Why are some leaves red or yellow, not green?
ASK! about Science and Technology
Leaves are green due to a pigment call chlorophyll in the plant cells. Chlorophyll helps a plant to convert light energy into chemical energy in a process called photosynthesis. This reaction produces glucose that the plant uses to grow. Excess is then stored, which is why we can get energy from plants.
Chlorophyll reflects the green wavelength of light, which is why leaves appear green. If a plant’s leaves are not green then, can it still photosynthesize to make food?
Yes they can. They may not look green, but there’s actually chlorophyll in the leaves still. Otherwise, they will not be able to make food and will die. The colour you see actually comes from the green colour of chlorophyll and deep red or yellow colours from pigments of various chemicals like anthocyanins, carotenes and xanthophyll.
Why bother to produce red pigments you ask? Well, these serve certain protective functions, such as from harmful UV rays anti-oxidant protection. These non-green pigments also assist photosynthesis. Some studies also predict that the red colour exuded by young leaves of some tropical trees warn animals from eating them. Upon maturity, these leaves rapidly turn green.
These red pigments occur in varying amounts in all leaves. The more they are present, the more red (or less green) the leaf appears. When seasons change from summer to fall, chlorophyll breaks down naturally so the red pigments appear more obvious.
References:
1. Stephen Reucroft, Can my plants with red leaves still do photosynthesis?, The Boston Globe, 14 July 2008, Factiva.com, 2 July 2009, http://eresources.nlb.gov.sg/
2. David W Lee, Why leaves turn red, 1 November 2002, Factiva.com, 2 July 2009, http://eresources.nlb.gov.sg/
3. Snyder Sachs, Jessica. “Photosynthesis.” New Book of Popular Science. 2009. Grolier Online. 2 July 2009
4. Kelly Bostian, World around you, Tulsa World, 2 November 2008, Factiva.com, 2 July 2009, http://eresources.nlb.gov.sg/
Originally answered by Ms Lim Hwa Shan, Adult & Young People’s Services
Found this question interesting? What do you think? Post your comments.
If you have a different question, please email to ask@nlb.gov.sg instead of sending a comment.
Sorry but I was looking for it myself.
Comment by Liu Xin — April 27, 2010 @ 2:16 pm
Your information was so stupid!why can\’t it be other coloured pigments instead of red?
Comment by Chin Cui Ning — May 3, 2010 @ 3:16 pm
Red is not the only colour. See “…deep red or yellow colours from pigments of various chemicals like anthocyanins, carotenes and xanthophyll.” These compounds occur as they have protective properties.
Comment by Ang Mei Jun — May 3, 2010 @ 3:28 pm