This is a re-post of a blog from 2023, but this time with the new film by WoodlandsTV, in which April Windle [of the British Lichen Society] examines the role of the many complex chemicals found in Lichens. Lichens are plant-like organisms that are rather unusual in that they are an amalgam of two (or occasionally three) organisms : a fungus and algae (or cyanobacterium). They are symbiotic systems, where the partners in the association work together for mutual benefit.  The fungus makes up the bulk of the lichen's form (known as the thallus), it is a complex network of fungal threads (hyphae) that surround the algal cells.  The algae (green algae or cyanobacteria) are essential to the symbiosis as they can photosynthesise, capturing carbon dioxide and providing both partners with organic carbon compounds (often in the form of sugar alcohols). Lichens produce an amazing variety of chemicals - many are secondary metabolites.  It is thought that some of these may  have medical / pharmacological properties.  Some species  of lichen are brightly coloured because of the chemicals.. The colour may vary from a golden yellow to a deep red. The pigments responsible for these colours belong to the anthraquinones.  However, these insoluble, phenolic pigments can have toxic effects. To avoid harm by these pigments, the lichen exports* the pigment from the fungal component of the symbiosis. [caption id="attachment_39795" align="aligncenter" width="675"] Moss and lichen growing together[/caption] The pigment then accumulates / crystallises on the surface of the lichen. The layer of pigment crystals reflects harmful radiation in the form of ultra-violet light and also blue light, whilst still allowing enough light to pass through for photosynthesis by the algae / cyanobacteria. Exposure to ultra-violet light can damage DNA, inducing mutations.  The pigmentl layer is effectively a ‘sunscreen’ for the lichen. * Recent work at Imperial College and RBG, Kew has identified the genes responsible for pigment production, and the transport of the pigment out of the fungal tissue. In the past, certain lichen pigments were often used to dye clothing materials.    Parmelia saxatilis, also known as grey crottle, was used to dye wool for Harris Tweed.  This lichen is often found growing on tree trunks and gives a red / brown colour to the material. For more information on the various chemicals found in Lichens, see the WoodlandsTV film below : The Chemical, Medicinal and Biofluorescent Properties of Lichen. [embed]https://youtu.be/AEc263aQ1rQ?si=00FwDTH5LljetQ0A[/embed] Curious fact : Some specimens of the lichen Rhizocarpon geographicum are thought to have lived for thousands of years.  

The first few weeks of owning a patch of woodland feel like the beginning of a long and special relationship. Every discovery is new; each adventure a first. A wood reveals it secrets slowly.   We’ve already tramped round every corner of the wood, tearing our shins on brambles, sniffing at fungi, clambering round stumps and totting up the oak, hazel, maple, cherry and rowan that thrive under our canopy of pine and larch. We’ve sat and looked and listened in all weathers, at every time of day. Starting a list of birds was the first thing to do: a mewing buzzard overhead, marsh tits pitching in the roving tit flock, the tap of woodpecker and nuthatch. Autumn – though this year so mild and late – soon announced itself with a first skein of pink-footed geese calling high and unseen over the wood, the first redwing chattering at the wood edge… sounds and colours change; the big wheel keeps on turning… We have always loved moths, for their beauty, their ubiquity, their astonishing variety. Moths range in size from the tiny micros whose larvae leave scribbled signatures across the leaves in which they live, to the powerful hawkmoths or that mythic blue-underwinged beauty the Clifden Nonpareil, a creature practically the size of a small bat, and probably the most sought-after moth among the old collectors with, in some years, just a single individual found across the country. For there’s also a rich and often eccentric history of moth recording in this country with most of the larger moths – the macros - having evocative vernacular names (though don’t confuse your Bright-line Brown-eye with a Brown-line Bright-eye!), and an array of techniques for acquiring them from pupa digging, plastering tree trunks with mixtures of treacle and rum, to light. Nowadays, moths are generally photographed and released rather than pinned; recording them is an excellent way of assessing the biodiversity of a site or tracking population changes. It was clearly time to break out the old moth trap.   And so it was that this September for the first time in years we dusted down the generator, filled the trap with fresh egg boxes for the anticipated moths to settle on, spread out our white sheet in a promising looking glade, and hoped to goodness that our 125W mercury vapour bulb would still fire up after all these years… As night came the light shed unfamiliar shadows through the wood; we waited, net in hand, taking care not to look directly at the blazing UV light; waited with a palpable sense of anticipation… what secret would the wood reveal? At first, nothing. And then a first furtive fluttering across the clearing to the trap – probably a Common Marbled Carpet though I’d have to check – and a plumper-bodied moth, and me there wracking my brains: it’s a noctuid, sure, but I’m so rusty – what’s-it-called? Flame? Flame Shoulder? Setaceous Hebrew Character…? ‘What the hell was that?’ said Beth Something ridiculously large had flapped out of the shadows and vanished. Knelt at the trap, I’d glimpsed it too from the corner of my eye. Could it be a hawkmoth on our very first trap, that would be very cool! I grabbed the net; we stood back and waited. I knew we had something beyond the ordinary when Beth yelled ‘There it is!’ and I swung the net and captured it on a second sweep. It was big all right! Anxious not to lose our catch, whatever it was, we shut ourselves in the toolshed and peered into the gently-opening net with our torch… The moth was the shape of a vulcan, practically size of a small bat, and more beautiful than anyone can do justice to: a marbled, lichenous beauty, zig-zagged and pocked and dabbed with greys and whites and blacks and – look! – when those forewings flick open an underwing black and banded with an impossible flash of blue… ‘It’s a Blue Underwing,’ we cried, ‘A Clifden Nonpareil…!’ An entry in my Aurelian’s Fireside Companion describes the experience soberly: ‘For a moment or two we gazed at it in speechless admiration, fearing almost to breathe lest it take flight…’.  I suspect we used a few more expletives than that!   And what a secret to reveal; our first trap in the new wood and we caught probably the best moth we could ever hope to find. One truly without compare.  Soon after the generator packed in; we were plunged into darkness. 2022, it transpires, has been a record year for Clifden Nonpareils, as it has been for many rare moths. Our Nonpareil could have been a wanderer from further south in England where a population has now reestablished itself on aspen and poplar after decades of extinction – or (and I find this the more romantic possibility) it could have been a migrant from the east, flapping its way across the North Sea to our northerly inland wood, and revealing itself, albeit briefly, to its astonished and delighted admirers…  By torchlight, we placed the moth on a tree stump, astounded to see something we’d always dreamt of finding. It sat there for a moment, as though contemplative, then showed a flash of blue petticoat as it shivered its huge and brindled grey wings. Shivered again. And flew off into the night. What will the seasons bring?

