Inetgrating Carbon and nitrogen metabolism

The dynamics between nitrogen, specifically NO3 and CO2 are discussed.

From
Stitt M. 1999. Nitrate regulation of metabolism and growth.
Curr Opin Plant Biol. Jun;2(3):178-86.

Recent research shows that signals derived from nitrate are involved in triggering widespread changes in gene expression, resulting in a reprogramming of nitrogen and carbon metabolism to facilitate the uptake and assimilation of nitrate, and to initiate accompanying changes in carbon metabolism. These nitrate-derived signals interact with signals generated further downstream in nitrogen metabolism, and in carbon metabolism. Signals derived from internal and external nitrate also adjust root growth and architecture to the physiological state of the plant, and the distribution of nitrate in the environment.


Coruzzi GM, Zhou L. 2001 Carbon and nitrogen sensing and signaling in plants: emerging 'matrix effects'. Curr Opin Plant Biol. 2001 Jun;4(3):247-53

Plants, like other organisms, have developed mechanisms that allow them to sense and respond to changes in levels of carbon and nitrogen metabolites. These mechanisms, in turn, regulate the expression of genes and the activities of proteins involved in C and N transport and metabolism, allowing plants to optimize the use of energy resources. Recent studies, which have involved molecular-genetic, genomic, and cell biological approaches, have begun to uncover the signals and components of C:N sensing and signaling mechanisms in plants. For sugar sensing, analysis of Arabidopsis mutants has revealed intersections with hormone and nitrogen signaling. For nitrogen sensing/signaling, recent progress has identified transcriptional and posttranslational mechanisms of regulation. In all, a complex picture is emerging in which C:N signaling systems are subject to a 'matrix effect' in which downstream responses are dependent upon cell-type, developmental, metabolic, and/or environmental conditions.

This is full pdf paper, worth a read.

http://www.plantphysiol.org/cgi/reprint/125/1/61.pdf

Another full paper that discusses some Carbon PO4 and Nitrogen feedback and control. Plant cells must have some sort of regulation to incorporate C, N and P together to operate efficiently.

Carbon metabolite feedback regulation of leaf photosynthesis and development -- Paul and Pellny 54 (382): 539 -- Journal of Experimental Botany

My point here is not to have you all understand everything contained in these papers. It is to realize that the CO2 can affect the N metabolism and vice versus, limiting NO3 can and does reduce the capacity of the plant to use CO2, the enzymes required for CO2 uptake are large and require a lot of N.

Likewise, for the plant to use N effectively, it needs the carbon skeletons/sugars etc to work with to link the Nitrogen together.

P is really important and limiting that will shut down and slow most all growth a great deal, when added back, the plant will rapidly start growing again.

You can see these effects on the whole plant level also, not just with gene expression using mRNA, or protein upregulation etc.

That level is voodoo to many folks, but it's clear what is going on to the plant scientyists to some degree, but many questions still remain.

What is clear, that these are not independent units, they all have feedback loops.

So the take home message here:
Maintain good non limiting stable nutrient levels and make sure to use the CO2 correctly.

If you reduce the levels too much too often, you can run into trouble and the recovery process can take several days.

Regards,
Tom Barr

 

Here's another good full article on N, Pi and enrichment with CO2 that does not get too bad.

Pi = inorganic phosphate, often used for things like ATPADP + Pi and many other processes.

Limiting this, limits energy and the plant down regulates growth.
This can also be explained at the protein level, the MRNA level and the genes themselves as well as comparing these gene homologs to other species of plants, animals, humans, Fungi etc to being able to predict the types of proteins and their similarly/"family tree".

But most folks do not want to go that small, they care more about general large macro level plant growth and responses.

But by looking at the small stuff, we can understand why and what works, and predict a great deal more. Even if you do not get everything, it's good to know that there research about that issue and that is can be modeled and explained.

If you limit PO4, that will slow the plant's uptake of NO3 down, you can see and measure this in our aquarium. You can also limit NO3 and note the effects on PO4 uptake and CO2 demand.

These push pull dosing routines mirror the molecular patterns as well and correlate well.

This becomes more complex as we add all these elements together.
But, they are regulating one another, just realize that if nothing else and give the plant everything it needs to grow well.

This article also discusses why it is important to maintain good lighting times and dark periods.

Sink regulation of photosynthesis -- Paul and Foyer 52 (360): 1383 -- Journal of Experimental Botany

Here's another few papers full:

Arabidopsis Seedling Growth, Storage Lipid Mobilization, and Photosynthetic Gene Expression Are Regulated by Carbon:Nitrogen Availability -- Martin et al. 128 (2): 472 -- PLANT PHYSIOLOGY

This one addresses NO3/NH4 and pH balancing with CO2:

Steps towards an integrated view of nitrogen metabolism -- Stitt et al. 53 (370): 959 -- Journal of Experimental Botany

Regards,
Tom Barr

 

Here's one on the time of day the plants use NO3 etc.

A Model for the Circadian Oscillations in Expression and Activity of Nitrate Reductase in Higher Plants -- YANG and MIDMORE 96 (6): 1019 -- Annals of Botany

Timing of NO3 deficiencies over the short and the long term:

Genome-Wide Reprogramming of Primary and Secondary Metabolism, Protein Synthesis, Cellular Growth Processes, and the Regulatory Infrastructure of Arabidopsis in Response to Nitrogen -- Scheible et al. 136 (1): 2483 -- PLANT PHYSIOLOGY

Uptake of NH4 vs control by Glutamine in Rice, a role in regulation of NH4 uptake transporters.

Feedback Regulation of the Ammonium Transporter Gene Family AMT1 by Glutamine in Rice -- Sonoda et al. 44 (12): 1396 -- Plant and Cell Physiology

Well, that should keep you busy and out of trouble for awhile.

Regards,
Tom Barr

 

Well, it'll give you plenty to ponder.
So if you get curious and complain there's nothing new to learn or areas to branch out into.............I got plenty of stuff.


Regards,
Tom Barr

 

Haha, that will teach you!

Regards,
Tom Barr