Wednesday, July 18, 2018

Floral morphogenesis in Camptotheca

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Camptotheca is endemic to China and there are limited data about the breeding system and morphogenesis of the flowers. Camptotheca is thought to be related to Nyssa and Davidia in Nyssaceae, which has sometimes been included in Cornaceae. However, molecular phylogenetic studies confirmed the inclusion of Camptotheca in Nyssaceae and its exclusion from Cornaceae. Gong et al. reveal developmental features of the inflorescence and flowers in Camptotheca to compare with related taxa in Cornales.

SEM image of a flower
Image: Gong et al. 2018

Gong and colleagues collected inflorescences and flowers of Camptotheca acuminata at all developmental stages and examined them with a scanning electron microscope and stereo microscope.

Camptotheca has botryoids which are composed of several capitate floral units (FUs) that are initiated acropetally. On each FU, flowers are grouped in dyads that are initiated acropetally. All floral organs are initiated centripetally. Calyx lobes are restricted to five teeth. The hypanthium, with five toothed calyx lobes, is adnate to the ovary. The five petals are free and valvate. Ten stamens are inserted in two whorls around the central depression, in which the style is immersed. Three carpels are initiated independently but the ovary is syncarpous and unilocular. The ovule is unitegmic and heterotropous. Inflorescences are functionally andromonoecious varying with the position of the FUs on the inflorescence system. Flowers on the upper FU often have robust styles and fully developed ovules. Flowers on the lower FU have undeveloped styles and aborted ovules, and the flowers on the middle FU are transitional.

Camptotheca possesses several traits that unify it with NyssaMastixia and Diplopanax. Inflorescence and floral characters support a close relationship with Nyssaceae and Mastixiaceae but a distant relationship with Cornus. Their results corroborate molecular inferences and support a separate family Nyssaceae.

Reference List

Gong, J., Li, Q., Wang, X., Ma, Y., Zhang, X., Zhao, L., … Ronse De Craene, L. (2018). Floral morphology and morphogenesis in Camptotheca (Nyssaceae), and its systematic significance. Annals of Botany, 121(7), 1411–1425. https://doi.org/10.1093/aob/mcy041

When plant biology meets physics…

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Great things are possible when disciplines that may be studied separately and distinctly are brought together. For example, and famously, when botany, zoology, bacteriology, mycology, protistology, virology, chemistry, physics, and anthropology (and maybe a few more ‘-ologies’ and non-ologies…) come together we get the new(-ish) discipline of ecology. More modestly, this item is concerned just with two sciences, botany and physics*. And its sole declared intention is to alert the readers of Plant Cuttings – who are a switched-on plant-minded bunch – to a special issue of Physics World.

A collage of physical phenomena
Image: Fastfission / Wikipedia

Although this is a journal that may not be on their radar as far as plant-related reading goes, April 2018’s issue featured many articles that take a physics perspective on plant matters. And, because Plant Cuttings is about service to the botanical community, I’ve done the hard work for you (and it took quite a while to do…) and tracked down freely-available copies of that issue’s plant physics articles.

So, you can now read about: Cornell University (USA) botanist Karl Niklas; the issues of growing plants in space; nano-strategies used by flowers for colour and pollinator-attraction; discover the connection between transpiration and cooling vehicles that travel at hypersonic speeds**; gain insights into how electric fields can affect root growth and regeneration***; and discover whether – or not – photosynthesis is ‘quantum-ish’. Happy to help put some ‘fizz’ back into your botany.

* More examples of ‘when botany meets physics’ can be found in the following Cuttings item, Flowers (it’s what angiosperms are all about!). For a good source of plant (and other lifeforms) and physics investigations, we recommend the Journal of the Royal Society Interface, which publishes “cross-disciplinary research at the interface between the physical and life sciences”.

** Since transpiration is primarily a xylem-related phenomenon, in the interests of balance we shouldn’t neglect that other long-distance vascular transport pathway – the phloem. For an update on the physics of phloem we recommend Kaare Jensen’s article.

