Science Fair Project Encyclopedia
Cistus (rock roses)
Reference: Kew (2004)
The Cistaceae (or rock rose family) is a rather small family of plants known for its beautiful shrubs, vastly covered by flowers at the time of blossom. This family consists of about 170-200 species in eight genera, distributed primarily in the temperate areas of Europe and the Mediterranean basin, but also found in North America and 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. The Cistaceae grow well on poor soils, and many of them inhabit gardens across Europe and the New World.
Cistaceae 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). 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 parietal with two or more ovules on each placenta. Fruit is a capsule, usually with five or ten valves (three in Helianthemum). Seeds are small, with hard water-impermeable coating, weighing around 1 gr (Thanos et al., 1992).
(Heywood, 1993; Hutchinson, 1973; Judd et al., 2002; Mabberley, 1997)
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 genus Tuber (Chevalier et al., 1975; Giovannetti and Fontana, 1982). 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 intersting 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. (Giovannetti and Fontana, 1982)
Cistaceae have also optimally adapted to the wildfires that frequently completely eradicate large areas of forest. The plants cast their seeds in the soil during the growth period, but the latter don't germinate right 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 together with their small size allows it 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 simutaneously and at the right time, and thus to obtain an important advantage over other plants in the process of repopulating the area. (Thanos et al., 1992; Ferrandis et al., 1999)
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 and England.
Some Cistus species, mostly C. ladaniferus 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 researches about using them as host plants for turffle 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. Nevertheless, no commercial uses have been made so far in this direction.
The following generic names inside Cistaceae were defined in various publications (IPNI, 2004), but their members were displaced into one of the eight primary genera (see table) by later research.
- Anthelis -- Aphananthemum -- Atlanthemum -- Crocanthemum -- Fumanopsis -- Gaura -- 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
- Chevalier, G., D. Mousain, Y. Couteaudier (1975). Associations ectomycorhiziennes entre Tubéracées at Cistacées. Annales de Phytopathologie 7(4), 355-356.
- Ferrandis, P., J. M. Herrantz, J. J. Martínez-Sánchez (1999). Effect of fire on hard-coated Cistaceae seed banks and its influence on techniques for quantifying seed banks. Plant Ecology 144 (1): 103-114. (Available online: DOI | Abstract | Full text (PDF))
- Giovannetti, G., A. Fontana (1982). Mycorrhizal synthesis between Cistaceae and Tuberaceae. New Phytologist 92, 533-537.
- Heywood, V. H. (ed.) (1993). Flowering plants of the world, pp. 108-109. London: Batsford. ISBN 0195210379.
- Hutchinson, J. (1973). The families of flowering plants: arranged according to a new system based on their probable phylogeny (3rd ed.), pp. 254-255. Oxford: Clarendon. ISBN 0198543778.
- IPNI (2004). The International Plant Names Index - Record on Cistaceae. Retrieved Nov. 15, 2004.
- Judd W. S., C. S. Campbell, E. A. Kellogg, P. F. Stevens, M. J. Donoghue (2002). Plant Systematics: A Phylogenetic Approach, 2nd edition, pp. 409-410 (Cistaceae). Sunderland, Massachusets: Sinauer Associates. ISBN 0878934030.
- Jussieu, Antoine Laurent de (1789). Genera Plantarum: 294. Parisiis.
- Kew (2004). List of genera in Cistaceae, in Vascular Plant Families and Genera Database, Royal Botanic Gardens, Kew. Retrieved Nov. 15, 2004.
- Mabberley, D. J. (1997). The plant-book: a portable dictionary of the vascular plants (2nd ed.), p. 160. New York: Cambridge University Press. ISBN 0521414210.
- 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 | Full text (PDF))
- Page R. J. The Cistus & Halimium Website - the bibliography contains many references to Cistaceae.
- Stevens P.F. (2001 onwards). Angiosperm Phylogeny Website (Cistaceae). Version 5, May 2004.
- Watson L. and M. J. Dallwitz (1992 onwards). The Families of Flowering Plants (Cistaceae)
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