Image: Wikimedia Commons.
There is a widespread belief that everything in/of/from/about America is bigger, better, faster, etc, than anything from elsewhere in the world. That is probably the best example of spin over substance ever foisted on an unsuspecting world, and is a true testament to the power of marketing and public relations.
Take, for example, the arresting title ‘This Could Be the Oldest Flowering Plant Ever Found in North America’. So prevalent is that view of American supremacy and so conditioned are we to its acceptance that many of us will have read that text and mentally added a comma after the words ‘ever found’ (and the importance of comma placement is legendary). The news story concerns a re-assessment of fossil plants stored away in the USA’s Smithsonian National Museum of Natural History. Originally thought to be a fern, reinspection and analysis by USA-based Nathan Jud and Leo Hickey now confirms that the fossil is an angiosperm (a flowering plant) between 125 and 115 million years old (Ma) – the Lower Cretaceous – named Potomacapnos apeleutheron.
While this is amongst the oldest flowering plants found in America, it is not the oldest known on Earth. That honour goes – currently! – to the unnamed bearers of ‘angiosperm-like pollen’ and the described genus Afropollis from Middle Triassic deposits in Switzerland that are 247.2–242.0 Ma, as unearthed by Peter Hochuli and Susanne Feist-Burkhardt. The pollen was studied using confocal laser scanning microscopy (CLSM), exploiting the autofluorescence still present in such ancient organic-walled microfossils. Quite dramatically, this announcement pushes back the origin of flowering plants another 100 Ma into history, which must be rather gratifying for the Swiss–German team. So, whilst national self-belief is a good thing to have (rather like patriotism), it mustn’t blind us to the fact that other countries may have more legitimate claims to ‘biggest and best’ (and which might stray into nationalism). And anyway, it’s only because of ‘accidents of history, geography and politics’ that scientific discoveries are tied to a particular place and claimed for, and/or by, individual countries. Science – and its discoveries – belongs to us all. There, I’ve said it (and with flowers…).
[As usual, Mr Cuttings has tried to be a little mischievous in this item. But it probably won’t halt the activities of those whose lifelong goal is to seek out the biggest, best, etc, so expect further archaefloral revelations from the good old US of A in due course (and maybe further afield…), as more store-rooms replete with rocky riches are rummaged through, re-examined, and re-assessed! And if a good bit of healthy, old-fashioned competition and rivalry can spur on all those engaged in the process of science to even greater things, then so much the better – for us all! – Ed.]
Image: Taro Taylor/Wikimedia Commons.
It’s a tribute to the fantasticness of plants – and photosynthesis in particular – that even animals want to be like them. Arguably, none more so than some sea slugs, which for many millennia have eaten seaweeds and integrated their chloroplasts into their bodies (a phenomenon known as kleptoplasty). The assumption that underlies such acquisitive behaviour is that the new owners use those sequestered verdant powerhouses as a fuel source for their own purposes. A lovely idea – and one that will have found its way into the textbooks, and featured in lectures based thereon. But! Gregor Christa et al. have concluded that, while such ‘stolen plastids’ display light-dependent CO2 fixation (i.e. photosynthesis), light is not essential for the studied sea slugs – Elysia timida and Plakobranchus ocellatus – to stave off starvation. Indeed, they conclude that the internalized plastids seem to be a slowly digested food source rather than a source of solar power. In other words, this is an example of plants feeding the planet (again!). However, another bonus of this work is that animals are still just animals and not proxy plants. Which is good, because, to paraphrase one Harold Woolhouse, if one wants to understand the biology of plants one will ultimately have to work on… plants.
[However, if you wish to study animals that penetrate each other in the head during sex, then that’s where sea slugs really come into their own. But if you want more on photosynthetic animals, check out this article by Sarah Rybak – Ed.]
Image: Britton & Brown. 1913. An illustrated flora of the northern United States, Canada and the British Possessions. Charles Scribner’s Sons, New York.
