Sense about Science ? equipping people to make sense of science and evidence
Plant science panel
Ash Dieback disease, GM crops, bees and pesticides, mycotoxins in food, biofuels... Plant research is central to decisions about future energy, land use wildlife, environmental protection, pest problems, nutrition and food safety. Leading research institutions and learned societies across the UK have come together to make themselves available in a public panel, where you can put down questions and opinions for response.
Please note: this panel is not for general horticultural advice.
Answers to your questions below
The rapid loss of soil aeration following waterlogging drives further changes in soil properties that can trigger release of essential plant nutrients such as phosphorus and nitrogen causing a major loss of soil fertility.
Another major risk to soil life and productivity comes from the input of pollutants such as toxic heavy metals and hydrocarbons from nearby flooded urban brownfield sites and roads. Post-flooding recovery of soils is greatly dependent on a range of factors such as soil organic matter content and subsequent land management.
For more information about soil protection, consult the Soil Strategy for England report published by the Department of Environment, Food and Rural Affairs (DEFRA, 2009)".
The speed of the recession depends on the size of the river and the magnitude of the event. Where out-of-bank flow has occurred and flood plains are flooded, it may take some time for water to recede. In large lowland areas, decline of floodwater by natural outflow and drainage through the subsoil may take days or weeks, especially if groundwater levels are high."
Fazir Khan, Civil Engineer: "There is always lag period between the peak rainfall event and the peak flood event. The peak discharge experienced during a flood event occurs some time after the peak rainfall event. This time can vary depending on the size and configuration of the catchment from minutes to hours to even days for very large catchments that flow to flatter low lands.
There can also be an exacerbation of the flood event in areas where there is tidal impact in the lower reaches. A rising high tide can sometimes coincide with a rising flood to create very high flood depths for the duration of the high tide in a given area. High tides can therefore by extension, if they coincide with floods, lengthen the time it takes for surface runoff to dissipate and therefore extend the time of the flooding in an affected area.
In summary, flooding can be experienced for some time after rainfall ceases because of flat slopes in the discharge channels, constrictions in watercourses and outfall drains; backwater effect caused by high tides and other physical characteristics of the catchment in question."
Some actions to reduce flood risk may be compatible with preserving environments for wildlife. For example, washlands on flood plains may provide storage for flood waters and habitats for plants and animals. However, rarely is flood water clean, and high loads of nutrients and pollutants brought onto the land with the floodwater can cause significant damage to valuable wildlife sites.
Planting woodlands in the upper reaches of catchments can encourage rainfall to infiltrate into the soil rather than runoff over the surface (depending on the soil type and amount of rain) and managing peatlands to retain water can provide benefits to wildlife and flood risk management.”
a) Flooding may be caused by the flow in rivers exceeding the capacity of the channel (fluvial flooding). This usually occurs after long periods of heavy rain. It is what rivers naturally do, and is why rivers have flood plains. The problem arises when we want to use the flood plains for other purposes (houses, agriculture, transport routes, etc.).
b) Rain falling on the land surface at a rate greater than it can be moved away by natural or man-made drainage causes pluvial flooding. This occurs during intense rainfall and tends to be quite localised and short in duration. Urban areas are prone to pluvial flooding when the drainage systems become overwhelmed or blocked.
c) High groundwater levels after prolonged rainfall result in groundwater flooding. Groundwater emerges at the surface in depressions and hollows and basements of houses.
d) Coastal flooding occurs when waves overtop coastal defences. This usually occurs when high tide coincides with low air pressure and high winds (tidal surge).
e) Finally, flooding can occur due to breaches or failure of infrastructure (such as dam failure).”
James Dent, Independent Consultant, Hydrology & Meteorology: "There are several types of flooding.
a) Fluvial. Flooding caused by streams and rivers in response to rain and in some cases snow-melt. Can be in response to local rainfall events or, as in recent months to widespread heavy rainfall over a prolonged period. This latter type of event will cause major floods on the largest catchments, e.g. Thames, Severn.
b) Pluvial. Flooding as a direct result of heavy, localised, and usually short duration rainfall, e.g. thunderstorms. Floods of this type are most common in small, steep catchments, e.g. Pennines, Welsh Valleys, and in urbanised catchments where large extents of paving prevent infiltration.
c) Groundwater. Occurs in relation to major water-bearing strata (aquifers), such as chalk, sandstone and alluvial sands. Groundwater levels rise as a result of prolonged rainfall, especially in winter, where there are only small losses by evaporation. It is common for groundwater flooding to come after major fluvial flooding events. The delay in the response to aquifers to inflow and outflow means that groundwater flooded areas will remain for several weeks after the fluvial flood event.
d) Coastal/Estuarine. Costs and estuaries are at risk of flooding from high tides. This flood risk will be enhanced by the natural tidal cycle and incidents of high, persistent on-shore winds. Tidal surges are caused by the influence of low atmospheric pressure, i.e. the passage of depressions. Adverse combinations of high tide, wind and atmospheric pressure can cause significant events like the North Sea Floods of 1953".
