A collection of papers on Extrafloral Nectaries has recently moved into Free Access at Annals of Botany. One of the papers raises the question, can a plant that never flowers have extrafloral nectaries?
Photo: Koptur et al.
Nectar secretion on fern fronds associated with lower levels of herbivore damage: field experiments with a widespread epiphyte of Mexican cloud forest remnants by Koptur et al. examines why ferns produce nectar. The paper starts with a brief review which includes a few facts that startled me. One is that extrafloral nectaries evolved before floral nectaries. This surprises me because I so deeply associate nectar with flowers. Another shock was that nectaries appear on ferns well before ants appear in the fossil record.
This shouldn’t be a surprise, but we’re so used to evolutionary stories being teleological, like plants evolved nectaries to reward insects, that it’s easy to forget that it’s a huge oversimplification that gets things very wrong. Nectaries didn’t evolve in order to do something with a purpose. Instead that plants with nectaries have a better chance of passing their traits to their offspring because they can reward insects. And what if there are no insects? Koptur et al. say that the early appearance of nectaries supports the ‘leaky phloem’ hypothesis, that sugars are forced out of the plant in weak developing tissues to ease hydrostatic pressure in the plant. This might explain how they formed, but once ants arrived did they help select ferns with better nectaries. Do the nectaries in ferns given them an evolutionary advantage?
The nectaries are on the leaves or fronds of the plant. Developing fronds are a prime target for herbivores, so if the ants were drawn into the leaves they could act as a defence. But do they. The experiment, like many of the best ones, sounds quite simple.
At its simplest, you find a plant with a suitable pair of young fronds. On one you paint over the nectaries with nail polish to prevent access to the nectar. You then see how the plants develop and compare the damage on the untreated leaf with the test leaf. Reality is messy, so they actually did a lot more than that to account for other factors – but the basic experiment was does access to the nectaries matter?
The results were clear. The fronds with blocked nectaries had four times the damage of the untreated fronds. The ferns benefited from hosting plants, and the ones that could attract them best got the best defence. The defence works best against invasive species that haven’t co-evolved with the fern and developed counter-defences against the ants.
It’s easy to see nectar as part of the plant’s reproductive strategy, or maybe as part of the reproductive system that’s been repurposed for something else. I think this paper neatly shows that there’s no need to assume any connection at all. There’s a lot more to nectar than bait for pollination.
Quora is a site for posting questions to the internet. Sometimes those questions get answer. For example Robert Frost, who has trained astronauts for the International Space Station, has answered the question: How are plants growing in the ISS?
Gravity is not the only difference between the Earth environment and the ISS environment. In the closed atmosphere of a spacecraft, volatile organic compounds (VOCs) can accumulate. VOCs need to be scrubbed from the air or seed production will suffer. There are elevated radiation levels that can cause mutations and affect growth. An experiment on Mir, that involved storing tomato seeds in space for six years found mutation rates up to 20 times higher in the space seeds than in the control seeds stored on the ground. And there are the spectral effects of using only electric lighting.
An autotrophic astronaut. Photo: NASA.
Because plants also respire, we have to have fans to circulate the air around the plants so that they don’t suffocate on their own exhalations. Even failed experiments can provide us with better understanding. An experiment to study plant lignin failed to produce healthy plant materials but taught us more about providing effective air movement.
You can read more at Quora.
Annals of Botany had an editorial meeting recently one of the topics that came up was how can authors increase the readership of their paper? One place that can have a surprisingly large impact is the abstract.
If you’ve spent an age trying to get all the details of your research right, it can be painful reducing everything to a couple of hundred words. However an abstract isn’t a mini-version of your paper, it’s a tool to get people to read your paper, and that means making it as easy as possible for people to see why they should care. There’s the full slidedeck up at Haiku Deck or press play above.
Image: From the ‘Voynich manuscript’.
Botany is not without its mysteries. And one that’s previously eluded solution for 600 years or so is that of the so-called Voynich manuscript, an illustrated codex (a book made up of a number of sheets) consisting of about 240 pages, hand-written in an unknown writing system. Carbon-dated to the early 15th century, there are nevertheless suggestions that it might not be an ancient language but a hoax. And, despite containing many images of plants and other biological entities, its message and purpose has remained obscure (although an imaginative botanical interpretation is that it might represent a mediaeval plant physiology treatise). However, Stephen Bax, Professor of Applied Linguistics at the University of Bedfordshire (UK) has now claimed to have begun to decipher the manuscript’s text.
Progress is slow, but amongst the first few words to have been revealed are juniper, taurus, coriander, Centaurea, chiron, hellebore, Nigella sativa, kesar and cotton. A confident Bax declared, ‘… my research shows conclusively that the manuscript is not a hoax, as some have claimed, and is probably a treatise on nature, perhaps in a Near Eastern or Asian language’. Clearly, some way to go before we have a final, complete version, and can use it as a set text in plant physiology classes (so don’t throw out Taiz & Zeiger’s Plant Physiology just yet!). But another ancient manuscript whose purpose is more obvious is the Tractatus de Herbis (‘Treatise on Medicinal Plants’), a manual of materia medica [‘a Latin medical term for the body of collected knowledge about the therapeutic properties of any substance used for healing (i.e., medicines)’] compiled during the 15th century. This tome has been reproduced in a limited edition facsimile replica of 987 copies (price available ‘on request’, though I suspect that if you’ve got to ask how much it is, you can’t afford it…). This limited edition is accompanied by a full-colour commentary volume by Alain Touwaide,Research Associate of the Department of Botany at the Smithsonian National Museum of Natural History, USA and Scientific Director of the Institute for the Preservation of Medical Traditions at the Smithsonian in Washington, DC (USA).