*** For more about the phenomenon of electrical signals originating in the root of vascular plants, see Javier Canales et al..

Reference List

Jensen, K. H. (2018). Phloem physics: mechanisms, constraints, and perspectives. Current Opinion in Plant Biology, 43, 96–100. https://doi.org/10.1016/j.pbi.2018.03.005

Canales, J., Henriquez-Valencia, C., & Brauchi, S. (2018). The Integration of Electrical Signals Originating in the Root of Vascular Plants. Frontiers in Plant Science, 8. https://doi.org/10.3389/fpls.2017.02173

Rarity and nutrient acquisition relationships before and after prescribed burning in an Australian box-ironbark forest

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Exocarpos cupressiformis – a relatively rare species in the box-ironbark ecosystem we studied–made a unique contribution to nutrient cycling. The leaf litter (photosynthetic stems) it shed contained concentrations of phosphorus and potassium that were 3.75 and 7.75 times greater, respectively, than average concentrations for leaf litter in the community. Both nutrients are scarce in the ecosystem. Where it occurs, this species likely plays an important role in community productivity. Image credit: John Patykowski.

Nutrient cycling is greatly influenced by dominant plants that contribute high amounts of leaf litter to soils; however, less-dominant and rare species can play key roles in nutrient cycling if they have unique nutrient acquisition traits and provide high-quality litter. In many parts of the world, wildfire is likely to become more frequent and intense under a changing climate, and the effect this will have on plant rarity and on species with unique nutrient acquisition traits, and thus nutrient cycling, remains poorly understood.

In a recent study published in AoB PLANTS, Patykowski et al.examined the relationship between nutrient acquisition strategies, senesced leaf nutrient profiles, and species rarity before and after prescribed burning in a nutrient-poor box-ironbark forest in southeastern Australia. Whilst no community-wide relationship between rarity and uniqueness of leaf nutrient profiles was found, some of the rarest species were functionally unique. Two hemiparasitic species were relatively rare in the ecosystem studied and differed greatly from other species due to high concentrations of phosphorous and potassium in senesced leaves. This study highlights the importance of identifying and conserving species with unique traits (such as hemiparasitism) to prevent loss of functional contributions to ecosystem function.

Reference List

Patykowski, J., Dell, M., Wevill, T., & Gibson, M. (2018). Rarity and nutrient acquisition relationships before and after prescribed burning in an Australian box-ironbark forest. AoB PLANTS, 10(3). https://doi.org/10.1093/aobpla/ply032

Why are/aren’t we following you on Twitter?

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iPhone with Twitter on a desk
Copyright: rvlsoft / 123RF Stock Photo

We’ve had some queries about why we follow who we do on Twitter, as we follow quite a few people. We also occasionally get asked by some people why we’re not following them. So here’s some explanation.

There a couple of reasons why we follow people on Twitter. One is to keep track of the zeitgeist. We track what is getting shared on Twitter to see what matters in botany. When n people share the same paper or news item a scanner sends a ping to us. That way we don’t have to be awake if a story catches some people’s eye when we’re asleep. Making that sample as bigger rather than smaller means that a small interest group isn’t going to skew what we find.

Who we follow

People who tweet links to news stories with some botany interest, or links to plant science papers. First though, we have to know that these people exist. The way we tend to find these people is they follow us. If we get a notification abc123 is following you, then we’ll look to see what abc123 is interested in, and if we see some botany links near the top of the profile we’ll follow them.

Another way to catch our attention is to retweet something we’ve posted. It doesn’t have to be one of our tweets. It could be something we’ve retweeted. That’s a little less likely to catch our attention, but it happens.

Who we don’t follow

People whose tweets are mainly politics. We actually think it’s a good thing for scientists to be politically engaged, so socially tweeting politics is good. However, Twitter is a tool for botany for us, so filling the scanner with political tweets is just going to make finding the botany more difficult.

