The interconnectedness of plant studies

Have you ever wondered how the monthly Plant Cuttings’ collection comes to be? Do you think Mr P Cuttings knows in advance what he’s going to write about each month? He has a notional idea of the items he wants to cover, but he usually has no idea where a news item will actually go once he’s started to put the piece together. [Ed. – should you be ‘sharing’ this with us? We don’t want to undermine your aura of all-knowing plant wisdomness…] Writing about plants is very much a case of “where are we going to go today”? Where will our journey of plant discovery take us? In some respects Mr Cuttings feels a little like celebrated English composer Sir Edward Elgar, who, when asked where his music came from, reputedly replied, “My idea is that there is music in the air, music all around us, the world is full of it and you simply take as much as you require”. Well, as with musical composition, so with plant-related stories; they – like the creations that inspire the tales – are everywhere.

Our journey begins

To provide an insight into the Cuttings’ column writing process – and highlight some recent plant-based news (that’s what the column is supposed to achieve, after all!) – we’ll take as our starting point this month a news story by “freelance science communicator” Jeremy Cherfas. Entitled, “World’s oldest tea discovered in an ancient Chinese emperor’s tomb”, Cherfas was interpreting the work of Houyuan Lu et al. for a wider, and more generalist audience than is likely to read the scientific report itself. Using evidence from phytoliths (crystalline bodies produced by plants) and organic compounds, the researchers confirm that the tea plant (Camellia sinensis) was grown – and presumably used if not actually consumed – at least 2100 years ago (several hundred years earlier than previously recorded). They also deduce that tea was carried towards central Asia by about 200CE, which – because of the location of the find – further suggests that a branch of the Silk Road ran across the Tibetan Plateau by the second to third century CE. With that as a starting point, where could we go? What links were forming in Mr Cuttings’ brain? What relevant stories had he chanced upon elsewhere that could be tightly woven into – or loosely associated with – this Tibetan tapestry of botanical bounty?*

Improve your image with tea…

Tea itself is an obvious link. But, not necessarily the beverage – fascinating though its history of use and social consequences are; that’s far too obvious for this column. But, how about something rather unobvious such as a medical imaging connection? Well, polyphenols (Claudine Manach et al., Am J Clin Nutr 79: 727-747, 2004) – extracted from green tea – have been used to coat water-soluble iron oxide nanocrystals. And these have been exploited by Lisong Xiao et al. who demonstrate that they give enhanced cellular imaging with MRI [Magnetic Resonance Imaging]. Although they used mice in their studies, anything that improves biomedical imaging must be welcome news in diagnosis and treatment of human medical conditions. Good though that result is, an obvious further connection with that mention of nanocrystals is concerns amongst plant biologists of the effects that such nanoparticles might have on plants if they ‘escape’ into the environment. Adding to those concerns, potential plant-harming consequences are illustrated by work by Arifa Sosan et al. who show that engineered silver nanoparticles are sensed at the plasma membrane and can dramatically [the authors’ own word, but Mr Cuttings’ emphasis] modify the physiology of Arabidopsis thaliana** plants. A view that’s reinforced by Le VanNhan et al. who’ve investigated the effects of Fe₂O₃ nanoparticles on physiology and insecticide activity in non-transgenic and Bt-transgenic cotton. Sticking with medicine, but this time the potential health benefits of drinking tea, Gael Myers et al., in the stilted language of a scientific paper’s conclusion, found that “higher intake of black tea and particular classes of flavonoids were associated with lower risk of fracture-related hospitalizations in elderly women at high risk of fracture”. In the interests of gender balance, I could then have extended the consumption of dietary flavonoids dimension to bring uplifting news that higher habitual intake of specific flavonoid-rich foods is associated with reduced incidence of erectile dysfunction. Which item has some relevance to another priapic angle on the original story in the next item…

