STRAINZ
Member
I read this on another site & thought some may find it interesting...mods, if it's too lengthy and not of use feel free to delete:
« Nitrogen Nutrition » :
INTRODUCTION :
Land vegetables usually take their Nitrogen in soil, under the form of nitrates or ammonium salts, resulting of organic decompositions by microorganisms of soil.
Notice the actinorhizian plants realize an ammonia synthesis from dinitrogen (N2) of air with symbiotic organisms (Rhizobium).
Nitrogen is a primary nutriment essential to vegetables; we can often read the amount of N in fertilizers (N-P-K).
It is a free macro-element in the soil-plant continuum, even inside the plant.
It will determine several key parameters of the plant’s life cycle. Let’s see them.
1/ Nitrogen in soil-plant-atmosphere continuum :
1.A/ Soil Nitrogen :
Under our climates in a good vegetable earth, Nitrogen content is about 1g/Kg of earth, so about 5T Nitrogen / hectare.
On this mass, 1% to 2% is under a mineral form (in average); the remainder is under an organic form, mainly humus.
Soil’s organic material mainly comes from vegetables waste, only a little amount of it comes from animals waste.
After being broken down and reorganized by micro flora, wastes are mineralized, under a form lot more easily assimilated by the plant.
That’s mainly NH4+ (and NH4OH), secondarily oxidized on the form of NO3-, CO2(and HCO3-), H2PO4-, with release of positive ions (CA2+, MG2+, K+, etc.) and negative ions CL-, which were more or less fixed to them.
There is also action of cellulolytic (cytophaga) and proteolytic bacteria (proteus), this transformation concerns mainly cellulose and proteins, it is fast (from a few weeks to a few months). It leads to transformation of 70% of soil’s humus.
Residues are on various forms, depending on kind of vegetables. We notably can find humic acids, fulvic acids, and humin.
1.B/Mineral Nitrogen :
The first step to development mineral nitrogen is ammonization, which is made by bacteria.
For example:
- Amins :
Carbon molecule-NH2 + H20 -> R-COOH + NH3
That’s a hydrolysis of a molecule with an amin part, which produces a carboxylic acid and an ammonia molecule.
- Amino-acids:
NH2-Carbon molecule-COOH+H2O -> R-CH2OH+CO2+NH3
That’s a hydrolysis of an amino-acid, resulting in Carbon Dioxide, ammonia and a primary alcohol.
The next step is nitrification to make nitrates. Two types of bacteria play a role here:
- Nitrous bacteria: they do nitrosation:
(NH4+)+(2/3 O2) -> (NO2-)+(H2O)+(2H+)
- Nitric bacteria: they do oxidation:
(NO2-)+(1/2 O2) -> NO3-
These reactions are oxidation-reduction.
2. Nitrogen use :
We’ll try to explain how the plant use Nitrogen for its development.
2.A/ Organic Nitrogen use :
Cannabis is able to assimilate Nitrogen on organic form when it is under the form of small molecules (amino-acids, glutamine, urea, uric acid) but the efficiency is low, comparative to nitric or ammonium feeding.
2.B/ Mineral Nitrogen use :
Most of grown plants have the best yield with nitrates. Reduction of nitrates costs energy to the plant, but this degradation is plugged with glucidic catabolism, so it promotes cetonic acid production.
Generally, young plants prefer NH4+ (but it is not a generality)
We have to notice the importance of PH:
Lowering the PH level helps absorption and assimilation of nitrates, and raising the PH level will helps absorption and assimilation of ammonium ions.
Also the content of sugars, particularly in the roots, which depends closely of the photosynthesis of the plant, conditions nitrogen use.
Indeed, cetonic acids are made with these solid carbohydrates, and cetonic acids will allow incorporation of Nitrogen under the form of amino-acids.
2.C/Nitrogen fertilizers :
We can classify them into 3 categories:
- Ammoniacal fertilizers:
Sulphate, Chloride, Phosphate of Ammonia.
They are acidifying fertilizers, used in earth and added when substrate is mixed. (background fertilizers)
They have the double advantage to become available to the plant as it goes along to need them without reaching a toxic amount, and to prevent them to be flushed by successive watering.
