The nutritional value of various species of duckweed (Lemnaceae) has long been known. However, what is new is an initiative, reported on by “The Telegraph”, to apply to the European Food Safety Authority (EFSA) to have Lemnaceae classified as a “novel food”. The application is to be lodged shortly by researchers from Wageningen University in The Netherlands.
This is great news: Duckweeds have excellent nutritional benefits, and their protein content especially makes them of interest for human consumption. Indeed, Lemnaceae are routinely being consumed as a healthy vegetable and/or food ingredient in major parts of the world (but not in the EU). I fondly remember the pizza with a sprinkling of fresh Lemna gibba which I enjoyed on numerous occasions. L. gibba, with the pronounced air-pockets in its fronds, gives a lovely popping sensation in the mouth, a little bit like an Aero-bar, but healthier.
If the application to the EFSA is successful, the culturing of, trade in, and use of Lemnaceae biomass in Europe will be much invigorated. The culture of Lemnaceae for human consumption will, however, need to be carefully considered to avoid the public being exposed to water-borne diseases and/or contaminants. Thus, the duckweed from a local drainage ditch is probably not a recommended vegetable! Conversely, the work by the EPA-funded Newtrients team at UCC is of major interest as it pioneers growth of Lemna minor on food-grade wastewater, i.e. the clean wastewater left after the production of cheese, yoghurt, milk-powder and other dairy products. Thus, a vision arises of the integrated, sustainable production of dairy produce and vegetables.
The workshop “UV-B and Climate Change; impacts on plants and vegetation” was held in Cork, Ireland, on 15 & 16 April 2019. The overarching aim of the workshop was to explore the interactive effects of UV-B and climate change parameters on plants and vegetation.
A total of 28 researchers attended the workshop, which was organised under the auspices of the International Association for Plant UV-research (UV4Plants). The workshop was hosted by University College Cork (UCC) and generously sponsored by the Irish Environmental Protection Agency (EPA) and Science Foundation Ireland (SFI). Attendees came from Ireland, Norway, Finland, Sweden, Hungary, Czech Republic, Slovenia, Germany, Belgium, France, and Mexico, and the group displayed a good gender balance (13/15) and a mix of early career stage (11) and more established researchers (17). The meeting was organised by Marcel Jansen (School of Biological, Earth and Environmental Sciences, University College Cork, Ireland) with the help of a Scientific Committee comprised of Éva Hideg (Department of Plant Biology, Institute of Biology, University of Pécs, Hungary) and Otmar Urban (Laboratory of Ecological Plant Physiology, CzechGlobe, Brno, Czech Republic).
Sunshine, heatwaves and drought
Attendees braved tough weather on Monday April 15 (54.6 mm rain; wind gusts of up to 45 knots, and a grand total of 0.0 hours of sunshine), but inside the meeting room the talk was all about sunshine, heatwaves and drought. Matt Robson (Helsinki), co-author of the recent quadrennial report of the UNEP Environmental Effects Assessment Panel, gave an introductory overview of anticipated changes in both UV-B and climate, emphasising the local character of many of the changes. Thus, climate change will be accompanied by decreasing UV levels in some places, but increasing levels in other places, especially those where tropospheric air quality is improving.
Phenology was central in the first session on Monday. Astrid Wingler (Cork) and Line Nybakken (Ås) discussed the complex effects of climate change on phenology, and how UV exposure can impede the climate change-induced delay in autumnal leaf shedding and/or bud set, thus impacting on the length of the growing season.
