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!
|Cryopreservation is used to store plant tissue and
seeds, freezing material at -196°C |
(-320°F) in these sealed tanks with liquid nitrogen!
|Tiny orchid seed is smeared on to the agar jelly mixture|
|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|
|Eventually roots and shoots develop from the germinated seed|
|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!|
|Micropropagation does not just involve seeds; here new shoots are developing on a miniature cutting|
|Some species are not terribly fond on the agar jelly cocktails, so a rough plug mixture is used instead|
|Even succulents can be raised with this method!|
|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|
|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.