Is there a downside for plants when they can’t sense ‘up’?

Looking at a tree, it can be hard to visualise the sheer volume of water being drawn up from the roots to the canopy. That volume of was is massive, and puts cells under a lot of pressure, so lignin, the substance plants use to strengthen cell walls, is an important product. But what happens to lignin if you take gravity away? Growth and Lignification in Seedlings Exposed to Eight Days of Microgravity by Cowles et al. is a study that aims to find out.

The experiment on STS-3 was growing pine seedlings with mung beans and oat seeds. There were a couple of targets. One was to examine how gravity affected the production of lignin. The other was to test the PGU, the plant growth unit, that would be used in following missions.

Plant Growth Unit

From Cowles et al.

To see the effect of gravity a PGU with similar plants was kept on Earth, so the development of the plants could be compared.

Germination of the orbiting plants was much like the 1g plants. However, Cowles et al. point out that the seeds have to be prepared before launch, which gave them twelve hours on Earth to germinate. They found that the flying plants grew less, and in the case of the seeds, roots were growing ‘up’ as well as ‘down’. Some of the plants that grew in orbit also contained less lignin.

There have been plenty of papers that went on to cite this research, most recently Expression of stress-related genes in zebrawood (Astronium fraxinifolium, Anacardiaceae) seedlings following germination in microgravity by Inglis et al. in Genetics and Molecular Biology from this year.

Recently in Annals of Botany there’s been Xylem Development and Cell Wall Changes of Soybean Seedlings Grown in Space and in the opposite directon Hypergravity Stimulus Enhances Primary Xylem Development and Decreases Mechanical Properties of Secondary Cell Walls in Inflorescence Stems of Arabidopsis thaliana by Nakabayashi et al.

This is interesting that it still gets cited because the results weren’t all significant. While the mung beans had less lignin, the oat and pine seedlings didn’t have significantly less and the experiment was relatively small. However, this flight wasn’t just about the results, it also worked to establish a method. By laying out the experimental technique used to analyse the plant Cowles et al laid down a baseline for other researchers to compare and improve their techniques.

The basic question they studied remains important. Understanding the processes that produce lignin could help with technology on Earth. For example, it would be helpful in producing biofuel if there were less lignin in it to start with. Launching plants and growing them in space would be a spectacularly inefficient way to do that. However for small samples, it can be a useful way to isolate one variable and help figure out the mechanics of lignin production.

You can read more posts on papers from our spaceflight supplement by clicking the STS-3 tag.

Today’s Papers

Cowles J.R., Scheld H.W., Lemay R. & Peterson C. (1984). Growth and Lignification in Seedlings Exposed to Eight Days of Microgravity , Annals of Botany, 54 (supp3) 33-48. DOI:

Chapple C. & Rick Meilan (2007). Loosening lignin’s grip on biofuel production, Nature Biotechnology, 25 (7) 746-748. DOI:

de Micco V., J.-P. Joseleau & K. Ruel (2008). Xylem Development and Cell Wall Changes of Soybean Seedlings Grown in Space, Annals of Botany, 101 (5) 661-669. DOI:

Inglis P.W., Ciampi A.Y., Salomão A.N., Costa T.D.S.A. & Azevedo V.C.R. (2013). Expression of stress-related genes in zebrawood (Astronium fraxinifolium, Anacardiaceae) seedlings following germination in microgravity., Genetics and molecular biology, PMID:

NAKABAYASHI I. (2006). Hypergravity Stimulus Enhances Primary Xylem Development and Decreases Mechanical Properties of Secondary Cell Walls in Inflorescence Stems of Arabidopsis thaliana, Annals of Botany, 97 (6) 1083-1090. DOI:

Transgenerational changes in seed longevity in Silene

Transgenerational changes in seed longevity in <i>Silene</i>

Transgenerational changes in seed longevity in Silene

Seed longevity, a fundamental plant trait for ex situ conservation and persistence in the soil of many species, varies across populations and generations that experience different climates. Mondoni et al.  study seeds from alpine and lowland populations of Silene vulgaris and show that seed longevity has a genetic basis but may show strong adaptive responses, which are associated with differential accumulation of mRNA via parental effects. They conclude that adaptive adjustments of seed longevity due to transgenerational plasticity may play a fundamental role for the survival and persistence of the species in the face of future environmental challenges, and that the location of regeneration may have important implications for ex situ conservation in seed banks.

Calibrating data in a weightless environment

A Test to Verify the Biocompatibility of a Method for Plant Culture in a Microgravity Environment by Brown and Chapman is an example of the basic science people needed to do with the shuttle.