A range of studies focussed on the co-exposure with high UV, high CO2, high temperatures, and drought. Otmar Urban (Brno) gave a detailed overview of the responses of various woody species exposed to combinations of UV and elevated CO2. The message was that UV potentially diminishes the increases in photosynthesis caused by enhanced CO2. Kristóf Csepregi (Pécs) reported on the interactions between UV and low temperatures, and how UV can induce cross-tolerance. Diana Sáenz de la O (Queretaro) and Louise Ryan (Cork) reported on interactive responses to UV and drought. The role of Reactive Oxygen Species was further detailed by Éva Hideg (Pécs) and Arnold Rácz (Pécs). Anikó Mátai (Pécs) reported that β-aminobutyric acid can induce antioxidant defences, and potentially modify UV-responses. Flavonoids are important antioxidants and their protective potential was highlighted in several talks. Regulation of flavonoid accumulation was explored by Els Prinsen (Antwerpen) and Jakub Nezval (Ostrava). Frauke Peschek (Kiel) reported on UV-induced DNA damage in the context of the changing seasons. Barbro Winkler (München) reported on “deep phenotyping”, and emphasised the availability of European platform facilities that are available for plant impact studies.
To comprehend the interactive effects of multiple climate parameters on plant growth, Ivan Couée (Rennes) presented a conceptual model that identified integrative signalling hubs, convergence points, in the plant. A talk by Juergen Kreyling (Greifswald), with the fascinating title “To replicate or not to replicate – that is the question” focussed on development of advanced experimental design that is suitable for complex climate studies. A strong case was made for unreplicated, gradient design.
A special scenario in the climate change context is the increasing distribution of plants to higher altitudes where UV levels are high. Two studies reflected on the environmental parameters that determine plant growth at high altitudes. Tadeja Trošt (Ljubljana) reported how slope orientation (i.e. north, south, east, west) affects biochemical and anatomical characteristics of plants in the Slovenian Alps, while Gaia Crestani (Pisa & Cork) reported on the adaptive strategy of maca, a crop grown in the Peruvian Andes at altitudes above 4000m.
Although the meeting was “plant focussed”, two highly relevant non-plant studies were presented. Knut Solhaug (Ås) presented the case of low and high melanin accumulating lichens. While melanin offers protection against high light, this is accompanied by warming of the lichens. This will present a complex trade-off with increasing global warming. Finally, Gary Kett (Cork) presented the interesting case of cultured pacific oysters which are threatened by various pathogens in warmer summers. The case was presented that UV radiation contributes to the lowering of pathogen infection rates, a finding with potentially commercial relevance.
Discussions focussed on the direction of future research and were led by Matt Robson (Helsinki), Åke Strid (Örebro), Wolfgang Bilger (Kiel) and Marcel Jansen (Cork). In the first discussion session, the emphasis was on the “perceived gap” between laboratory and field experiments, and on how this void can be bridged. Overall, the delegates were positive concerning the integration of laboratory and field sciences as the climate conditions in growth chambers are gradually becoming more realistic, especially with the development of high output LEDs.
It was recognised that one important reason to do laboratory research was to explore, in a more controlled environment, findings made under field conditions and/or hypotheses derived based on fieldwork. Conversely, it was argued that fieldwork should be inspired by advances in our understanding of fundamental plant responses, acquired in laboratory studies. Especially the use of characterised mutants in ecological studies should be encouraged as this can generate novel insights in plant responses. Furthermore, it was argued that “hybrid experiments” whereby plants are pre-grown in growth rooms prior to transfer to outdoor experiments, or alternatively, where plants are grown outdoors prior to exposure to UV or climate change under controlled lab conditions, can meaningfully contribute to bridging the knowledge gap between laboratory and field sciences. Overall, communication between disciplines was seen to be a factor of major importance, and this confirms the relevance of small discussion-intensive workshops such as this one, and others.
In the second discussion session, the focus was on the reason why so many of the “studies of interactive effects of climate change and UV” give such variable (or even unpredictable) responses. Various aspects were discussed, including the lack of consideration of leaf and/or plant developmental age. In the workshop, several studies showed that depending on leaf/plant age and/or exposure time, different physiological outcomes do occur. The species specificity of plant responses has also been noted. Finally, the quality (or lack of) UV measurements was discussed. This is a long-standing problem, relating to available equipment and/or calibration.
