Cistaceae

The Cistaceae are a small family of plants (rock-rose or rock rose family) known for their beautiful shrubs, which are profusely covered by flowers at the time of blossom. This family consists of about 170(-200) species in nine genera that are not very distinct, distributed primarily in the temperate areas of Europe and the Mediterranean basin, but also found in North America; a limited number of species are found in South America. Most Cistaceae are subshrubs and low shrubs, and some are herbaceous. They prefer dry and sunny habitats. Cistaceae grow well on poor soils, and many of them are cultivated in gardens.

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. The sepal arrangement is a characteristic property of the family.

The stamens are numerous, of variable length, and sit on a disc; filaments are free. The ovary is superior, usually with three carpels; placentation is parietal, with two or more ovules on each placenta. The fruit is a capsule, usually with five or ten valves (three in ''Helianthemum''). The seeds are small, with a hard, water-impermeable coating, weighing around 1 mg.Thanos, C. A., K. Georghiou, C. Kadis, C. Pantazi (1992). Cistaceae: a plant family with hard seeds. ''Israel Journal of Botany'' 41 (4-6): 251-263. (Available online
Abstract

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Recently the neotropical tree '' Pakaraimaea dipterocarpacea'' is placed here, following APG IV (2016)

Ecology

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 root fungi of the genus ''Tuber''.Giovannetti, G., A. Fontana (1982). Mycorrhizal synthesis between Cistaceae and Tuberaceae. ''New Phytologist'' 92, 533-537 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 of ''T. 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.

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 seeds germinate 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.

Systematics

Molecular analyses of angiosperms have placed Cistaceae within the Malvales, forming a clade with two families of tropical trees, Dipterocarpaceae and Sarcolaenaceae. Savolainen, V., M. W. Chase, S. B. Hoot, C. M. Morton, D. E. Soltis, C. Bayer, M. F. Fay, A. Y. De Bruijn, S. Sullivan, and Y.-L. Qiu. 2000. Phylogenetics of Flowering Plants Based on Combined Analysis of Plastid atpB and rbcL Gene Sequences. Syst Biol 49:306-362.Soltis, D. E., P. S. Soltis, M. W. Chase, M. E. Mort, D. C. Albach, M. Zanis, V. Savolainen, W. H. Hahn, S. B. Hoop, M. F. Fay, M. Axtell, S. M. Swensen, L. M. Prince, W. J. Kress, K. C. Nison, and J. S. Farris. 2000. Angiosperm phylogeny inferred from 18S rDNA, vbcL, and atpB sequences. Botanical Journal of the Linnean Society 133:381-461. Recent phylogenetic studies confirm the monophyly of Cistaceae on the basis of plastid sequences and morphological synapomorphies.Guzmán, B. and P. Vargas. 2009. Historical biogeography and character evolution of Cistaceae (Malvales) based on analysis of plastid rbcL and trnL-trnF sequences. Organisms Diversity & Evolution 9:83-99.

Within Cistaceae, eight genera are recognized, including five in the Mediterranean ('' Cistus'', '' Fumana'', '' Halimium'', '' Helianthemum'', '' Tuberaria'') and three in the temperate regions of North America ('' Crocanthemum'', '' Hudsonia'', '' Lechea''). These eight genera can be grouped into five major lineages within Cistaceae:
*a basal clade of the genus '' Fumana''
*the New World clade of '' Lechea''
*the '' Helianthemum'' s. l. clade, consisting of the sister groups '' Crocanthemum'' and '' Hudsonia'' from the New World, and '' Helianthemum'' s. s. from the Old World
*the '' Tuberaria'' clade
*a cohesive complex of '' Halimium'' and '' Cistus'' species

Cultivation and uses

''Cistus'', ''Halimium'' and ''Helianthemum'' are widely cultivated ornamental plants. Their soil requirements are modest, and their hardiness allows them to survive well even the snowy winters of Northern Europe.

Some ''Cistus'' species, mostly ''C. ladanifer'', are used to produce an aromatic resin, used in the perfume industry.

The ability of Cistaceae to create mycorrhizal relation with truffle mushroom (''Tuber'') prompted several studies about using them as host plants for truffle cultivation. The small size of ''Cistus'' shrubs could prove favorable, as they take up less space than traditional hosts, such as oak (''Quercus'') or pine (''Pinus''), and could thus lead to larger yield per field unit.

Cistaceae has been listed as one of the 38 plants used to prepare Bach flower remedies, a kind of alternative medicine promoted for its effect on health. However, according to Cancer Research UK, "there is no scientific evidence to prove that flower remedies can control, cure or prevent any type of disease, including cancer".

Symbolism

In the Victorian language of flowers, the gum cistus of the Cistaceae plant family symbolized imminent death.

Synonymous genera

These generic names inside Cistaceae were defined in various publications, but their members were synonymised with the eight accepted genera by later research.

* ''Anthelis''
* ''Aphananthemum''
* ''Atlanthemum''
* ''Fumanopsis''
* ''Helianthemon''
* ''Hemiptelea''
* ''Heteromeris''
* ''Horanthes''
* ''Horanthus''
* ''Ladanium''
* ''Ladanum''
* ''Lecheoides''
* ''Lechidium''
* ''Ledonia''
* ''Libanotis''
* ''Planera''
* ''Platonia''
* ''Pomelina''
* ''Psistina''
* ''Psistus''
* ''Rhodax''
* ''Rhodocistus''
* ''Stegitris''
* ''Stephanocarpus''
* ''Strobon''
* ''Taeniostema''
* ''Therocistus''
* ''Trichasterophyllum''
* ''Xolantha''
* ''Xolanthes''

Fossil record

†''Cistinocarpum roemeri'', a middle Oligocene macrofossil from Germany is described as an ancestor of extant Cistaceae. Tuberaria fossil pollen have been found in Pliocene.

References

External links

* Page R. G
The Cistus & Halimium Website
- th

contains many references to Cistaceae.
* Stevens P.F. (2001 onwards)
Angiosperm Phylogeny Website
. Version 5, May 2004.

{{Taxonbar, from=Q156282

Malvales families