If you have a new account, maybe just a name and a tweet saying “Hello World!”, then we won’t follow you because we don’t know who you are. There are a fair number of bots that follow people in the hope of getting an automatic follow back. We’d like to think we’re following humans.

Another kind of account we don’t follow from @botanyone is an account that mainly tweets photos of plants someone has seen. Again, that’s not supplying links into the system. On the other hand, we would follow an account like that on Instagram, where we have the handle @botany_too. If you think we should be following your Instagram account, then leave a comment below – or on one of our images on Instagram.

Finally, we tend not to follow gardening accounts. We like gardening and think more gardeners would be good thing – but gardening tends to be quite local interest. For example, I have a friend in Arizona who is interested in xeriscaping, to avoid using additional irrigation. In a Welsh garden often the problem is an excess of water instead of a lack. We probably don’t have much in common in the garden. However, a lot of gardeners have an interest in plants beyond their own patch, so being a gardener doesn’t you out from our follow list. It just doesn’t automatically put you on it either.

If you’re not followed, please don’t take it personally. @botanyone doesn’t follow either of my personal accounts because I’m far more likely to tweet about Formula E, or Welsh politics than botany on them.

What do we do with these links?

Not as much as we should. When I’m not busy and paying attention to the windows in the background, I’ll retweet things that are becoming popular. I’ll try to find the original tweeter to retweet when I see that.

We also compile the most popular links into our weekly email, The Week in Botany. On a Monday morning, I send out what we’ve posted to Botany One, the most popular news links, and paper links in an email. If you’ve seen an alert about an email list on the site, that’s what it’s about. Somewhere on my to-do list is find a way of getting breaking twitter news on to the site in a timely way. That’s not a small task.

The second reason is that by choosing the people we do, if I’m having a lousy day then I don’t have to look far in the @botanyone stream before I find someone who’s doing something interesting.

There are many ways of using Twitter. If we’re not following you, it’s not that we think you’re using Twitter the wrong way, just that we’re using it in a different way to you. Of course if you think we’re using Twitter the wrong way, you’re welcome to leave a comment below or tweet us.

Modelling polycyclic growth and leaf neoformation in trees

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Trees can adapt their architecture in response to climate change by adjusting growth processes such as leaf neoformation and polycyclic growth. Tondjo et al. present work aimed to improve the plant growth model GreenLab in order to take into consideration these processes through stochastic functions.

Schematic representation of a simulation of the GreenLab model
Schematic representation of a simulation of the GreenLab model: development and growth simulation cycle, the model outputs, field measurements, the inverse method and the hidden parameters computed from the model. *Specific implementations made in the teak model. Image Tondjo et al. (2018)

The model is tested using existing data collected on planted teak trees (Tectona grandis, Lamiaceae) in Togo, Africa. Simulations reproduced the observed tree architectures and biomass production at different ages satisfactorily. The main advantage of Greenlab is its mathematical formulation that allows direct and fast calculation of a single tree or a forest.

Reference List

Tondjo, K., Brancheriau, L., Sabatier, S., Kokutse, A. D., Kokou, K., Jaeger, M., … Fourcaud, T. (2018). Stochastic modelling of tree architecture and biomass allocation: application to teak (Tectona grandis L. f.), a tree species with polycyclic growth and leaf neoformation. Annals of Botany, 121(7), 1397–1410. https://doi.org/10.1093/aob/mcy040

Earpedia: Plants

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Amazon, through its Audible audiobook brand, is releasing free audio shows for subscribers. One of these was Zoopedia, a series looking at animals. It’s now been rebranded Earpedia, and the second series covers plants. It’s a mixed bag.

Earpedia follows the same comedy/fact genre popularised by Mark Steel, QI, The Unbelievable Truth and others. The narrator is Sue Perkins, with comedy skits interspersed around what she has said. In some ways it’s quite similar to the Mark Steel Lectures, which is no bad thing.

There are thirteen episodes of around ten to fifteen minutes long, each based on a plant. Venus Flytrap is among the picks, as you might expect, but there are some more unusual choices. Welwitschia mirabilis wouldn’t have been the first plant that came to mind if I were drawing up a list of thirteen but it’s comedy, not a botany course.