Schadenfreude (taking pleasure in the misfortunes of others) is not the most attractive of human traits, but it can be so satisfying. And I bet there’s more than a little of that throughout the world occasioned by the discovery that the model plant Arabidopsis thaliana seems not to be such a good model after all. And the reason for this global wave of ‘arabidisenchantia’ relates to a rather fundamental property of cells known as nonsense-mediated mRNA decay (NMD). NMD is a so-called surveillance pathway that reduces errors in gene expression by eliminating aberrant m(essenger)RNAs that would otherwise encode incomplete polypeptides. Important though this process is for cell survival, it had been assumed that plants used it in a different way to animals because a gene for a key protein – SMG1 (phosphatidylinositol 3-kinase-related kinase) – in the pathway had not been identified in Arabidopsis thaliana (afka* ‘the universal plant’), nor in fungi. However, and thanks to iconoclastic (albeit probably unintentionally) work by James Lloyd and Brendan Davies, we [arabothalocentric plant biologists and those who needs must rely on their abundantly-funded researches - which is pretty much all of the rest of us...] can all sleep more soundly in our beds. They show that SMG1 – the gene that codes for SMG1 – is not animal-specific, but is found ‘in a range of eukaryotes, including all examined green plants [my emphasis] with the exception of A. thaliana’. The misconception about the importance of SMG1 in plants appears to have arisen because the gene was lost from A. thaliana ’s genome 5–10 millions of years ago. Interestingly, SMG1 is found in the genome of the closely related A. lyrata… So, A. thaliana is unique after all(!), though not in quite the way its promoters (pun intended…?) might have liked. But if thale cress has carelessly lost this gene, what else has it lost (but which may have been retained by more typical plants)…? I predict more Arabidopsis applecart-upsetting in the future…
* afka = as formerly known as…
Image: Robert A. Rohde/Wikimedia Commons.
Many abiotic variables affect plants, e.g. levels of light, carbon dioxide and water. One of the most important of those non-biotic factors is temperature. Now, given its importance you could be forgiven for assuming that it is recorded accurately and correctly. Unfortunately, that isn’t always the case. Take for instance the temperature of the meristem (symbolised as Tmeristem), which is important in driving plant development. For such a crucial aspect of plant biology studies have largely relied on measuring the temperature of the air surrounding the plant (Tair). Tair is measured because it is assumed to represent the meristem temperature because plants are poikilotherms (organisms whose ‘internal temperature varies considerably … Usually the variation is a consequence of variation in the ambient environmental temperature’). Whilst that assumption may seem reasonable – and it does save the would-be investigator the trouble of penetrating the umpteen layers of developing leaves, etc, that may sheathe the apical meristem, it is nonetheless an assumption. And the veracity of assumptions must be tested, which is what Andreas Savvides et al. did. Guess what they found! That’s right: Tmeristem differed from Tair – ranging between –2.6 and 3.8 °C in tomato, and –4.1 and 3.0 °C in cucumber(!). As the team conclude, ‘for properly linking growth and development of plants to temperature… Tmeristem should be used instead of Tair’.
If you’re now intrigued by detecting temperatures within cells, you might like to explore the nanoscale thermometer developed by G. Kucsko et al. Using ‘quantum manipulation of nitrogen vacancy (NV) colour centres in diamond nanocrystals’ it can detect temperature variations as small as 44 mK(!) and can measure the local thermal environment at length scales as low as 200 nm(!!). Or, if you want a more biological approach, check out the genetically encoded sensor that fuses green fluorescent protein to a thermosensing protein derived from Salmonella, as showcased by Shigeki Kiyonaka et al. Although proof of this particular principle was demonstrated with thermogenesis in the iconic mitochondria of brown adipocytes (and the somewhat less iconic endoplasmic reticulum of myotubes), the team envisage it could be used to investigate this phenomenon in other living cells. Maybe even within the cone cells of tropical cycads that undergo impressive increases in temperature, where Tcone can be markedly greater that Tair. In view of concerns about global temperature changes and effects of temperature on regulation of such economically important processes as flowering, accurate temperature information in planta – and an appreciation of the temperature that plants are actually responding to – is likely to become increasingly important.
[For a useful set of slides summarising Savvides et al.’s work, visit slideshare.net. For a less physics-oriented interpretation of the Nature nanoscale thermometry article try the accompanying ‘News and Views’ item by Konstantin Sokolov – Ed.].
Image: David Iliff/Wikimedia Commons (CC-BY-SA 3.0).
