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Showing posts with label colchicine. Show all posts
Showing posts with label colchicine. Show all posts

Saturday, October 5, 2013

Colchicum autumnale, Meadow Saffron or Autumn Crocus, Colchicaceae


































Meadow saffron, sometimes known as autumn crocus, also has the rather salacious name of 'naked ladies' which supposedly stems from its lack of leaves when the flowers appear in autumn; the leaves sprout in spring and wither away in summer. The lilac flowers are very attractive to bees.

 This is a rare British native wild plant and most specimens that turn up – like those above, beside a road in Weardale – are garden escapes. To my mind they perform best when grown in grass like those in the photograph; when they’re cultivated in bare soil the floral tubes often grow very long and the flowers fall over in the autumn wind and rain, but some surrounding grass gives them support.



























































The plant has a long history of cultivation and in 1776 the botanist and doctor William Withering, writing in his Botanical Arrangement of all the Vegetables Growing in Great Britain mentioned that ‘cultivation produces a great variety of colours and makes the blossoms double’.

 In the wild meadow saffron was ruthlessly eliminated because it’s extremely poisonous to grazing livestock, thanks to the presence of toxic colchicine in all parts of the plant. Like many plant poisons colchicine has been used medicinally, in very low doses, to treat gout. Benjamin Franklin, himself a gout sufferer, is supposed to have introduced the plant to the United States for that very purpose. There have been accidental fatalities with poisoning from either eating the plant (its leaves resemble very lush wild garlic) or using it as herbal medicine at lethal concentrations, so one wonders how many of those who followed William Withering’s advice survived, when he wrote ‘This is one of those plants that upon the concurrent testimony of ages was condemned as poisonous; but Dr. Storck of Vienna hath taught us that it is a useful medicine. The roots have a good deal of acrimony. An infusion of them in vinegar, formed into a syrop by the addition of sugar or honey, is found to be a very useful pectoral and diuretic. It seems in its virtues very much to resemble squill, but it is less nauseous and less acrimonious’.

Colchicine is used by plant breeders to double the number of chromosomes in plants, because the drug allows the chromosomes to divide without the cell they are in dividing, so doubling the number of chromosomes in the cell - a phenomenon known as polyploidy. More chromosomes per cell tend to produce larger cells and larger cells lead to larger plants and better crops.


All sorts of unnaturally large plants, ranging from strawberries to hyacinths, have been bred using this long-standing form of genetic manipulation, which has been in use for over a century. Crossing a colchicine-induced tetraploid, which has double the normal chromosone complement, with a diploid plant that has the normal complement of chromosomes produces plants called triploids, with three sets of chromosomes per cell, which are seed- sterile – a common breeding technique for producing seedless fruit such as bananas.


Wednesday, November 4, 2009

Glory Lily Gloriosa superba (Colchicaceae)



This spectacular lily is a native of Africa, where it is the national flower of Zimbabwe, and also of India where it is the state flower of Tamil Nadu. It’s a climber, using its leaf-tip tendrils (see backing photo for the title panel of this blog) to cling to supports. If it’s left to scramble through other plants in a conservatory it will grow to a couple of metres tall and typically produces 5-6 blooms. The plant grows from an underground tuber and is easy to cultivate in a warm conservatory in summer, but you need to be careful to keep the tubers dry during winter, otherwise they rot off very easily. All parts of the plant are poisonous and the tubers particularly so, since they contain the toxic alkaloid colchicine (from which the family name is derived). Like many poisonous plants it has a long history of use in folk medicine and along with several related genera that contain colchicine it has been used to treat gout – see http://www.patient.co.uk/medicine/Colchicine.htm . In Africa and India there has recently been a resurgance in interest in extracting a broad spectrum of medicinally useful and antimicrobial compounds from the plant, even to the extent of growing it as a crop, but it’s those flame-like flowers that make it horticulturally interesting. It's often sold under the names flame lily, Gloriosa superba Rothschildiana or G. rothschildiana, and there are yellow-flowered cultivars available. Older literature places it in the plant family Liliaceae. One distinctive floral peculiarity is the way in which the stigma bends through 90 degrees and pokes out of the side of the flower. This is possibly an adaptation to pollination but there seems to be little information on the pollinators of this plant, other than that bumblebees and purple sunbirds (Nectarinia asiatica) http://en.wikipedia.org/wiki/Purple_Sunbird have been seen visiting it.



Flower viewed from below