As a comedy, the episodes are uneven in quality. It’s said that when you run out of ideas, you can always try a knob joke. It was a bit disappointing that it’s where the series started with banana. It’s a pity because later episodes are much better. I thought the coconut episode did well in capturing the staggering usefulness of the plant. The facts worked with the humour instead of feeling like they were marking time to the next joke.

A few of the other episodes gave the impression the plants were chosen because they were opportunities for penis jokes. Though it works better in the Titan Arum and Squirting Cucumber episodes, possibly because the banana is a bit more of a cliche.

Would you like the series? Maybe not, but if you’re reading this, then you’re probably not in the target audience. The audience isn’t people interested in plants. It’s people who find Sue Perkins’s programmes funny. As a series about plants for people who aren’t interested in plants, it works well. Plants are portrayed in a positive light and as something that people can be interested in.

Humour is a personal taste, but even if it doesn’t work for you it might be worth listening to a couple of episodes to see how plants can be connected to popular interests. As well as coconut, there’s Quercus suber and Drakaea livida.

Given it’s free, the only real grumble I have is the need to have an Amazon account to pick it up. You can see other reviews at Goodreads.

Defence signalling marker gene responses to hormonal elicitation differ between roots and shoots

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Plants responses to environmental stresses are regulated by signalling hormones, such as jasmonic acid, salicylic acid, ethylene and abscisic acid. Plant scientists commonly use marker genes to study which signalling pathways are activated, however, these markers were designed and tested for shoot responses in Arabidopsis thaliana. It is unclear whether the paradigms based on experiments on above-ground organs of A. thaliana are entirely transferable to shoots and roots of other species.

Summarizing scheme of the changes in phytohormone levels and related marker genes in Brassica rapa shoots and roots after local hormonal elicitation. Image credit: Papadopoulou et al.

A recent study by Papadopoulou et al. published in AoB PLANTS investigated the regulation dynamics of hormonal-related marker genes in both roots and shoots of the non-model plant Brassica rapa. The study showed some of the commonly used molecular markers developed in A. thaliana did not show specific responsiveness to single hormone applications in B. rapa. Moreover, the same marker gene may respond differently to hormone application in roots and shoots. These findings suggest that marker gene responses can be organ and species specific and should be interpreted with caution.It is therefore advisable to combine analyses of multiple marker genes with those of phytohormone levels to ascertain more certainly which hormonally regulated defence pathways are activated.

Reference List

Papadopoulou, G. V., Maedicke, A., Grosser, K., van Dam, N. M., & Martínez-Medina, A. (2018). Defence signalling marker gene responses to hormonal elicitation differ between roots and shoots. AoB PLANTS, 10(3). https://doi.org/10.1093/aobpla/ply031

On nectaries and floral architecture

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Nectaries are the most interesting organs in flowers – at least to me. Compared to other floral organs (i.e. perianth organs, stamens and carpels), the position of nectaries is not necessarily fixed within the floral morphology. This makes them especially interesting to evolutionary studies. Additionally, and most importantly, nectaries produce nectar. In many angiosperm flowers, nectar is the primary reward offered to a potential pollinator. To ensure that ideally only legitimate pollinators can access the reward (and in that way successfully transfer pollen), flowers are often “built” around the nectary or the nectar. This is where floral architecture becomes important.

Floral architecture

Comparison between flowers of borage and viper's bugloss
Figure 1: Comparison between flowers of borage (Borago officinalis; left) and viper’s bugloss (Echium vulgare; right) with their respective floral formulas displayed below to visualise the difference between floral organisation and floral architecture in the sense of Endress (1996).

