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The corn is feeding sugars to the microbes that do the nitrogen-fixing, this has to mean some energy cost to the corn itself. Can anyone comment if this makes a
by sampo 8y ago
The corn is feeding sugars to the microbes that do the nitrogen-fixing, this has to mean some energy cost to the corn itself. Can anyone comment if this makes a notable dent in the yield of the corn, compared to a situation when the corn gets the nitrogen for free from fertilizers? Or perhaps the extra energy expenditure is so small that it doesn't matter in practice?
Of course, in situations when a farmer simply cannot afford to buy nitrogen fertilizers, the potentially lower yield doesn't matter, because the only alternative is no yield at all.
- fabian2k 8y agoNitrogen fixation is a very expensive process in terms of energy, and it has to be as N2 is a really stable molecule and it simply takes a lot of energy to convert it to something else. No way to get around the thermodynamics of that reaction. I did a quick search and found an abstract of an old paper (https://www.nature.com/articles/267149a0 https://www.nature.com/articles/267149a0) that estimates around 15% of total energy used for nitrogen fixation. The value probably depends a lot on various factors, but it is certainly a significant amount.
- dnautics 8y agoIt's not just that, but biology has evolved nitrogenase only once (it's not trivial) and the process is very inefficient. Something like five? Molecules of hydrogen get produced, that's not counting the six hydrogen atoms that get incorporated in to the ammonia. It's enough of a big deal that some microorganisms salvage the leftover hydrogen for energy. There are some microorganisms that salvage their neighbors leftover hydrogen. Also nitrogenase is very porous and oxygen sensitive so for photosynthetic organisms sequestering the nitrogen fixation away from co2 fixation is a major challenge. Nostoc deals with it by evolving terminal cell differentiation... Cyanothece has a night/day genetic switch, and higher plants fix nitrogen as far away from the leaves as possible.
- raverbashing 8y ago> but biology has evolved nitrogenase only once (it's not trivial) and the process is very inefficient. Something like five? Molecules of hydrogen get produced, that's not counting the six hydrogen atoms that get incorporated in to the ammonia. It's enough of a big deal that some microorganisms salvage the leftover hydrogen for energy. There are some microorganisms that salvage their neighbors leftover hydrogen. Wow that's crazy. And to think life absolutely depends on it, so I guess it used natural sources of ammonia. (And to think the same substance that's so dear to plants is excreted by animals, including us)
- dnautics 8y agolife doesn't depend on it, there's plenty of ur-ammonia around.
- masklinn 8y ago> It's not just that, but biology has evolved nitrogenase only once (it's not trivial) I don't know, on the one hand it may have evolved only once[0], on the other hand it seems to have been hit fairly early on (1.5~2.2Ga, quickly following significant expansion of oxygen production so the needs for additional bioavailable nitrogen could have been a direct consequence of that and just not necessary before) and spread around by lateral genetic transfer, significantly lowering the chances that it'd evolve again. [0] it may also have evolved multiple times in a short time-span, and have had no need to re-evolve since
- dnautics 8y agofair point, we can never know for sure, but there are other mechanisms (like carbon fixation) that have clearly been multi-evolved... you would think that biology would at least have found an oxygen tolerant version for the modern era, as it has for carbon fixation (RuBisCo is not the only way)
- dredmorbius 8y agoThere are numerous biological mechanisms which seem to have evolved only once. That's not to say there is not a better way, but the task of outcompeting an established incumbent is formidable. RNA, DNA, mitochondria, flowering plants, much of mammalian brain structure (including emotions), offhand. Various enzymes and hormones are remarkably consistent across vaast swathes of the genetic tree.
- novia 8y agohttps://arstechnica.com/science/2018/05/plants-repeatedly-got-rid-of-their-ability-to-obtain-their-own-nitrogen/ https://arstechnica.com/science/2018/05/plants-repeatedly-go... So, yes, it is an energy intensive, demanding process, but we NEED to make the corn plants do it. Every plant would rather pass the buck to another plant species (or our species) and not have to deal with the trouble of making their own nitrogen. But when we provide nitrogen, in the form of fertilizer, for the plants, the environmental impact is immense. The fertilizer washes off into the nearby stagnant bodies of water, creating huge algal blooms that can suffocate whatever was trying to live in that water. https://en.wikipedia.org/wiki/Algal_bloom https://en.wikipedia.org/wiki/Algal_bloom
- raverbashing 8y agoI'm thinking Algal Blooms could be a potential solution to carbon sequestration
- chicob 8y agoIf one buries them afterwards. If not, they will eventually die, rot and release the carbon back to the atmosphere. But eutrophication has other issues: it is harmful for animal life and it unbalances the ecosystem, degrading biodiversity and overall making natural carbon sequestration poorer. Maybe in a controlled setting, one could use a dragnet to harvest algae and use it for fertilization. That would certainly improve the efficiency of nitrogen usage.
- infogulch 8y agoAgreed, but we need a bit more control of them than "dump nitrogen into bodies of water that happen to be nearby farmland".
- Reason077 8y agoPhytoplankton are basically algae, and they’re a huge natural carbon sink when they die and fall to the bottom of the ocean. It’s just that we’re overwhelming this sequestration mechanism by digging up and burning dead phytoplankton much faster than new ones grow to replace them.
- joelhaasnoot 8y agoThe article mentions on of the downsides being 9 month growing cycles, vs the 3 months for corn grown currently.
- roel_v 8y agoHere in Western Europe there is only one harvest of corn a year anyway (mostly for fodder), with a nitrogen fixer sown in and ploughed under later summer/fall. Are there places where multiple harvests per year of corn is possible?
- yetihehe 8y agoBut a 9 month growing cycle means that this corn won't have enough time to grow.
- lostlogin 8y agoI’d be worried about the summer months too and not just the winters if this year is any guide.
- exhilaration 8y agoMexico, apparently, where this plant was found!
- chicob 8y agoEven before checking what the data says, if this is a symbiosis instead of a simple infection, I would say the corn will benefit by large, and the energy balance will be in favor of corn. Plants get energy from the sun, but can only use it to grow if the right nutrients are available. Nitrogen is needed for protein synthesis and must be readily available. So this is a win-win for corn and bacteria. Synthetic NPK fertilizers are a way of giving plants what they need: generally, farmers will almost always put nitrogen regardless of what the soil already has, which has unintended consequences. So this symbiosis has an added bonus for human communities. Another way of making nitrogen available to plants is to plant mixed crops. The problem with corn is that the shoots are too close to each other to allow anything else to grow, which is something common in large scale agriculture, whose current practice is to make use of large patches of land dedicated to a single annual crop. Whatever is left from the harvest should and must be reintegrated into the soil.