A2 nitrogen fixation + denitrification

[chips31]

hi, is this right?

nitrogen fixation by root nodules takes the nitrogen gas from the soil and converts it into ammonium compounds. This (after nitrification) allows plants to take up nitrogen in the form of nitrates.

denitrification occurs in anaerobic conditions and converts the nitrates which aren't taken up by plants (due to lack of oxygen so plants don't survive) into nitrogen gas. The nitrogen gas then returns to the cycle.

thanks

[JackBean]

the fixation sound fine to me. The denitrification sounds to me, like if you meant to by done by plants, but I think it's done by bacteria

[chips31]

ok, thankyou

[JackBean]

You're welcome, but I still don't get the denitrification

[chips31]

I think its that denitrifing bacteria in the soil convert the excess nitrates into nitrites and then nitrogen gas so that the nitrogen can be put back into the cycle. Otherwise in waterlogged soil, there would be a load of nitrogen in the form of nitrates that wouldn't be used. In effect I think its the opposite of nitrification.

[JackBean]

I'm taking it back. Why should plants uptake nitrogen as nitrates? Why not incorporate ammonia into amino acids?

Regarding your last post, there are bacteria converting NO3- to NO2- and bacteria converting NO2- to N2

[chips31]

Sorry but I have no idea. I guess they have to uptake nitrogen as nitrates because thats the only form that they can absorb? How would they convert ammonia into amino acids? I thought that ammonification converted amino acids to ammonia so that it could be nitrified??

[JackBean]

So, plants uptake nitrate and convert it with nitrate reductase and nitrite reductase down to ammonia. Plants with symbiotic bacteria (like Leguminosae http://www.biolib.cz/en/taxon/id3273/) can convert nitrogen to ammonia.
This ammonia is than incorporated into amino acids like Glc and Gln by GS-GOGAT system.

[jwalin]

just putting up your question again jackbean
why don't the plants use ammonia directly?

[JackBean]

ammonia is toxic

[jwalin]

So, plants uptake nitrate and convert it with nitrate reductase and nitrite reductase down to ammonia.

but they do make it. but somehow if they can use the NH3 directly then won't it be helpful.

what do you think can be done so this is possible
just imagine by genetic engineering and transformation you get the changes you are willing to do then what mechanism could be used so as to make it possible

was a bit confusing.

[JackBean]

in this system with symbiotic bacteria, the ammonia is immediately incorporated into Glu and Gln by above mentioned GS-GOGAT system, which has very low K_M for NH3