| Cistaceae | |
|---|---|
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| Cistus incanus | |
Scientific classification | |
| Kingdom: | Plantae |
| Clade: | Tracheophytes |
| Clade: | Angiosperms |
| Clade: | Eudicots |
| Clade: | Rosids |
| Order: | Malvales |
| Family: | Cistaceae Juss.[1] |
| Genera[2] | |
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TheCistaceae are a small family of plants (rock-rose orrock rose family) known for their beautifulshrubs, which are profusely covered byflowers at the time ofblossom. This family consists of about 170(-200) species[3] in eight genera[2] that are not very distinct, distributed primarily in the temperate areas ofEurope and theMediterranean basin, but also found inNorth America; a limited number of species are found inSouth America. Most Cistaceae aresubshrubs and lowshrubs, and some areherbaceous. They prefer dry and sunny habitats. Cistaceae grow well on poorsoils, and many of them are cultivated ingardens.
They often have showy yellow, pink or white flowers, which are generally short-lived. The flowers are bisexual, regular, solitary or borne in cymes; they usually have five, sometimes three, petals (Lechea). The petals are free, usually crumpled in the bud, and sometimes in the open flower (e. g.Cistus incanus). It has five sepals, the inner three of which are distinctly wider, and the outer two are narrow and sometimes regarded as bracteoles. Thesepal arrangement is a characteristic property of the family.
Thestamens are numerous, of variable length, and sit on a disc; filaments are free. Theovary is superior, usually with three carpels; placentation is parietal, with two or more ovules on each placenta. Thefruit is acapsule, usually with five or ten valves (three inHelianthemum). The seeds are small, with a hard, water-impermeable coating, weighing around 1 mg.[4][5][6][7][8]
Recently theneotropicaltreePakaraimaea dipterocarpacea is placed here, followingAPG IV (2016)[9]
The ability of Cistaceae to thrive in many Mediterranean habitats follows from two important ecological properties:mycorrhizal ability and fast renewal after wildfire.Most Cistaceae have the ability to create symbiotic relationship with rootfungi of the genusTuber.[10][11] In this relationship, the fungus complements the root system in its task of absorbing water and minerals from the soil, and thus allows the host plant to dwell on particularly poor soils. In addition, an interesting quality ofT. melanosporum is its ability to kill all vegetation except the host plant within the reach of its mycelium, and thus to give its host some sort of "exclusiveness" for the adjacent land area.[11]
Cistaceae have also optimally adapted to the wildfires that frequently eradicate large areas of forest. The plants cast their seeds in the soil during the growth period, but they do not germinate in the next season. Their hard coating is impermeable to the water, and thus the seeds remain dormant for a long period of time. This coating together with their small size allows these plants to establish a large seed bank rather deep in the soil. Once the fire comes and kills the vegetation in the area, the seed coating softens or cracks as a result of the heating, and the surviving seedsgerminate shortly after the fire. This mechanism allows the Cistaceae to produce a large number of young shoots simultaneously and at the right time, and thus to obtain an important advantage over other plants in the process of repopulating the area.[4][12]
Molecular analyses ofangiosperms have placed Cistaceae within theMalvales, forming a clade with two families of tropical trees,Dipterocarpaceae andSarcolaenaceae.[13][14] Recentphylogenetic studies confirm themonophyly of Cistaceae on the basis ofplastid sequences and morphologicalsynapomorphies.[15]
Within Cistaceae, eight genera are recognized, including five in theMediterranean (Cistus,Fumana,Halimium,Helianthemum,Tuberaria) and three in the temperate regions ofNorth America (Crocanthemum,Hudsonia,Lechea). These eight genera can be grouped into five major lineages within Cistaceae:
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Cistus,Halimium andHelianthemum are widely cultivatedornamental plants. Their soil requirements are modest, and their hardiness allows them to survive well even the snowy winters of Northern Europe.
SomeCistus species, mostlyC. ladanifer, are used to produce an aromatic resin, used in theperfume industry.
The ability of Cistaceae to create mycorrhizal relation withtruffle mushroom (Tuber) prompted several studies about using them as host plants for truffle cultivation. The small size ofCistus shrubs could prove favorable, as they take up less space than traditional hosts, such asoak (Quercus) orpine (Pinus), and could thus lead to larger yield per field unit.
Cistaceae has been listed as one of the 38 plants used to prepareBach flower remedies,[16] a kind ofalternative medicine promoted for its effect on health. However, according toCancer Research UK, "there is no scientific evidence to prove that flower remedies can control, cure or prevent any type of disease, including cancer".[17]
In the Victorianlanguage of flowers, thegum cistus of the Cistaceae plant family symbolized imminent death.
These generic names insideCistaceae were defined in various publications,[18][19] but their members weresynonymised with the eight accepted genera by later research.
†Cistinocarpum roemeri, a middleOligocenemacrofossil fromGermany is described as an ancestor of extant Cistaceae.Tuberariafossil pollen have been found inPliocene formations ofGermany.[20]
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