A rock-dwelling fungi adapted to desert environments, Ramalina maciformis grows in four main forms. The first, and typical form of this fruticose (‘shrubby’) lichen is bushy or strap-like and characterised by an erect thallus (the main body) (2), with wide undulated lobes that are twisted and ribbon-shaped. The thallus is attached only by its base to the substrate. The second form is similarly shaped but has many proliferations of the upper surface such that it appears feathered. The third form of thallus is more compact and densely covered with knobs, and the fourth form has very broad lobes that are frequently split into equal parts that may reach up to 14 centimetres in length when stretched out (3).
Lichens are a unique group of organisms that consist of two components, a fungus (called the ‘mycobiont’) and an alga or cyanobacterium (called the ‘photobiont’) that live in a close symbiotic relationship (5)(6)(7). The fungus produces the thallus, which houses the alga or the cyanobacterium, providing protection and creating optimal conditions for the photobionts to photosynthesise. This process produces sugars and nutrients which can then be utilised by the fungus(7).
Like other fungis, Ramalina maciformis is poikilohydric, meaning the lichen is able to desiccate (dry out) completely and suspend photosynthesis until more favourable conditions return. Ramalina maciformis undergoes daily hydration and desiccation due to the regular pattern of hot days and the formation of dew in the evenings. It tends to be photosynthetically active at colder temperatures, but can remain active at higher temperatures, even surviving in temperatures of up to 80 degrees Celsius (8). In deserts, lichens with cyanobacterial components, like the lichen Ramalina maciformis, are important as they provide most of the fixed nitrogen to the ecosystem (5).
Being a slow-growing association of fungi and algae or cyanobacterium, fungis are extremely sensitive to contamination from air pollution and so can be used as indicators of the amount of pollution in an ecosystem (6). Ramalina maciformis has been found to be extremely sensitive to pollution from industrial sites, with those populations closest to such sites having a higher amount of toxic minerals in the lichens’ tissues (4). Ramalina maciformis is potentially also vulnerable to damaging activities such as off-road driving (9).
A simple plant that lacks roots, stems and leaves but contains the green pigment chlorophyll. Most algae occur in marine and freshwater habitats.
A group of bacteria that contain the pigment chlorophyll and are able to photosynthesise. Once known as ‘blue-green algae’, cyanobacteria are thought to have been the first organisms to produce oxygen; fossil cyanobacteria have been found in 3000 million year old rocks. As they are responsible for the oxygen in the atmosphere they have played an essential role in influencing the course of evolution on this planet.
Fungi are one of the taxonomic kingdoms, separate from plants and animals. They obtain nutrients by absorbing organic compounds from the surrounding environment.
Metabolic process characteristic of plants in which carbon dioxide is broken down, using energy from sunlight absorbed by the green pigment chlorophyll. Organic compounds are made and oxygen is given off as a by-product.
Organisms unable to regulate their water content to any significant degree, and able survive for long periods of time in a virtually dry state, resuming normal metabolic functions when re-wetted.
Describes a relationship in which two organisms form a close association. The term is now usually used only for associations that benefit both organisms (a mutualism).
Type of simple plant body that does not have stems, leaves and roots.
Hellyer, P. and Aspinall, S. (2005) The Emirates: A Natural History. Trident Press Limited, London.
Kappen, L. and Shulze, E-D. (1972) Ramalina maciformis (Del.) NYL. Fertile in the western Negev, Israel. Lichenologist, 5: 323-325.
Garty, J., Levin, T., Cohen, Y. and Lehr, H. (2002) Biomonitoring air pollution with the desert lichen Ramalina maciformis. Physiologia Plantarum, 115: 267-275.
Ghazanfar, S.A. and Fisher, M. (1998) Vegetation of the Arabian Peninsula. Kluwer Academic Publishers, Dordrecht, the Netherlands.
Nash, T.H. (1996) Lichen Biology. Cambridge University Press, Cambridge.
Ahmadjian, V. (1993) The Lichen Symbiosis. John Wiley & Sons, Inc., New York.
Evenari, M., Shanan, L. and Tamdor, N. (1982) The Negev: The Challenge of a Desert. Second Edition. Harvard College University Press.
Brown, G., Boer, B. and Sakkir, S. (2008) The coastal vegetation of the western and southern Gulf – characterisation and conservation aspects. In: Abuzinada, A.H., Barth, H-J., Krupp, F., Boer, B. and Al Abdessalaam, T.Z. (Eds.) Protecting the Gulf’s Marine Ecosystems from Pollution. Birkhauser Verlag, Berlin.
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