Carrots and beta-carotene

Still waiting for your carrot-induced night vision to kick in? You might have a long wait.

The myth that carrots help you see in the dark began during World War II to try and hide the rapid improvement of British radar. We needed an explanation for why our pilots could suddenly take down enemy planes in the dead of night, so propaganda posters were produced spreading the line that carrots could help you to see during the blackouts.

Unfortunately carrots can’t improve a healthy person’s night vision, but you can see why the enemy might have been fooled. Carrots are rich in the orange-red coloured pigment beta-carotene, which our bodies convert into vitamin A to use in vision.

betaCARROTene

Beta-CARROTene! Geddit?! Image mutilated from originals on Wikipedia here and here.

 

Beta-carotene 

Plants use chlorophyll to harvest light energy for photosynthesis, the process by which they convert carbon dioxide and water into sugars (and oxygen). Chlorophyll isn’t brilliant at soaking up the blue wavelengths of light, so beta-carotene steps in alongside it to mop up the blue and indigo rays. When we eat it, beta-carotene is broken down into retinal, one of the vitamin A compounds. It lets us see blue light at pretty similar wavelengths to those it absorbs in plants.

photosynthesis spectrum

Beta-carotene and other carotenoids help plants absorb blue light at 450-570nm wavelengths. Image adapted from Wikipedia

 

Antioxidant effect

Photosynthesis is performed by reaction centres in plant cells called photosystems. As well as light harvesting, beta-carotene can be added to these complexes for its antioxidant properties. If too much light reaches photosystems, they can produce highly reactive singlet oxygen molecules. Singlet oxygen can cause a lot of damage to cells, but beta-carotene is able to quench its effects before DNA, proteins and lipids are adversely affected. Whilst we don’t photosynthesise, our cells can be the victims of chemically reactive damaging compounds produced by our metabolism. Luckily beta-carotene from our diet retains its antioxidant effects, helping to prevent cell damage and cancer. That’s a better reason than “night vision” to eat your veg!

Pretty colours

tomato

Beta-carotene gives tomatoes their red colour. Source: Scott Bauer, Wikipedia

Plants use beta-carotene to produce beautifully colourful flowers to entice pollinators and fruits for other hungry animals to distribute their seeds. To that end, apricots, sweet peppers and tomatoes are all very high in beta-carotene.

It’s not altogether clear why root vegetables like carrots and sweet potatoes are so rich in beta-carotene, since none of the above benefits seem to apply.

 

Use in GM

Many people living in the developing world do not have access to foods containing enough beta-carotene. They become deficient in vitamin A, which can lead to blindness and death in extreme cases.

Golden_Rice

Golden rice has been engineered to produce beta-carotene in its grains. Source: Wikipedia

Now, genetic modification (GM) of food is a complicated topic that I don’t want to get into in this post, but there is a fairly famous crop specifically designed to target vitamin A deficiency. Golden Rice has been engineered to produce beta-carotene in the rice grains by adding one gene from maize (corn) and another from Erwinia, a type of bacterium. The proteins encoded by these two genes work together to produce beta-carotene.

Maybe it can’t help you see in the dark,  but beta-carotene is vital for healthy vision and cancer-preventing antioxidant effects. Keep munching those carrots.

What’s all this then?

Hi, I’m Sarah Jose and I’m in my second year of a PhD in plant sciences at the University of Bristol.

I’m sitting here writing because I want to tell the world about how AWESOME plants are! There are a lot of blogs out there about human-y subjects like medicine and psychology, but I want to get into how plants can do all the fantastic things that we take for granted.

I love writing about science (both academically and in the “real world”), so I started this blog to start some conversations about fantastic plant research. I’m talking to non-scientists about what has been found and why it’s great. 

A bit about my work

I should probably add a bit about my research so far, since it’s unlikely to be published for me to blog about any time soon!

I am looking into the link between the development of the microscopic pores on the leaves (known as stomata) and the waxy surfaces of the plant. Stomata let CO2 into the leaf fOpen and closed barley stomataor photosynthesis, but whilst open they let water escape. Plants have to open and close these pores to balance having enough CO2 with not dehydrating too much. The waxy surfaces on leaves help by not letting water escape from anywhere else. A few genes have been found that affect both the amount of wax and the amount of stomata that a plant produces, and I want to find out exactly what’s going on!

Why is this important? We’re going to need to feed a lot more people in the future, growing more crops in less land using less water. If we can understand how and why different types of leaf wax affect stomata development and water loss from plants, we can apply this to crops in the real world. This might mean genetically modifying plants to produce different types of leaf wax, but it might also be as simple as finding new waxy types of plants grown by conventional plant breeders.

barley

Keep in touch

If you enjoy an article, please leave a comment. If not, leave one to say what you disagree with. Whether you are a plant nerd like me or an accidental stumbler into my path, stay for a while and lets talk plants!

I tweet about science-y things: @JoseSci

I write about the environment and research at the University of Bristol for the Cabot Institute blog. You can find highlights on my Around the Web page above.