Saturday, 27 October 2012

The Pervert's Guide To Plants

Are you a deviant who likes to hear saucy stories? Have you grown tired of the tame tales that your fellow humans have to tell you? If so, then step right this way. The mind-blowing wonders of a plant's sex life are far, far weirder than anything you will find in Fifty Shades of Grey. 

For starters, in the plant world there is sperm flying all over the place - literally! Pollen cells are a plant's sperm cells (I don't mean metaphorically, they are actually called 'sperm cells'). Just like human sperm cells they are produced in the male sexual organs, contain half the amount of genetic material (DNA) required to produce a new individual, and fertilise egg cells to produce embryos.

Pollen grains (shown here) contain sperm cells. A fact which puts hay-fever in a whole new light. 
Unlike human sperm, pollen isn't usually transferred by direct contact between a male and a female. Instead it is carried on the wind or by unwitting insects, birds and small mammals who are drawn in by the beauty of flowers and the promise of sweet nectar. The animal gets dusted with pollen while visiting one flower and then unknowingly carries it to the next flower that it visits, where it deposits some of the pollen onto the egg cells, resulting in fertilisation. Plants, in other words, use wild animals to carry their sperm into the female sex organs of other plants. The bee orchid, perhaps the most ingeniously perverse and sexually manipulative of all plants, has evolved to look like a female bee so that horny male bees will fly over and hump it. In doing so, the bee gets covered in sticky pollen which it then unintentionally carries to the next orchid and deposits on the eggs. (Incidentally, humans also seem to find orchids sexual: the word 'orchid' itself comes from the Greek word for 'testicle'. Apparently the roots look like balls. I'm not convinced.)

To a male bee, this is preeeeety sexy.
Given that they rely on the wind and hungry (and sometimes horny) animals as couriers for their sperm, it is not surprising that plants are never monogamous: they usually have sex with many different partners. Often a single male will fertilise many females at the same time (a practice which does occur in human societies, but is generally frowned upon). But it is not just the males who tend to be highly promiscuous - a single female can be fertilised by the pollen of many different males and carry the embryos of all of their offspring (inside seeds) at the same time. (I was fairly sure this never happened in humans, but according to these internet randomers, it occasionally does...).

The distinction between male plants and female plants is often not a valid one. In many plant species every plant has both male and female sexual organs. In other words, the plant kingdom has a lot of hermaphrodites. Usually the male sexual organs (stamens) are located around the female ones (ovaries). Given the temptingly close positioning of the pollen (orange circles in the image below) and the eggs (green blobs labelled 'ovule') you might wonder if plants are ever caught having sex with themselves. The answer is an enormous yes. Self-pollination is rife, and they don't just do it for fun, it is a common mode of reproduction. Domesticated wheat plants, for example, tend to release all of their pollen before the flower opens, meaning that none of it escapes. It all stays within the flower resulting in self-fertilisation.

Phwoar
So there you have it, plants are promiscuous, manipulative and just plain weird. If that's not enough for you, then I suggest you check out what the fungi have to offer. Oh, and remember to delete your internet history.

Thursday, 25 October 2012

More Links

A sexy new blog post is on its way. In the meantime, I will compensate for my laziness with links to things that other people wrote/made:



Wednesday, 17 October 2012

Golden Rice: A GM crop designed to fight malnutrition

It is well known that there a lot of people in the world today who are malnourished. Unfortunately, this problem is actually two problems. The first is that people do not have enough food to eat. The second is that people don't have access to the right type of food. One of the most serious examples of this second problem is vitamin A deficiency. This post is the story of Golden Rice, a genetically modified (GM) crop designed to help prevent vitamin A deficiency. 