Also, the pathogen [disease-causing organism] that causes blight is constantly changing, and current pathogen races can overcome resistance in the most commonly grown potato varieties in the UK. Importantly, the gene we trialled, Rpi-vnt1, confers resistance to all currently circulating UK strains (and we can never have ‘too many’ resistance genes). We are cloning additional such genes"
Read more about the research here.
Typically, soil pores contain air and water, both of which are needed for plant growth. When the pore space of soil (or rock) is completely full of water, we have ‘groundwater’. Groundwater usually exists because of some subsurface flow barrier (e.g. a layer of reduced permeability). The surface of the groundwater is often evident as a ‘water table’: If you dig a hole in the ground to reach the water table this would be the level of standing water in the hole. Water table elevation rises and falls according to groundwater recharge and discharge. Where the water table intersects the ground surface we have a ‘spring’. And with very wet conditions, groundwater discharges can take place where they may not be expected and cause surface flows – or, alternatively, groundwater can flood basements and other structures below the surface.”
Do we need more man-made rivers in low lying areas?
“Low-lying areas don’t have enough elevation difference to support soil drainage and river flows, and hence can easily become water-logged and flood. Agricultural drainage is often used to improve the ability of such soils to transmit water. Subsurface drains would normally connect to a system of open ditches and streams. These are part of the natural landscape and traditionally would become inundated during wet conditions, and act as a temporary store of water. Improved drainage removes this storage and passes the water downstream – where it may create new flooding problems. So having more man-made rivers may help a local problem, but may worsen conditions downstream.”
What do people mean when they talk about trapping flood water on higher land?
“Various agricultural practices in upland areas can help to store water in the landscape. For example, planting trees improves the ability of the soil to accept and retain water, and small reservoirs can trap water for farm use. These practices can reduce flood risk downstream. However, other practices, such as drainage, will reduce water storage and can make matters worse downstream.”
How can we get rid of water faster?
“Getting rid of water faster may often mean creating a problem for someone else downstream. The most ‘efficient’ way would be to change the natural river system into a concrete, un-vegetated channel designed to move water fast and efficiently. But this then loses the natural ecological function of the river system.”
On a positive note, British researchers have recently developed a hybrid grass which can improve the soil structure through deep rooting. This could actively reduce the run-off from upland pastures, thus mitigating the risk of flooding further downstream.”
Should farmers build more ditches and why?
Paul Temple: “It's not a case of building more ditches, but of carrying out proper maintenance on existing ones. Strategic reservoirs, to give water holding capacity, should be part of a future plan to provide irrigation.”
What will the impact of a flood be on different kinds of crops and trees? e.g Will farmers have to plant something different next year? Will prices go up? (Rebecca Gale)
Paul Temple: “Flooding basically kills roots - for annual crops, in a short time; grass can manage a little longer. If the water table rises some tree roots shallow off and the trees either die or are vulnerable to wind damage.
Wet soils lose their structure and ‘growing ability’, needing either a severe drying out or deep cultivation to put this right. Flooded soils become compacted and anaerobic with soil life (critically, worms) dying. A permanent pasture that is flooded and destroyed in this way will take several years to re-establish the same root system.
In terms of the impact on crops, Spring sowing will be delayed. Prices, however, are less likely to be directly affected - unless the crop is high value vegetables not easily replaced. A final point is that any production we lose needs replacing with imports, i.e from another country where land is not flooded. Most farms have someone with generations of experience and all of them see flooding as failure!”
The green pigment, chlorophyll, absorbs red and blue light and on to higher energies, covering the solar spectrum quite well in the UV. In fact, proteins containing chlorophyll may have existed simply as UV screens before they evolved to photosynthesise.
But the pure chlorophyll pigment is a bad idea as a sun screen. It would absorb the UV and visible light but then react with O2 (the molecule not the company) and the excited O2 would then kill your cells. This reaction has been studied as a way of killing cancer cells. In the natural environment carotene molecules prevent excited chlorophyll wreaking havoc.
So Alana’s idea of keeping chlorophyll in its native cell is a better bet as a UV screen. That said, it is quite hard to keep a plant cell alive outside a plant. Algae or photosynthetic bacteria may do better since they are used to the free-living, unicellular lifestyle but even those get contaminated with other microbes or just die.