If you’re going to run plant experiments, then the plants will need to perform basic function in order to live. One example is taking up water and this was a problem. Soviet experiments and theoretical work suggested the way plants reacted to soil moisture in orbit was very different to how they behaved on Earth. This would have a major effect on any experiment results because unusual behaviour could be due to whatever it was you were experimenting for, or it could just be the way it goes in microgravity.

STS-3 carried what NASA called ‘bio-engineering tests’ to see if botanical experiments with their systems were practical. The test has HEFLEX, the Helianthus Flight Experiment. The question HEFLEX was to look at was how sunflower nutation happened in orbit. This is the spinning effect of the stem in growing seedlings. You can see Arabidopsis doing this in the time-lapse video below.

There was a problem with STS-2 which meant that the experiments for that mission were cut short. STS-3 had the opposite problem, the mission was longer than HEFLEX would be, but it still allowed researchers to compare the effects of soil moisture.

Graph of results.

Comparison of shoot lengths of 8-9-day-old plants from STS-3 Mission (solid dot) and those from 1g control test (hollow dot). The same experiment hardware was used for both tests.

Tests showed plant responses seemed to be comparable, and additional post-landing inspection also show the effects of launch and re-entry were no big problem.

This research went on to be cited in a few papers, and you can pick up Circumnutations of Sunflower Hypocotyls in Satellite Orbit for free from Plant Physiology, which had Brown and Chapman among the authors. But the chain doesn’t stop there.

Nutation remains a puzzle in plant sciences. Circumnutation as an autonomous root movement in plants in AmJBot dates from 2012 (again free access). AoB PLANTS, the open access plant journal has a paper Petiole hyponasty: an ethylene-driven, adaptive response to changes in the environment by Polko et al. Both of these papers refer back to Brown et al’s PlanyPhys paper, despite being terrestrial papers. This first paper, specialising in how a lab on the space shuttle worked, is part of a chain of research. It shows launching seedlings away from the planet can bring us closer to understanding life upon it.

You can read more posts on papers from our spaceflight supplement by clicking the STS-3 tag.

Today’s Papers

Brown A.H. & Chapman D.K. (1984). A Test to Verify the Biocompatibility of a Method for Plant Culture in a Microgravity Environment, Annals of Botany, 54 (supp3) 19-31.

Brown A.H., Chapman D.K., Lewis R.F. & Venditti A.L. (1990). Circumnutations of Sunflower Hypocotyls in Satellite Orbit, Plant Physiology, 94 (1) 233-238. DOI: 10.​1104/​pp.​94.​1.​233

Migliaccio F. & A. Fortunati (2012). Circumnutation as an autonomous root movement in plants, American Journal of Botany, 100 (1) 4-13. DOI: 10.3732/ajb.1200314

Polko J.K., A. J. M. Peeters & R. Pierik (2011). Petiole hyponasty: an ethylene-driven, adaptive response to changes in the environment, AoB Plants, 2011 plr031-plr031. DOI: 10.1093/aobpla/plr031

Bloody royal French gourd debunked

Image: Peter Woodard/Wikimedia Commons.

Image: Peter Woodard/Wikimedia Commons.

One of the most unusual plant-based items that has come to my notice recently is this rather ‘quirky’ item that sheds a forensic botany light on an episode of ‘regicide à la française’ when King Louis XVI had an unfortunate appointment with Madame la Guillotine. Big issues of whether mere mortals have the right to execute divinely ordained monarchs and the politics of late 19th century Europe aside, what is the plant connection? It’s not the wood that may have been used to construct the fearsome ‘engine of despatch’ (a euphemism if ever there was…), the guillotine. That would be far too obvious for Monsieur P. Cuttings (although the role of plant products in execution and torture has been given a fascinating scholarly treatment by Simcha Lev-Yadun of the University of Haifa- Oranim, Israel, in his paper ‘The ancient and modern ecology of execution’).‎ Rather, it concerns a gourd (the fruit of a member of the pumpkin family, the Cucurbitaceae) – which allegedly contained a handkerchief that had been stained with blood from the ill-fated monarch. (No, I don’t know why anybody might want to do this: chacun à son gout, I guess.) A fanciful tale certainly, but nevertheless one that we might like to believe. Sadly, when the DNA of the blood was subjected to various modern-day tests and analyses by Iñigo Olalde et al. this lovely story did not stand up – much like the late king himself after his sanguine appointment – to 21st century scrutiny. In a statement as beautifully crafted as the ‘pyrographically decorated’ gourd itself, the team conclude that, ‘although we cannot totally discard that the gourd’s sample belongs to Louis XVI on our genomic data alone, several lines of evidence, including the ancestry analysis and the functional interpretation of the genome fail to provide definitive support for the attribution of this specimen to the beheaded French king’. Le fin, enfin? (c’est la vie… or mort even…).