A major concern is that many experiments involve just one UV-dose and/or one climate change condition. Related to this, there is no reason to believe that UV (and climate parameter-induced) responses will necessarily be linear, and it can be speculated that a mild increase in temperature together with a mild increase in UV cause cross-tolerance, but a higher increase in temperature together with a substantial increase in UV cause cross-sensitivity (i.e. aggravated stress). This relates to the point that for practical reasons many research groups are restrained to do small experiments, which do not necessarily capture the complexity (i.e. full dose response) of the interactions between climate change and altered UV. Therefore, the final session of the meeting focussed on the development of joint “phytometer” experiments whereby similar experiments are performed simultaneously in different countries. This positive engagement is an important outcome of the workshop, and practical benefits of the meeting will be reaped over the coming years. Mirroring this positive outlook, the meeting started in a howling rainstorm on April 15 (Fig. 1), but ended up with much brighter weather on the 16th (Fig. 2).
Marcel Jansen University College Cork M.email@example.com
The latest UNEP-report on the effects of stratospheric ozone depletion has now been published.
The “Montreal Protocol on Substances that Deplete the Ozone Layer” is a global agreement to protect the Earth’s ozone layer by phasing out the production and consumption of ozone-depleting substances, such as CFC’s. The global agreement was signed in 1987 and is an example of a highly successful international effort to protect the biosphere. In fact, the Montreal Protocol has helped to avoid large, and potentially catastrophic, increases of solar UV‑B radiation in the biosphere. As part of the Montreal Protocol, the Environmental Effects Assessment Panel assesses impacts of ozone layer depletion and changes in UV-radiation. The panel is made up of scientists from throughout the world, and especially experts in photobiology and photochemistry. Prof. Marcel Jansen is the Irish co-author of the report.
The 2018 report, “Environmental Effects and Interactions of Stratospheric Ozone Depletion, UV Radiation, and Climate Change: 2018 Assessment Report”, also known as the “ninth Quadrennial Assessment”, has now been published. The full report can be downloaded directly from the UNEP website (https://ozone.unep.org/science/assessment/eeap). The 381-pages report captures the latest scientific understanding on impacts of ozone layer depletion. The ninth Quadrennial Assessment places strong emphasis on the novel challenge of interactive effects of ozone depletion and climate change on human health and the environment.
Chapter 3, entitled “Linkages between stratospheric ozone, UV radiation and climate change: Implications for terrestrial ecosystems”, assesses the effects of stratospheric ozone depletion and associated changes in ultraviolet-B radiation (UV‑B, 280-315 nm) on terrestrial biota, and especially the role of climate change in mediating effects of UV‑B radiation on organisms and ecosystems. The report states that “in some regions ozone depletion is itself contributing to climate change such that ecosystems are being affected by the consequent ozone-driven changes in temperature, precipitation and UV‑B radiation”. In other cases interactive effects of ozone depletion, UV‑B radiation and climate change impact directly on terrestrial organisms and ecosystems, including agricultural systems. Thus, co-exposure to UV‑B and drought, heat or elevated CO2 levels result in new challenges for living organisms, and for the scientists studying these interactive effects.
UV-B and Climate Change; impacts on plants and vegetation
Announcing a small, discussion-intensive workshop that will focus on the interactive effects of UV-B and climate change on plants.
Where: Cork, Ireland
When: April 15-16, 2019
You are warmly invited to participate in a workshop organised under the auspices of UV4Plants, the International association for plant UV research. The meeting will take place at University College Cork, Ireland. The main organiser is Prof. Marcel Jansen (UCC), and the scientific committee comprises Prof. Éva Hideg (University of Pécs, Hungary) and Prof. Otmar Urban (CzechGlobe, Brno, Czech Republic).
The objective of the workshop is to bring together plant scientists with an interest in the interactive effects of UV-B and climate change parameters on gene-expression, molecular signalling, anti-oxidant-defences, physiology, growth, fitness and ecology of plants. Of special interest are talks on the combined effects of UV-B and environmental variables, such as drought, extreme temperatures, or photoinhibitory light and on the potential role of UV-B radiation in climate change adaptation.
