Acer - Maple
Acer - text taken from Wikipedia
Acer is a genus of trees and shrubs commonly known as maples. The genus is placed in the soapberry family Sapindaceae. There are approximately 132 species, most of which are native to Asia, with a number also appearing in Europe, northern Africa, and North America. Only one species, Acer laurinum, extends to the Southern Hemisphere. The type species of the genus is the sycamore maple Acer pseudoplatanus, one of the most common maple species in Europe. Most maples usually have easily identifiable palmate leaves (with a few exceptions, such as Acer carpinifolium, Acer laurinum, and Acer negundo) and all share distinctive winged fruits. The closest relative of the maples is the small east Asian genus Dipteronia, followed by the more widespread genus Aesculus (buckeyes and horse-chestnuts). Maple syrup is made from the sap of some maple species. It is one of the most common genera of trees in Asia. Many maple species are grown in gardens where they are valued for their autumn colour and often decorative foliage, some also for their attractive flowers, fruit, or bark.
Acer pseudoplatanus
Acer pseudoplatanus, known as the sycamore in the British Isles and as the sycamore maple in the United States, is a species of maple native to Central Europe and Western Asia. It is a large deciduous, broad-leaved tree, tolerant of wind and coastal exposure.
Although native to an area ranging from France eastward to Ukraine, northern Turkey and the Caucasus, and southward to the mountains of Italy and northern Iberia, the sycamore establishes itself easily from seed and was introduced to the British Isles by 1500. It is now naturalised there and in other parts of Europe, North America, Australia and New Zealand, where it may become an invasive species.
The sycamore can grow to a height of about 35 m (115 ft) and the branches form a broad, rounded crown. The bark is grey, smooth when young and later flaking in irregular patches. The leaves grow on long leafstalks and are large and palmate, with five large radiating lobes. The flowers are greenish-yellow and hang in dangling flowerheads called panicles. They produce copious amounts of pollen and nectar that are attractive to insects. The winged seeds or samaras are borne in pairs and twirl to the ground when ripe. They germinate freely in the following spring.
In its native range, the sycamore is associated with a biodiverse range of invertebrates and fungi, but these are not always present in areas to which it has been introduced. It is sometimes planted in urban areas for its value as an ornamental. It produces a hard-wearing, creamy-white close-grained timber that is used for making musical instruments, furniture, joinery, wood flooring and kitchen utensils. It also makes good firewood. The rising sap in spring has been used to extract sugar and make alcoholic and non-alcoholic drinks, and can be processed into a syrup similar to that of the sugar maple. Bees often collect the nectar to make honey.
Description
The sycamore is a large, broad-leaved deciduous tree that reaches 20–35 m (66–115 ft) tall at maturity, the branches forming a broad, domed crown. The bark of young trees is smooth and grey but becomes rougher with age and breaks up into scales, exposing the pale-brown-to-pinkish inner bark.
Sycamore shoot tip in winter with a green terminal bud and paired green lateral buds.
The buds are produced in opposite pairs, ovoid (approximately oval in shape) and pointed, with the bud scales (the modified leaves that enclose and protect the bud) green, edged in dark brown and with dark brown tips, 0.5–1 centimetre (1⁄4–3⁄8 in). When the leaves are shed they leave horseshoe-shaped marks called leaf scars on the stem. The leaves are opposite, large, 10 to 25 cm (4 to 10 in) long and broad, palmate with 5 pointed lobes that are coarsely toothed or serrated. They have a leathery texture with thick veins protruding on the underside. They are dark green in colour with a paler underside. Some cultivars have purple-tinged or yellowish leaves. The leaf stalk or petiole is 5 to 15 cm (2 to 6 in) long, is often tinged red with no stipules or leaf-like structures at the base.
The functionally monoecious or dioecious yellow-green flowers are produced after the leaves in early summer, in May or June in the British Isles, on pendulous panicles 10 to 20 cm (4 to 8 in) long with about 60–100 flowers on each stalk. The fruits are paired winged seeds or samaras, the seeds 5 to 10 mm (1⁄4 to 3⁄8 in) in diameter, each with a wing 20 to 40 mm (3⁄4 to 1+5⁄8 in) long developed as an extension of the ovary wall. The wings are held at about right angles to each other, distinguishing them from those of A. platanoides and A. campestre, in which the wings are almost opposite, and from those of A. saccharum, in which they are almost parallel. When shed, the wing of the samara catches the wind and rotates the fruit as it falls, slowing its descent and enabling the wind to disperse it further from the parent tree. The seeds are mature in autumn about four months after pollination.
The sycamore is tetraploid (each cell having four sets of chromosomes, 2n=52), whereas A. campestre and A. platanoides are diploid (with 2 sets of chromosomes, 2n=26).
Botany
Sycamore trees produce their flowers in hanging branched clusters known as panicles that contain a variety of different flower types. Most are morphologically bisexual, with both male and female organs, but function as if they were unisexual. Some are both morphologically and functionally male, others morphologically bisexual but function as males, and still others are morphologically bisexual but function as females. All of the flower types can produce pollen, but the pollen from functionally female flowers does not germinate. All flowers produce nectar, the functionally female flowers producing it in greater volume and with a higher sugar content.
Sycamore trees are very variable across their wide range and have strategies to prevent self-pollination, which is undesirable because it limits the genetic variation of the progeny and may depress their vigour. Most inflorescences are formed of a mixture of functionally male and functionally female flowers. On any one tree, one or other of these flower types opens first and the other type opens later. Some trees may be male-starters in one year and female-starters in another. The change from one sex to the other may take place on different dates in different parts of the crown, and different trees in any one population may come into bloom over the course of several weeks, so that cross-pollination is encouraged, although self-pollination may not be completely prevented.
The sycamore may hybridise with other species in Acer section Acer, including with A. heldreichii where their natural ranges overlap and with A.velutinum. Intersectional hybrids with A. griseum (Acer section Trifoliata) are also known, in which the basal lobes of the leaf are reduced in size, making the leaves appear almost three-lobed (trifoliate).