Indeed, NH4+ ions are fixed to colloids of soil, and are exchanged by H+ ions from the plant.
So, NH4+ absorption will not modify the substrate’s PH.
- Nitric fertilizers :
Nitrates of Sodium, Calcium or Potassium.
They are suitable to fast interventions. It is recommended to use them when the plant needs them.
- ammonia-nitric complex :
They allow to combine the advantages of both : an immediate provision to the plant, and also a progressive provision used depending of plant’s intake evolution.
3/Nitrogen assimilation :
Nitrates reduction:
The reduction usually start in the root, although a lot of species also do this reduction in the leaves with light (there are not any photoreceptor in the roots, but the power of reduction of leaves is NADPH2 and power of reduction of roots is NADH2, so the leaves are better reduction factories)
The reduction means a benefit of 8 electrons:
(NO3-)+(8H+)+(8e-) -> NH3+(2*H2O)+OH- (9-;1-) = 8-
This reduction is done with two steps, which follow very fast: reduction of nitrates to nitrites, then reduction of nitrites to NH3:
(NO3-)+(2H+)+(2e-) -> (NO2-)+(H2O)
(NO2-)+(6H+)+(6e-) -> (NH3)+(H2O)+(OH-)
That was established in 1924 by S.ECKERSON (USA).
Some other intermediate steps are plausible but we can’t verify them, like transition with hydroxylamin NH2OH. Indeed, nitrites are toxic at high amount, that corroborates the fact than reduction is done continuously and with non-lethal amounts for the vegetable organism.
4/Nitrogen Use before blooming cycle :
4.A/Growing cycle :
Nitrogen is very dependent on Carbon : broadly speaking, feeding with high Nitrogen level promotes vegetative development to the detriment of reproductive system.
On the contrary, a rich carbon feeding promotes blooming. That’s why an active photosynthesis is essential.
So the ratio Carbon/Nitrogen is very important. In average this ratio is about 20 (in mass).
Around this average, of course we can’t fix accurate measures, development of the plant depends a lot of this C/N ratio:
C/N very high: poor vegetative development (Nitrogen deficiency)
C/N high: lush fruit development
C/N low: vigorous vegetative development
C/N very low : poor vegetative development (Carbon deficiency)
It was established, about plants depending on photoperiod (so, including Cannabis), that saccharose amount in phloem sap increases a lot when blooming photoperiod starts.
This saccharose influx, without being the decisive factor, is an important factor of blooming induction, but is not a blooming signal.
4.B/Movements and storage during stretch cycle :
- Case of a soil with a high level of Nitrogen :
During stretch, the plant will increase the number of Nitrogen carriers (HATS) in its roots, and also increase the amount of metabolization enzymes: nitrate reductase and nitrite reductase.
Then all this nitrogen taken in soil will rise in the plant with raw sap.
This brutal increase of nitrogen concentration will induce the plant to build a buffer area to store that transitional nitrogen.
That means an increase of total volume of stems, and an inhibition of secondary buds’ dormancy.
So in this case the storage is done in stems and buds of the not much developed secondary apex, and in tertiary apex too….
- Case of a soil with a low level of Nitrogen :
The plant does not act on its roots, to avoid using energy unnecessarily because there is not enough Nitrogen in soil.
In this case nitrogen will be re-concentrated in the stem in aid of a precocious senescence of old leaves, always from bottom to top, with a degradation of amino-acids stored in the stem.
Because the plant does not have enough nitrogen to do a complete inhibition of buds’ dormancy, nitrogen will be stored essentially in the stem and in the secondary buds near the canopy, thanks to a lux-dependent mechanism.
In conclusion, we can say the major part of nitrogen will be stored in the buffer stems elaborated during stretch cycle and in the buds too.
Nitrogen concentration in the stem, and the number of inhibited buds, will vary depending of nitrogen concentration in the soil.
5/Stock usage after blooming induction :
After blooming induction, the buffer area becomes not useful under this form.
The area with the most important sink strength will be able to guide Nitrogen influx thanks to osmotic and hydric pressures.
These pressures use two mechanisms:
- The first one is an osmotic link; the source cell will store elements in its vacuole to make a decreasing gradient of solute from source to it.
