Autumn leaves become clear

September 29, 2000

One of the most striking features of nature is the autumnal colours of leaves. Why leaves change pigment so dramatically is a mystery.

The conventional explanation is that the green pigment used to assist photosynthesis degenerates at this time of year. But this theory broke down with the discovery ten years ago that losing the green pigment chlorophyll merely renders leaves colourless, while trees seem to manufacture new pigments that produce red and yellow.

Why should leaves go to this trouble when they are about to die?

Marco Archetti, an evolutionary biologist at the University of Perugia in Italy, has come up with an explanation, which is published in the Journal of Theoretical Biology.

Archetti knew that aphids use colour to select a leafy tree in autumn on which to lay eggs.

These tiny insects cause substantial damage to host trees. Archetti believes that the aphids probably use leaf colour as a guide to which trees are the least able to mobilise defences.

Brightly coloured leaves could therefore be acting as a deterrent signal to aphids, as the ability to produce new pigments so near winter is a sign of the tree's vigour.

Also, as aphids are green, they are more likely to show up to predators against a red or yellow background.

According to Archetti, each tree is competing to produce the brightest leaves to avoid attack - hence the riot of colour.

Raj Persaud

You've reached your article limit.

Register to continue

Registration is free and only takes a moment. Once registered you can read a total of 3 articles each month, plus:

  • Sign up for the editor's highlights
  • Receive World University Rankings news first
  • Get job alerts, shortlist jobs and save job searches
  • Participate in reader discussions and post comments
Register

Have your say

Log in or register to post comments

Most Commented

James Fryer illustration (27 July 2017)

It is not Luddism to be cautious about destroying an academic publishing industry that has served us well, says Marilyn Deegan

Hand squeezing stress ball
Working 55 hours per week, the loss of research periods, slashed pensions, increased bureaucracy, tiny budgets and declining standards have finally forced Michael Edwards out
Jeffrey Beall, associate professor and librarian at the University of Colorado Denver

Creator of controversial predatory journals blacklist says some peers are failing to warn of dangers of disreputable publishers

Kayaker and jet skiiers

Nazima Kadir’s social circle reveals a range of alternative careers for would-be scholars, and often with better rewards than academia

hole in ground

‘Drastic action’ required to fix multibillion-pound shortfall in Universities Superannuation Scheme, expert warns