Tag Archives: DNA

Living light: the crucial miracle of photosynthesis

Maple leaves and ferns in the forest on Peterson Bay, Homer, AlaskaTo love plants is to be in awe of photosynthesis. Even when you know how it works, it’s still a miracle. And a crucial, we-wouldn’t-be-here-without-it miracle. Its ramifications are so vast that once it showed up, it dictated all of the evolution that followed.

It’s also complicated. There is, for example, a catalyzing enzyme involved called ribulose 1,5-bisphosphate carboxylase oxygenase, with a personality as confounding as its name. Mercifully, we don’t need to go fully into those weeds. For most of us, it’s magic enough to know that somehow sunlight turns into sugar. But it’s so fascinating that I’d like to invite you to take a walk with me through this lovely, cool forest, and on out into the history of life on earth.

Photosynthesis happening in a forest in the Wynn Nature Center in Homer, Alaska by Betsey Crawford

We’re walking in a sea of green because pigment molecules called chloroplasts in the tree leaves and fern fronds absorb all color wavelengths except the green ones. Those are reflected off the plants, and the highly sensitive cones in our eyes pick up the wavelengths and relay the information to our brains. So we see soothing, cooling green, a color widely associated with the serenity surrounding us in this quiet woodland.

Yet, every leaf and frond around us is pulsing with activity. Photons from sunlight hit the chloroplasts and their energy gets moved from one pigment molecule to another until it reaches special molecules in interior cells. There the energy excites electrons, which makes them pop into orbitals farther from their nuclei. Full of verve, these animated electrons start a cascade through surrounding, helper molecules, creating energy that pulls hydrogen ions into the center of the cell. 

Intense green leaves of red monkey flower (Erythranthe lewisii) and false hellebore (Verastrum viride) mean more photosynthesis. Photo by Betsey Crawford

Red monkey flower (Erythranthe lewisii) and a huge leaf of false hellebore (Verastrum viride). Most of the photos accompanying this post are from the north, where leaves are large and intensely green to capture all the light they can during short summers.

Missing electrons need to be replaced, and this first part of the process replaces them by splitting water molecules and grabbing electrons from the hydrogen atoms, whose remaining ions join the gang in the center of the cell. The oxygen disperses through the stomata, holes in the leaves that open and close as needed. This is the oxygen we breathe. The carbon dioxide we have been exhaling then floats into the stomata to be used in the next part of the cycle.

As the hydrogen ions in the cell’s center get more concentrated, they immediately want back out, pushing their way through an enzyme that creates ATP, the same energy storage molecule that our mitochondria create for us, by a similar electron process.

A wild flower meadow on Hudson Bay Mountain in Smithers, British Columbia., showing the wide variety of leaves for photosynthesis even in one small area.. Photo by Betsey Crawford

A wild flower meadow on Hudson Bay Mountain in Smithers, British Columbia., showing the wide variety of photosynthesizing leaves even in one small area.

Having run through their energy, these electrons enter a new cycle where they are re-energized by more photons to create NADPH. Thus the electromagnetic light energy from the fusion reaction in a star 93 million miles away becomes chemical energy in microscopic cells brushing our shins as we walk, along the way providing the oxygen we need for life. 

The chemical energy — NADHP and ATP — is then used by another process to take a gas — carbon dioxide — from the air and convert it to a solid state in the form of carbohydrates, which are strings of carbon molecules of varying complexity. (This is where the catalyst with the endless name comes in.) Thus carbon dioxide turns into food, as well as being ‘fixed’: removed from the atmosphere and stored in plants. This is why preserving and replanting forests are crucial to reversing global warming.

Prairie grasses in the Pawnee National Grassland, Colorado

Prairie grasses in the Pawnee National Grasslands, Colorado

There are variations in the whole process, even in the woods. The leaves at the top of the trees, in the full glare of the sun, are likely to be smaller and thicker than the understory leaves. That way they protect themselves from the full force of the sun’s energy. The lower leaves tend to be larger, thinner and more horizontal, and the ferns grow many wide fronds, allowing them to catch all the photons they can from the sunlight filtering through the treetops. Because it tends to be cool and moist in the woods, photosynthesis carries on with little hitch.