Thus I would predict that bacterial/algal sunscreen might work for a short time in principle but would be fairly smelly, possibly slimy and certainly green: a tricky prospect for the sales department.
Selenium is not essential to plant growth but is essential to human health as it forms part of some important anti-oxidant enzymes. In some countries, including the UK, dietary intake of selenium is below recommended levels. Finland has even added supplementary selenium to cereal crop fertilisers, although other non-grain crops such as broccoli are known to be better selenium accumulators.
Selenium is thought to be taken up by plants through the same pathway as sulphate resulting in competition between the two chemicals (Ellis and Salt 2003) and so an abundance of one may inhibit uptake of the other. Flavonoids are most commonly known as plant pigments which add to the colour of fruits and petals. Selenium enrichment in tomatoes resulted in an increase in some flavonoid chemicals (Schiavon et al 2013) but a decrease in other beneficial compounds, especially containing sulphur, in broccoli (Finley et al 2005). The underlying mechanism remains unclear.
View article here
"This finding applies equally to all DNA found in our food. Our food contains large amounts of DNA and GM plants typically contain one extra gene added to at least 25,000 existing genes. The minute amounts of DNA from our food able to pass into the bloodstream do not cause us any problems. DNA from GM plants would be no different."
The article claims that:
- toxins resident within GM foods can dangerously enter (and are entering) the human organism.
- pregnant women and their fetuses had detectable levels of the toxins in their blood.
- these research findings show that GMO products contain toxins that can be absorbed by humans, and that they may cause serious side effects.
Can you comment on this article/study please, and whether it makes any sense?
see study here
See article on RNAi insecticides here
"The potential advantage of RNA gene silencing is that it is very specific and so can be used to turn off a single gene which may only occur in one organism. By targeting essential genes, it is theoretically possible to control the population of a single type of pest. However, it is difficult to get RNA into cells (where it can have an effect) because all organisms produce a form of RNAse; an enzyme which rapidly digests and neutralises the biological effects of RNA. This is one of many reasons why RNA gene silencing has yet to be established as a pesticide. The presence of RNAse in humans is also why it is highly unlikely that food containing modified RNA will cause any health effects in consumers."
"It is worth considering that we eat plant and animal RNA on a daily basis without any associated adverse effect simply because we digest RNA very effectively. Moreover, the introduction of RNA-based pesticides will be subject to national and international controls which include a requirement for companies to demonstrate the environmental and consumer safety of their products."
Link to article
So the question is: is it true that the nutritional content of food produced by modern agricultural methods has declined?
"Genetic engineering is 40 years old. It is based on the naive understanding of the genome based on the One Gene - one protein hypothesis of 70 years ago, that each gene codes for a single protein. The Human Genome project completed in 2002 showed that this hypothesis is wrong."
"The whole paradigm of the genetic engineering technology is based on a misunderstanding. Every scientist now learns that any gene can give more than one protein and that inserting a gene anywhere in a plant eventually creates rogue proteins. Some of these proteins are obviously allergenic or toxic."
This is in light of your comment in answer to another question in which Dr Gia Aradottir said '..the important outcome is what proteins the genes code for.'
See Gia's original answer in Q1 here
I also have heard it said numerous times that 90 per cent of Denmark's ash trees have died as a result of the disease.
The figure of 90 per cent fatality rate seems to be widely cited as the average fatality rate for this disease. Yet this figure applies to one country, Denmark, and not, as far as I can tell, to Europe as a whole.
Do we know what the average death rate is for ash trees infected with this disease - i.e. the rate for Europe as a whole, not just one country.
"It's much more difficult to answer the second part of the question - does this apply across Europe? All we can say is that many trees are affected across Europe, and the disease is now throughout most of the ash range in countries that have been affected for some years by the disease (eg Poland, Lithuania, Sweden, Norway and Denmark). So in those countries probably the majority of ash trees are affected by the disease and a high proportion, but not all, will have died as result of the disease either directly or indirectly. In the case of the latter, trees can be so weakened by the year on year effect of Chalara that they can succumb to other tree pathogens such as honey fungus (Armillaria) and these may be the final 'killing agents'."
"It's difficult to give exact figures because it would mean a huge survey effort to define the numbers of trees and then those affected/dead in all the various countries where ash is now affected by Chalara, so that's probably why there are no clear unambiguous figures for every country affected by Chalara."