Plants make use of sunlight in order to photosynthesise and grow.  However, not all wavelengths of light are useful to plants.  The red and blue wavelengths of light are absorbed by chlorophyll and used in photosynthesis.  Green light is reflected, hence we see green leaves etc.  Another component of sunlight is ultra-violet light.  Whilst UV light can help our skin manufacture vitamin D, it can also do considerable damage to the skin and cause premature ageing and skin cancers.  As this is the case, we are advised to apply sun screen to exposed skin as it helps prevent sunburn, skin cancer and premature ageing.  But what of plants?  Do they also protect themselves from UV irradiation / damage?  Some new research suggests that the plant cuticle has a role. The cuticle is usually a thin layer made up of fatty/waxy material that covers the outside (the epidermis) of the plant.  Its ‘primary’ function is a barrier to the evaporation of water from the underlying tissues.  It also prevents tissues becoming waterlogged as its ‘repels’ rain / water (see headline image) and it also resists the entry of pathogens / micro-organisms.  In most flowering plants, the cuticle tends to be thicker on the top of the leaf (aka the adaxial surface) which is exposed directly to incoming light. Though the cuticle is usually a thin layer, in plants living in arid environments, it can be quite thick to limit water loss. Since the waxy cuticle repels water (i.e. is hydrophobic), the adhesion of water to the cuticular surface is minimised so globules form.  Some plant leaves (eg. Nasturtiums and the Lotus) exhibit ultrahydrophobicity, so that they essentially become self-cleaning surfaces. Now, the rôle of the cuticle in protecting plants from UV damage is unravelling.  Research at the University of Malaga has shown the cuticle can quench UV light.  It does this though the phenolic compounds present in the cuticle.  Phenolics are rings of carbon atoms, with hydroxyl (OH) groups attached.  Examples are the cinnamic acids [e.g. p-coumaric acid]. When these molecules absorb UV light, they change shape momentarily.  On changing back to the original state, the absorbed energy is released but at a longer wavelength, which is far less damaging than UV light. As these molecules do not react this way to red and blue light, the red and blue wavelengths can pass into the leaf to be used in photosynthesis. [caption id="attachment_38494" align="aligncenter" width="700"] The leaves of some plants have quite amazing surfaces, some are hairy whilst others have protective spines.,[/caption]

Flowers have various ways of tempting pollinating insects to visit them.  Indeed, some have very complex mechanisms to promote pollination and fertilisation, for example, the bee orchid.  In order to attract pollinating bees, the orchid has evolved “bee-look-alike” flowers.  These draw the bees in with the “promise of sex”.  They attempt to mate with the flower, landing on the velvety lip of the flower and pollen is transferred.  The bee leaves ‘frustrated’.  However, the right species of bee doesn't live in the U.K., so here bee orchids self-pollinate. Read more...