Once we walk out of the woods into a meadow of grasses, there are challenges that require further variation. In the cool, damp spring, grasses are in heaven, soaking up water and sunlight, feeding their blades and roots, developing seeds. Once summer brings its hot, dry weather, many grasses go dormant until fall or even the next spring. The ones that don’t, like the sturdy crabgrass in your lawn, have adopted photosynthetic habits that allow them to keep going in heat and aridity.

Engelmann's prickly pear cactus (Opuntia engelmannii) in Saguaro National Park, Tucson, Arizona by Betsey Crawford

The pads of cacti are modified stems which do the photosynthesizing. The spines are modified leaves, holding air around the flesh to protect it from the sun. This is an Engelmann’s prickly pear cactus (Opuntia engelmannii) in Saguaro National Park, Tucson, Arizona.

If we walk further on, into the desert, the problems of heat and dryness become acute. Desert plants, like cacti and agave, want to keep their stomata closed during the day to preserve water. Instead, they open them as the evening cools, and have evolved a way to take in and store carbon dioxide in the form of malate at night. This they turn into ATP and NADPH during the day, with their stomata closed. It’s a far less efficient way to provide energy for the plant than the photosynthesizing in our woods, which is why desert and other succulent plants grow so slowly.

In addition to helping maintain the appropriate levels of oxygen and carbon dioxide in our fragile atmosphere, plants nourish themselves and the entire living world. We breathing creatures are carbon-based life: carbon forms the backbone of every molecule in our bodies. We’re entirely dependent on plants’ ability to take the carbon dioxide from our own respiration and not only replace it with the oxygen we need but also to offer those carbon molecules to us in edible forms. That’s what allows us to make our own ATP to fuel this lovely walk among the chloroplasts. Photosynthesis is the most important biochemical process on the planet.

Pacific rhododendron (Rhododendron macrophylla) in Rhododendron Park on Whidbey Island, Washington. Evergreens can perform photosynthesis all year, but are much less efficient in winter. When cold enough, the process can shut down altogether. Photo by Betsey Crawford.

Pacific rhododendron (Rhododendron macrophylla) in Rhododendron Park on Whidbey Island, Washington. Evergreens can photosynthesize all year but are much less efficient in winter. When cold enough, the process can shut down altogether.

Given its importance, it’s no surprise that it showed up relatively early in the earth’s life. Early forms of photosynthesis are thought to have begun about 3.5 billion years ago, its various systems developing over time. Chloroplasts didn’t evolve until 2.5 billion years ago. When photosynthesis began, there was little free oxygen on earth. Early practitioners were microscopic, anaerobic bacteria, most likely using hydrogen sulfide, better known as swamp gas, to do their work. 

About 2.4 billion years ago, oxygen released by photosynthesis began to build up in the atmosphere, leading to what is known as the Great Oxygenation Event. The existing bacterial species weren’t adapted to it and began either to die out or find their way to anaerobic environments. With the evolution of mitochondria, which essentially use oxygen the way chloroplasts use carbon dioxide, species were able not only to adapt but to harness a much stronger energy source. Fueled by this huge boost to metabolism, life on earth blossomed into ever more diverse and complex life forms and ecosystems.

Salmonberry (Rubus spectabilis) in Brandywine Provincial Park, British Columbia by Betsey Crawford

Salmonberry (Rubus spectabilis) in Brandywine Provincial Park, British Columbia

Besides our dependence on plants, there are a lot of wonderful connections among us. We all inherited our carbon from the very beginning of the universe, when the first particles coalesced into mighty mother stars who, with their enormous heat and compression, made the elements that form every subsequent thing. When we give a baby a fresh string bean to munch on, we’re watching 13 billion-year-old carbon join forces in ever new forms.

We share up to 25% of our DNA with plants, remnants of our ancient, shared bacterial ancestors. Mammalian hemoglobin and plant chlorophyll have the same chemical composition, though where hemoglobin is built around iron, chlorophyll uses magnesium. When we eat chlorophyll, it helps hemoglobin with its work of cleansing and strengthening our blood and increasing oxygen uptake. Chloroplasts and the mitochondria we share with plants have a similar history. Each formed when separate species of bacteria found it so worthwhile to join forces that they’re still at it, one cell inside the other, all while wrapped in their own membranes and keeping their separate DNA. Perhaps the most successful mergers of all time. Both make ATP — adenosine triphosphate — the fundamental fuel of the breathing planet.