[If you want to view the Voynich manuscript – for free! – it is available on-line. Even if the majority of the words are elusive, the images are quite wondrous… For more Voynich images and interpretations – e.g. putative plant identifications – Ellie Velinska’s blog is worth a visit – Ed.]
A few links have come in through the feeds today on urban botany. It could be interesting if you can’t get away for a holiday. Urban Botany, Urban Art and the Instagram Effect by Hollis Marriot at In the Company of Plants and Rocks blogs a botanical tour around Laramie. The juxtaposition of natural and urban elements like graffiti, can be striking.
She points on to Lucy Corrander who blogs at Loose and Leafy. I like her post on the wild plants of Southampton High Street which includes:
If I have a mission, it’s to persuade people that every street is a garden. Not has a garden, note; but is one.
As she finds, it can be a tough claim to defend, but given the tenacity of plants, she might well be right.
Returning to plants and art, the tenacity can be an artistic tool in itself. I wandered on to Moss Graffiti, using moss as the ink for art. which Heavy Petal covered this back in 2007, so I’m quite slow. There’s a number of Pinterest images up, some very impressive and a how to guide at Stencil Revolution.
Although atmospheric carbon dioxide (CO2) levels are currently rising, the last 30 million years witnessed great declines in CO2, which has limited the efficiency of photosynthesis. Rubisco, the critical photosynthetic enzyme that catalyses the fixation of CO2 into carbohydrate, also reacts with oxygen when CO2 levels are low and temperatures are high. When this occurs, plants activate a process known as photorespiration, an energetically expensive set of reactions that release one molecule of CO2.
C4 photosynthesis is a clever solution to the problem of low atmospheric CO2. It is an internal plant carbon-concentrating mechanism that largely eliminates photorespiration: a ‘fuel-injection’ system for the photosynthetic engine. C4 plants differ from plants with the more typical ‘C3′ photosynthesis because they restrict Rubisco activity to an inner compartment, typically the bundle sheath, with atmospheric CO2 being fixed into a 4-carbon acid in the outer mesophyll. This molecule then travels to the bundle sheath, where it is broken down again, bathing Rubisco in CO2 and limiting the costly process of photorespiration.
The evolution of the C4 pathway requires many changes. These include the recruitment of multiple enzymes into new biochemical functions, massive shifts in the spatial distribution of proteins and organelles, and a set of anatomical modifications to cell size and structure. It is complex, and it is also highly effective: C4 plants include many of our most important and productive crops (maize, sorghum, sugarcane, millet) and are responsible for around 25% of global terrestrial photosynthesis. A new paper in eLife examines how this process may have evolved, first to correct an intercellular nitrogen imbalance, and only later evolved a central role in carbon fixation.
Heterodichogamy and thrips-pollination in Platycarya strobilacea
Heterodichogamy, a dimorphism in which two morphs coexist in a population and undergo synchronous reciprocal sex changes, is an extremely rare and poorly understood sexual system. Fukuhara and Tokumaru study Platycarya strobilacea (Juglandaceae) and demonstrate that it is heterodichogamous based on observations of inflorescence architecture, sexual expression and pollination biology. Pollination by thrips is suggested by their frequent presence with attached pollen grains, the scarcity of other insect visitors, the synchronicity of thrips number in male spikes with the maturation of female flowers, and the morphological characters shared with previously reported thrips-pollinated plants.
*Or winter reading for our followers in the better hemisphere.
In the northern hemisphere, the summer break is upon us. If you’re looking for some light reading to take with you on holiday, what would you recommend? Kirkus Reviews has a short article on recent ecological science fiction, Seeders by A.J. Colucci looks like it could be interesting, combining plant neurobiology with horror. io9 has their own list from 2011, which includes a few I haven’t read as does SF Signal from 2012. Alan Cann has read The Windup Girl by Paolo Bacigalupi, which I realise is another book I haven’t read.
Is there a science fiction book you’d recommend that tackles plants in a credible way?
If you prefer your SF to feel like work, then you’re not limited just to moving from science to fiction. Recently a few have tried going the other way in the Science of Tatooine Blog Carnival. Matt Shipman explains Why a Bunch of Science Writers Are Writing About a Fictional Planet, including Malcolm Campbell’s speculative Tatooine’s tangled bank – plants evolve in a galaxy far, far away
A while back Annals Editor Pat Heslop-Harrison was asking what ten plants should botanists know about. I’ve taken it a bit further with a Buzzfeed post on the 7 Plants That Changed Your Life.
I’ve tried to pick seven plants with global consequences, but I’m not entirely happy with the list. The seven plant limit means I’ve missed out a lot of important plants. For example, there are no marine plants on the list. Nothing that really address important evolutionary steps that plants made, so no mosses or ferns,
So what plants would you add to the list and why? I’d be interested to see if our readers could compile another list of another seven plants that would be equally good, or better.
Leave your suggestions below, or at Buzzfeed or on our Facebook page.