With balance notion, that will attract the nitrogen stored in stems, but not the nitrogen stored in buds.
- The second mechanism is a loss of osmotic pressure by osmoticum synthesis, like sugars and others, to make a decreasing gradient too.
About the buds, the sink strength caused by blooming induction, completely blocks nitrogen in buds and attracts nitrogen stored in stems, too.
This nitrogen is mainly under the form of amino-acids. These ones will be stored to excess in the bracts, then, if nitrogen concentration is suitable, the plant will create some resource leaves.
Resource leaves are small leaves with a global photosynthetic activity lower than zero (they are no auto-sufficient).
The job of these leaves is to hold nitrogen and to maintain the sink strength with photosynthetic activity.
In conclusion, nitrogen is mainly mobilized by the future buds and by the leaves of these buds.
5.A/Case of Sinsemilla :
If there are not any seeds, the entirety of nitrogen goes into bracts and resources leaves, and can’t get out of them. It is mainly stored under the form of amino-acids and some Ammoniacal by-products.
In this case the sink strength is so important, even if the rest of the plant die, these parts will stay green.
The only way to push out this nitrogen is to increase temperature, to decrease hygrometry, and to severely flush the plant.
5.B/Case of seeded plants :
In this case the major part of nitrogen is transferred to the seeds with the Micropyle, and is stored under the form of amino-acids, HSP proteins, and stock proteins.
In this case it would be better to avoid flush cycle and to keep providing small amounts of nitrogen during all the blooming cycle.
5.C/Nitrogen use and senescence beginning :
During stretch cycle, the plant will stimulate its nitrogen absorption with its roots to create material stock to feed future seeds. During this period the plant has the maximum ability to absorb nutriments.
However that metabolism increase, leading to an over-activation of nitrogen and others nutriments anabolism, will seriously exhaust the roots of the plant.
This will consecutively lead to a COMPLETE deterioration of the roots’ nitrogen carriers and to a deterioration of 20% to 50% of others nutriments’ carriers.
Only the aquaporins (water passive carriers) will stay intact.
Following that, plant will store absorbed nitrogen in new material, and when stocks became empty, plant will destroy its old leaves to get back more nitrogen, leading to senescence.
Global mechanisms of senescence are genetically controlled, and will vary depending of the strain, about date of beginning, length and intensity.
A precocious senescence often results of a nitrogen feeding leak during the stretch cycle, and that is very difficult to regulate.
6/Nitrogen-blooming links :
Nitrogen plays two big roles with blooming:
- Beginning of the maximum vegetative post-grow floral multiplication (stretch).
Indeed the nitrogen amount stored in buffer areas will dictate the floral induction intensity, because only this nitrogen will be available to the plant, because of the loss of efficiency of the HATS with nitrogen of the soil.
Paradoxically this amount collected during this period will determinate the appearance date of the first reproductive organs, but also their future number (in the case where there are not any foliar exogenous feeding added).
So it is very important to not neglect the provisions of this nutriment during grow cycle, but during stretch cycle too.
- Beginning of senescence and maturation of flowers (bracts, trichomes, pistils...).
Senescence is the way whereby the nitrogen trapped in old adult leaves will be re-mobilized by an extremely strong sink strength from buds.
This senescence only happens when the plant has totally lost its ability to absorb nitrogen with its roots.
This is very important because this senescence produces foliar abscission of old leaves and material which became no essential.
Plant takes advantage of it and clears out a maximum of toxic elements which were stored in these parts (only these ones which are not affected by osmotic pressure).
Once these old parts of the plant have fallen down, sink strength will become extremely strong and the plant will be able to absorb anew others nutriments in optimal way (in spite of its roots weakness).
That fact, dictated by Nitrogen, will allow the plant to receive a runoff of nutriments (mainly P/K/S and citrate/maltate) which will induce a strong global maturation of the plant.
Maturation will start in areas with the most important sink strength, and so forth (from top to bottom and from main stem to extremities).
Last step, once sink strength is well balanced, the secondary compounds oxidation signal is sent (long-range protection of seeds carrying organs), leading to a maturation of these secondary metabolites (like THC and its by-products).
