Andrew Diatoms perhaps use C4 Photosynthesis. A couple of papers on the subject.
http://www.ncbi.nlm.nih.gov/pubmed/11069177 Unicellular C4 photosynthesis in a marine diatom. Reinfelder JR <http://www.ncbi.nlm.nih.gov/pubmed?term=Reinfelder%20JR%5BAuthor%5D&cauthor=true&cauthor_uid=11069177> 1, Kraepiel AM <http://www.ncbi.nlm.nih.gov/pubmed?term=Kraepiel%20AM%5BAuthor%5D&cauthor=true&cauthor_uid=11069177> , Morel FM <http://www.ncbi.nlm.nih.gov/pubmed?term=Morel%20FM%5BAuthor%5D&cauthor=true&cauthor_uid=11069177> . Author information <http://www.ncbi.nlm.nih.gov/pubmed/11069177#> "Abstract Nearly 50 years ago, inorganic carbon was shown to be fixed in microalgae as the C3 compound phosphoglyceric acid. The enzyme responsible for C3 carbon fixation, ribulose-1,5-bisphosphate carboxylase (Rubisco), however, requires inorganic carbon in the form of CO2 (ref. 2), and Rubisco enzymes from diatoms have half-saturation constants for CO2 of 30-60 microM (ref. 3). As a result, diatoms growing in seawater that contains about 10 microM CO2 may be CO2 limited. Kinetic and growth studies have shown that diatoms can avoid CO2 limitation, but the biochemistry of the underlying mechanisms remains unknown. Here we present evidence that C4 photosynthesis supports carbon assimilation in the marine diatom Thalassiosira weissflogii, thus providing a biochemical explanation for CO2-insensitive photosynthesis in marine diatoms. If C4 photosynthesis is common among marine diatoms, it may account for a significant portion of carbon fixation and export in the ocean, and would explain the greater enrichment of 13C in diatoms compared with other classes of phytoplankton. Unicellular C4 carbon assimilation may have predated the appearance of multicellular C4 plants." *http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1976569/* C3 and C4 Pathways of Photosynthetic Carbon Assimilation in Marine Diatoms Are under Genetic, Not Environmental, Control1 <http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1976569/#fn1>,[W] <http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1976569/#fn2>[OA] <http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1976569/#fn3> Karen Roberts <http://www.ncbi.nlm.nih.gov/pubmed/?term=Roberts%20K%5Bauth%5D>, Espen Granum <http://www.ncbi.nlm.nih.gov/pubmed/?term=Granum%20E%5Bauth%5D>, Richard C. Leegood <http://www.ncbi.nlm.nih.gov/pubmed/?term=Leegood%20RC%5Bauth%5D> ,* and John A. Raven <http://www.ncbi.nlm.nih.gov/pubmed/?term=Raven%20JA%5Bauth%5D> "ABSTRACT Marine diatoms are responsible for up to 20% of global CO2 fixation. Their photosynthetic efficiency is enhanced by concentrating CO2 around Rubisco, diminishing photorespiration, but the mechanism is yet to be resolved. Diatoms have been regarded as C3 photosynthesizers, but recent metabolic labeling and genome sequencing data suggest that they perform C4photosynthesis. We studied the pathways of photosynthetic carbon assimilation in two diatoms by short-term metabolic 14C labeling. In *Thalassiosira weissflogii*, both C3 (glycerate-P and triose-P) and C4 (mainly malate) compounds were major initial (2–5 s) products, whereas*Thalassiosira pseudonana* produced mainly C3 and C6 (hexose-P) compounds. The data provide evidence of C3-C4 intermediate photosynthesis in *T. weissflogii*, but exclusively C3photosynthesis in *T. pseudonana*. The labeling patterns were the same for cells grown at near-ambient (380 *μ*L L−1) and low (100 *μ*L L−1) CO2 concentrations. The lack of environmental modulation of carbon assimilatory pathways was supported in *T. pseudonana* by measurements of gene transcript and protein abundances of C4-metabolic enzymes (phospho*enol*pyruvate carboxylase and phospho*enol*pyruvate carboxykinase) and Rubisco. This study suggests that the photosynthetic pathways of diatoms are diverse, and may involve combined CO2-concentrating mechanisms. Furthermore, it emphasizes the requirement for metabolic and functional genetic and enzymic analyses before accepting the presence of C4-metabolic enzymes as evidence for C4 photosynthesis." So there is no need to upgrade photosynthesis or grow super crops, just grow more Diatoms. Regards Bhaskar On Monday, 6 October 2014 14:43:49 UTC+5:30, andrewjlockley wrote: > > Poster's note : I don't use the #Mustread tag lightly, but this technology > has enormous potential implications for biogeochemical cycling on > geological timescales. The rise of C4 plants has given us today's global > climate. It's therefore critically important that geoengineers get involved > in this debate. It's not inconceivable that a mistake here could end up > snowballing us. Whilst unlikely, comprehensive evaluation of such risks is > critical. > > > http://www.newscientist.com/article/mg22429892.900-should-we-upgrade-photosynthesis-and-grow-supercrops.html?full=true#.VDJboCO3PFo > > Should we upgrade photosynthesis and grow supercrops? > > 06 October 2014 by Michael Le Page > Magazine issue 2989. > > A long-awaited breakthrough by crop scientists raises some thorny issues > for conservation. What about a radical solution?PLANTS are badly out of > date. They gained their photosynthetic machinery in one fell swoop a > billion years ago, by enslaving bacteria that had the ability to convert > sunlight into chemical energy. Plants went on to conquer the land and green > the earth, but they also became victims of their own early success. Their > enslaved cyanobacteria have had little scope to evolve, meaning plants can > struggle to cope as the atmosphere changes.The free-living relatives of > those bacteria, however, have been able to evolve unfettered. Their > photosynthetic machinery is faster and more efficient, allowing them to > capture more of the sun's energy.Scientists have long dreamed of upgrading > crop plants with the better photosynthetic machinery of free-living > cyanobacteria. Until recently all attempts had failed, but now they've > taken a huge step forward.A joint team from Cornell University in New York > and Rothamsted Research in the UK has successfully replaced a key enzyme in > tobacco plants with a faster version from a cyanobacterium (Nature, vol > 513, p 547). Their success promises huge gains in agricultural productivity > – but is likely to become controversial as people wake up to the > implications.The enzyme in question is called RuBisCo, which catalyses the > reaction that "fixes" carbon dioxide from the air to make into sugars. It > is the most important enzyme in the world – almost all living things rely > on it for food. But it is incredibly slow, catalysing only about three > reactions per second. A typical enzyme gets through tens of thousands. It > is also wasteful. RuBisCo evolved at a time when the atmosphere was rich in > CO2 but devoid of oxygen. Now there's lots of oxygen and relatively little > CO2, and RuBisCo has a habit of mistaking oxygen for CO2, which wastes > large amounts of energy.Its inefficiency is the main factor limiting how > much of the sun's energy plants can capture. The version found in most > plants has become better at identifying CO2, but at the cost of making it > even slower. Meanwhile, free cyanobacteria found a way to concentrate > CO2 around RuBisCo, so that they could keep the faster version.Hence the > desire to upgrade crop plants by adding cyanobacterial machinery, which > could boost yields by about 25 per cent (New Scientist, 22 February 2011, p > 42). What's more, such plants will need less water, because they don't need > to keep their pores open as much, meaning they can better retain > moisture.That is what the Cornell and Rothamsted collaboration is working > towards. They are not there quite yet: a few more parts of the > cyanobacterial system need to be transferred for their plants to take full > advantage. But the work is a massive step forward.It now seems certain that > supercrops with "turbocharged photosynthesis" will be growing in our fields > in a few decades, if not sooner. This seems like great news in a world > where demand for food, biofuels and plant materials like cotton continues > to increase, and where global warming will have an ever greater impact on > crop production. More productive plants means greater yields.But there is a > danger too. Critics of genetic modification have long argued that GM crops > will spread in the wild, or that their modified genes will "pollute" wild > relatives, with disastrous effects. So far these fears seem exaggerated. > There are monster plants running rampant through many countries, but they > are not GM creations – they are invasive species.This is not surprising: > most GM traits are not useful to wild plants. A trait such as herbicide > resistance is only useful to plants growing in areas where herbicides are > used, such as in fields and road verges.Upgrading photosynthesis is a > different story. If biologists succeed in boosting it by 25 per cent or > more, the upgraded plants are going to have a big advantage over their > unmodified cousins. And that could spell trouble.There is a precedent. > About 30 million years ago some plants evolved a way to concentrate > CO2 like cyanobacteria do. These are called C4 plants, and although they > make up only 4 per cent of plant species, they account for 25 per cent of > plant biomass. Look out over a grassy savannah and just about every living > thing you see will be a C4 plant.If we fill our fields with supercrops and > plant forests of supertrees it seems inevitable that they will turn feral > and, like C4 plants before them, come to dominate some ecosystems – though > it might take millennia. That prospect will horrify many. When anti-GM > campaigners start protesting against the introduction of turbocharged > crops, they will have a point: the wisdom of growing superplants in open > fields is definitely debatable.But the arguments in favour – boosting > agricultural yield to feed more people with less land while also sucking > more CO2 out of the atmosphere – are also powerful. And there's another > side to it. Wild animals need to eat too, and we're not leaving much for > them. An ecosystem based on superplants would support more life overall.If > society decided to go ahead, another choice would almost certainly come up. > We could just stand by and let boosted grains, vegetables and trees run > wild, possibly driving some other plant species to extinction. Or we could > level the playing field by upgrading many wild plants too.This may seem > like a shocking idea. But the reality is that we are way, way past the > point where we can preserve Earth the way it was before we came to the > fore.We are already well into the Anthropocene. The areas we think of as > wild and untouched are nothing like they were before our ancestors arrived. > The apples and bananas we feast on are much-mutated monsters compared with > their wild relatives.If we are going to reshape plants so that they can > make more food, why not do it in a way that benefits most life on Earth, > not just us humans?This article appeared in print under the headline > "Turbocharge our plants"Michael Le Page is a features editor at New > Scientist > -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/geoengineering. 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