OK, I know, this item is the real ‘money doesn’t grow on trees’ story you were expecting. So, I’ll try not to disappoint. Melvyn Lintern et al. provide the first evidence of particulate gold (Au) within natural – i.e. not from laboratory experimentation (and therefore which evidence doesn’t count..?) – specimens of living biological tissue. The living biological tissue in question is that of the iconic Australian plant species eucalyptus, the gum tree. Apparently, and hitherto, reports of Au from plant samples have led to questions as to whether the Au was within the tissues (and therefore absorbed) or adsorbed onto the external surfaces as a result of aerial contamination. The team consider their discovery to demonstrate active biogeochemical absorption of Au, and it may therefore be used as a sort of bioassay (quite how quantitative this is may require further testing – maybe even experimentation…) to indicate the presence of soil-based Au deposits within the reach of the tree’s roots (the presumed route for uptake of the metal from the soil). The overall effect of this study is a little spoilt by the final sentence of the abstract, which begins, ‘This observation conclusively demonstrates active biogeochemical adsorption of Au…’. Shouldn’t that ante-penultimate word be absorption? Potential use of plants as agents to absorb metals – and other compounds – from soils and waters has been widely touted as a method for cleaning up such environments and comes under the broad category of phytoremediation. However, the fact that some plants may accumulate economically important metals – such as gold – has long been recognised and underlies the practice of geobotanical prospecting, which apparently dates as far back as the 5th century BCE in China. Whilst this study isn’t necessarily proposing use of eucalyptus in a bioindicator capacity, the authors do suggest that the gold therein might be extractable on a commercial basis. For more on this topic, see Sheoran et al.’s articles on ‘phytomining’ in general and of that for gold in particular. Anyway, I think somebody’s missing a trick here. What’s the iconic Australian animal species? The herbivorous koala, which famously has a diet rich in leaves of… eucalyptus. Now, applying the well-known principle of biomagnification – whereby organisms higher up the food chain accumulate materials from what they feed on – if koalas can be persuaded to eat only Au-loaded gum-tree leaves, then maybe their faecal pellets may contain gold, but concentrated to much higher levels than those found within their food source. Just a little nugget (!) of information I’m happy to share. All somebody needs to do is harvest the stuff (but isn’t that why postgrads/postdocs were invented..?). What’s that you say, where there’s muck there’s brass? Indeed! After all, we all know how expensive coffee is when made from the ‘beans’ that have been peristaltically massaged and ‘processed’ by passage through the alimentary tract of the Asian palm civet! And in a more scientifically imaginative – though similarly scatologically-inclined – ‘muck = brass’ way the veracity in this wise saying is verified by work in Australia’s antipodean neighbour, New Zealand. Exhibit A, the evidence base that is the coprolite (‘fossilized feces’) recently exploited by Jamie Wood et al. [http://dx.doi.org/10.1073/pnas.1307700110] to discern information about the ecology of four sympatric (species living in the same geographical area) species of moa – flightless herbivorous birds, which became extinct in New Zealand about 600 years ago. Unfortunately, there’s insufficient space for the details of the study here, but it involves identification of vegetation from pollen, aDNA (ancient DNA), and plant macrofossils within the bird droppings (and therefore inferences about moas’ diet and habitat). This is a great example of that admirable ‘rolling-up-your-shirt-sleeves-and-getting-your-hands-dirty’ dedication to the cause of true science; definitely not merely going through the motions(!). What, after all, is more valuable than brass, or even gold? Knowledge! Well, some sorts of knowledge anyway, because, and rather vaguely, the Antipodean team’s ‘golden gum tree’ article just mentions ‘Eucalyptus trees’; there’s no further taxonomic help to their identity in the Supplementary Information either. So, although the article itself is Open Access, maybe naming the species concerned is too commercially sensitive for general consumption?
Image: Wikimedia Commons.
It’s a little naughty to consider these two elements together, I know, because this may unintentionally add to the confusion that often ensues in class when you ask students to tell you the full chemical names for elements with the symbol P – phosphorus – and K – potassium. Oh, the near-Pavlovian, knee-jerk temptation for them to say potassium for P (but not nearly as annoying as those who spell phosphorus with an additional ‘o’ – phosphorous…). Anyway, and since there is so much out there in the cybersphere dealing with phosphorus, I will only flag up Professor John Raven’s typically thoughtful review of the evolution of autotrophy (‘self-feeding’, e.g. photosynthesis, but not restricted to that plant-like process) in relation to requirement for P, ‘the ultimate elemental resource limiting biological productivity through Earth’s history’. Written to redress a perceived imbalance in emphasis that has hitherto concentrated on the roles of C, N and Fe in the evolution of autotrophy and right that historical wrong, Raven’s review ranges widely, from the origins of life, to the roles of P in organisms, PUE (phosphorus use efficiency), to growth-limitation via an effect on water use efficiency (WUE) from P insufficiency.