Ferns in this woods in British Columbia catch the last light of day. Photo by Betsey Crawford

Ferns in this woods in British Columbia catch the last light of day.

Evolution has no need to keep inventing the wheel. If the DNA we inherited from those ancestral bacteria still work, great! If the methods of producing energy work for plants, why not animals? The same plans get reused, with some evolutionary tinkering. Because our building blocks came from those ancient mother stars, people like to say that we are stardust. Via photosynthesis, we are sunlight. Between the systems we inherited from and share with plants and the fact that they ultimately become part of every cell in our bodies, you could also say we’re recycled plants. An idea that, while not quite so lofty, thrills me no end.

It’s all a marvel. I breathe out carbon dioxide and it’s returned to me nicely packaged in carrots, apples, beans, sweet potatoes, squash. Amazing! The history is stunning, all the way back to the carbon formed at the beginning of the universe. We owe thanks to photosynthesis, and its introduction of atmospheric oxygen, for all the blooming, breathing life everywhere on the globe. We owe it every minute of our lives, every thought we have, every bite we eat, every breath we take, every flower and creature we treasure. I love the science that explores and tracks and theorizes about how this fascinating process operates. But ultimately, we are left with wonder. The whole parade is one miracle after another.

Blue clematis (Clematis occidentals) in Waterton Lakes National Park, Alberta, Canada by Betsey Crawford

Blue clematis (Clematis occidentals) in Waterton Lakes National Park, Alberta, Canada

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Transcendence on the headlands

Douglas iris (Iris douglasiana) taken at King Mountain, Tiburon, California by Betsey Crawford

Douglas iris (Iris douglasiana)

One of the most transcendent moments of my life happened on the Marin headlands, within view of the glittering city of San Francisco and the elegant curve of the Golden Gate bridge. It was March 9, 2014, and the wildflower season had started. I had been hiking and photographing them for three hours, working my way uphill, out of sight of the ocean. I’d come through a variety of landscapes: the mostly dry meadows at the beginning of the hike, full of California poppies, cut through by a stream that gave willows a foothold. Then the rocky ups and downs of the even drier hills, their gravelly trails edged with pockets of shooting stars and milk maids. As I got closer to the juncture with the coastal trail, chaparral gradually took over, filling the air with the pungent smell of sagebrush.

California poppy (Eschscholzia californica) Golden Gate National Recreation Area, California by Betsey-Crawford

California poppy (Eschscholzia californica) Golden Gate National Recreation Area, California

By the time I got to the top of the headland, tired, ready to head downhill and find my car, it was dusk. The Pacific, living up to its name, lay serene and luminous ahead of me. In memory, the city isn’t there. It was all silver light, on the rolling hills behind me, the pale gray twilit leaves, the stone escarpment in front of me, on the  sea, in the air. The warm spice of the feathery sage filled me, contrasting with the cool light.

Blue-eyed grass (Sisyrinchium bellum) taken at Terra Linda Open Space Preserve, San Rafael, California-by-Betsey-Crawford

Blue eyed grass (Sisyrinchium bellum), Terra Linda Open Space Preserve, San Rafael, California. Each flower is about the size of a quarter.

As I began to move again, I was suddenly overcome with the wildness of the place, and my place in it. Completely aware of this living, breathing convergence of life — the soft wind off the shimmering ocean, the ancient rocks, the growing dark, the scent from the ghostly plants, the woman walking. I was both dissolved into it and moving, whole, embodied, through it, a wild creature myself. I felt a great, exultant love for every pulsing molecule around me, and equally for the feeling of being in it, part of it, the part that could move through itself, through the lingering heat and the cooling breeze. That could feel the silver light work its way through my cells.

