CHLOROPHYLL ANYONE?
What Your Balcony Plants Are Really Up To

by Peter W. Gribble
It’s a race as intense as the one for the COVID-19 vaccine, but this one has accelerated over the past ten years.

In the weird science department of botany, recent discoveries and developments may likely provide humanity with fresh avenues for energy sources and better light-absorbing crops using an ancient process in existence for at least a billion years. An example of it may be sitting beside you in your apartment; a common houseplant quietly undergoing photosynthesis.

Photosynthesis is an elegant, complex and sometimes baffling process by which plants use sunlight to combine carbon dioxide and water to synthesize carbohydrates and expel oxygen. This is accomplished with the chlorophyll molecule and the organelle cellular body known as the chloroplast. Life, as we know it on our planet, would not exist without them.

All plant fertilizers you buy in the store have three numbers on the packaging indicating the amount of each of the main ingredients called NPK. N is for nitrogen (good for green growth); P is for phosphorous (good for roots and flowers) and K for potassium (kalium in Latin - which aids in fruit production and general hardiness). Some fertilizers include a list of trace elements depending on the plant’s needs. One of them, magnesium (Mg) is essential for chlorophyll’s curious structure because an atom of magnesium acts as a hub for four nitrogen atoms serving as links for the molecular side chains and the anchor for the hydrocarbon tail. There are now nine known varieties of chlorophylls differentiated by which part of the spectrum they absorb light. The two chlorophylls (a and b, sometimes written Chl a and Chl b) in land plants are green because they absorb mostly in the blue and the red portions of sunlight’s spectrum.

A chloroplast is an example of endosymbiosis, in which one organism (the chloroplast) lives happily inside another’s cytoplasm (in this case, a plant cell) to their mutual benefit. The original encounter is thought to have occurred at least a billion years ago and was so successful that all land plants, algae and cyanobacteria (blue-green algae) evolved from it. The added benefit was the land plant-based variety gave the world its oxygen. Four primary lineages of chloroplasts exist.

Green single-cell chlorella algae microscopic conceptual 3D illustration. Or something like that! Check your notes.

Land plants’ chlorophyll is embedded into specialized membranes of chloroplasts, which is where sunlight initiates the complex 17-step process of photosynthesis. Simply, water (H2O) is split, freeing hydrogen to form two storage compounds that in a secondary process, capture carbon dioxide to create various carbohydrates such as glucose. Luckily for us, oxygen is released as waste.

The colours of the rainbow or light refracting through a prism show to the human eye the range we can see of visible light. In 2008, at Washington University in St. Louis, things got weird when it was discovered the rare cyanobacterium Acaryochloris marina living on the underside of a green sponge-like marine animal known as a sea squirt, was altering its chlorophyll by means of a single enzyme to create a rare form of chlorophyll, chlorophyll d (Chl d), to absorb the “red edge” or the infrared long-wavelength light invisible to the human eye.

Later, Imperial College London in 2018 announced “textbook changing stuff” (their words) with their finding that the “red limit” for photosynthesis had been crossed. When some cyanobacteria were grown under near-infrared light, the standard chlorophyll-a-containing systems shut down and different systems containing a different chlorophyll (chlorophyll f) took over. The surprise was that chlorophyll f was not just harvesting the light, it was playing the key role in photosynthesis under shaded conditions, using lower-energy infrared light to do the complex chemistry. “This is photosynthesis beyond the red limit and changes our understanding of the basic mechanism of photosynthesis.… It will also tailor the way we hunt for alien life and provide insights into how we could engineer more efficient crops that take advantage of longer wavelengths of light.”

And that’s what all those innocent looking succulents are up to out on your balcony!

It got even weirder in the same year when Rutgers University-New Brunswick reported, “an amazing achievement akin to adding solar panels to your body, a Northeast sea slug Elysia chlorotica sucks raw materials from algae to provide its lifetime supply of solar-powered energy.”

It must be part of the new normal when humanity starts envying sea slugs.

These examples are exciting because if a bacteria can alter chlorophyll’s structure to improve light absorption and sea slugs can collect a lifetime supply of free energy; humanity will not be far behind learning how it’s done.

Just as new approaches to create the COVID-19 vaccine using messenger RNA are tricky and time-consuming, building new forms of synthetic biology are not easy tasks either. Nature took several hundred million years to fine-tune photosynthesis but in May 2020, Max-Planck-Gesellschaft announced their research network was “on the trail of building artificial cells as sustainable green bioreactors. We have succeeded in developing a multifluidic platform for the automated construction of cell-sized photosynthesis modules. The artificial chloroplasts are capable of binding and converting the greenhouse gas carbon dioxide using light energy.”

It may sound like science fiction, but we are certainly living in interesting times. Your collection of succulents by the window may hold the secret to humanity’s next energy breakthrough ... or perhaps it’s in your aquarium tank.

Humanity’s urgencies and those of the planet are forcing our entry into a new world where messenger RNA-based vaccines can sidestep our old reliance on antibiotics combating disease and where emergent possibilities for new, clean energy systems are based on ancient dynamics.

So in this second round of lockdown and isolation, our houseplants are our complex organelles in our apartment cytoplasm; collecting light, providing air, moisture, company and connection ... might as well cozy up to them.

Cheers! Happy Holidays! Here’s to you and yours, to greenness, to chlorophyll!

PS: For a more traditional holiday season column, see my December 2019 column on the seven points of poinsettias, and for a rundown on distinguishing features among cut Christmas tree varieties, see the December 2018 column.