Photosynthessence: the story
Corn roots secrete toxins with an elegant-sounding name, pronounced benz-ox-ah-zin-oyeds. Although, in corn talk, benzoxazinoids are important enough to use shorthand, BXDs. This class of compounds is well-known among plant-herbivore scientists as a direct defense against the soil-dwelling beetle larvae that attack supporting roots like a behind-the-knee takedown. So, in addition to being biochemically fascinating, understanding and ramping up the ways in which plants can act out of self-defense attracts $$$ and the curiosity to unveil delightful surprises.
For example, my postdoc advisor was a key player in the team that discovered the incredible interaction between corn roots and predatory nematodes. Yes, nematodes, like the genetic lab rats that teach us lessons about metabolism and mutations, C. elegans, nematodes are (everywhere!) in nature, in plants, and in soil, where they eat all manner of living beasts. A beetle larva is only one of the excellent places a predatory nematode, or entomopathogenic (EPN, entomo= insect; pathogenic= infect maliciously) nematodes could enter, release bacteria that kill the beetle before she becomes beetle-shaped, preserving the larval carcass as a nursery for more nematodes to catch more beetles in the act of destroying corn fields. This is all great, but how can microscopic nematodes find tiny beetle larvae in a corn field? Nematodes have a sense of smell, and corn roots have the scents to draw them near. Specifically, roots send out beta-caryophyllene, which is a 15-carbon molecule (one of many plant sesquiterpenes) that floats easily in the air and through air pockets in the soil, guiding nematodes to their beetle dinners. To reiterate how cool this is, beetles chew, plants smell, nematodes hunt. And we humans apply. We apply this interaction to ecosystem scales to understand how nematodes as predators tug on the web of life. And we apply the principles of predation to fields to rely less on noxious pesticides and more on biological control.
Controlling problems with biology sounds great. This idea is what drew me to attend a meeting on “Phytobiomes and plant health: from basics to application”, which is where an important idea crystallized to form my philosophy of photosynthessence on my train ride home.
We pick the same or different seats after the coffee break, all scientists have their own habits. I tend to sit beside potential note-passers. Options seem scarce, however, before the invited talk from a famously-productive expert on BXDs. If benzoxazinoids are toxic to the corn plant's herbivores, what can they do to the microbial communities in the soil? His team manipulated soil treatments and plant genes and in the end, a very simple observation led to the brilliant discovery that sent me spinning. Without being able to make "defensive" BXDs, plants were not as green. Chlorophyll levels were higher in plants able to synthesize root toxins. What? How could the costs of making extra secondary metabolites help plants increase their investment in photosynthetic machinery? Well, the assembly line in the chloroplast transports highly unstable negatively-charged electrons. This angsty dance of electrons is chaperoned by the positive pull from iron. Iron also participates in making chlorophyll, so iron-deficient plants appear less green, just like the BXD-inhibited plants. As it turns out, a paper from the 70s showed that the particular shape and reactivity of BXD-like compounds are perfectly suited to mine iron out of its rock forms in soil. Corn plants extract iron with BXDs! Sure BXDs are also toxic, so which function came first, defense or nutrient acquisition?
While this science was "so two-thousand and eight"(teen), we are so "two-thousand and [che]late": of course photosynthesis drives biochemical production! Maybe in more ways than we even know.
From the train, golden-green light beams across Swiss hillsides in technicolor the way light does during epiphanies. Of course. It has always been about photosynthesis. Not only as an undercurrent in plant resource allocation, but in my own story. I acted out carbon dioxide and sunlight for 6th graders at Outdoor School; I cut out paper chloroplasts and ATPs for my fellow undergrads in peer-led teaching. I listened to the entire audiobook of Lab Girl five times the summer I was defending my PhD with an ever-growing crush on Hope’s ability to research photosynthesis through rocks. Photosynthesis was there on that sunny but cold winter day- what is going on in leaves today? Actually, electrons are excited but the lead singer, RuBisCO is a terribly slow enzyme, so without the ability to turn excited molecules into the bonds of sugar, plants use other pigments as backup singers to avoid the chaos of electrons without a purpose.
My notes scrawl with fragments of delight from the conference. If what I found to be so beautiful about the BXD story and many others was the core chemical reaction of plant biology, the most central to what it means to be a plant is also driving the distinctly flavored and scented and poisonous patterns in nature, then how can I put the scents into photosynthesis? Photosynthescents? And then as my inner voice read aloud, I heard it--a deeper chord than I meant to strike: photosynthessence.
"Essence" is a very hard concept to define because it is the property of a thing that makes it that thing. Essential oils are extracts that encapsulate the aromas of a plant because the secondary metabolism of that plant is so distinctly defining that the oils the plants produce can be a stand-in for the concept of that plant. By putting essence into photosynthesis, I am implying that the ways in which plants engineer chemicals to interact with the world are essentially, inherently, connected to what it takes to make sugars out of light and air.
Plant biochemistry fundamentally influences the function of all terrestrial ecosystems on our planet. There is a narrowing through one biochemical reaction, a filter made of elementary school diagram components: CO2, water, nutrients and light. A plant must navigate its world to achieve these fantastic 4, even when supply falls short of demand. Plants use chemical engineering, such as the BXD-iron example, but also by making organic acids that can work the night shift in order for CAM plants like cacti to do photosynthesis in the heat of the desert, or rather, in the cool of the night. A third photosynthetic innovation involves an architectural remodel and four-carbon-long precursors. C4 grasses feed the world. Plants form symbioses with fungi and bacteria, bartering precious sugars for even more limited resources, nitrogen and phosphorus to make proteins and ATP.
