Occasionally
when a plant species is difficult to propagate with traditional methods or in
danger of extinction, and in many cases very often both, we must place our
faith in science and the lab-coated coves initiated in such sorcery!
Micropropagation is the growing of plants from seed or tiny pieces of plant
tissue in sterile, laboratory conditions, and is utilised to cultivate those
dreadful nuisances that are indifferent to a tray of John Innes and a bit of
bottom heat. Kew’s Micropropagation Unit was set up in 1974 and produces
thousands of plants each year to repopulate endangered species in a series of
labs dedicated to this cultivation.
Orchids
are one of the success stories at Kew, with this plant family in particular need
of specialist techniques. Although they often produce thousands of seeds orchids
rely upon fungi in the soil for germination, as theses dust-like seeds lack an
endosperm, the part of a seed where a small food store powers the initial stages
of germination, before the first leaves are unfurled and photosynthesis becomes
the main engine for plant growth. The soil fungi form a symbiotic
relationship with the tiny seed, laying on the food that enables germination! This
happy matrimony is undoubtedly heart-warming, but from a propagation perspective
is insanely difficult to recreate in the potting shed, needing the usual temperature
and moisture requirements plus that blasted fungi. As usual science holds the
key with micropropagation enabling germination without fungus, in a process
called asymbiotic germination that provides all of the nutrients that the
fungus would normally supply. This propagation usually does not involve soil,
but instead various cocktails of sugars, minerals and vitamins solidified in
agar jelly, which holds the concoction together and gives the plants something
to root into. The development and success of these techniques has resulted in
the saving of species such as the beautiful Lady’s Slipper Orchid, Cypripedium
calceolus, which had been reduced to one single specimen left in the wild but
was repopulated and reintroduced in a collaboration between Kew and English
Nature!
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Cryopreservation is used to store plant tissue and
seeds, freezing material at -196°C
(-320°F) in these sealed tanks with liquid
nitrogen! |
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| Tiny orchid seed is smeared on to the agar jelly
mixture |
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| Sincere apologies for the quality of this image, but
looking down the lens of a microscope we can see thin grains of orchid seed and
the round, swelling seed that has already began to germinate |
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| Eventually roots and shoots develop from the
germinated seed |
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| Seedlings are ‘potted on’ to glass jars, where they
continue to develop before eventually being finally transferred to traditional
soil potting mixtures and then reintroduced to the wild! |
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| Micropropagation does not just involve seeds; here new
shoots are developing on a miniature cutting |
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| Some species are not terribly fond on the agar jelly
cocktails, so a rough plug mixture is used instead |
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| Even succulents can be raised with this method! |
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| Carnivorous plants, Dionaea muscipula, can be seen
here. As the nutrients in the agar mixture are used up, yellowing leaves on the
plants indicate the time to pot on to a soil based medium |
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| It’s propagation, but not as we know it! |
A little off the beaten track, but I hope this offers
an insight into some of the madness going on here at Kew! As an aside the good
eggs over at Tweed Pig have kindly featured me in their ‘pin-up’ series, please
click here to take a look.