"Plants are the main source of food for Man and animals. Crop plants have been slowly improved, in one sense genetically modified, by farmers and plant breeders to give the highly efficient varieties we farm today. The early methods to develop new varieties were relatively passive, making simple crosses in the field. However, over the last century, plant breeding techniques have required more human intervention to provide useful genetic variation. Methods such as wide-crossing between species that would not hybridise in the wild, artificial mutagenesis to generate random changes in genes or marker assisted selection became increasingly used. Over the last thirty years, plant breeders have learned how to move single, specific genes form one organism to another by a method called ‘recombinant DNA technology’. Crops made by this method are what we know as GMOs and fall into EU legislation for testing and labelling. Many scientists see recombinant DNA technology as one more step (albeit an important one) in the continual development of ever better and predictable plant breeding methods."
"What I can say is that the studies that have been done into gene transfer from the eaten plant material to bacteria in the gut have revealed that the risk of gene transfer is extremely small. Although, one can never exclude such possibilities in biology, it is less likely that pathogenic bacteria will acquire antibiotic resistance in this way compared to other ways."
"If you want to learn more, please see the following links and the references included. http://www.jic.ac.uk/corporate/about/publications/gm-debate/armg.htm"
There are a number of scientific studies which indicate that some pesticides may have “anti-androgenic” activity: an effect which interferes with the normal response of the body to male hormones. The actual quantity of such pesticides in the food we eat is subject to very strict controls and so it is unlikely that the concentration of any one pesticide would be sufficient to cause a measureable effect. In saying that, the effects of some pesticides may be additive. That is, exposure to a number of substances (at a low dose) may result in an overall dose which may be sufficient to cause an effect. However, no studies in humans have established a link between pesticide residues and male infertility.
It is worth considering that we are exposed on a daily basis to a wide variety of chemicals present in our diet and environment which may potentially affect fertility. So, sticking to organic food would probably not make much difference to our total daily intake. It is also worth pointing out that whilst organic foods may generally contain less pesticide residues, it doesn’t necessarily eliminate exposure. The type and amounts of pesticides used on all crops are subject to strict controls which are monitored and enforced by the UK’s Food Standards Agency (FSA).
"In principle, responsible fertiliser application in optimal environmental conditions is unlikely to be detrimental; however, it is likely to affect tree volume and in doing so may affect timber quality. Whether this effect is considered detrimental or beneficial is likely to depend on how timber quality is defined."
2) Do many of the of the scientists there belong to environmental Groups/NGOs?
3) Do both the funding sources and the various affiliations of the senior staff there tend to skew the type of research that they are covering ?
~60% from BBSRC in the form of Institute Strategic Program Grants and competitive responsive mode grants
~10% from other Exchequer sources including DEFRA, DECC, DIfD, NERC
~4% Foundations such as The Lawes Agricultural Trust, Bill and Melinda Gates, Perry Foundation, Felix Cobbold etc
~12% Industrial research collaborations
~5% Levy boards and crop research agencies (HGCA, BBRO, AHDB etc)
~2% royalties, licence fees etc"
"2) Yes, but not (as far as I know) in the more extreme end of the spectrum such as GM-freeze etc. Typically, we have staff who are members of RSPB, Butterfly Conservation, Wildlife Trust, FoE, CPRE etc. However, staff are not required to divulge involvement in any NGO or political organisation."
"3) Funding from BBSRC and other research councils is for work covered in their strategic plans (e.g. http://www.bbsrc.ac.uk/nmsruntime/saveasdialog.aspx?lID=3719&sID=6953 ) and therefore the funding sources do play a role in determining which areas are studied. However, the funding bodies, including industry, have no say in how a Rothamsted scientist interprets her/his own results. The principles of academic freedom apply in Institutes just as they do in Universities."
"Like other plant cells, root cells are enclosed by a membrane, which in turn is surrounded by a cell wall. While the cell wall is permeable to water and most nutrients, specific transport proteins are required to take up nutrients, such as nitrate, phosphate or potassium, into the root cells. Water and nutrients are transported from the roots to the shoots in a system called xylem. On their way from the soil into the xylem nutrients have to cross cell membranes at least twice: (i) to get into the centre of the root which is sealed off by a hydrophobic strip that prevents transport through the cell wall; (ii) to be loaded into the xylem."
"Nanoparticles can, in theory, follow the same route, but they can also enter the roots through wounding. Whether or not they are taken up and transported to the shoots depends on e.g. their size, surface charge and also the plant species. There is concern that nanoparticles taken up by plants may be toxic to the plants themselves or accumulate in the food chain. On the other hand, it may be possible to use nanoparticles for the delivery of fertilisers, herbicides or pesticides."