[This story is reminiscent of those concerning bottles of wine bought for vast sums of money in the belief that their contents are of immense value. In those cases (pun not intended, but duly noted…) the owners apparently never drink the contents for fear of discovering that the ‘wine’ is actually worthless. Seemingly for some things it’s simply best ‘not to know’; we seem prepared to accept that some cherished beliefs may not stand up to scrutiny so we choose not to scrutinise them. After all, if we studied everything we’d know everything. Sometimes it’s just nice to leave a few ‘mysteries’… – Ed.]

30 years of Astrobotany in Annals of Botany

“In the newspapers I used to read about shuttles going up and down all the time, but it bothered me a little bit that I never saw in any scientific journal any results of anything that had ever come out of the experiments on the shuttle that were supposed to be so important.”

Richard Feynman – What Do You Care What Other People Think?

STS-3 Shuttle mission launching

STS-3 departs on its mission. Photo: NASA.

On 22 March 1982, at 11:00 local time, the STS-3 mission, manned by Lousma and Fullerton launched in the space shuttle Columbia. Over the next eight days the shuttle was a platform for a few plant science experiments. A year and a half later these experiments were the basis of most of an Annals of Botany supplement Experiments on Plants Grown in Space.

It’s not that surprising Richard Feynman hadn’t seen these results. It’s easy to forget what a difference electronic communications have made. This issue of Annals of Botany would not have been issued as a PDF. Anyone wanting to see the results would have to physically locate an issue at a local library, not just click – which made it difficult for the public to access. NASA would also be issuing paper releases, and the news was the next shuttle flight not the one several missions back. So some science of immense public interest was kept to a few specialists.

The supplement has been digitised, and with current papers Annals of Botany makes its papers free access a year after print publication. In this case the delay is around thirty years. Quite a few things have changed since then, so the first paper in the supplement is a useful primer. Status and Prospects by Halstead and Dutcher gives a sense of the state of play for botany in the early 1980s.

It’s easy to be accustomed to space flight, and most ISS launches are not inherently newsworthy. The space shuttle was the vehicle that started the West’s perception of space travel as a mundane event. Halstead and Dutcher looked forward to the prospect of regular and affordable spaceflight.

Hindsight comes from Paul et al. and their paper Fundamental Plant Biology Enabled by the Space Shuttle in AmJBot. They comment on how plant science changed on shuttle flights, eventually taking advantage of the long-term missions offered by the International Space Station. One of the features of their paper is they point out there’s more to botany in space than the effect of gravity. By eliminating gravity you can explore other tropisms. They give a couple of examples, you can test for phototropism obviously, by manipulating light. But they also point out that subtle effects like ionic gradients become visible, once you eliminate the effect of gravitropism.

Aside from plans to colonise Mars, basic science means that exploration of microgravity and extreme environments will continue to be growth areas in botany. Over this week, we’ll be looking at the papers in our Space Shuttle issue and the science that they inspired after publication. Posts will be going live daily.

Today’s Papers

Halstead T.W. & Dutcher F.R. (1984). Status and Prospects, Annals of Botany, 54 (supp3) 3-18.

Paul A.L., Wheeler R.M., Levine L.G. & Ferl R.J. (2013). Fundamental Plant Biology Enabled by The Space Shuttle, American Journal of Botany, 100 (1) 226-234. DOI: 10.3732/ajb.1200338

Floral elaiophores of Vitekorchis, Cyrtochilum and Oncidium

Floral elaiophores of <i>Vitekorchis</i>, <i>Cyrtochilum</i> and <i>Oncidium</i>

Floral elaiophores of Vitekorchis, Cyrtochilum and Oncidium

Molecular approaches have been used to investigate the phylogeny of subtribe Oncidiinae, resulting in the recent re-alignment of several of its genera. Davies et al. compare the floral elaiophores (oil glands) of four species formerly assigned to Oncidium (Oncidiinae), namely Gomesa longipes, Vitekorchis excavata, Cyrtochilum meirax and florally dimorphic Oncidium heteranthum. They find that, except for C. meirax, which lacks obvious elaiophores, this structure occurs on the labellar callus, has glabrous and trichomatous regions, and comprises a single-layered, secretory epidermis lacking palisade cells, the oil being produced either by smooth endoplasmic reticulum or as plastoglobuli within elaioplasts. Subsequent stages of secretion differ little between species, with the oil traversing the cell wall and accumulating beneath the distended cuticle. Floral dimorphism has little effect on elaiophore structure.