California buttercup (Ranunculus californicus) King Mountain, Tiburon, California, by Betsey Crawford

California buttercup (Ranunculus californicus) Ring Mountain, Tiburon, California

I would love to live in that state of open-souled awe every moment of my life. All sorts of things — grocery store lines, traffic, dentist appointments, the grief at a loved one’s illness —  work against such a possibility. I am often, in the poet Wordsworth’s words, surprised by joy; but after opening his poem with that line,  the rest speaks only of loss. Transcendence routinely rises, and is swept away by the mundane. The memories — I still remember another night of silvery, windy light under a full moon when I was 18 — can stay a long time. And there are many small, seemingly inconsequential moments of joy — a sleepy child’s arms around your neck, sunlight filling a winter room,  the sudden call of cicadas, telling you midsummer has arrived. But feeling completely dissolved into the natural world I love so much is rare, and I have been hugging that moment since.

Blue dicks (Dichelostemma capitatum) taken at King Mountain, Tiburon, California by Betsey Crawford

Blue dicks (Dichelostemma capitatum) Ring Mountain, Tiburon, California

Though perfectly happy to feel transcendence without figuring out why we have this wonderful ability, as a lover of all things DNA I am intrigued by philosopher and psychologist Nicholas Humphrey’s theory that awe has been chosen by evolution to more firmly attach us to life on this earth. The more delight we take in living, the more we will strive to survive and reproduce. He feels that our pleasure in being alive and connected to the beauty and enchantment around us is the basis for an innate spirituality, something we knew long before we created religions to explain it.

Western columbine (Aquilegia formosa) Golden Gate National Recreation Area, California by Betsey Crawford

Western columbine (Aquilegia formosa) Golden Gate National Recreation Area, California

I’m a little resistant to reducing awe to the biological imperative to reproduce, though I love the idea that evolution would choose something so entrancing to ground us to our planet. I prefer the thought — echoing cultural ecologist Thomas Berry, Buddhist Alan Watts, cosmologist Carl Sagan — that consciousness is the result of the long, slow evolution of the universe’s ability to contemplate itself, to turn eyes on its wildflowers and silver seas, ears to its birdsong and rushing water, skin to the feel of stone, of bark.

Milk maids (Cardamine californica) Golden Gate National Recreation Area, California by Betsey Crawford

Milk maids (Cardamine californica) Golden Gate National Recreation Area, California. The individual flowers are the size of a dime.

But even this lovely thought doesn’t quite reflect what I felt that evening on the Marin headlands. I didn’t feel that I was the universe reflecting on itself, I felt like I was the universe. And not merely one infinitesimal expression of it. And not — though I love this fact — that I and the radiant molecules around me were all made of the same elements, descended from the same stars. I felt, briefly and gloriously, that there was no distinction between me and the vast, wild, perilous, gorgeous cosmos.

Checkerbloom (Sidalcea malviflora) King Mountain, Tiburon, California by Betsey Crawford

Checkerbloom (Sidalcea malviflora) King Mountain, Tiburon, California

I’d love to have you on the journey! If you add your email address, I’ll send you notices of new adventures.

Spruce family planning

One of the first things we noticed when we drove into Alaska in July was that vast stands of spruce — and Alaska is full of vast stands of spruce — were dark brown at the top. Seeing them from a distance, as we drove through a valley, we wondered if they were suffering from a disease that was killing them from the tips. When we got closer, we realized they were laden with cones. At first, I assumed this was a normal approach to long summer days, but found, on a guided walk through the Wynn Nature Center in Homer, that 2015 was a mast year for white spruce.

White spruce (Picea glauca) with many cones during a mast year in Alaska. Photo by Betsey Crawford

Female cones tend to cluster toward the top of the tree, in this case white spruce (Picea glauca).

Mast refers to the products of trees — cones, acorns, catkins — and many species have mast years, when they produce an above-normal abundance of seeds. Spruce cones are the primary food of Alaskan red squirrels. The squirrels live on the forest floor, digging tunnels under and around the roots of the trees, where the cones can fall right at their doorstep. They eat the seeds at the base of the female cone scales, tossing the rest of the scale and the remaining ‘cob’, out their front doors, where the ever-mounting detritus becomes a whole environment in itself.