The K contribution is a consideration of the so-called potassium paradox. For many years K has been added – in the form of KCl – to soils as a fertiliser in efforts to improve agricultural productivity of corn and other grain crops (despite K being one of the most abundant elements in the earth’s crust and being more readily available than N, P or S…). Indeed, so universal is the presumption that K is needed that artificial fertilisers are typically defined by their NPK rating, because K is usually added along with the major plant-growth-limiting nutrients N and P. A study by Saeed Khan et al. has questioned the basis of traditional tests to detect K soil levels – and hence the justification for additional inputs thereof – and even the need for K fertilisation at all. Indeed, their work showed instances of an increase in soil K level in the absence of artificial inputs – ascribed to return of K from plant residues to the soil. Furthermore, their extensive survey of more than 2100 yield-response trials confirmed that not only is KCl addition unlikely to increase crop yield, but – in more than 1400 instances – such K fertilisation actually led to a ‘detrimental effect… on the quality of major food, feed and fiber crops, with serious implications for soil productivity and human health’. As the authors explained, ‘Potassium depresses calcium and magnesium, which are beneficial minerals for any living system’; for example, diets low in Ca can also trigger human diseases such as osteoporosis, rickets and colon cancer. Another major human health concern arises from the chloride in the KCl, which mobilises Cd (cadmium) in the soil and promotes accumulation of this heavy metal in cereals. A paradoxical situation, indeed!
[Ed. - for more on the nutritional complexities and intricacies of phosphorus, try Prof. Raven's recent Frontiers in Plant Science article entitled "RNA function and phosphorus use by photosynthetic organisms".]
Image: Marvin Smith/Wikimedia Commons.
We are often reminded that water is a ‘most interesting/odd/peculiar/amazing/incredible compound’ with many fascinating properties – both physical and chemical, and biological. And its roles within plant biology are many and varied. But no matter how well we think we understand water, there are always more surprises to uncover. Take, for example, Juergen Burkhardt and Mauricio Hunsche’s intriguingly entitled Hypothesis and Theory article, ‘“Breath figures” on leaf surfaces – formation and effects of microscopic leaf wetness’. ‘Breath figures’ is a term used in material science to describe the condensation, as well as the linked wetting and de-wetting processes, on different kinds of surfaces, which the article’s authors extend to the surfaces of leaves. The water is mainly maintained by transpired vapour that condenses onto the phylloplane and onto attached leaf surface particles. However, with an estimated thickness of less than 1 μm, this microscopic layer is approximately two orders of magnitude thinner than morning dewfall (the more widely known form of condensation upon leaves); it is therefore easily overlooked(!) and consequently un(der)appreciated. The authors hypothesise that microscopic leaf wetness occurs on almost any plant worldwide, often permanently. Since it can constitute a continuous thin layer even on otherwise hydrophobic leaf surfaces, and can enhance dissolution, emission and reaction of specific atmospheric trace gases such as ammonia, SO2 or ozone (which compounds can be injurious to plant health), it is a topic fully deserving of an airing. As the authors conclude, ‘The omission of microscopic water in general leaf wetness concepts has caused far-reaching, misleading conclusions in the past…’.
[I don’t know if breath figures have any connection with ‘frost flowers’, but as a nod in the direction of ‘winterval’ and those almost-forgotten frosty days of December in the northern hemisphere, and in an attempt to gladden the heart – and lighten the spirit and maybe lift the soul at this dark time of the year – I’m happy to illustrate this item with an example of this other, intriguing water-based phenomenon. For more on that topic, do visit Illinois State University’s Emeritus Professor James Carter’s ‘My World of Ice’ site – Ed.]
Image: Archie Portis/Wikimedia Commons.
The ability of plants – and other plant-like organisms that aren’t in the Plant Kingdom (such as the Protists, algae and seaweeds, and the prokaryotic Moneran cyanobacteria) – to manufacture their own organic food from the simple inorganic materials carbon dioxide (C and O – two nutrients in one!) and water (H and O; ditto) using light energy in the process known as photosynthesis never ceases to amaze. But there are those who need to be reminded of how amazing photosynthesis is, and how fundamental green things are as the conduit by which energy is converted from a physical, electromagnetic form to a chemical form that is then available to the plants, and all those organisms who consume them (whether directly or indirectly).