The long and winding road…

We could have wandered further down the Silk Road***. As an ancient trade route its overland component is famed as the pathway along which silk – and much, much more! – was brought from China to Europe and the West. One of the most celebrated Europeans to have tramped that trail is 13th Century Venetian traveller and journalist Marco Polo, who, amongst his many exploits, is credited with introducing bamboo, clove, ginger, cotton, sugar cane, indigo, rhubarb, pepper and nutmeg to Venice and the West. However, there’s much more to that route than simply a circuitous conduit for Chinese condiments – as explored in Peter Frankopan’s 2015 book The Silk Roads: A new history of the world. But, and signor Polo’s botanical exploits aside, you might well ask, what’s the plant connection with the Silk Road? Fear not, it’s there; silk is a protein filament product of the larvae – ‘silkworms’ – of the silk moth (Bombyx mori) who feed primarily upon … leaves of the mulberry tree (Morus spp.). Developing the more romantic notions that mention of the Silk Road, conjures up, e.g. Kublai Khan and Xanadu, and Uzbekistan’s second largest city, the exotic sounding Samarkand, I could have introduced an aphrodisiac dimension with the Tibetan caterpillar fungus, Ophiocordyceps sinensis****. Also known as Himalayan Viagra, satisfying the demand for this ‘medicine’ – which is both highly-prized and highly-priced – is having serious consequences, e.g. ethnic tensions in the region [for comments on this piece, go to The Economist]. And that could so easily have led us down the path to explore the fascinating world of Traditional Chinese Medicine (TCM), which used many plants and plant products.

Camellia, not everybody’s cup of tea?

From Cherfas’ musing that finding the tea stashed away in an emperor’s tomb (the originating news story for this item, remember..?) – and also surely one of the grandest of tea caddies! – was probably indicative that the commodity was so highly prized that only emperors could enjoy it, I could have extended this to rice with mention of the origin and spread of black rice, so-called ’emperor’s rice’. But that was touched upon in a December Cuttings item, so I won’t. However, one of the best examples of a plant-derived foodstuff designated for beings whose status is higher than that of an emperor is chocolate. Derived from the cocoa plant, whose scientific name of Theobroma cacao translates as food of the gods, chocolate has been a highly-prized luxury item since before Europeans discovered its use amongst the Aztecs of present-day Mexico. Brought to Europe in the late 15th Century, it was one of the benefits of the so-called Columbian Exchange, “the exchange of diseases, ideas, food crops, and populations between the New World and the Old World following the voyage to the Americas by Christopher Columbus in 1492”. Indeed, there is a suggestion that it was Christopher Columbus himself who first brought cocoa beans to Europe. And, don’t forget that chocolate is not only a solid ‘food’, but also makes a satisfying beverage – somewhat like tea in that regard. And the tales told of life in the chocolate houses of Georgian England paint a fascinating picture of life amongst the so-called upper-classes and the social role of this plant-derived commodity. Tales that are every bit as fascinating as those which surround tea and that other ‘notorious’ plant beverage, coffee.

Forensically fascinating phytoliths

The fact that phytoliths helped to confirm the identification of the tea plant in the original story is great because I’ve been practically itching to pen a phytolithological piece for positively ages. That mention, and the timely publication of Clemon Dabney III et al.’s methodological paper which documents a novel method to characterize silica bodies in grasses, gives me the perfect opportunity so to do. Typically phytoliths are tiny silica bodies that develop within plant cells. Their shape, etc. can be unique and therefore characteristic of certain genera, species or other taxonomic groupings of plants. Importantly, these tiny opals (yes, as in the semi-precious stone of the same name) are released from the cells once their walls have decomposed or otherwise been broken down and can last for a very long time in the soil, etc. This means that phytoliths have great forensic value, e.g. as a tool for investigating agricultural origins and crop dispersals around the world. Or, when stuck on the teeth of long-dead humans (along with such vegetable detritus as starch grains) as so-called calculus, when it can give important clues to the plant-based nutrition of ancient peoples. This latter approach has demonstrated the importance of sweet potato (Ipomoea batatas) – one of the “the world’s healthiest food”s – to the inhabitants of Rapa Nui (Easter Island). But, all phytoliths are not made of silica, the tea paper concerned phytoliths of calcium oxalate, calciphytoliths. Such calcium oxalate deposits within plants have been inferred to assist in their defence against herbivory, which onslaught would otherwise reduce potential yield of crop plants. And this economic botany consideration has led to the suggestion that engineering calcium oxalate formation in plants could be used as a strategy to enhance plant protection from herbivores – although the evidence presented therein suggest that this approach has “phenotypic consequences” on plant growth and development…

