Yellow Witch’s Hair lichen (Alectoria sarmentosa) growing in the Babine Mountains. (Jim Pojar photo)

Yellow Witch’s Hair lichen (Alectoria sarmentosa) growing in the Babine Mountains. (Jim Pojar photo)

The Nature Nut

Rosamund Pojar

Lichens are some of my favourite organisms. It is estimated that six to eight per cent of the earth’s surface is covered by lichens and they are found growing on all different types of substrates. When, and if, we get some rain the lichens will rapidly suck up the moisture and become more obvious.

A lichen (pronounced LY- ken) is a complex organism composed of algae and/or cyanobacteria (blue green ‘algae’) living within a tangle of fungal threads (or hyphae).

Lichens can withstand considerable drying. The fungal threads (hyphae) wrap around and help to protect the algal cells from desiccation and subsequent death. The algae carry out photosynthesis and produce starches and sugars (food) for the fungus. So, by living together, they benefit each other in a mutualistic association called symbiosis. Both partners get their water and minerals largely by absorption through their surfaces.

We are not exactly sure how the fungus and algal cells come to live together, but some think that the fungi are actually “farming” the algae. Lichens come in many colours from bright green to brownish or black in moist places and yellows, reds, oranges, and browns in drier habitats

There are lots of different lichen growth forms, but the three main ones are as follows.

Crustose lichens are very flat and crusty and difficult to remove from their substrate e.g., tree bark, rocks, soil, etc. Look closely at the trunk of an aspen tree. The crusty areas that are not smooth and silky like the tree’s bark are lichens.

Foliose lichens are flattened with a distinct upper and lower surface – often a different colour. They can be easily removed from their substrate.

Fruticose lichens do not have a distinct top and bottom but tend to grow either upright like miniature bushes or hang downwards as a mass of tangled threads. They are also easily removed. See the photo of the hanging fruticose Witch’s Hair lichen.

Reproduction can be vegetative (asexual) where a small clump or ball of fungal and algal cells separate from the parent plant. Sexual reproduction also occurs by producing spores in various fruiting structures which are often smooth flat, or slightly cup-shaped, disc or as bumps or squiggly lines. Often, they are a different colour than the lichen itself.

Lichens can be eaten (with care), used as a source of dyes, used for air pollution monitoring, can fix nitrogen and are important in many other ways.

Contrary to somewhat popular opinion, lichens do not kill conifer trees but only grow on dead branches. I will talk about some uses of lichens next week.

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