Floral architecture is a term which is not commonly used. One reason for that might be that there are several terms describing various phenomena related to floral architecture. Some of these terms are focusing only on a specific aspect. Others are quite general and inclusive, but imprecise. I prefer the definition for floral architecture provided by Endress (1996). He differentiates between floral organisation and floral architecture. Under this definition, floral organisation describes the number and position of organs in a flower. Floral architecture describes and takes into account the relative sizes of floral organs, their degree of fusion and synorganisation (“spatial and functional connections between organs of the same or different kind leading to a homogenous functional structure”, (Ronse De Craene 2010, p. 412).
One illustrative example: borage (Borago officinalis) and viper’s bugloss (Echium vulgare) might look completely different at first glance (Figure 1). But if you break their appearance down to the number of organs, you will notice that their floral organisation is identical: 5 sepals, 5 petals, 5 stamens, 2 carpels, 1 nectary disk at the base of the ovary. What makes them appear different is, in fact, their floral architecture.

Geraniales – insights into nectaries and floral architecture

Nectaries of three species of the Geraniales
Figure 2: Nectaries of three species of the Geraniales. From left to right: Pelargonium australe (Geraniaceae); part of the receptacle wall has been removed to show the inside of the receptacular cavity and the gland. Melianthus comosus (Melianthaceae); cup-shaped nectary. Greyia flanaganii (Francoaceae); young flower with ten nectariferous appendages. Perianth organs removed.

Geraniales are a particularly interesting group, where we studied the nectaries (Jeiter, Weigend, et al. 2017) and later the relationship between nectaries and floral architecture (Jeiter, Hilger, et al. 2017). Geraniales are a medium sized order with a sub-cosmopolitan distribution. Most of the species are placed in the family Geraniaceae with approximately 830 species. The remaining c. 45 species are included in four different families (Palazzesi et al. 2012). In our first paper (Jeiter, Weigend, et al. 2017), we studied the diversity in floral nectaries (Figure 2) and flower morphology. We found that despite huge differences in appearance (i.e., floral architecture), there is a high degree of similarity in floral organisation. Apart from switches in merosity (number of floral organs per whorl), major changes occurred in the androecium and to some extent in the corolla. We were able to show that changes in nectary gland number and position can be explained by simple shifts in their position in relation to the filaments. In this first article, we studied species from all genera of the whole order.

SEM micrographs of different developmental stages of Hypseocharitaceae and Geraniaceae flowers.
Figure 3: SEM micrographs of different developmental stages of Hypseocharitaceae and Geraniaceae flowers. Perianth organs have been removed. Clockwise from top left to bottom left: Young flowers of Hypseocharis bilobata, pre-anthetic flower of Geranium pratense, anthetic flower of Erodium manescavi, young inflorescence of Erodium manescavi showing various developmental stages.

In our second article (Jeiter, Hilger, et al. 2017), we focused on the families Geraniaceae and Hypseocharitaceae (Figure 3). In these two families, differences in floral organisation occur in the number of fertile stamens and the number of whorls in the androecium. The only exception is the genus Pelargonium, showing a high degree of variability in the androecium (Figure 4), as well as in the perianth. We used an ontogenetic approach combining scanning electron microscopy (SEM) and light microscopy (LM) to study the development of the nectary glands and their relation to the other floral organs. We found that the nectary glands in all five genera studied arise in late flower development and are formed from the receptacle at the bases of the filaments of the antesepalous stamens. The receptacle is not only involved in the formation of the nectary glands, but also in changes in the floral architecture. The most prominent example is Pelargonium, where four of the five nectary glands, present in the other genera, are reduced. The remaining gland is placed in an elongated receptacular cavity easily mistaken for the petiole. In other genera, the receptacle forms a short, column-like structure, the so-called anthophore, lifting the inner floral organs, or the receptacle forms shallow invaginations, which partially enclose the slightly sunken nectary glands.

implified floral diagram of a Geranium species
Figure 4: Simplified floral diagram of a Geranium species (Geraniaceae). Floral formular: * K5 C5 A5+5 G(5). The inner, white circle indicates the anthophore, a part of the receptacle that lifts the inner floral organs (i.e., petals, stamens, gynoecium). The nectary glands (blue) are formed by the receptacle and partially lifted by the anthophore.