Stem anatomy and growth forms in perianth-bearing Piperales

Stem anatomy and growth forms in perianth-bearing Piperales

Stem anatomy and growth forms in perianth-bearing Piperales

The order Piperales has the highest diversity of growth forms among the earliest angiosperm lineages, including trees, shrubs, climbers and herbs. Wagner et al. trace anatomical and morphological traits among the perianth-bearing Piperales in order to detect trends in growth form evolution and developmental processes, and show that growth form divergence is accompanied by changes in stem anatomy and appropriate biomechanical properties. They propose that the highly specialized climbing habit is a derived form that evolved with the diversification of Aristolochia, and might have been a key feature for the diversification of this genus.

The root-soil interface, ancient climates, sustainable agriculture – what’s new in Annals of Botany this week

The root-soil interface A multi-imaging approach to study the root-soil interface
Dynamic processes occurring at the soil–root interface crucially influence soil physical, chemical and biological properties at a local scale around the roots, and are technically challenging to capture in situ. This study presents a novel multi-imaging approach combining fluorescence and neutron radiography that is able to simultaneously monitor root growth, water content distribution, root respiration and root exudation.


Evidence for cryptic northern refugia in the last glacial period in Cryptomeria japonica
Distribution shifts and natural selection during past climatic changes are important factors in determining the genetic structure of forest species. In particular, climatic fluctuations during the Quaternary caused changes in the distribution ranges of plants, and thus affected their genetic structure. This study focusses on the responses of the conifer Cryptomeria japonica to past climatic changes during the last glacial maximum.


Sustainable intensification in agricultural systems
Agricultural systems are amended ecosystems with a variety of properties. Modern agroecosystems have tended towards high through-flow systems, with energy supplied by fossil fuels directed out of the system. In the coming decades, resource constraints over water, soil, biodiversity and land will affect agricultural systems. Sustainable agroecosystems are those tending to have a positive impact on natural, social and human capital, while unsustainable systems feed back to deplete these assets, leaving fewer for the future. Sustainable intensification a process or system where agricultural yields are increased without adverse environmental impact and without the conversion of additional non-agricultural land. This review analyses recent evidence of the impacts of sustainable intensification in both developing and industrialized countries, and demonstrates that both yield and natural capital dividends can occur.


Diversification and the evolution of dispersal ability in the Brassiceae
Dispersal and establishment ability can influence evolutionary processes such as geographic isolation, adaptive divergence and extinction probability. Through these population-level dynamics, dispersal ability may also influence macro-evolutionary processes such as species distributions and diversification. This study examined patterns of evolution of dispersal-related fruit traits, and how the evolution of these traits is correlated with shifts in geographic range size, habitat and diversification rates in the tribe Brassiceae (Brassicaceae).


Halloween Special: First record of bat-pollination in Tillandsia

First record of bat-pollination in Tillandsia

Bats are responsible for pollinating several species of plants. A new paper in Annals of Botany reports for the first time bat-pollination of a species in the genus Tillandsia.

Bromeliaceae is a species-rich neotropical plant family, of which Tillandsia is the most diverse genus and includes more than a third of all bromeliad species. The flowers of some species show characteristics typical for pollination by nocturnal animals, particularly bats and moths. The authors find that nectar production is restricted to the night hours, and the most frequent visitor and the only pollinator is the nectarivorous bat Anoura geoffroyi. This is the first report of chiropterophily within the genus Tillandsia, and the results suggest an ongoing evolutionary switch from pollination by birds or moths to bats.

Aguilar-Rodríguez, P.A., Krömer, T., García-Franco, J.G., Knauer, A., & Kessler, M. (2014) First record of bat-pollination in the species-rich genus Tillandsia (Bromeliaceae). Annals of Botany, 113 (6): 1047-1055. doi: 10.1093/aob/mcu031

(Sorry, we’ll try to make next year’s Halloween special much scarier than this.)

Belowground legacies of Pinus contorta invasion and removal result in multiple mechanisms of invasional meltdown

14095R1 Ian Dickie thumbnailInvasive plants alter plant communities and transform landscapes aboveground, but also have strong belowground effects that are potentially even more important to ecosystem outcomes. In a new study published in AoB PLANTS using management treatments of the widespread invasive tree, Lodgepole Pine, Dickie et al. found that pines and pine removal transform belowground ecosystems, increasing ectomycorrhizal inoculum and driving a change from slow-cycling fungal-dominated soils to fast-cycling bacterial-dominated soils with increased nutrient availability. This results in increased growth of graminoids, particularly exotic grasses, and facilitation of Douglas-fir establishment, hindering ecosystem restoration. The results highlight the importance of considering multiple species interactions in invasion, particularly in terms of belowground legacies.