It Takes Two To Tango
From majestic rusty plains dotted with sunken Mars-like craters, to gaping fissures of vivid greens and purples, one wouldn’t expect to find such psychedelic sights here on Earth!
Whether you think they resemble the surfaces of alien planets or simply appreciate the exotic personality they bring to the natural world around us, our planet would not be the same without Lichens.
Better yet, lichens exist almost everywhere on Earth! – From eerie graveyards to rocky coastlines, from sweltering deserts to the frozen plains of Iceland, sooner or later you’re bound to discover the world of lichens at your very fingertips!
But like the saying goes, it takes two to tango.
Lichens are no exception it would seem. Scientifically speaking, lichens are the product of not one, but two different organisms! – That is, they represent a harmonious, symbiotic partnership between an alga and a fungus.
Like Shakespeare’s ‘star struck lovers’, this dynamic fungal-algal duo is almost inseparable, going to great lengths to grow together in the most unforgiving of places.
Nothing is off limits, with leaves, bark, rocks and even other lichens making for prime real-estate.
Many ‘daring’ lichen duos grow as epiphytes (on trees) with some even found dangling precariously from tree-branches.
Like all good relationships, the secret to the longevity of this fruitful partnership lies simply in the fact that both parties mutually benefit from this alliance.
Whilst the photosynthetic alga or ‘photobiont’ supplies its fungal partner with energy-rich photosynthetic products such as carbohydrates (sugars), the fungal filaments ‘heroically shield’ the algae from the harsh dangers of the surrounding environment.
Naturally, with such a myriad of pairings possible between these algae and fungi, and with fungi able to pair with multiple algae, it is not surprising that so many different types of lichens exist!
Generally speaking, lichens are classified into one of four major growth forms:
- Crustose Lichens = These lichens grow closely on the surface of the substrate, forming a ‘crust-like’ layer.
- Squamulose Lichens = These lichens form minuscule scales called ‘squamules‘ which overlap whilst others may resemble loose pebbles aggregated into compact clusters.
- Foliose Lichens = Resemble loose, flat sheets that are not tightly fixed to the substrate or ‘growth surface’.
- Frucitose Lichens = These lichens are proud to be different and really stand out from the crowd! They form upright, branching tubes that protrude from the substrate surface.
But the real burning question is: “How do lichens obtain their outstanding colours?”
For lichens of the standard ‘green’ variety, their colour typically arises from the chlorophyll pigments of the underlying algae located inside the fungal filaments.
On the other hand, some of the more ‘exotic’ lichens owe their appearance to a range of specialised chemical pigments.
- ‘Groovy Orange’ and ‘Bright Yellow’ lichens contain a kaleidoscope of coloured chemical pigments including pulvinic acid, vulpinic acid, pinastric acid and leprapinic acid just to name a few! A study published in 1979 in the ‘Journal of Separation Science’ managed to successfully isolate the numerous acids found in yellow-series lichens.
- ‘Vibrant Red’ lichens owe their startling tinges of red to chemicals called ‘anthraquinones‘
A joint study published in ‘New Phytologist’, conducted in partnership with the Agricultural University of Norway, recently discovered that these additional pigments in lichens provide a degree of UV-protection, such as in the case of the common orange lichen, Xanthoria parietina.