7/Nitrogen-Ethylene links
Cannabis is not a climacteric plant, so ethylene has no action on its maturation.
It’s a stress hormone, which can cause foliar abscission and the activity blocking of vegetative or floral meristems.
A nitrogen deficiency causes mineral negative stress, can stimulate ethylene production if coupled to a hydric stress.
In the same way, a nitrogen excess coupled to over- or under-watering will stimulate ethylene production, and cause abscisic acid synthesis, leading to chlorosis and to a loss of leaves.
8/Resources management :
8.A/Regeneration :
To regenerate a plant, nitrogen feeding is an essential element of growth revival, but depends on the roots system health.
Like we said before, NH3 is mainly deteriorated in the roots, so it is preferable to take care of Rhizogenesis first (AIA, AIB or rooting stimulators) before adding nitrogen, and preferably ammonium-nitric complexes, to have both an immediate and a more durable effect.
8.B/Nitrogen, leaves and photosynthesis :
We can make some links between nitrogen, leaves and photosynthesis…
Nitrogen -> leaves -> photosynthesis
Photosynthesis + nitrogen absorption -> leaves -> photosynthesis
Conclusion: Give a lot of nitrogen to your plants during growing cycle, and they will well give back to you…
8.c/Nitrogen removal :
To limit bad tastes, it can be interesting to remove a maximum of nitrogen from the plant, not too soon to not loose yield, but not too late to assure a better quality of final product.
General conclusion and improvements ways:
After these quite complex explanations, here is what we had to remember.
During growing cycle, nitrogen is very requested by the plant, but only at roots level, and every foliar addition will decrease nitrogen and other nutriments absorption by roots, so it will slow down the general development of the plant.
During stretch cycle, nitrogen absorption is very strong because this one is stored in buffer areas like stems and petioles.
A foliar feeding can be added at this time to allow the plant to express all its potential of reproduction organs. At this time the final mass of the buds is determined by the plant.
More the source potential of stock organs will be weak, more the architect genes responsible for the number, the size, and the density of Buds will be active.
Then in blooming cycle, plant lost between 70% and 95% of its ability to absorb Nitrogen with roots, and other elements which require an active carriage too.
To compensate for a Nitrogen deficiency or any other nutriment deficiency except P & K, a foliar feeding will be the best way.
You also can, after 2 to 3 weeks of blooming induction, adding some calcium nitrate by foliar way, that will add nitrogen to increase the final mass and also add calcium which is the secondary messenger the most important for plants, this calcium will allow the plant to metabolize its resources to the maximum.
Author : exo
Trad : leMarcel
sources hysiologie végétale 2eme cycle, 6e édition de l'abrégé, DUNOD
nutrition- développement; R.Heller,R.Esnault,C.Lance
synthèse et mise en page par ER²
Source Malagoli et al 2004,2006,2006
SMRI pour l'analyse isotopique des mouvement d'azote par le rapport N13/N15 et N/C.
Diepenbrock W. 2000. Yield analysis of winter oilseed rape (Brassica
napus L.): a review. Field Crops Research 67: 35–49.
Dreccer MF, Schapendonk AHM, Slafer GA, Rabbinge R. 2000.
Comparative response of wheat and oilseed rape to nitrogen
supply: absorption and utilisation efficiency of radiation and nitrogen
during the reproductive stage determining yield. Plant and Soil 220:
189–205.
Gabrielle B, Denoroy P, Gosse G, Justes E, AndersonMN.1998.Amodel
of leaf area development and senescence of winter oilseed rape. Field
Crops Research 57: 209–222.
Habekotte´ B. 1997. Identification of strong and weak yield determining
components of winter oilseed rape compared with winter wheat.
European Journal of Agronomy 7: 315–321.
Hocking PJ, Randall PJ, DeMarco D. 1997. The response of dryland
canola to nitrogen fertilizer: partitioning and mobilization of dry matter
and nitrogen, and nitrogen effects on yield components. Field Crops
Research 54: 201–220.
Jensen LS, Christensen L, Mueller T, Nielsen NE. 1997. Turnover of
residual N-15-labelled fertilizer N in soil following harvest of oilseed
rape (Brassica napus L.). Plant and Soil 190: 193–202.
