436 Horticulture Today
Copyright Goodheart-Willcox Co., Inc.
Explant material may be obtained from several sources,
including:
• Single cells from plants.
• Small pieces of plant tissues from leaves, stems, shoot
tips, fl owers, or embryos.
• The apical meristem (a swelling of cells at the furthest
tip of a plant shoot or the bud), Figure 17-9.
• Undifferentiated masses of cells that are from
parenchyma and lack a defi ned function, called a
callus, found on other explants.
Just as the work surfaces, tools, and existing environment
must be sanitized, the explant material must be completely
sterile. To sterilize the explant, technicians wash the plant
material in a bleach or peroxide solution. In addition, explants
may be dipped in ethanol or isopropyl alcohol. The explant is
placed on the growth medium in a test tube or petri dish with
sterilized forceps or tweezers, Figure 17-10. Once the explant is
established, it is ready for reculturing in stage 2.
Stage 2: Multiplication
In stage 2, the explants established in stage 1 are transferred (with sterilized
tools) to a second medium containing nutrients needed for the plant material to
multiply. This medium is referred to as the multiplication medium. To prevent
contamination, technicians use standard aseptic techniques (cleaning and PPE) as
well as a laminar fl ow hood and sterilized forceps during this procedure. Forceps
may be sterilized by dipping them in alcohol and “fl aming” them with a small
fl ame, and dipping them into two separate sterile water containers.
B
Debu55y/Shutterstock.com
Figure 17-9. A—This apical meristem of a plant has been dyed and magnified under a
microscope. B—The apical meristem of asparagus is beneath the terminal leaf buds.
A
Jubal Harshaw/Shutterstock.com
Mihai Simonia/Shutterstock.com
Figure 17-10. Extreme caution must
be made when taking an explant to
another stage of micropropagation.
Using sterile tools is essential.