Awesome autumn leaves: colour chemistry explained
- Friday, 30 September 2016
Autumn: when we can finally stop complaining about it being too hot on those rare sunny summer days, and before it’s too cold to go outside without a hundred layers. Conkers litter paths, pumpkin-spiced food and drinks are everywhere, and it’s finally time for your favourite pair of boots.
One of the best things about this season are the spectacular autumn hues. But why do green leaves turn to red or orange, and how do the trees know when summer is over? We break down the science for you below.
Science made simple
Leaf science isn’t as confusing as all the long words and technical terms make it sound. It all comes down to the fact that different chemical pigments in leaves determine the colours we see.
When there’s more of one particular pigment, leaves appear certain colours. When that pigment is reduced and others are found in greater quantities, other colours become more visible.
Kaleidoscope of colours
During spring and summer, chlorophyll helps plants with the process of photosynthesis. This essentially turns carbon dioxide, water and the light from the sun into sugars for the tree. The green from chlorophyll masks other colours throughout the warmer, sunnier months.
Then, as nights start to grow longer and less sunlight is available, this change signals to trees that autumn is on the way. The production of chlorophyll slows and then stops completely. This is the point where the golden hues of autumn finally become visible.
A group of chemicals called carotenoids are always found in leaves, as they help to protect plants from damage from too much sunlight. Once the dominant green of chlorophyll is reduced, their colours become much bolder.
Xanthophyll, a type of carotenoid, is responsible for the yellow colours we see in plants as it persists in the leaves even when the chlorophyll has disappeared.
Golden orange hues also come from carotenoids. These pigments start disappearing at the same time as chlorophyll does, but at a much slower rate, so their colours last well into autumn.
Beta carotene is a type of carotenoid, and is responsible for giving plants and many edible goodies their orange colouring. You can find it in foods such as sweet potato, carrots and apricots.
While all trees have chlorophyll and carotenoids, not all produce anthocyanin, the pigment that causes leaves to turn red. Anthocyanin is only found during part of a tree’s growing season, and is produced from sugars that are trapped in leaves as the tree prepares to shed them.
You’re more likely to see brighter reds in a year where spring and summer have been warmer, drier and sunny. This year’s summer has seen above-average levels of sunshine, which will hopefully mean this autumn will be extra colourful!
Awesome autumn destinations
So, now that you know why autumn produces such wonderful colours, it’s time to get out and see them for yourself. There are more places to experience autumn’s golden hues in Scotland than we can count on all our fingers and toes combined. To give you a bit of inspiration, we’ve put together our top 10 favourite places, with help from staff around the country.
Leaf your troubles behind
Leaves aren’t just pretty to look at – you can have lots of fun with them as well. Have a look at our autumn activities to see some of our favourite things to do with all the different colours of leaves that cover the country.
Where is your favourite place to see autumn colours? Let us know below or enter our photo competition by 28 October and win some great prizes.
For questions and complaints, please contact us directly.