Revolver architecture

Floral architecture is strongly influenced by receptacular growth; however, the other organs of the flower are of course also involved and sometimes highly synorganised. Endress (2010) describes the formation of a revolver architecture in Geranium robertianum. Revolver architecture is a particular type of floral architecture, where separate compartments are formed. Each compartment holds part of the total nectar reward of the flower. As a consequence of revolver architecture, a potential pollinator has to probe every separate compartment to harvest all the nectar of the flower. This increases handling time and the movement of the pollinator on the flower (Video 1), which increases the likelihood of pollen being transferred and ultimately the seedset.

Video 1: Unidentified bee on Geranium spec. The Flower shows a simple form of revolver architecture. The bee rotates around the central axis of the flower to probe every separate compartment and to collect the full reward of the flower.

Revolver architecture arose several times independently in the angiosperms. But although it is a widespread phenomenon, it is surprisingly poorly studied. The best-known example of flowers with revolver architecture is Aquilegia (Ranunculaceae, Ranunculales) where the nectar leaves form spurs of sometimes impressive length. Other examples are Codon (Codonaceae, Boraginales; Jeiter et al. 2016) with septa between the filament bases and the corolla tube, and Nasa (Loasaceae, Cornales; Weigend and Gottschling 2006) with five staminodial nectar scales. In Geranium robertianum, six organs in four whorls are involved in the formation of separate compartments, each with a nectary gland at its base (Endress 2010). We observed a similar type of architecture in species closely related to Geranium robertianum (e.g., Geranium maderense, Figure 5, Geranium sect. Robertium; Jeiter, Hilger, et al. 2017) with a similarly elaborate form of synorganisation. However, revolver architecture in its simplest form is common to most actinomorphic Geraniaceae. Additionally, we observed, that groups of three stamens either through lateral broadening of the filaments or doubling in the antepetalous whorl of stamens play a major role in floral architecture in both families studied.

SEM micrograph of an anthetic Geranium maderense flower showing the complex synorganisation and revolver architecture.
Figure 5: SEM micrograph of an anthetic Geranium maderense flower showing the complex synorganisation and revolver architecture. The large nectary gland is visible in the foreground. Each petal is modified and forms a complex with the antepetalous stamen. Between the petal bases five separate compartments are formed: revolver architecture.

One limitation of our studies, combining a morphological, anatomical and ontogenetic approach using SEM and LM, was the problem of visualising how the organs are arranged in three dimensions within the flowers. Both methods (SEM, LM) are unfortunately limited in their resolution of complex three-dimensional structures. While SEM requires the removal of floral parts for visualisation, LM can only be done with material of limited size and usually pre-anthetic flowers, amenable to serial sectioning – a time consuming technique that requires a lot of practice, some luck, and high frustration tolerance. One way to understand floral architecture could be to employ 3D-imaging techniques, which could help to overcome obstacles arising from the use of ‘classical methods’ such as SEM and LM.

Conclusions

The clear definition of floral architecture helps to clearly focus on that level of floral structure. The study of floral architecture, not only in relation to pollinator interaction, but also in combination with reward presentation (e.g. nectar), could help to better understand the evolution of the morphologically highly integrated structure known as flower.

Reference List

Endress P.K. (1996). Homoplasy in angiosperm flowers In: Sanderson MJ, Hufford L, eds. Homoplasy – The recurrence of similarity in evolution. San Diego, California, United States: Academic Press, 303–325. Check libraries on WorldCat

Endress, P. K. (2010). Synorganisation without organ fusion in the flowers of Geranium robertianum (Geraniaceae) and its not so trivial obdiplostemony. Annals of Botany, 106(5), 687–695. https://doi.org/10.1093/aob/mcq171

Jeiter, J., Danisch, F., & Hilger, H. H. (2016). Polymery and nectary chambers in Codon (Codonaceae): Flower and fruit development in a small, capsule-bearing family of Boraginales. Flora – Morphology, Distribution, Functional Ecology of Plants, 220, 94–102. https://doi.org/10.1016/j.flora.2016.02.010