The den of a red squirrel (Tamiascuurus hudsonicus) in the roots of a white spruce (Picea glauca) by Betsey CrawfordEvery few years, to keep ahead of the voracious squirrels, who can each hoard up to 9,000 cones a season, the trees produce extra cones. When our guide, Ruth, was telling us this, we joked that spruce had family planning all figured out. And that got me thinking about what we actually meant by those light words. What had they figured out? How had they figured it out? What in the spruce had ‘noticed’ that producing more cones every few years meant they could insure enough offspring without spending the energy to produce extra cones every year?

redsquirrel_looking_over_shoulder

Thanks to the Alaska Department of Fish and Game for this photo. No squirrel would stand still for me.

We know, if only from watching our dogs go into a decline the second we pull out a suitcase, that animals have consciousness and an emotional life. We don’t put it on a par with our own, and don’t, as a rule, apply any concept of consciousness to plants, though there is a growing, and utterly fascinating, body of work dedicated to exploring what plants know and feel.

In my work as a landscape designer, I would ponder why gardens grew better for some people and not others, given that their care was basically the same. I had a client who was extremely ornery. I learned quickly to call him in the morning so I didn’t run into his afternoon drinking. Despite a sense of humor and a certain amount of charm, he could be hard to be around. But his landscape was one of my all-time favorite jobs. He was an artist and a bon vivant. He loved beauty. He had been a photographer for Life magazine, and his house was full of lovely things from all over the world. His garden, despite his routine grumpiness, grew like mad.

The leafy den of a red squirrel (Tamiascuurus hudsonicus) in the roots of a white spruce (Picea glauca) by Betsey Crawford

I loved the different decors that went with squirrel doors.

A counterexample was a couple in their thirties, successful professionals, extremely nice, though not necessarily warm or charming. Their house was rather bleakly furnished. Every time we met, they both stood with their arms tightly folded the entire time. Their garden did the same thing. It dutifully grew, but it never took off into the kind of riotous abundance that my ornery client’s did.

Another couple with whom I worked for many years started out with a garden that grew grudgingly for a while. But, after both successfully recovered from cancer, it was fascinating to see how they and their garden changed. My clients seemed more at ease, more open. They renovated their house and painted every room a different luminous color from the sea and sky outside. Their garden grew more and more luxuriantly, and even unusually deep in color.

Blue flowers in an East Hampton, New York, garden. Designed and photographed by Betsey CrawfordThough the idea of sharing a doctor’s waiting room with a bunch of plants has enormous appeal, spruce will clearly never follow our example on family planning: make appointments, discuss options, get a prescription, go to a pharmacy, remember to use whatever we get there. Instead, every few years, usually following a warmer prior summer, they will produce extra cones. To do this they have to ‘know’ something. To grow riotously for one person and not for another indicates a capacity to respond. To grow toward the light indicates a capacity to see. Plants don’t have the neurology we use to translate vision into images, as far as we know, but the chemical process is not that far from our own, and some of the genes that direct it are the same. Nature can’t be bothered to give every living thing its own personal set of genes, so both humans and plants have inherited genes from our common, ancient, bacteria ancestors.

Many dens of red squirrels (Tamiascuurus hudsonicus) in the roots of a white spruce (Picea glauca) by Betsey Crawford

Squirrel apartment building

I love all this because I love to contemplate our interconnectedness. I love the idea that I am, literally, in the same family tree with the spruces I pass on my hike. That I share up to 80% of my DNA with the squirrel chittering at me, up to 25% with the branch she sits on and the cone she’s about to hide. The ferns brushing my shins, the moss on the edge of the path, the fungal mycelium strands winding through the soil under my feet — these are all kin, descendants, like me, of our unicellular forebears. And, as carbon-based forms, we are all descendants of the earliest stars, whose death launched carbon into the universe.

We live in a world where we differ from all other humans across the globe by less than 1% of our DNA. Nevertheless, we’re having a hard time convincing our very tribal selves that we are all related. Given that challenge, seeing spruce trees and squirrels as family may seem like a low priority. But I find that feeling embedded in the life force that is also the forest makes it easier to remind myself, in the constant brush of personality that makes up everyday life, that underneath our wide-ranging but superficial spectrum of differences, we are all — every one of us — intimately connected.

White spruce (Picea glauca) cones on the forest floor during a mast year in Alaska. Photo by Betsey Crawford

 

 

I’d love to have you on the journey! If you add your email address I’ll send you notices of new adventures.

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