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Tea and Terps · Episode 1
The first episode: Nik brews his favorite tea in the world, a single-tree Phoenix oolong, then reads a paper that asks why plants trust carbon to an enzyme that looks broken.
The cup
Nik opened the series with what he calls the best tea he has ever had: Danhu Old Bush, a Phoenix oolong from Danhu village on Phoenix Mountain in Guangdong. Every leaf comes from a single old tree, picked once a year in spring over a window of a few days, and it gives only a few pounds of tea.
Phoenix oolongs are named for their fragrances, honey orchid and night-blooming jasmine among them, and Nik traces their craft back roughly nine hundred years on this one mountain. The making takes a great deal of work: plucked at midday in the sun, rattled through the night to bruise the leaf edges, pan-fired, rolled and then roasted over charcoal, sometimes for months.
What Nik noticed
Special notes
A spring harvest from a single old tree. Nik has followed this same tree across several vintages.
Nik's picture for oxidation is a sliced apple browning. Rattling bruises only the edges of an oolong leaf, so it opens with reddened margins around a green center.
Chapter by chapter
Press any time to play the episode from that moment. While it plays, the chapter you are in lights up.
Rubisco
The paper Nik reads, Abir Igamberdiev's 2015 article on the control of Rubisco, opens with a puzzle. Rubisco is the enzyme that fixes carbon dioxide into sugar, and it is the most abundant protein on Earth. It is also slow, managing only about three reactions a second, and it cannot fully tell carbon dioxide from oxygen. Grab oxygen by mistake and the plant has to spend energy cleaning up.
A lot of scientists have concluded that Rubisco needs redesigning, faster or choosier, and some engineering work has produced real gains. Nik disagrees with that conclusion. The paper argues that Rubisco only looks broken when you study it on its own: wired into the fast enzymes that feed it and the photorespiration that protects it, the whole system works well.
The point here basically is that Rubisco seems really slow and sloppy.
Nik
| Compared | Rubisco | Carbonic anhydrase |
|---|---|---|
| Its job | Fixes CO2 onto a five-carbon sugar | Turns CO2 and bicarbonate into each other |
| Speed | Less: About three reactions a second | More: Up to about a million a second |
| How common | The most abundant protein on Earth | A family of zinc enzymes in every leaf |
| In the paper | The slow engine | The fast supply line |
Carbon supply
The textbook picture has carbon dioxide drifting in through the stomata and straight into Rubisco. The paper argues for something more deliberate. In a leaf, Rubisco outnumbers the CO2 around it by two to three orders of magnitude, so the enzyme cannot be waiting on stray molecules from the air.
Instead, much of the carbon dissolves into the cell's water, a large share of it as bicarbonate, and carbonic anhydrases, among the fastest enzymes known, turn it back into CO2 right where Rubisco needs it. The paper ties that release to the splitting of water in photosynthesis, so electrons, protons and carbon arrive together. Nik presents it the way the paper does, as a well-argued hypothesis rather than settled fact.
maybe it's a multi-step operation where the plants are first solubilizing passively
Nik
The route the 2015 paper argues for. It is a hypothesis about how the supply is controlled, not a fertilizer trial.
Oxygen
Life in sunlight and oxygen is harsh. The air holds about 209,000 parts per million of oxygen and only about 420 of carbon dioxide, so a plant spends its days pulling a trace gas out of an atmosphere that is constantly trying to oxidize whatever it builds.
That is why Nik refuses to call photorespiration a mistake. When CO2 runs short and light keeps pouring in, Rubisco's work on oxygen gives the energy somewhere to go and recovers much of the carbon, instead of letting electrons back up and damage the leaf. His comparison is a car: better to spin your tires than to break an axle.
would you rather burn your tires or break your axles?
Nik
Parts per million in dry air, drawn to scale. The carbon dioxide bar is that thin.
Carbon
Weigh a dried plant and almost half of it is carbon. Nitrogen, phosphorus and potassium together make up a few percent. Nik's point is that a plant is not chasing those nutrients for their own sake: nitrogen and magnesium build chlorophyll, phosphorus carries energy, and the whole machine exists to catch sunlight and store it in carbon.
His larger claim, the thesis of the series, is that plants navigate an energy landscape rather than an NPK one. They use the elements as tools to capture, move and hold energy, and the carbon compounds they build, sugars, organic acids and terpenes, are where that energy ends up.
So plants are obsessed with carbon.
Nik
Typical shares of a plant's dry weight (Epstein's classic figures; species vary). Most of the oxygen and hydrogen is built into the same carbon compounds.
Real structures
Five molecules from the episode, rendered from real PubChem geometry rather than drawn. Pick one to read why it matters, then turn it in three dimensions.
The five-carbon sugar Rubisco attaches CO2 to. The six-carbon product splits at once into two three-carbon molecules, which is why plants like tea and cannabis are called C3 plants.
Structure data: PubChem open chemistry database
When Rubisco takes oxygen instead of CO2, it makes a two-carbon fragment that the plant turns into glycolate and walks through photorespiration, recovering most of the carbon along the way.
Structure data: PubChem open chemistry database
How fixed carbon travels. Leaves load it into the phloem and ship it to roots, flowers and fruit, as energy and as building material.
Structure data: PubChem open chemistry database
The most abundant catechin in tea. When a leaf's edges are bruised, the browning enzyme turns catechins like this into the reddish compounds that color an oolong's margins.
Structure data: PubChem open chemistry database
One of the floral terpenes Nik names in Phoenix oolong. Tea leaves hold much of their aroma bound to sugars, and processing frees terpenes such as linalool, part of why a Phoenix oolong fills a room.
Structure data: PubChem open chemistry database
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The foundation
Nik ends the carbon story with what depends on it. Using sunlight to pull electrons from water and fix carbon in an atmosphere full of oxygen is a rare ability in biology. No fungus can do it, and among microbes only the photosynthetic ones can, cyanobacteria above all, whose ancestors became the chloroplast.
On land, almost everything else lives on what plants fix. Decomposers such as Trichoderma break down residues plants left behind, and the carbon in every cell of your body was once pulled from the air by photosynthesis, most of it by plants.
plants are taking a flash of light and stretching it out into a lifetime of experience
Nik
Moments worth rewinding
Moments from the clip archive. Each one plays the full episode from where it starts, and the short plays on its own.
One story goes that a farmer gave his finest tree an unappealing name so the neighbors would not steal cuttings.
White, green, oolong and black teas differ mainly in how far the leaf's catechins are allowed to oxidize.
Rattling bruises only the edges of the leaf, so an opened oolong leaf shows reddened margins around a green center.
In a leaf, Rubisco outnumbers the carbon dioxide around it a hundred to a thousand times, one of the puzzles the paper takes on.
About 209,000 parts per million of oxygen against about 420 of carbon dioxide, and a plant still builds itself from the carbon.
Photorespiration gives a leaf somewhere to send energy when carbon runs short, instead of letting it back up and do damage.
In the water-water cycle, electrons taken from water on one side of a membrane are used to turn reactive oxygen back into water on the other.
Decomposers break down what plants leave behind, so the soil's life runs on carbon a leaf fixed first.
Keep listening
Episode 1 lays the foundation, carbon and craft, and every later episode builds on it.
Episode 2 · The one afterEnergy and WuyiEnergy, and what it lets a plant build, over a Wuyi rock oolong.
Episode 5Pigments and GyokuroPigments and gyokuro: the colors of a leaf, from chlorophyll to anthocyanins.
Episode 6Flavors and Oriental BeautyOriental Beauty, a tea that needs insects to bite it, and the chemistry of what we smell.
