It was a barren world. Dark igneous rocks, treacherously jagged and raw from the relentless battering of the wind and rain, spanned across the land. There may have been a flash of blue or a tint of orange nearby some hot sulphuric volcanic spring, evidence of small colonies of bacteria thriving on an otherwise inhospitable planet. Sharp objects of varying sizes smashed against each other in storms, constantly moving across this harsh, barren landscape. The only thing that stilled this ceaseless bombardment of solidified lava was water, where the sediment finally settled to rest.
This is no alien planet. This is Earth in the Late Ordovician, somewhere around 450 million years ago. Here the land was without plants. No roots to hold down the broken rock fragments. The planet was empty. Almost. Beneath the calm warm waters of the seas, there lay a hidden world teaming with life. Beautiful, enigmatic creatures of the most delicate and bizarre shapes darted through the water as if it were air, while below others scurried to hide beneath the soft sediment. Long, spindly sea lilies drifted back and forth while armour-headed fish swam past. Trilobites with elaborate spines poking out here and there swam gracefully, effortlessly over the sediment, whilst hidden under their hard outer shell, dozens of little legs kicked furiously.
Clinging to the water’s edge were seaweeds; thin, floppy red and green seaweeds that were periodically exposed to the baking heat of the sun by the fluctuating tide. Liverworts were around too: flat with green, translucent lettuce-like leaves, but a closer affinity to algae than plants, protected by water, venturing only a few tens of metres from the edge where they had the safety of incoming tides or regular flooding.
Perhaps the greatest event ever to have happened on our planet was when plants adapted to life on land. Walking through thick woods, where trees are covered in moss and lichen, where we can smell the wild garlic around us while watching bees and dragonflies zip through the dappled light, or sitting on a hill overlooking endless rolling hills of luscious green grass, would not be possible if it wasn’t for this event. For starters, you wouldn’t be here reading this.
But it was no easy move for our very distant relative to get a firm grip on solid land. One woman has spent her life studying just how this happened, and what it meant for life on Earth.
Professor Dianne Edwards (born in 1942) is a research professor at Cardiff University. Born in the coastal city of Swansea, Professor Edwards spent much of her youth enjoying and exploring the spectacular Gower Peninsula. With gorgeous turquoise waters, unspoilt clear sandy beaches, and gloriously green grassy cliffs, this is a stunning part of the world. And clearly an inspirational place too. After completing her undergraduate and doctoral degrees at Canterbury University, she went on to lecture at Cardiff University. Here, she teaches undergraduates, and supervises postgraduates whilst continuing her research into the evolution of land plants.
Since 1965, Professor Edwards has been publishing articles about early plants. From the anatomy of some of the earliest plants, to 400 million year old fossilised millipede poo, she has helped shape our understanding of these early ecosystems of the land as plants took a firm hold. One exceptional site stands out, with evidence of these colonies of cells we take for granted every day. And Professor Edwards has studied them in detail.
The picturesque quaint village of Rhynie, Aberdeenshire sits on top of sediments that are over 400 million years old. Known as the Rhynie Chert, this is a frozen glimpse into the past when things were beginning to happen on land for the first time. To hold the Rhynie Chert in your hand, you would see a light grey rock with splashes of a slightly darker grey. Not so impressive. But slice it up, grind it down until it is wafer thin, and press your eyes against the microscope, and evidence of a lost world is brought to life. Cross sections of tiny plant stems lay there, along with mites, early spiders and arthropods. You will see something else too: small balls with clear structures to them. These little balls are one of the keys for colonising the land.
Land plants (Embryophytes) all produce spores (or the more familiar pollen equivalent). Looking for these microscopic reproductive balls is what Professor Edwards did. And with good reason: their very presence provides clues as to how the first plants arrived on land.
Professor Edward’s zeal for understanding early plant life never wilted. After 50 years, her publications are still going strong. She studied the fossilised tissue of Cooksonia (named for #trowelblazer Isabel Clifton Cookson!), a very early genus of land plant from the Silurian, around 430 million years ago, which she discovered was the earliest plant with vascular tissue. Peering through her trusty microscope, Professor Edwards also analysed the essential adaptation for survival; the teeny, tiny holes on plant leaves which allow the plant to exchange chemicals without being drowned by the rain or scorched by the sun: the stomata.
As well as a founding fellow of the Learned Society of Wales, and its inaugural Vice-President for Science, Technology and Medicine, Professor Edwards is also the President of the Linnaean Society. Keen on sharing her passion for botany through education activities, she was one of the founders of the National Botanic Gardens of Wales, for which she received her CBE in 1999: here people can explore the parks and find out more about plants. Nature is more beautiful the more closely we look.
Written by Jan Freedman, who says:
“There are those teachers at school and University that make a real impact on you when you are growing up. More often than not, we do not get the chance to really thank those inspirational people. In my undergraduate palaeontology modules at Cardiff University, I was extremely lucky to have been taught by Professor Edwards. Whether in a practical lesson peering down a microscope at fossil spores, or engaging with her class about the first incredible plants, to us, Professor Edwards was a legend. We all were astounded by her endless knowledge and her ability to share her enthusiasm and passion onto her students so we understood it with ease. We all knew. But she never did. Because we never told her how amazing she was. Or that she was inspirational. Or that after a lecture she gave, we got it. Until now. It is never too late to say thank you. From a student of yours you very likely never knew (1999-2002), thank you Professor Edwards.”
Edited by Suzie
Images provided by The Royal Society and Dianne Edwards and used with permission.