Platanaceae
Platanaceae, the "plane-tree family", is a family of flowering plants in the order Proteales. The family consists of only a single extant genus Platanus, with eight known species.[3] The plants are tall trees, native to temperate and subtropical regions of the Northern Hemisphere. The hybrid London plane is widely planted in cities worldwide.
Pollination is anemophilous; flowering begins at the start of spring when the new leaves are sprouting. The heads that sustain the fruit normally shed the year after they have matured, during the autumn. Dispersion of the individual fruiting bodies, with their thistledown, is anemochorous (they are sometimes dispersed by water as a secondary mechanism).
The plants grow in cool situations in temperate climates and are frequently found on the banks of rivers and streams. They are totally absent from dry or excessively cold areas.
They contain cyanogenic glycosides derived from tyrosine, flavonoids belonging to the proanthocyanidins group (e.g. prodelphinidin) and flavonols (kaempferol, quercetin, myricetin), in addition to triterpenols (including betulinic acid). They lack ellagic acid, saponins, and sapogenins.
The main use for a number of the species is to provide shade in pedestrian areas in temperate regions, particularly the London plane-tree (Platanus x hispanica), which is widely distributed throughout Europe and North America. It is highly resistant, probably due to so-called hybrid vigour, although its use requires caution due to their allergy-producing thistledown. The parent species are also grown for the same effect, but with poorer results as they are less resistant to contamination, among other reasons. The wood is used in cabinetmaking, paneling, and other interior work, and is also prized for its long burn time.
A large number of fossils of this family have been recorded from the Lower Cretaceous (98-113 million years ago, Platanocarpus). The examples from that time had very small pollen (8-10 μm) and a developed perianth and they lacked hairs at the base of the nucule. It is thought to have had entomophilous pollination. During the mid Cretaceous, the fossilized forms with platanoid leaves became mixed with pinnate leaves (Sapindopsis) or pedatisect leaves (Debeya, Dewalquea), and these forms lasted until the Eocene. The leaves with typical stipules belonging to the sub-genus Platanus are very common in Palaeocene formations (60 M years ago). It is thought that the only modern genus, Platanus, is a relict that can be considered a living fossil. It must have been polyploid during its evolution judging by the size of its stomata.