One way we’ve often done this is to impress upon our students the importance of Rubisco, Ribulose-1,5-bisphosphate carboxylase-oxygenase, the enzyme that ‘catalyzes the primary chemical reaction by which inorganic carbon enters the biosphere’ in photosynthesis, with statements such as Rubisco is the ‘most abundant protein on Earth’. (And which represents a major sink for another essential nutrient – nitrogen (N), an essential component of amino acids from which such proteins are made…) Impressive, certainly, but is such a statement accurate? Well, examining that enzyme in single-celled marine algae, Jenna Losh et al. conclude that ‘unlike in plants, Rubisco does not account for a major fraction of cellular N in phytoplankton’ but constitutes less than 6% of total protein in those microalgae (cf. up to 50% in ‘plants’).
What might one conclude from this? We must try to avoid terrestrial bias in our plant biology! Whilst members of the Plant Kingdom might dominate terrestrial biomes, non-Plant Kingdom members are the major photosynthetic organisms in aquatic habitats, which occupy more than two-thirds of the Earth’s surface. Oh, and never ignore the small things!
We often hear that money doesn’t grow on trees. And on one level that is patently true. However, on another it may have the ring of truth. For example, if the tree in question makes a compound with useful medicinal properties then its exploitation may lead to the generation of profits for those who grasp that opportunity. Aha, so you might think we are talking about development of aspirin, often used as an analgesic to relieve minor aches and pains, as an antipyretic to reduce fever, and as an anti-inflammatory medication derived from salicin found in such trees as willows, or the bitter-tasting, antipyretic, antimalarial, analgesic, anti-inflammatory alkaloid quinine from trees of the genus Cinchona. Not on this occasion.
Nauclea latifolia. Photo by Scot Zona. CC BY.
Rather, we are here concerned with work by Ahcène Boumendjel et al., which has demonstrated the presence of (1R,2R)-rel-2-[(Dimethylamino)methyl]-1-(3-methoxyphenyl) cyclohexanol in root bark of the sub-Saharan shrub Nauclea latifolia, commonly known as African peach or pincushion tree). That gloriously named organic compound is a centrally acting opioid analgesic used to treat moderate-to-moderately-severe pain and is more commonly known as the commercially important drug Tramadol.
Sounds ‘useful’? Yes. However, the real significance of the discovery isn’t of ‘yet another pain-killer provided by nature, aren’t plants great’, but the fact that tramadol is a synthetic molecule previously only known as one of human invention and design. Although this study is apparently the third reported case of the occurrence of a synthetic and clinically-used drug in natural sources, it is the first documented instance of the occurrence of such a drug at clinically relevant concentrations in a plant source (to the best of the authors’ knowledge). That nature seems perfectly capable of producing it on its own begs the question of how many other human-created drugs might exist in other plants. Perhaps perchance a putative, plentiful phytological pharmacopeia patiently awaits? And another reason to marvel at the biosynthetic abilities of non-sentient organisms that haven’t spent years learning their craft at pharmacy school. Good – and timely – news also for the relief of the pain of hangovers that often accompany those imbibitionally indulgent parties that accompany such major post-New Year events as 25th January’s Burns’ Night?
[Rumours that Nauclea saplings can only be purchased from garden centres against a physician-authorised prescription are just that. Neither Mr Cuttings nor the Annals of Botany condone experimentation with, or self-administration of, extracts of Nauclea – Ed.]
Nauclea latifolia by Scott Zona/Flickr. This image licensed under a Creative Commons by licence.
Some sad news came from Kew yesterday.
Nymphaea thermarum isn’t simply rare, it’s also very unusual. It’s a water lily that doesn’t grow in water. Sadly these days it doesn’t grow anywhere in the wild as its home has been damaged by human action. In fact it’s astonishing that it grows anywhere at all because Nymphaea thermarum is a freak.
Nymphaea tells you the plant is a water-lily, but it’s the thermarum bit that hints at what is so strange about it. Thermae were the hot baths the ancient Romans liked, and Nymphaea thermarum likes a bit of heat. Its home was by a thermal spring in Rwanda. Normally a water-lily grows in deep water, not in this case. The plant had adapted to squat in the damp mud by the side of the spring. Unfortunately changes in water use have stopped water getting to the spring’s surface. The mud has dried and, in the wild, the plant is extinct.
All that remained were a few plants in saved by botanists.
Nymphaea thermarum. Photo by pilot_micha/Flickr.
This was bad news, but they know what they’re doing in Kew so if anywhere could grow more, then they could. Except they couldn’t. They tried and tried, but the plant would germinate, but it would not grow. The scientists were left watching the plant go extinct before their eyes, and it seemed they had nothing they could do.