Tuesday, 4 August 2015

Caster Oil Plant's explosive release of toxic seed

Caster Oil Plant, native to the Eastern Hemisphere, probably Africa, is now a rampant weed in much of the world. In Victoria it is only occasionally established, near gardens from which it escapes, but it extends through a broad strip of southern and eastern Australia.

It's a very successful weed because it grows vigorously in a range of habits, flowers much of the year, produces copious seed after only one year's growth and that seed is distributed by animals, water, on our shoes and just by itself up to five metres following an explosive release from the capsule.

Ricinus communis belongs to the plant family Euphorbiaceae, most of which have odd flowers. Generally if you can't work out what family a plant is in, and its flowers are a bit wacky, it's a euphorb.

Like most euphorbs, Caster Oil Plan has two kinds of flowers, girl ones and boy ones. The boy ones are packed full of branching stalks topped with anthers full of pollen. They look like this:

The girls look almost medieval, like some kind of  tiny mace decorated by a fancy red feathered crown.  The feathery crown is the style, where the pollen lands to pollinate the flower. The spines are ornamentation, perhaps to ward of predators (and see toxins below).

I gather that on the right day you can hear these capsules split, sending seeds ricocheting off the ground, signs and your head. They then look like this.

The seed contains Castor Oil, used since at least 4000 BC (based on seeds found in Egyptian tombs) for lamp fuel and god bothering. In generations just a little before mine it was also promulgated as a laxative, even being used in extreme dosage for torture during the Second World War by Italians under the control of Mussolini. Before you rush out to purchase a bottle for personal use, do see below regarding its toxicity.

Cleopatra reputedly used it to whiten her eyes. Again, see below regarding toxicity and note that it reputedly also causes temporary blindness on contact with eyes. In China it has been used for dressing wounds as well as various internal complaints. Again, see below...

By most accounts you must avoid applying the plant to any part of your body, or vice versa. The claim on Missouri Plants website, and many others, is that this plant is 'more toxic than any other plant to humans'. The culprit is something called Ricin.

Ricin is found throughout the plant, but more so in the seed. This molecule has two parts, one to get it inside an animal cell, the other to replace an essential part (an enzyme) in the pathway to producing protein within a cell. All this means that you die if you consume more than about half a gram of pure ricin if I've done my maths correctly.

However it turns out that it is more difficult to be poisoned that it seems. It is extremely emetic, which means if you ingest any you are most likely to vomit it back out again. And the molecules are large and difficult to get into an aerosol, so you are unlikely to inhale it.

Which is all very well but I'd recommend you definitely don't eat, drink or inhale it. Remember that pests making the mistake of eating the plant usually don't eat anything again.

Images: All images from the Reserva Ecol√≥gica de Buenos Aires in Argentina, taken when I visited in April this year. 
More reading: There are plenty of other potential uses for this plant, in medicine and extracting metals such as Cadmium from soils.


Stuart Read said...

Fascinating plant - Leo Schofield worked wonders with an extra red/purple cultivar in a striking border at Bronte House, Sydney. Periodically there are media reports of ricin poisoning by deliberate, as well as accidental, means, e.g. in the UK. Then again, daffodils and rhododendrons are toxic - good reason why cattle and sheep leave them well alone in paddocks. Life's dangerous just getting out of bed, really!

Tim Entwisle said...

Depends on where you sleep but point taken!