Jeiter, J., Hilger, H. H., Smets, E. F., & Weigend, M. (2017). The relationship between nectaries and floral architecture: a case study in Geraniaceae and Hypseocharitaceae. Annals of Botany, 120(5), 791–803. https://doi.org/10.1093/aob/mcx101

Jeiter, J., Weigend, M., & Hilger, H. H. (2016). Geraniales flowers revisited: evolutionary trends in floral nectaries. Annals of Botany, 119(3), 395–408. https://doi.org/10.1093/aob/mcw230

Palazzesi L, Gottschling M, Barreda V, Weigend, M. (2012). First Miocene fossils of Vivianiaceae shed new light on phylogeny, divergence times, and historical biogeography of Geraniales. Biological Journal of the Linnean Society, 107(1), 67–85. https://doi.org/10.1111/j.1095-8312.2012.01910.x

Ronse De Craene LP. (2010). Floral diagrams: an aid to understanding flower morphology and evolution. Cambridge, New York: Cambridge University Press. Check libraries on WorldCat

Weigend, M., & Gottschling, M. (2006). Evolution of Funnel-Revolver Flowers and Ornithophily in Nasa (Loasaceae). Plant Biology, 8(1), 120–142. https://doi.org/10.1055/s-2005-873034

Non-structural carbohydrate dynamics in shrubland under drought-induced die-off

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The relationship between plant carbon economy and drought responses of co-occurring woody species can be assessed by comparing carbohydrate (C) dynamics following drought and rain periods, relating these dynamics to species’ functional traits. Lloret et al. studied nine woody species coexisting in a continental Mediterranean shrubland that experienced severe drought effects followed by rain.

Spanish scrubland.
Spanish scrubland. Photo: Lloret et al.

The authors measured total non-structural carbohydrates (NSC) and soluble sugars (SS) in roots and stems during drought and after an autumn rain pulse in plants exhibiting leaf loss and in undefoliated ones. Lloret and colleagues note that previous authors have said stored non-structural carbohydrates are never fully depleted under average conditions because a certain concentration of soluble sugars is required to sustain immediate plant functions such as osmoregulation, transport and signalling. If a drought lasts for long enough, this should be visible as a decline in NSC reserves.

The team measured the effect of drought on a plant by examining leaf loss, leading to a dieback of the canopy. They compared plants that showed loss of more than half of their canopy against plants that showed of loss of less than a quarter of the canopy. Using the canopy cover, to categorise the plants, they could then sample them to see what carbohydrates the plants had stored.

The scientists found that during drought, NSC concentrations were overall lower in stems and roots of plants experiencing leaf loss, while SS decreases were smaller. Roots had higher NSC concentrations than stems. However, after seasonal rain, SS increased, while NSC did not. Lloret and colleagues say: “This suggests that newly assimilated C after seasonal pulses of rain was insufficient to meet C demand for new tissue growth after a prolonged drought.” The carbohydrates that could have been stored were instead being put to use building new leaves.

Regarding the SS they added: “The significant increase in SS after the autumn rain does suggest a general increase in physiological activity, as sugars were mobilized for growth and metabolic demands.”

Drought is an increasing concern as climate changes, with the potential for rainless periods to be both more frequent and longer. What Lloret and colleagues show is that even with rain, the effects of drought can continue to build up in plants. They conclude: “Persistent long-term drought, even when interrupted by occasional rain pulses, could eventually deplete NSC stocks to the point that canopy recovery is no longer possible.”

