Populus
Populus is a genus of trees common in the northern hemisphere. They are often called just poplars. The genus has 25–35 species in three sub-groups, which are called poplars, aspens, and cottonwoods.
| Populus | |
|---|---|
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| Foliage of Populus tremula | |
| Scientific classification | |
| Kingdom: | |
| (unranked): | |
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| Order: | |
| Family: | |
| Tribe: | Saliceae[1] |
| Genus: | Populus |
| Type species | |
| Populus tremula | |
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In the September 2006 issue of Science, it was announced that the Western Balsam Poplar (P. trichocarpa) was the first tree to have its full DNA code sequenced.[2]
Reproduction
The flowers are mostly dioecious (rarely monoecious) and appear in early spring before the leaves. They are borne in long, drooping catkins. The male flowers have a group of 4–60 stamens on a disk. The female flower is a single-celled ovary in a cup-shaped disk.
Pollination is by wind. The fruit is a two to four-valved capsule, green to reddish-brown, mature in mid summer. It contains tiny light brown seeds surrounded by tufts of long, soft, white hairs which help wind dispersal.[3][4][5]
Ecology
Poplars of the cottonwood section are often wetlands or riparian trees.[6] The aspens are among the most important boreal broadleaf trees.[3]
Poplars and aspens are important food plants for the larvae of a large number of Lepidoptera species. Pleurotus populinus, the aspen oyster mushroom, is found exclusively on dead wood of Populus trees in North America.