Vitamin A is an essential part of a healthy diet. Not having enough of it leads to night blindnessanemia, and a weakened immune system, with particularly bad effects in children and pregnant women. The effects on the immune system are particularly troubling since most of the countries that suffer from vitamin A deficiency also have high rates of infectious diseases. Vitamin A deficiency weakens a person's immune system leaving them vulnerable to these diseases. Infection with disease often then leads to a reduced appetite and reduced absorption of any vitamin A that is consumed, meaning that the person becomes even more vitamin A deficient, which in turn makes them even more vulnerable to disease. It is a vicious cycle.

The easiest way to get enough vitamin A is to eat animal products, but if the human body doesn't get enough from that source then it can also make its own vitamin A from another chemical, called beta-carotene. Beta-carotene is an orange-coloured pigment found in many fruits and vegetables - for example, it gives carrots their orange colour. When you eat fruit and veg that contains beta-carotene your body turns that beta-carotene into vitamin A. Unfortunately, there are many people in the world, especially in Africa and South Asia, who do not get enough vitamin A because their diet is not high in meat or vegetables. Instead, their diets are mainly based around rice, and while the rice plant itself does produce beta-carotene, it does so only in the leaves and stem. No beta-carotene is found in the grain (the part that people eat). This means that vitamin A deficiency is a big problem in these regions. Approximately one third of the world's preschool-age children are estimated to be vitamin A deficient and when only Africa and South-East Asia are considered, this figure rises to approximately 44-50%. It has been estimated that making enough vitamin A available to all of the world's children would prevent around 2 million child deaths per year.

This is where Golden Rice comes in. Golden Rice is a variety of rice that has been genetically modified to make it produce beta-carotene in the grain. Since beta-carotene is an orange pigment, this means that the rice grains are orange instead of white (as shown on the left in the picture below), which is where the name 'Golden Rice' comes from (okay, so orange and gold aren't quite the same colour, but I guess 'orange rice' would have sounded a bit rubbish).

Golden Rice grains (left) and normal rice grains (right)

At the moment, Golden Rice is still going through the regulatory process that all new GM crops have to go through. Once it is ready to be used, the seeds will be given to poor farmers around the world for free. It has been bred with local varieties in the regions that it is being given to, so that it has the same characteristics as the rice that people are used to. Farmers won't have to change their growing practices and consumers won't have to change their cooking habitsThe only difference will be that they will be getting a healthy dose of beta-carotene with each bowl of rice they eat. Just like normal rice, farmers will be able to reuse the seed from one harvest in order to grow rice for the next season. This means that the new seeds only have to be distributed to each region once. 

Although Golden Rice has not yet been given to any farmers, the project has been underway for at least twenty years. Scientists began working on it in 1992 and it was in 1999 that they first managed to produce rice that made beta-carotene in its grains. However, the levels of beta-carotene produced were considered too low. Although this rice would have provided more beta-carotene than normal rice, it did not have high enough levels to completely fulfill the needs of people who are eating little else than rice. The experiments continued and by 2005 the scientists had managed to get the beta-carotene up to a much higher level. It has been shown that about 100-150g of this new version of Golden Rice can provide about 60% of a child's daily vitamin A requirement. Since then, the rice has been going through various tests to prove that it is safe for people to eat and that it won't harm the environment. The people behind the project are currently working with regulators in some target countries and hope to transfer Golden Rice seed to some farmers in the next few years. 

Many of the people who work on the Golden Rice project feel that progress so far has been unnecessarily slowed down by excessive regulation of GM crops. One the plant's two co-inventors, Ingo Potrykus, wrote an article in the scientific journal Nature in which he argued that there is no logical reason for new GM crops to have to undergo any more tests than other types of new crop. He argues that the the current regulations on GM crops are putting unnecessary financial and time constraints on the development of crops that could otherwise be preventing death and suffering. 

There are others, however, who think that Golden Rice seeds should never be given to any farmers at all. For example Greenpeace, who are opposed to all GM crops, have written articles criticizing the Golden Rice project (for example, this one and this one). Not only do they think that the new rice is a dangerous, untested technology, they also feel that it is completely unnecessary given the other strategies that are available to combat vitamin A deficiency. 

