Maximum Yield Australia/New Zealand March/April 2018 | Page 37

The medium most commonly used in tissue culture is agar
gel, which holds the plant material in place at the base
of the flask. This gel substrate provides all the nutritional
requirements of the new tissue as well as directs growth
and development of the new plantlets by containing various
hormones. The most commonly used hormones in agar gel
are cytokinins to stimulate shoot development and auxins to
stimulate new root development. An agar medium will also
contain carbohydrates, such as sucrose or glucose; vitamins,
such as thiamine (B1), nicotinic acid, and pyridoxine; and
other compounds essential for the species being cultured.
Advantages of Tissue Culture
For indoor gardeners who have a few prized plants that
require propagation, tissue culture is a method worth
considering. Growers who use vegetative propagation
usually select their best plants to multiply, but a single
plant can only provide a handful of cuttings, making
bulking up numbers slow. However, using basic tissue
culture methods, even a small grower can rapidly produce
high numbers of clones from a single plant, either for their
own use or for sale. New plantlets, once they have come
through the culture process, can be easily shipped to other
growers while still in their sterile tissue culture flasks.
In fact, many orchid varieties can now be purchased as
flasks of tissue cultured plantlets, which are ready to be
shipped around the world to new growers, potted up, and
grown on. Overall, it’s a cost-effective way of buying and
selling newer plant material. Tissue culture flasks can also
be used to store or hold plantlets maintained in a sterile,
disease-free environment in vitro as future propagation
stock, taking up less space than mature specimens.
The Process
describes a wide range of
procedures that all involve taking
small parts of plants, tissues, or cells
and growing them inside sterile
containers in which the environment
can be carefully controlled.”
olan
The most widely used tissue culture method is based on
adventiti ous shoot formation, where a small piece of plant
(root, leaf, stem, bulb scales, or similar) is taken and induced
to produce many small shoots through the application of
the correct plant growth hormone. Normally, such plant
parts would not produce new shoots, let alone masses of
them, but the conditions inside the tissue culture flask and
the application of a plant growth regulator stimulates this
growth to occur. These shoots, once sufficiently developed,
are divided up into individual clumps and grown on in
another flask where they are induced to form new tiny roots
by application of another plant growth hormone. From there
onwards, the young plant is grown on until it is large enough
to leave the protected environment of the flask, be potted up,
and grown on in a nursery situation.
The tissue culture media inside sterile flasks can also be
used to germinate very small seeds or spores. Orchid seeds
are so small, they appear like a fine dust and have embryos
that are not fully developed. In the wild, these seeds are
dependant on a symbiotic relationship with certain microbes
in the bark of trees, which provide nutrition for germina-
tion. However, orchid seeds can be raised in tissue culture
media that supplies the inorganic salts and sugars required
for germination. Fern spores can also be raised in this way,
and the use of tissue culture media and aseptic methods
improves the rate of multiplication of ferns from spores.
“THE TERM ‘tissue culture’
Preparing plant material for tissue culturing.
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