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Why leaves change colour in autumn.

London, Oct 25 (ANI): A scientist has come up with a new theory for why leaves change their colour and then drop from trees in autumn.

Professor Brian Ford, writer and broadcaster, believes leaf drop occurs in order to excrete excrete /ex·crete/ (eks-kret´) to throw off or eliminate by a normal discharge, such as waste matter.

ex·crete
v.
To eliminate waste material from the body.
 waste products from the tree.

The president of the Cambridge Society for the Application of Research said, "We have long understood the importance of the leaf as the organ of energy capture, through photosynthesis, and of homeostasis homeostasis

Any self-regulating process by which a biological or mechanical system maintains stability while adjusting to changing conditions. Systems in dynamic equilibrium reach a balance in which internal change continuously compensates for external change in a feedback
, via transpiration transpiration, in botany, the loss of water by evaporation in terrestrial plants. Some evaporation occurs directly through the exposed walls of surface cells, but the greatest amount takes place through the stomates, or intercellular spaces (see leaf). ."

But the leaf is also an excretophore a means of consigning unwanted wastes to the void. This is why all plants drop leaves.

He found that, shortly before they are shed, levels of potentially harmful components such as tannins and oxalates in leaves increase.

"The levels of heavy metals in abscised leaves are also raised, and they are clearly there to be excreted rather than stored," The Telegraph quoted Ford as saying.

He argued that leaves do not simply die when plants run low on water, as plants, which live in water, such as water lilies, also shed leaves.

"In autumnal landscapes, when plants leaves turn red and brown and are suddenly shed it is important to bear in mind what is happening. The plants are having their annual, well, excretion," Ford said.

"It does, though, mean that the colouration of leaves in autumn will never seem quite the same again," he added. (ANI)

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Publication:Asian News International
Geographic Code:4EUUK
Date:Oct 25, 2010
Words:250
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