And about " higher dry weight ".....
Nitrogen exists in multiple stable oxidation states, contributing to the variety, versatility, and complexity of
nitrogen-containing compounds. In addition to inorganic ions, N is found in plants in the form of
amides, amines, amino acids and proteins, nucleic acids, and alkaloids, etc.
After Nitrate NO3- is absorbed in the roots, nitrate assimilation proceeds in the roots or shoots (depending
on species and availability of nitrate). The first step is conversion in the cytosol to the higher energy ion
nitrite NO2-, then to ammonium ion NH4+, and finally to the amide group in glutamate.
These steps are energy consuming, requiring overall approximately 12 ATPs(from photosynthesis..thus the extra red at region 620-640 nm .C3 plants have more Ch B than Ch A) per nitrate nitrogen converted to
glutamine.
Energy and Carbon Consumed: Nitrogen fixation energetics are complex and confusing. See above
regarding number of ATPs consumed.(from photosynthesis..thus the extra red at region 620-640 nm .C3 plants have more Ch B than Ch A).
Although the conversion of N2 plus H2 to NH3 is exergonic (ΔG < 0),
the industrial production of NH3 is endergonic. Moreover, “the enzymatic reduction of N2 by nitrogenase
also requires a large investment of energy ... although the exact changes in free energy are not yet
known.” The overall reaction shown in the equation above leads to a ΔG0’
of about -200 kJ mol-1 and is therefore on paper exergonic—a seeming contradiction. Some of the energy
supplied however is wasted in the reduction of H+ to H2, which is lost... (details omitted) A plant uses 25%
of the energy it expends in the shoots and roots simply in assimilating nitrogen from nitrate to
ammonium—even though this assimilated nitrogen ends up being less than 2% of the dry plant
weight. The reaction rate is slow—approximately 5 N2 are fixed per second per nitrogenase complex.
Plants also consume 12 gram of organic carbon per gram of N2 fixed.
Absorption of nitrate(NO3) at the roots requires initial conversion to nitrite NO2-, a cytosol reaction catalyzed by
nitrate reductase and requiring NADH or NADPH
(from photosynthesis..thus the extra red at region 620-640 nm .C3 plants have more Ch B than Ch A).
Nitrate reductase is the main molybdenum (Mo)-containing
protein in plant tissues, and Mo deficiency can lead to accumulation of nitrate(NO3)..
One useful tip :
Toxicity of ammonium and nitrate
Ammonium at high levels in tissues are toxic to both plants and animals because it can dissipate
transmembrane proton gradients . Animals have a strong aversion to its smell. Plants reduce
intracellular toxicity by storing excess ammonium in the vacuole.
Nitrate can be stored at high levels in plants without injury. However, its concentration should be limited
in animal and human food plants. If humans or animals such as livestock eat plants containing high
levels of nitrate, they can experience methemoglobinemia following conversion of nitrate to nitrite. In
addition, nitrate may be converted in animals to nitrosamines, which are potential carcinogens having the
general formula R1N(-R2)-N=O)
Nitrate assimilation
Nitrite reductase reduces nitrite NO2- (which is highly reactive and potentially toxic) to ammonium. This is a redox reaction which takes place in chloroplasts or root plastids, and which utilizes reduced ferredoxin from the PS electron transport chain.(from photosynthesis..thus the extra red at region 620-640 nm .C3 plants have more Ch B than Ch A) A small
percentage of the nitrite reduced (0.02 - 0.2%) is converted to nitrous oxide N2O by this reaction.
Plants exposed to high levels of nitrates at their roots translocate nitrate or its products to the shoot. They exhibit varying ratios in the xylem sap of nitrate, amino acids, amides, and (in tropical legumes) ureides, and therefore require varying proportions of nitrate reductase in the shoot versus root tissues.
Ammonium assimilation
Ammonium toxicity is avoided by rapid conversion to amino acids—
these reactions take place in the cytosol, root plastids, or chloroplasts.
Some of the reactions involving ammonium and amino acid synthesis include :
• Ammonium combines with Glutamate (glutamic acid, which has 1 N atom) to form Glutamine (which has 2 N atoms).This reaction requires the enzyme glutamine synthetase (GS), hydrolysis of ATP, and a divalent cation such as Mg2+, Mn2+, or Co2+
( Cobalt can be supplied from Vit. B12 aka Cyanocobalamin ).
This is the first of two reactions that assimilate ammonium.
• Ammonium combines with 2-Oxoglutarate to form Glutamate via glutamate dehydrogenase. This is the second of two reactions that assimilate ammonium, and requires oxidation of NADH or NADPH(from photosynthesis..thus the extra red at region 620-640 nm .C3 plants have more Ch B than Ch A)
• Elevated glutamine stimulates glutamate synthase activity, which converts Glutamine plus 2-
Oxoglutatate to 2 Glutamates.
• Glutamate combines with Oxaloacetate to yield Aspartate and 2-Oxoglutarate.
• Glutamine combines with Aspartate to form Asparagine and Glutamate (a transamination reaction requiring asparagine synthase and ATP(from photosynthesis..thus the extra red at region 620-640 nm .C3 plants have more Ch B than Ch A)).
The remaining amino acids are synthesized by transamination reactions catalyzed by aminotransferases, such as aspartate aminotransferase...
The amino acid Asparagine serves as a stable compound with, like glutamine, a relatively high-N content,and is used to transport and store N, as well as to serve as a protein precursor.
More N (dry mass / plant cell proteins ) assimilated by the plant(s) ,more energy (number of photons to drive PS ,thus red.. ) needed...
And vice versa...
Also ,of course ,More PS ,means more Carbon
Hydrates...
Meanin' more energy (simple sugars ) and also more plant mass ( polymerised sugar molecules to form long or /and complex chains aka cellulose / hemicellulose /lignin /pectin /ect,as main plant "building " material ...Mainly at stalks and branches... )
But flowers need also a good deal of N and K assimilation ,along with long/complex sugar chains...
Still ,one has to be really careful ,not to utilise too much red..
( Or the ..guh..uhm...Kinda " wrong " wls of red ...) ...
Stomata close ,CO2 is starting to be limited...
Let alone the Phytochrome ratio anomalies & alterations ....
Everythin' should be in " balance "...
No room for "extremes" or "compromises " here...
Otherwise one needs more than 400 Watt of leds to get a decent harvest...
No way, back to those powers....
250 Watt at max,instead...
Goal is to have a better yield (both regardin' quality & quantity ) -than from 400 Watt HPS-,
with 250 Watt (or less).With the "right" config & combo of leds...
Astir team won't stop until this is accomplished,with the easiest,most flexible and cheapest way,possible...
Meanin',as
overall (
average indoor gardener's-wise ) efficiently,as possible ..