Botanical missfits 1: lichens

Botanists nowadays talk a lot about the concept of "plant blindness" ; this refers to the idea that, despite living surrounded by plants, and depending on them for food and oxygen, many people fail to even notice any of the plants around them. It’s a frustrating thing if you are a botanist, though I don't mean to get in a high horse here, I personally didn’t ever notice even the most obvious plants around me until I got into botany like a year ago.

But plants aren’t the worst victims of this blindness, because, in my humble opinion, that price belongs to the lichen, and it’s not even close.

A lot of people actually don’t even know what a lichen is, which is honestly understandable, most of them look like stains of dried up paint plastered on rock and they aren’t nearly as important economically making them generally easy to miss.

But despite being so inconspicuous,this remarkable group of organisms that covers about 7% of the earth's surface, has one of the most intriguing stories to tell in all of biology and today I wanna talk about that for a while.

Ok, so what is a lichen then? 

As some of you may know, a lichen is not one organism but the result of a symbiosis where fungus provides protection for an algae which in term gives it food via photosynthesis. 

Cool, but that’s just the basic arrangement, since it's been recently discovered that most species also join up with yeasts, which seem to be essential in allowing the partnership to take place. Blue green bacteria or cyanobacteria also can join in, providing essential nitrogen for the rest of the group, forming structures known as cephalodia.

They are thus a bit of a weird thing to categorize as a species simply because it’s not just one thing; one species of lichen is a composite of many different species.

*the cyanobacteria are not always present 

The main body of the lichen, what you can see with the naked eye, are fungal thread like filaments known as hyphae, these threats densely condense into the leathery body, as you can see in the diagram above.

This btw is the same thing that happens in mushrooms as their bodies are not made of true tissue with individual cells but condensed threats, the hyphae, in a weird form of croche.

This threats constitute the main body of most fungi, while mushrooms are just it’s reproductive structures 

On top of providing physical protection from water loss and predators, the fungus also can synthesize chemicals like pigments for protection against the sun (sunscreen basically) or antimicrobials for pathogens like bacteria. 

The algae on the other hand are microscopic and can´t be seen with the naked eye but they are the ones that provide energy for the whole organism (since fungi cannot make their own food but, and need to eat like us animals). 

What’s interesting is that In most cases this algae is perfectly able to live on its own while the fungal partner is fully dependent on it to survive and within the lichen itself algae are somewhat metabolically stressed and completely unable to reproduce, unlike its partner which doesn't seem to mind the symbiosis at all.

This paints a somewhat less harmonious picture of the relationship where the photosynthetic provider is more or less parasitised by its fungal captor which calls the shots in everything. However the benefits of living together are undeniable and the protection allows both members to colonize areas that neither of them could approach alone, and live for much, MUCH longer (the oldest lichen in the world has lived for a fucking jawdropping 8,600 years).

Rather than parasitism or mutualism my favorite way of describing the partnership is as that of a fungus that discovered agriculture (as put by lichenologist Trevor Goward), the same way we humans may control the growth and reproduction of something like corn while spreading it all over the globe, in exchange for sustenance.

It’s a weird friendship, but they make it work :)

And all of these relationships are subject to change depending on the species, because either partner can be dependent on the other, both can be reliant on the symbiosis or both can be perfectly fine on their own or and will join together under some circumstances, a process we don't really understand all that well.

This is not the only unknown when it comes to lichens, unfortunately our understanding of them is kinda poor, since the group is chronically understudied

Their lack of immediate economic interest for the group has generally made it pretty difficult for scientists to get funding for research, however, they have some uses 

Traditionally the main use of lichens has been as a way of monitoring air quality, because they are pretty good at absorbing garbage in the air and different species are sensitive to different pollutants. This means you can tell stuff like the amount of nitrogen pollution around you just by looking at what species are around and how healthy they are. The specifics get pretty elaborate and i did not do as much research into this topic, so feel free to do you research, there’s even a fucking app for this!

More resilient long lived species can also give insight about the changes in certain chemicals in the air in the long term, as seen on the diagram below.

Another thing that has aroused interest in them is their capability for survival, as I’ve mentioned before that lichens are hardy, in fact they are probably the hardiest organisms you can see with the naked eye living everywhere from deserts to tundras , and that of all people has caught the attention of astrobiologist.

Rhizocarpon geographicum is species that grows in northern mountainous regions all around the world, during the freezes of winter, Rhizocarpon will empty all of the water out of its cells and go dormant, allowing it to live through particularly cold times, this is the before mentioned 8,600 year old lichen. In this dormant dried up state it will resist pretty much everything, this resilience has made researchers ask the question they always ask when they see a tough organism, and they  throw it into space. 

In this case they put it through 10 days of the literal vacuum of space and against all odds it came back mostly unharmed, which is making this species a model for life in outer space.

Cities are another inhospitable environment lichens are able to survive in. I’m currently staying in the US to visit family and have been astounded by the amount of urban lichen that can be found around when compared to the Canaries.

Good fucking lord I miss the Canaries.

So, especially now that temperature absolutely nuts and no plant dares flowering i’d advise you to try and appreciate your local lichen diversity, because i can tell you from  experience, you may have never have paid attention to them but once you start noticing them you’ll see lichen EVERYWHERE, so go out and cure that plant blindness, makes the world a bit more fun I promise.

:)