Greenhouse gas (carbon dioxide) is not beneficial to plants, as once thought

[Cees Binkhorst]

REPLY TO: D66 at nic.surfnet.nl

Hieronder de originele tekstbron, waarin het accent toch meer ligt op
het voorkomen van een nitraat-tekort, en daarbij verstoringen in
mineralen-evenwicht in grond te voorkomen.

Groet / Cees

http://www.news.ucdavis.edu/search/news_detail.lasso?id=9479
In their most recent study, Bloom’s team examined the influence of
elevated carbon dioxide levels and, in some cases, low atmospheric
oxygen concentrations, on nitrate assimilation in wheat and Arabidopsis
plants using five different methods.

Data from all five methods confirm that elevated levels of carbon
dioxide inhibit nitrate assimilation in wheat and Arabidopsis plants.
The researchers note that this effect could explain why earlier studies
by other researchers have documented a 7.4-percent to 11-percent
decrease in wheat grain protein and a 20-percent decrease in total
Arabidopsis protein under elevated carbon dioxide levels.

“This indicates that as atmospheric carbon dioxide concentrations rise
and nitrate assimilation in plant tissues diminishes, crops will become
depleted in organic nitrogen compounds, including protein, and food
quality will suffer,” Bloom said. “Increasing nitrogen fertilization
might compensate for slower nitrate assimilation rates, but this might
not be economically or environmentally feasible.”

He noted that farmers might be able to increase their use of
nitrogen-rich ammonium fertilizers to ease the bottleneck of nitrate
assimilation in crops but would have to carefully manage fertilizer
applications to avoid toxic accumulations of ammonium in the plants.

To develop solutions for dealing with the impact of major increases in
atmospheric carbon dioxide levels on crops, further research is needed
on how plants assimilate nitrate and ammonium, Bloom said.

On 05/15/2010 11:53 AM, Cees Binkhorst wrote:
> REPLY TO: D66 at nic.surfnet.nl
>
> Hoe zit het dan met CO2 die in Nederlandse kassen wordt gepompd?
> Neem aan dat Wageningen daar toch wel goede metingen op heeft losgelaten.
>
> B.v.: Bij het ras Reagan Elite White was het aantal huidmondjes het
> hoogst bij 500 ppm CO2; bij het ras Feeling Green was het aantal
> huidmondjes het hoogst bij 1500 ppm CO2.
> E.e.a. in http://ocap.media-factory.nl/files/Nieuwsbrieven/OCAP_NR15.pdf
>
> Zou me nog iets kunnen voorstellen bij gewassen die jarenlang aan extra
> CO2 worden blootgesteld, maar met gewassen die worden geoogst is dat
> niet het geval.
> Wijngaard in een kas wellicht wel? Daar wordt slechts deel van plant
> geoogst, en dan ook nog het deel dat niets direct met CO2 van doen heeft.
>
> Groet / Cees
>
> On 05/15/2010 10:34 AM, Henk Elegeert wrote:
>> REPLY TO: D66 at nic.surfnet.nl
>>
>> Rising carbon dioxide levels may hinder crop
>> growth<http://www.vancouversun.com/Rising+carbon+dioxide+levels+hinder+crop+growth/3031640/story.html>
>>
>>
>> Greenhouse gas is not beneficial to plants, as once thought
>>
>> BY AMINA KHAN, DAILY TELEGRAPH MAY 14, 2010 9:00 PM
>>
>>
>>
>> So much for a hoped-for bright spot to global warming.
>>
>> Some biologists had theorized that rising greenhouse gas levels would
>> encourage plant growth over the long term because of the increased
>> amount of
>> carbon dioxide in the atmosphere. Plant physiologists from the
>> University of
>> California, Davis, may have dashed those hopes.
>>
>> They've shown that too much carbon dioxide, which plants need for energy,
>> can inhibit a plant's ability to assimilate nitrates -- nitrogen-based
>> nutrients pulled from the soil that plants use to make enzymes and other
>> essential proteins.
>>
>> Without those essential proteins, plant health -- and food quality -- may
>> suffer, the researchers say in a study published online in the journal
>> Science.
>>
>> Scientists had previously observed that a rise in carbon dioxide
>> levels --
>> 39 per cent globally since 1800, according to the Intergovernmental
>> Panel on
>> Climate Change -- would boost photosynthesis, the sunlight-fuelled
>> process
>> by which plants make sugar.
>>
>> But previous studies showed that after an initial spike in sugar-making
>> activity, photosynthesis appeared to level off, even if the carbon
>> dioxide
>> rate remained high.
>>
>> "Here we have this quandary where we thought rising carbon dioxide levels
>> might actually have some benefit, but it proves to be wrong. . . . Over a
>> period of time, be it weeks or years, that stimulation disappears," said
>> lead author Arnold Bloom, a professor in the department of plant
>> sciences at
>> UC Davis.
>>
>> Other studies showed that after plants were exposed to excess carbon
>> dioxide, their protein content also dropped.
>>
>> In a series of five experiments, Bloom and his colleagues found an
>> explanation. The team exposed plants to high carbon dioxide (or low
>> oxygen),
>> fertilized them with nitrates and tracked how much nitrogen they
>> successfully incorporated into their systems.
>>
>> In each case, the researchers found that the more carbon dioxide
>> exposure,
>> the less plants were able to assimilate nitrogen. Without enough
>> nitrogen,
>> the plants could not make as many proteins, including those enzymes
>> used in
>> photosynthesis -- and thus, would be unable to take advantage of all that
>> extra carbon dioxide in the air anyway.
>>
>> The findings have significant implications for agriculture, biologists
>> said.
>>
>> They suggest that, as global warming continues and carbon dioxide levels
>> rise, food may become poorer in quality and less nutritious, and
>> farmers may
>> have to worry about lower-quality crop yields that could perhaps be more
>> prone to pest infestations (as plant eaters may have to eat more to
>> get the
>> same nutritional value as before).
>>
>> The study "has some very important real-world implications," said Harvard
>> University plant physiologist Noel Michele Holbrook, who was not
>> involved in
>> the study.
>>
>> "How do we think about the idea of breeding for more productive crops,
>> and
>> what sorts of attitudes for breeding are going to pay off in the long
>> run?
>> We're facing really important challenges in terms of food production and
>> quality of food."
>>
>> ... "
>>
>> ... according to the Intergovernmental Panel on Climate Change?
>>
>> Wat neemt 'the Intergovernmental Panel on Climate Change' zoal nog
>> meer aan
>> en waarvoor het bewijs ten ene male ontbreekt?
>>
>> Henk Elegeert
>>
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