clone. These pieces are placed on sterile agar jelly with
nutrients and hormones. With luck, the pieces will develop into small plantlets
that can be transferred into regular media and grown like ordinary plants.
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