Laine´ P, Ourry A, Macduff JH, Boucaud J, Salette J. 1993. Kinetic
parameters of nitrate uptake by different catch crop species: effects
of low temperatures or previous nitrate starvation. Physiologia
Plantarum 88: 85–92.
Lawlor DW. 2002. Carbon and nitrogen assimilation in relation to yield:
mechanisms are the key to understanding production systems. Journal
of Experimental Botany 53: 773–787.
Leleu O, Vuylstecker C, Teˆtu JF, Degrande D, Champolivier L,
Rambour S. 2000. Effect of two contrasted N fertilisations on
rapeseed growth and nitrate metabolism. Plant Physiology and
Biochemistry 38: 639–645.
Lemaire G, Gastal F. 1997. N uptake and distribution in plant canopy. In:
Lemaire G, ed. Diagnosis of the nitrogen status in crops. Heidelberg:
Springer Verlag, 3–43.
Lemaire G, Onillon B, Gosse G, ChartierM,AllirandJM.1991. Nitrogen
distribution within lucerne canopy during regrowth: relation with
light distribution. Annals of Botany 68: 483–488.
Malagoli P, Laine´ P, Le Deunff E, Rossato L, Ney B, Ourry A. 2004.
Modeling N uptake in Brassica napus L. cv Capitol during a growth
cycle using influx kinetics of root nitrate transport systems and field
experimental data. Plant Physiology 134: 388–400.
Merrien A, Palleau JP, Maisonneuve C. 1988. Besoins en e´le´ments
mine´raux du colza cultive´ en France. In: Physiologie et e´laboration
du rendement du Colza. Paris: Cetiom Editions, 34–46.
Nanda R, Barghava SC, Rawson HM. 1995. Effect of sowing date on
rates of leaf appearance, final leaf numbers and areas in Brassica
campestris, B. juncea, B. napus and B. carinata. Field Crops Research
42: 125–134.
Rossato L, Laine´ P, Ourry A. 2001. Nitrogen storage and remobilisation in
Brassica napus L. during the growth cycle: nitrogen fluxes within the
plant and changes in soluble protein patterns. Journal of Experimental
Botany 52: 1655–1663.
Sanetra CM, Ito O, Virmani SM, Vlek PLG. 1998. Remobilisation of
nitrogen from senescing leaves of pigeonpea (Cajanus cajan (L.)
Milsp.): genotypic differences across maturity groups? Journal of
Experimental Botany 49: 853–862.
Schjoerring JK, Bock JGH, Gammelvind L, Jensen CR, Mogensen VO.
1995. Nitrogen incorporation and remobilisation in different shoot
components of field-grown winter oilseed rape (Brassica napus L.)
as affected by rate of nitrogen application and irrigation. Plant and Soil
177: 255–264.
Smith CJ, Whitfield DM, Gyles OA, Wright GC. 1989. Nitrogen fertilizer
balance of irrigated wheat grown on red-brown earth in southeastern
Australia. Field Crops Research 21: 265–275.
Tittonel ED, Chaput JP, Letoublon F, Bonnot O. 1988. Besoins
en e´le´ments mine´raux du colza cultive´ en France. In:
Physiologie et e´laboration du rendement du Colza. Paris: Cetiom
Editions, 68–72.
Triboı¨-Blondel AM. 1988. Mise en place et fonctionnement des
feuilles de colza d’hiver : relations azote-carbone et se´nescence. In:
Physiologie et e´laboration du rendement du Colza. Paris: Cetiom
Editions, 111–120.
« Nitrogen Nutrition » :
INTRODUCTION :
Land vegetables usually take their Nitrogen in soil, under the form of nitrates or ammonium salts, resulting of organic decompositions by microorganisms of soil.
Notice the actinorhizian plants realize an ammonia synthesis from dinitrogen (N2) of air with symbiotic organisms (Rhizobium).
Nitrogen is a primary nutriment essential to vegetables; we can often read the amount of N in fertilizers (N-P-K).
It is a free macro-element in the soil-plant continuum, even inside the plant.
It will determine several key parameters of the plant’s life cycle. Let’s see them.