With a name for my biochemical worldview, I immediately deploy the concept as if it were my research steed, destined like in all the fairytales to carry me off into the academic sunset, aka to a faculty position. I search within my datasets for a way to prove that leaf adaptations to maximize light exposure could possibly explain the scent differences between flowers. I write emails to potential postdoc advisors pitching a grant proposal that can "eventually predict secondary metabolism and chemical ecological interactions with greater precision by understanding how plants have adapted to incorporate and allocate raw materials (carbon, nitrogen, micronutrients, etc). My hypothesis is that all interactions are as they are because they work well with the particular requirements of photosynthesis, but understanding the intricacies of which components are limiting or lead to a propensity towards a particular chemical pathway might be a link still missing in plant defense theory." I planned out a life studying the essence of photosynthesis through the scents and flavors of the natural world. I scheduled skype dates to propose how I could test for evidence of photosynthessence, not by measuring photosynthesis directly, but instead, how insects and microbes and other plants respond to the legacy effects, aka the hangover, of photosynthesis, one biochemical reaction to rule them all. But even dressed up in its fanciest academic power suit, photosythessence is not prepared to do this job.
I could force it to continue showing up to work in a blazer, but it seems most at ease in yoga pants. The fundamental problem is that I am lacking a question that I want to answer. I have always lacked a question. Or rather, the opposite: I have never felt like I lack information, being too busy spending as much time and curiosity I reveling in the beauty of what I do know. This is a deep insecurity of mine in calling myself a scientist because if I am not driven to move the earth to discover new data, the implication I tell myself is that is I am not curious, but from experience, I know this to not be true. If there were one question I wish I could imitate, it is Dr. Margaret Wertheim's
"What does it mean that the math is in the world?"
Which, I am realizing as I write this, is Margaret's great philosophical question to understand in her life and it is not an experimental question. Even a mathematician at the lake BBQ last week said,
"Wow. In reality, that is a spiritual question."
So it is entirely unfair that I have subconsciously expected myself to create an equivalent notion through finding the right experimental angle and contortioning data into a philosophy. I literally had the epiphany during my first year of my postdoc that I will never find a research question that can encapsulate the beauty of what it means to be alive. And yet, I continue to strain my mental health by bullying myself to collect enough data to have a voice with substantive authority. As if being qualified enough will give me permission to unveil the spiritual layer of beauty in the world.
Do not get me wrong--I love the intimacy of careful attention. Never am I in closer contact with beauty than after hours of zooming in close enough to count wing veins to name the species of fly. And collecting a rigorous dataset demands sample sizes large enough to spend days in the field of view of the microscope the lets me count antennal segments to know who the fly is I have the pleasure of knowing up close. Seeking out Beech forests across Europe, I witness the same flower open under different canopies. Even in the lab as I click on each scent "peak" in our chemical analysis, the barcode of ions flashes familiar and I know one of the scents that I, and the pollinators presumably, use to smell out that flower. This too, I love.
So what is missing? Why am I flailing to find a Wertheim-level question when I can spend all day with the beautiful phenomena itself, translating ion fragments into scents?
Dr. Robin Wall Kimmerer knew, and she told me via audiobook as I made my pilgrimage across Beech forest longitudes. As a first-year botany student, her equivalent of a math-in-the-world question was, why do Goldenrods and Asters look so beautiful together? But beauty, she was told, is art and not science. Co-flowering, her advisor had the chance to respond with "yes and", sending her to discover how bright yellow complements royal purple in bee vision, making both plants more successful, specifically because of this beauty. Instead, she suppressed her innate relationships with the plants in order to build a proper career in science, only to later discover she had neglected their "songs", wisdom known through traditional knowledge from the plants themselves, which she knew through her familial relationships with nature and her intuition about beauty. She tells the rest of the story while healing my relationship with nature by writing Braiding Sweetgrass.
"When I am in their presence, their beauty asks me for reciprocity, to be the complementary color, to make something beautiful in response."
I want to make something beautiful in response. This is non-negotiably what I want to do. It is what I must bring forth to save myself.
I should reiterate that science does not inherently prevent me from wholeheartedly loving the world. I may very well write a grant next month and fall in love with a new way of collecting data. But even so, no matter how I spend my days, what I do know is that I must protect this philosophy I have brought forth and named. I wanted my own math-in-the world question. And inventing a concept halfway between plant biochemistry and what is essential in life, I feel closer to myself. It was almost secretly spiritual enough that I could disguise that part of me while moving forward in a normal scientific life, uninformed by spirit and beauty. But I have to stop yelling at my data or my day job to be my transcendence. I have to stop avoiding the spiritual because I am afraid I am not allowed a voice without data-supported rigor, for it is precisely the spirit that I ache to know and create. So here I will draw a circle around photosynthessence and, as Joseph Campbell explains and Elizabeth Gilbert resurrects, I get to call everything within that circle, sacred.
And when it is sacred, I am free to explore the beautiful metaphor of what it means to create sweetness from light. Plants literally sustain, sweeten, flavor, and fragrance. And as for us humans, we savor scents and flavors in a forest as in a cocktail and we learn. Each of us holds the potential to support lives, make it all sweeter, and with all of the interesting people I know, we undoubtedly flavor one another's lives. So let us be each other's essential oils, calming soothing, enlivening-- but that demands we first learn the secrets of making our own sweetness, which of course, starts with fine-tuning our ability to sense the light in being alive.