Anna Gardner
answered on 10 Jun 2019:
last edited 10 Jun 2019 10:41 am
Hi there!
Collectively known as evergreens these are the trees that are always green because they keep their leaves all year round.
Evergreens can include: Conifers (Christmas tree type trees), Holly bushes, eucalypts (the trees Koalas like) and most rainforest trees.
Conifers include trees such as pines, spruce and hemlock and mostly live in colder areas.
Evergreens are really important for providing protection (for animals) against the weather when all the other trees have lost their leaves in the autumn (known as deciduous trees).
If evergreens keep their leaves all year, this means they are very good at taking in and storing lots of carbon dioxide (via photosynthesis). This means they can ”sequest” carbon. They lock carbon in, reducing the amount of carbon dioxide (CO2) in the atmosphere. This is really good because carbon dioxide levels in our atmosphere are rising (due to burning fossil fuels and deforestation). Rising CO2 can lead to increased global temperatures that is largely a bad effect for many ecosystems and wildlife.
Leaves change colour in autumn because the plant wants to reabsorb some of the nutrients before dropping it’s leaves (as they are vulnerable to frost and could cause damage to the tree under the weight of snow, so the plant drops its leaves and goes in to a hibernative state living on stored sugars).
The chlorophyll breaks down, the green color disappears, and the yellow to orange colors become visible, other chemical changes may occur, which form additional colors through the development of red anthocyanin pigments. Some mixtures give rise to the reddish and purplish fall colors of trees such as dogwoods and sumacs, while others give the sugar maple its brilliant orange.
So the colour depend on what pigments are in that species of tree, so when the chlorophyll breaks down the other pigments show through. I don’t know which trees do not contain brown/red pigments but I’m sure with a little research you can find some plants without carotenoids or anthocyanins.
Comments
Emma commented on :
Leaves change colour in autumn because the plant wants to reabsorb some of the nutrients before dropping it’s leaves (as they are vulnerable to frost and could cause damage to the tree under the weight of snow, so the plant drops its leaves and goes in to a hibernative state living on stored sugars).
The chlorophyll breaks down, the green color disappears, and the yellow to orange colors become visible, other chemical changes may occur, which form additional colors through the development of red anthocyanin pigments. Some mixtures give rise to the reddish and purplish fall colors of trees such as dogwoods and sumacs, while others give the sugar maple its brilliant orange.
So the colour depend on what pigments are in that species of tree, so when the chlorophyll breaks down the other pigments show through. I don’t know which trees do not contain brown/red pigments but I’m sure with a little research you can find some plants without carotenoids or anthocyanins.