1/ Nitrogen in soil-plant-atmosphere continuum :
1.A/ Soil Nitrogen :
Under our climates in a good vegetable earth, Nitrogen content is about 1g/Kg of earth, so about 5T Nitrogen / hectare.
On this mass, 1% to 2% is under a mineral form (in average); the remainder is under an organic form, mainly humus.
Soil’s organic material mainly comes from vegetables waste, only a little amount of it comes from animals waste.
After being broken down and reorganized by micro flora, wastes are mineralized, under a form lot more easily assimilated by the plant.
That’s mainly NH4+ (and NH4OH), secondarily oxidized on the form of NO3-, CO2(and HCO3-), H2PO4-, with release of positive ions (CA2+, MG2+, K+, etc.) and negative ions CL-, which were more or less fixed to them.
There is also action of cellulolytic (cytophaga) and proteolytic bacteria (proteus), this transformation concerns mainly cellulose and proteins, it is fast (from a few weeks to a few months). It leads to transformation of 70% of soil’s humus.
Residues are on various forms, depending on kind of vegetables. We notably can find humic acids, fulvic acids, and humin.
1.B/Mineral Nitrogen :
The first step to development mineral nitrogen is ammonization, which is made by bacteria.
For example:
- Amins :
Carbon molecule-NH2 + H20 -> R-COOH + NH3
That’s a hydrolysis of a molecule with an amin part, which produces a carboxylic acid and an ammonia molecule.
- Amino-acids:
NH2-Carbon molecule-COOH+H2O -> R-CH2OH+CO2+NH3
That’s a hydrolysis of an amino-acid, resulting in Carbon Dioxide, ammonia and a primary alcohol.
The next step is nitrification to make nitrates. Two types of bacteria play a role here:
- Nitrous bacteria: they do nitrosation:
(NH4+)+(2/3 O2) -> (NO2-)+(H2O)+(2H+)
- Nitric bacteria: they do oxidation:
(NO2-)+(1/2 O2) -> NO3-
These reactions are oxidation-reduction.
2. Nitrogen use :
We’ll try to explain how the plant use Nitrogen for its development.
2.A/ Organic Nitrogen use :
Cannabis is able to assimilate Nitrogen on organic form when it is under the form of small molecules (amino-acids, glutamine, urea, uric acid) but the efficiency is low, comparative to nitric or ammonium feeding.
2.B/ Mineral Nitrogen use :
Most of grown plants have the best yield with nitrates. Reduction of nitrates costs energy to the plant, but this degradation is plugged with glucidic catabolism, so it promotes cetonic acid production.
Generally, young plants prefer NH4+ (but it is not a generality)
We have to notice the importance of PH:
Lowering the PH level helps absorption and assimilation of nitrates, and raising the PH level will helps absorption and assimilation of ammonium ions.
Also the content of sugars, particularly in the roots, which depends closely of the photosynthesis of the plant, conditions nitrogen use.
Indeed, cetonic acids are made with these solid carbohydrates, and cetonic acids will allow incorporation of Nitrogen under the form of amino-acids.
2.C/Nitrogen fertilizers :
We can classify them into 3 categories:
- Ammoniacal fertilizers:
Sulphate, Chloride, Phosphate of Ammonia.
They are acidifying fertilizers, used in earth and added when substrate is mixed. (background fertilizers)
They have the double advantage to become available to the plant as it goes along to need them without reaching a toxic amount, and to prevent them to be flushed by successive watering.
Indeed, NH4+ ions are fixed to colloids of soil, and are exchanged by H+ ions from the plant.
So, NH4+ absorption will not modify the substrate’s PH.
- Nitric fertilizers :
Nitrates of Sodium, Calcium or Potassium.
They are suitable to fast interventions. It is recommended to use them when the plant needs them.
- ammonia-nitric complex :
They allow to combine the advantages of both : an immediate provision to the plant, and also a progressive provision used depending of plant’s intake evolution.