We are pleased to host four invited keynote lectures as part of the workshop:
• Prof. Juergen Kreyling (Greifswald University, Germany) on experimental design of multifactorial experiments (see his recent paper Kreyling et al. “To replicate, or not to replicate–that is the question: how to tackle nonlinear responses in ecological experiments”. Ecology Letters 2018)
• Prof. Ivan Couée (University of Rennes, France) on environmental sensing of climate change by plants (see his recent paper; Bigot et al. “Pivotal roles of environmental sensing and signaling mechanisms in plant responses to climate change”. Global Change Biology 2018).
• Dr Matt Robson (University of Helsinki, Finland) on the latest UNEP-EEAP report entitled “Linkages between stratospheric ozone, UV radiation and climate change: Implications for terrestrial ecosystems”.
• Prof. Otmar Urban (CzechGlobe, Czech Republic) on interactive effects of UV-Radiation and atmospheric CO2 concentration (see recent paper Plant Physiology and Biochemistry, 134, pp.20-30)
Apart from the keynote talks there will be opportunities for short talks (15+5 minutes) and speed talks (5 minutes) by delegates. Early stage researchers are encouraged to present their research. Discussions will, amongst others, focus on developing a predictive model for the interactive effects of UV-B and climate change parameters on plants. This will be a small, discussion intensive 2-day meeting (oral presentations only), and the number of attendees will be limited to 30.
The meeting lasts one and a half days, starting Monday April 15 at 9am, and finishing Tuesday April 16 at 2pm. Participants are advised to arrive in Cork on April 14th.
Registration is by contacting Prof. Marcel Jansen at firstname.lastname@example.org
Registration and Abstract forms are available for download below. Applicants are requested to send both forms to Prof. Marcel Jansen at email@example.com not later than February 15, 2019. Following registration, participants will receive an invoice with instructions on how to pay registration fees by bank-transfer. Cash payment is possible in exceptional circumstances and only when agreed with Prof. Jansen in advance.
We encourage all attendees to submit an abstract and to present a talk. There will be no poster presentations. Registration will be on a first-come, first-served basis, and those presenting a talk will receive preference.
The workshop fee is €145.- for UV4Plants members (€165.- for non-members) and registration is open until Monday, 1 April 2019. The fee covers the book of abstracts, three coffee/tea breaks, two lunches and a social dinner on Monday evening.
There are direct flights to Cork from most major UK airports as well as from Amsterdam and Paris. Alternatively, there are direct (and considerable cheaper) flights to Dublin from most major European airports. From Dublin delegates can either take a direct, long-distance bus to Cork (every hour during the day, every two hours at night time) or a train (every hour during the day, requiring local bus journey to railway station). There is a range of different types of accommodation in Cork, and availability will not be a problem in the spring season.
Friday 21 September was Culture Night in Cork, and many venues opened their doors for the evening to show their activities.
The School of Biological, Earth and Environmental Sciences (BEES) in UCC was also open. Some 450 visitors were able to get close to hedgehogs, shark jaws, lava, amazing plants and fossils. Many students explained the research project they are working on.
The display of the AQUASUS project in the glass houses explained how duckweed can be used to treat wastewater from fish farms, after which it can be used as animal feed.
Indoors the project on the Impacts of Microplastics in Irish Freshwater (IMP) explained the problem of small pieces of plastic. Many people know about plastic in our oceans, but it causes problems in our rivers as well.
On Monday 3 September minister John Halligan T.D., Minister of State for Training, Skills, Innovation, Research and Development, visited the School of BEES, UCC. We were delighted to show him details of our research for the AQUASUS project. AQUASUS looks at the natural ability of duckweed and algae to thrive in and purify polluted water, producing both clean water for fish farms and a supply of animal feed, as duckweed and algae are edible and high in protein.