Reference List

Lloret, F., Sapes, G., Rosas, T., Galiano, L., Saura-Mas, S., Sala, A., & Martínez-Vilalta, J. (2018). Non-structural carbohydrate dynamics associated with drought-induced die-off in woody species of a shrubland community. Annals of Botany, 121(7), 1383–1396. https://doi.org/10.1093/aob/mcy039

Inspiring the Botanists of the future

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Part of the goal of Plant Cuttings items is to share news of botanical research with the wider plant-minded community, the better to advertise that wonderful example of human scientific endeavour. And that’s fine for promoting the work of established plant scientists. But what about the not unimportant – i.e. very important – matter of trying to ensure ‘continuity of supply’? How do we enthuse the new botanists to replace those who will eventually retire, etc. (and whose own future discoveries and contributions to botanical knowledge may one day be shared via a Plant Cutting)? To help with that, and another aim of these items, is to inform the current crop of plant practitioners of ‘tools’ and resources that they can use to inspire the next generation of plant biologists. So, here’s a round-up (no glyphosate-related pun intended; these items are intended to ‘cause to flourish’ rather than kill…) of some that caught my eye recently.

Female botanist
Copyright: belchonock / 123RF Stock Photo

First – although in no particular order of importance– is the initiative of Prof. Lena Struwe (of the USA’s Rutgers University)*. Called Botany Depot, this resource aspires to be “a global website for creative ideas and materials for teaching botany in the 21st century for all ages and levels”. Whilst the focus of most of those resources is on existing students and inspiring plant knowledge and understanding within that important audience, it is equally necessary to reach out to the general public and help them to appreciate the importance of plant science and plants more generally. Developing projects and activities to achieve that admirable aim was part of the outcomes of the ASPB Conviron Scholars Program. Organised by the ASPB (the American Society of Plant Biology), the programme’s participants were drawn from a global pool of talented and aspiring plant scientists from the USA, the United Kingdom, Nigeria, and Belgium. Many of the projects are suitable not only for informing but also enthusing the general public with plant science. They should also work well with students (who, after all, until they commit to a plant science career, are also members of the general public…), and can be explored here.

A personal interest of mine is exploring the inter-relatedness of plants and people. That is catered for by Herbaria 3.0. Although it’s arguably less ‘academic’ in focus than some of the other resources considered in this item, it encourages the sharing of stories about plants and people, especially those that cause us to recall and reflect upon the important role that plants play in all our lives. The more such stories are shared, the more people might realise how important plants are. This in turn might also help to inspire a desire to study them further. All of the resources mentioned have the goal of sharing the excitement and joy that one gets from knowing about plants. If that helps to enthuse, inspire, and create the next generation of plant biologists, that is a job well done.

At the other end of the spectrum of ‘outreach’ and spreading the message that plants are cool (too!…) and worthy of study, is a mention of Plant Roots and Light, a blog by Dr Kasper van Gelderen (Universiteit Utrecht, The Netherlands). Kasper is an established plant scientist whose research focuses on the integration of shade avoidance signals from the shoot to the root and vice versa. His blog concentrates on those aspects of his professional life, with the intention to introduce this work to a broader audience. Real plant scientists blogging about their work (or using other social media platforms), with passion, is another great way of inspiring more and future plant scientists – and is another free resource to use and share. Blog on, Kasper – et al.!**

 

* Regular readers of Plant Cuttings might recognise this name, for it’s the same person that runs the Better Botanical Business Bureau, which appears as the Botanical Accuracy blog site. The latest item to appear there [when this Cutting was written] was a surgical dissection of a press release from the UK’s University of Bristol. Entitled “Plants colonized the earth 100 million years earlier than previously thought”, it purports to report the science behind Jennifer Morris et al.’s paper “The timescale of early land plant evolution”. However, rather than just itemise the perceived deficiencies and inaccuracies in the press release (and explain why they are deficient and/or inaccurate…), Prof. Struwe also helpfully provides a reworked version of the press release. In that way she is attempting to educate those who report on the work of botanists. After all, it is important to have the important work of botanists reported in the most accurate way possible.

** One was tempted to say ‘High Five’ to Kasper, as an appreciative pun that alludes to his work with the HY5 transcription factor. But that might be far too specialist for the more generalist audience a Plant Cutting item is trying to reach. So I resisted the temptation…

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