Farming on the roof of the world

Alternatively, I could have brought in a more direct human-food link with the agricultural detective work of Jade d’Alpoim Guedes et al. The starting point for their investigation was trying to understand the agricultural system that could develop in such a challenging environment as the high-altitude Tibetan plateau. Going against the grain of prevailing views they propose that the combined abilities of wheat (Triticum aestivum) and barley (Hordeum vulgare) both to tolerate frost and having low heat requirements encouraged their use by farmers in the second millennium BC in this region and successfully enabled their spread into the high-altitude margins of western China. These cereals successfully supplanted the former staple grain crop of the region, millets. The fact that population-sustaining yields of anything can be achieved in such an environment is testament both to the hardiness of the human population that lives and farms there and to the physiological versatility of the cereals, the botanical backbone of civilization.

Keeping it on the level…

Yes, I could have developed the starting point in any one of those ways, but what have I chosen to end on? An item that demonstrates the customary – and I trust appreciated – ‘one never quite knows where it will lead’, quirkiness that is the hallmark of a Plant Cutting. The word plateau – which is used a lot in the context of the topography of Tibet – brings to mind flatness, like that part of a graph where there is no further increase in the y axis values despite values on the x axis getting larger. And that – inevitably (!) – gets me to a comment by a certain Dr David Lawlor (formerly of Rothamsted Research) on an item on the Annals of Botany blog site. In that observation he reminds us all of the need for precision in science communication, especially regarding use of the poorly (or, frequently, never!) defined term ‘level’. I do hope this news item hasn’t strayed too far from the straight and narrow (though, since it is not a formulaic, strait-laced scientific journal article, hopefully a little bit of poetic licence is permitted..?).

Journey’s end…

What I hope these plateauesque, phytological peregrinations demonstrate is that botany is not just about the plants (or the fungi…). Indeed, for Mr Cuttings it’s never just about the plants; it is the interaction between plants and people that is important. After all, it is mankind’s relationship to the green world that has helped define our past and present on this planet, and is likely to dictate our future.*****

* Noting that the article deals with a Chinese emperor in Tibet, but also wishing to steer clear of politics, Mr Cuttings will not develop this story along the lines of the relationships between the Tibetans and the Chinese, who now claim ownership of that Himalayan kingdom. And, besides, even Mr Cuttings would be hard-pushed to find a direct plant angle in that saga!

** It’s timely at this point to mention the Tansley Review that celebrates a half-century of Arabidopsis research – Nicholas Provart et al., and the accompanying video.

*** Mr Cuttings is at pains to point out that the historical Silk Road referred to here should NOT be confused with the on-line black market site for dealing in drugs(!). However, it is not inconceivable that ‘drugs’ – whether illegal or otherwise – may well have moved along the Silk Road proper.

**** If you wonder how a fungal entry is justified here, Mr Cuttings is shamelessly playing the ‘Melbourne Code’ card. That international code of nomenclature specifies the rules for the naming of plants, algae, and … fungi.

***** And in a nod back to the Elgar quote, this month’s news collection is effectively six variants on a single theme, somewhat reminiscent of – or maybe in homage to? – Ralph Vaughan Williams [another celebrated English composer] and his musical composition Five Variants of Dives and Lazarus. But, as 6 is better than 5, the superiority of botany even above music is thereby underscored…