The project is funded by European Maritime Fisheries Fund (EMFF), administered by Bord Iascaigh Mhara (BIM) on behalf of the Department of Agriculture, Food and the Marine.
Congratulations to Darren Reidy who defended his PhD thesis on July 24, 2018. Darren’s research focused on the question why some aquatic plants become highly invasive outside their natural distribution area. This is an important question as alien aquatic plants are a major threat to biodiversity and a considerable amount of money is spent on their management and control. Being able to recognise potentially invasive species, before they are widely distributed in their new environment, may facilitate management, and reduce management costs.
In his PhD research, Darren mapped the distribution of invasive, alien aquatic plants in county Cork, Ireland. A shocking observation was that more than 50% of water bodies in Co. Cork contain at least one alien, invasive plant species. This number is nearly twice as high as anticipated.
Darren’s PhD study also emphasised the ease with which many aquatic alien plants can spread. In some cases pieces of stem material as short as 1 cm are highly viable. This emphasises the importance of good hygiene for those involved in fishing, boating, diving and other water sports as many aquatic plants can demonstrate impressive clonal growth from small propagules.
A scientifically exciting part of Darren’s thesis, that is however quite sobering from a water management perspective, is the genetic study of the genus Myriophyllum in Ireland. This work which was in close collaboration with Ryan Thum at Montana State University, showed that traditional taxonomic analysis might not be enough to identify invasive alien species in Ireland. In fact, what appeared as Myriophyllum aquaticum comprised several further species, some of which are of major concern as invasive aliens.
Darren’s work emphasises the importance of both early discovery, and correct identification of invasive aquatic plants, as once established, these species can spread rapidly from small propagules, and are notoriously difficult to eradicate.
Professor Marcel Jansen has been awarded a prestigious SFI Investigator award for work on UV‑emitting LEDs.
At a ceremony in Dublin, Professor Mark Ferguson, Director General of Science Foundation Ireland (SFI), formally announced the awards in the presence of Minister John Halligan T.D., Minister of State for Training, Skills, Innovation, Research and Development. The Minister expressed his strong support for Science and Ireland, and in his speech emphasised the importance of teaching the STEM topics across the entire curriculum from primary school on wards.
The project led by Professor Jansen is entitled “Exploiting narrow‑band UV‑LEDs for Sustainable, Innovative, Technology‑Enabled Cropping (UV‑SINTEC)”. UV‑SINTEC is a joint project between Professor Marcel Jansen (School of Biological, Earth and Environmental Sciences -BEES) and Dr Alan Morrison (Department of Electrical and Electronic Engineering -EEE). UV‑SINTEC will exploit novel ultraviolet (UV)‑emitting LEDs to pioneer a new form of precision agriculture. UV light can improve crop quality in terms of nutritional quality, plant architecture and resistance to pests. This has positive impacts on the sustainability of food production, and human health and well‑being. The SFI‑funded study will develop state‑of‑the‑art LED technology that will enable manipulation of UV doses and spectra, and advance our understanding of how plants respond positively to UV wavelengths. This has not been possible until now due to the limitations of current UV technologies. The pioneering combination of electronic engineering and plant biology will generate innovative technology enabling the horticultural industry to sustainably grow crops with enhanced quality.
The project which will start 1/12/2017 will initially employ 6 new researchers (post graduate, post doctoral, or research assistant) but further spin‑offs, both commercial and academic, are expected.
In the most recent issue of the Duckweed Forum, Marcel Jansen, with co-workers Neil Coughlan, Simona Paolacci, Ronan Bonfield, and Tom Kelly summarised some of their recent work on duckweed dispersal (ISCDRA Duckweed Forum issue #17, 2017-04). The paper “Flying duck(weed)s” can be downloaded as part of this issue of Duckweed Forum from http://lemnapedia.org/wiki/Duckweed_Forum#2017-04.
