434 Horticulture Today
Copyright Goodheart-Willcox Co., Inc.
To prevent the introduction of disease or pests, the explants’ surface must
also be sanitized of all bacteria, fungi, viruses, and pests before being introduced
to the sterile environment. The explants may need to be subcultured if bacteria,
fungus, or viruses arise from within the surface of the sanitized tissue. This type
of contamination is called endogenous contamination.
While working, the technician (culturist) must maintain sterility in the
entire work area. Actions that should be taken to ensure sterility include
washing and sterilizing the work area (tabletops, fl oors, and tools), proper
hand washing, and keeping doors or windows near the work area closed.
Traffi c fl ow through the area should also be kept to a minimum.
Growth Media
Growth media are combinations of nutrients, growth regulators
(hormones), and water used to grow and sustain the explants or cells in vitro.
These substances, or the concentration of the substances, are manipulated and
changed for various stages of growth. The medium must be sterile and may be
either a liquid or a gel. Inorganic salts, vitamins, sugars, and trace elements are
also included in various amounts in the growth medium.
The medium will always have a water base. A gelling
agent is added to the medium to form a gelatin-type
texture. Gelling agents vary, but they are often derived
from algae (agar). Many commercial micropropagation
labs use alternative gelling agents derived from elements
such as corn or potato starch. As the explants develop,
they are recultured or transferred into a different test tube
or petri dish containing nutrients and growth regulators
needed for the next growth stage, Figure 17-6.
Stages of Micropropagation
There are fi ve stages of micropropagation.
Each stage plays a vital role in the production and
transitioning of a plant from an in vitro environment
into a natural environment.
Did You Know?
Certain types of agar
can be used as a
vegetarian alternative to
gelatin. Agar is used in
countless foods, such
as ice cream, preserves,
and soups.
Safety Note
Micropropagation
Fire, ethanol, alcohol, and bleach are used to sterilize work areas,
equipment, and plant materials. It is imperative that these elements be
stored properly and used following a strict protocol to prevent worker injury
and equipment damage. Always wear the appropriate personal protective
equipment (PPE) and keep hair tied back and sleeves and clothing snug
when working with fire. Know where the closest eyewash station and fire
extinguishers are before beginning the micropropagation process. You
should also review pertinent safety data sheets (SDS) before working with
chemicals.
luchunyu/Shutterstock.com
Figure 17-6. Plants can be recultured in growth
medium. These tobacco plants have been
recultured to secure more tobacco plants.