In general, I tend to agree with the scientists from the Golden Rice project on these issues. However, a full discussion of my reasons for this would take a few more posts, and it is certainly something that I plant to write about in the future. For now though, I just wanted to present the basics of the story. Anyone who wants to read more about the Golden Rice project, or the science that enabled it should take a look at www.goldenrice.org and anyone who wants to read some of the arguments being made against it should have a look at some of these articles: 

Thursday, 11 October 2012

Some Links


Monday, 8 October 2012

A new challenger for title of 'world's coolest plant'?

Carnivorous plants (plants that eat animals) are very important to a plant science fan like me. This is because they are the only plants which are universally regarded as cool. Of course, I think that all plants are totally super wicked awesome, but that is generally not something that I choose to say out loud in front of other humans. Carnivorous plants give me an opportunity to talk about plants in public places, without concealing my identity, and yet not give away just how much of a massive plant-nerd I am. If I was trying to get all of my favorite plants into a trendy nightclub, I would send the carnivorous plants first. They would have no trouble getting in. Then if the daisies and sunflowers got stopped because they 'didn't meet the dress-code' or 'weren't on the list', the carnivorous plants could turn around and say, "it's cool man, they're with us".

 By far the most famous of the carnivorous plants is the Venus Flytrap. There is a good reason for this: it's truly bad-ass, as David Attenborough will tell you (well, okay, he doesn't use those exact words). With it's touch-triggered jaws of eternal doom, the Venus Flytrap is the uncontested coolest of the cool. Or is it?

 A few weeks ago, a group of six German-based scientists published a paper in which they promote another contender for the title of coolest kid in the plant kingdom: the Pimpernel Sundew. Much like the Venus Flytrap, this sundew doesn't just have a bad-ass name, it also has a bad-ass way of catching its prey. Like all sundews, it has special leaves covered in drops of glue, which trap and suffocate insects allowing the plant to digest them, but that's not the exciting bit. The Pimpernel Sundew takes things up a notch in a way that hasn't been observed in any other plant species. Surrounding the sticky leaves, it has a ring of 'snap-tentacles' that act as catapults. Every time an unsuspecting insects lands one of these mini-catapults, the tentacle snaps quickly and flings the helpless animal onto the inner leaves where it meets its gluey fate. If you can can't imagine just how awesome this heartless insect-munching machine is, then I suggest you watch this video, which the researchers included with their paper:

video

 Although they don't quite come out and say it in their paper, the researchers clearly think that the Pimpernel Sundew deserves at least as much street-cred as the Venus Flytrap. In their introduction, they make a point of mentioning that the catapults "can bend within a fraction of a second, similar to the speeds reported for the Venus Flytrap". This is scientist-speak for "mine's just as quick as yours". They also clearly think that public recognition for the coolness of this catapult of insect death is long-overdue. They note that although the fly-flinging mechanism was first discovered in 1974, "remarkably, these fascinating observations and interpretation received no consideration until 2010, and trapping action in D. glanduligera has not been documented or investigated in depth until now."

 Although they did do some actual experiments and did manage to work out a biological mechanism by which the catapults are able to snap so quickly, I think the real reason for publishing this paper is clear. The authors are obviously fed-up with the Venus Flytrap stealing the limelight. They think that the Pimpernel Sundew is way more cool, and they've decided that it's time to tell the world. 

 This is an exciting time to be a carnivorous plant. The Venus Flytrap's long reign as undisputed champion of cool is being threatened and we may soon have a new world's coolest plant. At the very least, there will be a bit more room for debate. My guess is that, just like Superman vs. Batman, Ketchup vs. Brown Sauce and Lenny vs. Carl, this battle is one that will rage on forever. 


[NOTE: Because the paper was published in the open-access journal PLoS ONE (woo!), you can read the whole thing for free at:  http://dx.doi.org/10.1371/journal.pone.0045735]