Duckweed Forum is a very attractive bulletin, published by ISCDRA. The “International Steering Committee on Duckweed Research and Applications” (ISCDRA) is an organisation of duckweed researchers and users, and its aim is to strengthen and synergistically connect duckweed academic research with the application communities, and to educate and increase public awareness about the importance and potential of duckweeds for a more sustainable future. As part of its activities, ISCDRA regulates the international registration of duckweed clones, and publishes the “Duckweed Forum”.
Marked differences in physiological and morphological traits have been found between different species of Lemnaceae, and between different clones of species. Traits like relative growth rates, salt tolerance, and starch content can vary a lot. This makes different clones and/or species more suitable for some applications than others. This also triggers the question, how to prevent the mixing of “undesirable” species or clones with selected Lemnaceae when these are grown under outdoor conditions for applications such water remediation. Perhaps more fundamentally it triggers the question, how do duckweeds disperse?
In the case of Lemnaceae, it has been argued that rapid drying out of fronds will limit the distance of dispersal, and that the frequency of transport will be low. However, the reality appears different. Neil Coughlan developed a simple system to quantify dispersal of L. minor. Quite surprisingly, Neil observed a total of 67 separate dispersal events (transfer of at least one frond) over a period of 20 weeks, and across 6 replicate stake and bowl structures. In total 156 colonies comprising 317 fronds were found to be transferred to receiving bowls in a relatively short period (full details see Coughlan et al., 2017), and this was attributed to birds. The question remains, however, over what distances Lemnaceae can be dispersed, a question that focusses heavily on desiccation tolerance of the plants.
Lemna minuta taken out of the aquatic medium was found to have lost viability after just 90 minutes at a Relative Humidity (RH) of 44% and a temperature of 21˚C (Coughlan et al., 2015). At a slightly higher RH of 58% (T = 23˚C) Lemna minuta still displayed some viability after 4 hours out of the aquatic medium (Coughlan et al., 2015). Neil Coughlan’s research showed that between the feathers near the posterior neck of a mallard duck, the RH is around 65% and the temperature 23˚C. Near the inner crural (upper part of the leg), the RH is even higher at around 77% with a temperature of 24˚C. Interestingly, the downy feathers of the inner crural were also found to retain entangled Lemnaceae fronds more effectively than areas of less downy plumage, such as the back of the neck. All in all, we reckon that Lemna minuta can be entangled between feathers, and survive flights of up to four hour’s duration. Given an average speed for mallards of 65 km/h-1, we argue that duckweed dispersal over distances of up to 250km is realistic, although much shorter distances (< 50km) are likely more common. This underlines the mobility of Lemnaceae.
So where does that leave the duckweed industry? There are two practical considerations for Lemnaceae cultivation systems:
(1) preventive steps need to be taken if one wants to avoid bird-mediated contamination of an outdoor Lemnaceae culture (e.g. dilution of a selected clone by non-selected, native clones)
(2) preventive steps need to be taken to avoid introduction of selected alien species or clones into the local environment.
At present, substantial efforts are involved in control of Landoltia punctata in Florida USA, where this is an alien, invasive species. Similarly, Lemna minuta is the focus of management efforts in various European countries. There is absolutely no evidence that the introduction of L. punctata in Florida, or L. minuta in Europe is associated with cultivation of these species by the Lemnaceae industry. Nevertheless, the industry needs to adopt a responsible approach when cultivating alien species of Lemnaceae, and prevent their spread in to the surrounding environment in order to maintain the positive public perception of duckweed applications as being eco-friendly and sustainable.
Coughlan N.E., Kelly T.C., Jansen M.A.K., 2015. Mallard duck (Anas platyrhynchos)-mediated dispersal of Lemnaceae: a contributing factor in the spread of invasive Lemna minuta? Plant Biology17, 108–114.
Coughlan, N.E., Kelly, T.C. and Jansen, M.A.K., 2017. “Step by step”: high frequency short-distance epizoochorous dispersal of aquatic macrophytes. Biological Invasions19, 625-634.
Site management by Sandra Jansen