Aspen is the common name for trees of the Salicaceae family have, most of them in part, Populus sect. Populus, from (poplar) genus Populus Some species in this section are:.
* Populus alba: White Poplar (northwest Africa, southern Europe, east to central Asia)
* adenopoda Populus: Chinese Aspen (China, south of P. tremula)
* Populus grandidentata: Bigtooth Aspen (eastern North America, south of P. tremuloides)
* Populus sieboldii: Japanese Aspen (Japan)
* Populus tremula: Common, Sweden, trembling or Eurasian Aspen (northern Europe & Asia)
* Populus tremuloides: trembling, shaking or American Aspen (northern & western North America)
* Populus × canescens: Grey Poplar (hybrid P. alba × P. tremula)
Aspens, apart from deviating White Poplar (Populus alba), are distinguished by their nearly round leaves on mature trees, 4-12 cm in diameter with irregular rounded teeth. They kept very flat leaf stem, which causes the leaves twist and flutter in the wind a little. This juvenile leaves on young seedlings and root sprouts differ from adult leaves, which is nearly triangular, showing here the typical leaf shape of most other poplars, they are also often much larger, 10-20 cm. The five typical aspens are distinguished from each other by leaf size and the size and spacing of teeth in adults leaves. White Poplar leaves are very different in the five-lobed, covered in thick white down, and only slightly flattened leaf stem.
Unusual ability of Populus leaf petioles twisted and bent because the average may not be fully understood. It is estimated to help protect trees from severe winds, perhaps by helping to eliminate the energy more uniformly throughout the canopy It is also thought to increase the rate of photosynthesis throughout the tree by reducing exposure to sunlight extreme outer leaves. (thus reducing photoinhibition) by presenting the leaf at an angle tilted toward the sun throughout the day, while at the same time allow more light to lower leaves are generally more-shade. This would enable leaves throughout the tree to photosynthesize more efficiently Other theories have been advanced is that the constant motion helps the growth of trees:. Constant movement is thought to increase the intake air with the leaves, and therefore the level of carbon dioxide fixation of carbon from the air.
The North American trembling aspen leaves are known to alter spectacular tints of red and yellow in autumn, popular among tourists
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