Wednesday, September 15, 2010

Fall(ing) Aspen

stamp size, 2" x 1"
Aspens, apart from the aberrant White Poplar, are distinguished by their nearly round leaf on mature trees, 4-12 cm in diameter with irregular rounded teeth. They are carried on strongly flattened leaf stems, that cause the leaves to twist and flutter in slight breezes. The juvenile leaves on young seedlings and root sprouts differ markedly from the adult leaves, being nearly triangular, showing here the typical leaf shape of most other poplars; they are also often much larger, 10–20 cm long. The five typical aspens are distinguished from each other by leaf size and the size and spacing of the teeth on the adult leaves. White Poplar leaves differ in being deeply five-lobed, covered in thick white down, and having only a slightly flattened leaf stem.

stamp size, 1.25" x 1"
The unusual ability of the leaves of Aspen to twist and bend due to the flattened petioles may not be fully understood. It is thought to help protect the trees from severe winds, perhaps by helping dissipate energy more uniformly throughout the canopy.  It is also thought to improve the rate of photosynthesis throughout the tree by reducing the exposure of the outer leaves to extreme sunlight (thus reducing photoinhibition) by presenting the leaves at an oblique angle to the sun throughout the day, while at the same time allowing more light through to the lower leaves which are generally over-shaded. This would enable leaves throughout the tree to photosynthesize more efficiently. Another theory that has been advanced is that the constant motion aids the tree's growth: the constant movement is thought to increase the intake of air by the leaves, and hence the rate of carbon fixation from the air's carbon dioxide.

The Quaking Aspen of North America is known for its leaves turning spectacular tints of red and yellow in the autumn, popular among tourists.

stamp size, 1.25" x .5"

 ~source:  Wikipedia

3 comments:

Mama Cache said...

*smile*

They are adorable. I find myself measuring in the air with my fingers -- so cute and little!

By the way, loved the info and the page composition. The aesthetic and bookish sides of me are well blended this morning. Thanks.

Stacy Christian said...

Love them! We have two Quaking Aspens in our yard, but they are still saplings.

Ari C'rona said...

Too cool! Love the colors! :o)

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