Science can help save rare plants, but it takes luck, too

Royal botanist Car­los Mag­dalena on em­brac­ing serendipity

The Washington Post Sunday - - OUTLOOK - Twitter: @Plantmes­siah Car­los Mag­dalena is the se­nior trop­i­cal botan­i­cal hor­ti­cul­tur­ist at the Royal Botanic Gar­dens, Kew, in Lon­don and the au­thor of “The Plant Mes­siah,” from which this es­say is adapted.

It was a frosty early morn­ing at the Royal Botanic Gar­dens in Kew, Lon­don, and I stood fac­ing the green­house bench. In front of me was a café mar­ron plant, a gor­geous shrub that never stops bloom­ing, with dark green leaves and snow-white jas­mine-like flow­ers. It had been grown from cut­tings taken from a plant on Ro­drigues, an is­land in the In­dian Ocean.

I should say the café mar­ron plant: It was the last of its kind. The species could be prop­a­gated ar­ti­fi­cially by cut­tings, but the last lone­some spec­i­men had failed to set seeds for decades, and the plants grown from cut­tings didn’t, ei­ther. Tech­ni­cally, it was ex­tinct — a spec­i­men could be kept ar­ti­fi­cially alive, but it would never re­pro­duce in the wild. It was a text­book def­i­ni­tion of what con­ser­va­tion­ists call a “liv­ing dead” species.

I’m the trop­i­cal se­nior botan­i­cal hor­ti­cul­tur­ist at Kew. I de­cided to use my free time to see if a kind of ar­ti­fi­cial in­sem­i­na­tion would save the plant: Take a scalpel, cut across the fe­male parts of the flower and in­sert some pollen. In hun­dreds of at­tempts, one grain of pollen might pro­duce a seed. It

was the sum­mer of 2003, and though my first cut did not yield any im­me­di­ate re­sult, it gave me a clue that en­abled me to find suc­cess.

Why bother try­ing to re­cover one plant species? For starters, 60 per­cent of our calo­rie in­take comes from just three species of plants: rice, maize and wheat. If that crop pro­duc­tion were to col­lapse, hu­mankind would face star­va­tion, with our only hope be­ing that some of the 50,000 species that have recorded uses for con­sump­tion could come to the res­cue. An additional 28,000 species have recorded medic­i­nal uses. So with the ex­tinc­tion of each species, our food pal­ette and our phar­macy be­come poorer and smaller. Yet we take plants for granted; we too of­ten dis­miss their ben­e­fits. Kew’s “State of the World’s Plants” re­ported that 1,730 new species were dis­cov­ered in 2016 — an en­cour­ag­ing num­ber. But roughly 80,000 species — 1 in 5 — are be­lieved to be at risk of ex­tinc­tion. There are 60,000 more that we be­lieve we have not yet dis­cov­ered.

You can’t pro­tect what you don’t know; you can’t use a plant that you can’t find, whose home you can’t ob­serve, whose preva­lence is un­cer­tain. We’re in dan­ger of los­ing our bio­di­ver­sity. Sav­ing plants rep­re­sents part of a greater mis­sion to ex­tend plan­e­tary sur­vival.

New tech­nol­ogy is tak­ing these ef­forts be­yond the hor­ti­cul­tural meth­ods nor­mally used to prop­a­gate. One dra­matic ex­am­ple of plant res­ur­rec­tion is the case of Si­lene steno­phylla, a plant in the cam­pion fam­ily dis­cov­ered by Rus­sian re­searchers in north­east­ern Siberia, as they re­ported in 2012. Fruit tis­sue of this species had been pre­served in per­mafrost at a depth of more than 100 feet, where it lay for some 30,000 years. Sci­en­tists us­ing in vitro tis­sue cul­ture and clonal mi­cro­prop­a­ga­tion — a tech­nique that in­volves plac­ing plant tis­sue in a flask with sugar and nu­tri­ents un­der ar­ti­fi­cial light­ing — were able to re­gen­er­ate plants from small tis­sue sam­ples, which led to pot-grown plants that flow­ered, fruited and, ul­ti­mately, set seeds.

A promis­ing line of science has emerged in re­cent years us­ing DNA analysis. One such project is be­ing un­der­taken by Kew: the Plant and Fun­gal Trees of Life, which we hope to com­plete by 2020. The project uses very pre­cise DNA se­quenc­ing to bet­ter un­der­stand the re­la­tion­ships be­tween species, with the goal of forg­ing a com­pre­hen­sive evo­lu­tion­ary tree. Such a re­source can then be paired with pocket de­vices such as the MinION DNA se­quencer, which al­low for real-time DNA analysis in re­mote ar­eas. The tech­nol­ogy is still in its ear­li­est days, but such de­vices could al­low sci­en­tists to quickly iden­tify plants in the field and cross-ref­er­ence them against tax­o­nomic cat­a­logues, to bet­ter rec­og­nize when they’ve stum­bled upon a plant that is so rare as to be threat­ened by ex­tinc­tion.

Even with these ad­vances in tech­nol­ogy, though, plants can fail for any num­ber of rea­sons. In my ex­pe­ri­ence, the best tool in a hor­ti­cul­tur­ist’s tool­box is de­ter­mi­na­tion. Some­times it is only when a plant con­sumes all your wak­ing thought that you find a break­through.

In 2009, I re­ceived from the botanic gar­den in Bonn, Ger­many, a small batch of seeds for the Nym­phaea ther­marum, the small­est known species of wa­ter lily in the world, which had been found in the 1980s in a sin­gle lo­ca­tion in south­west Rwanda. We at Kew were swap­ping plants with the hor­ti­cul­tur­ists in Bonn, and I had spot­ted the Nym­phaea ther­mar

um in their col­lec­tion. When I asked them to send me seeds, Bonn warned that this species was almost im­pos­si­ble to grow from seeds, which made me even more in­trigued. I sowed them us­ing stan­dard meth­ods, in which seeds are grown on the sur­face of a pot con­tain­ing loam, placed un­der­wa­ter. It was busi­ness as usual at first — they ger­mi­nated, look­ing like blades of grass be­fore pro­duc­ing seed leaves, a char­ac­ter­is­tic unique to wa­ter lilies.

Not long af­ter, though, the seedlings fol­lowed the same fate as in Bonn — they stopped grow­ing, be­gan to look sickly, and, almost as quickly as they had ap­peared, they were gone.

I ex­per­i­mented with tem­per­a­ture, pH, the con­cen­tra­tion of salts, light. I tried us­ing tap wa­ter, then wa­ter fil­tered by re­verse os­mo­sis. I tried a va­ri­ety of pot­ting mixes. Nothing worked — ev­ery plant hung in there, look­ing sorry for it­self for three or four weeks, then, as the seed ran out of food, grad­u­ally melted away. What on earth was going on? For weeks, I was pre­oc­cu­pied with the fate of the Nym­phaea ther­marum. Night and day, I racked my brain for a way to crack the code. One evening, I was at home cook­ing tortellini. As I stirred and the wa­ter bub­bled, it came to me: CO2. Car­bon diox­ide dis­solves poorly in wa­ter. Es­pe­cially in a small tank, it is de­pleted quickly. Per­haps the plant was be­ing starved of the gas it needed to sur­vive.

I be­gan ex­per­i­ment­ing with wa­ter lev­els, al­low­ing the plant’s leaves to peek out above just half a cen­time­ter of soil from a shal­low tray rather than sub­merg­ing it fully, so it could be ex­posed to the high con­cen­tra­tions of car­bon diox­ide in the air from its first mo­ments. I placed my bet on the last 10 seeds avail­able to me. I re­sowed them, trans­planted them, ex­posed them to vary­ing lev­els of heat, light and mist.

Even­tu­ally, I found the right pa­ram­e­ters, and ev­ery­thing changed. Within two weeks, I could see a dra­matic im­prove­ment; about a month later, a proper lily pad ap­peared. They were grow­ing like ev­ery other wa­ter lily in the gar­den.

One day, a Ger­man pro­fes­sor came burst­ing through the doors of the trop­i­cal nurs­ery, shout­ing: “Where are they? Where are they?” He wanted, needed, to see if what he had heard was true: that the Nym­phaea ther­marum had been made to grow again. He wore the broad­est grin I had ever seen — I thought he was going to ex­plode.

Be­fore I be­gan to play with the seeds of the Nym­phae ther­marum, I knew that there were about 50 plants left in Rwanda and only two in Bonn — this was part of why I had been so drawn to these beau­ti­ful lilies. What I did not know was that the plants re­main­ing in the wild had all died off in the mean­time, when work­ers at a new con­crete quarry di­verted the wa­ter from the only hot spring where this species grew to build a laun­dry fa­cil­ity. Around the same time, the only plants grown at Bonn had died. Worse, a rat got into the green­house in Bonn from which my seeds had come, and there were none left there.

I didn’t re­al­ize it, but I had been play­ing with the last seedlings on the planet. But I wouldn’t have done any­thing dif­fer­ent if I’d known the stakes. If we are to pro­tect, cher­ish and nur­ture the bio­di­ver­sity of our world, we can’t let the scale of the task scare us away. Plants truly have the power to save us: They pro­duce en­ergy, raw materials, fibers, food and medicine, and they gob­ble up the car­bon diox­ide our mod­ern lives force into the air. We have no choice but to try to save them, if we are going ot save our­selves, too.

You can’t pro­tect what you don’t know; you can’t use a plant that you can’t find, whose home you can’t ob­serve.

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