3/Nitrogen assimilation :
Nitrates reduction:
The reduction usually start in the root, although a lot of species also do this reduction in the leaves with light (there are not any photoreceptor in the roots, but the power of reduction of leaves is NADPH2 and power of reduction of roots is NADH2, so the leaves are better reduction factories)
The reduction means a benefit of 8 electrons:
(NO3-)+(8H+)+(8e-) -> NH3+(2*H2O)+OH- (9-;1-) = 8-
This reduction is done with two steps, which follow very fast: reduction of nitrates to nitrites, then reduction of nitrites to NH3:
(NO3-)+(2H+)+(2e-) -> (NO2-)+(H2O)
(NO2-)+(6H+)+(6e-) -> (NH3)+(H2O)+(OH-)
That was established in 1924 by S.ECKERSON (USA).
Some other intermediate steps are plausible but we can’t verify them, like transition with hydroxylamin NH2OH. Indeed, nitrites are toxic at high amount, that corroborates the fact than reduction is done continuously and with non-lethal amounts for the vegetable organism.
4/Nitrogen Use before blooming cycle :
4.A/Growing cycle :
Nitrogen is very dependent on Carbon : broadly speaking, feeding with high Nitrogen level promotes vegetative development to the detriment of reproductive system.
On the contrary, a rich carbon feeding promotes blooming. That’s why an active photosynthesis is essential.
So the ratio Carbon/Nitrogen is very important. In average this ratio is about 20 (in mass).
Around this average, of course we can’t fix accurate measures, development of the plant depends a lot of this C/N ratio:
C/N very high: poor vegetative development (Nitrogen deficiency)
C/N high: lush fruit development
C/N low: vigorous vegetative development
C/N very low : poor vegetative development (Carbon deficiency)
It was established, about plants depending on photoperiod (so, including Cannabis), that saccharose amount in phloem sap increases a lot when blooming photoperiod starts.
This saccharose influx, without being the decisive factor, is an important factor of blooming induction, but is not a blooming signal.
4.B/Movements and storage during stretch cycle :
- Case of a soil with a high level of Nitrogen :
During stretch, the plant will increase the number of Nitrogen carriers (HATS) in its roots, and also increase the amount of metabolization enzymes: nitrate reductase and nitrite reductase.
Then all this nitrogen taken in soil will rise in the plant with raw sap.
This brutal increase of nitrogen concentration will induce the plant to build a buffer area to store that transitional nitrogen.
That means an increase of total volume of stems, and an inhibition of secondary buds’ dormancy.
So in this case the storage is done in stems and buds of the not much developed secondary apex, and in tertiary apex too….
- Case of a soil with a low level of Nitrogen :
The plant does not act on its roots, to avoid using energy unnecessarily because there is not enough Nitrogen in soil.
In this case nitrogen will be re-concentrated in the stem in aid of a precocious senescence of old leaves, always from bottom to top, with a degradation of amino-acids stored in the stem.
Because the plant does not have enough nitrogen to do a complete inhibition of buds’ dormancy, nitrogen will be stored essentially in the stem and in the secondary buds near the canopy, thanks to a lux-dependent mechanism.
In conclusion, we can say the major part of nitrogen will be stored in the buffer stems elaborated during stretch cycle and in the buds too.
Nitrogen concentration in the stem, and the number of inhibited buds, will vary depending of nitrogen concentration in the soil.
5/Stock usage after blooming induction :
After blooming induction, the buffer area becomes not useful under this form.
The area with the most important sink strength will be able to guide Nitrogen influx thanks to osmotic and hydric pressures.
These pressures use two mechanisms:
- The first one is an osmotic link; the source cell will store elements in its vacuole to make a decreasing gradient of solute from source to it.
With balance notion, that will attract the nitrogen stored in stems, but not the nitrogen stored in buds.
- The second mechanism is a loss of osmotic pressure by osmoticum synthesis, like sugars and others, to make a decreasing gradient too.
About the buds, the sink strength caused by blooming induction, completely blocks nitrogen in buds and attracts nitrogen stored in stems, too.
This nitrogen is mainly under the form of amino-acids. These ones will be stored to excess in the bracts, then, if nitrogen concentration is suitable, the plant will create some resource leaves.
Resource leaves are small leaves with a global photosynthetic activity lower than zero (they are no auto-sufficient).
The job of these leaves is to hold nitrogen and to maintain the sink strength with photosynthetic activity.
In conclusion, nitrogen is mainly mobilized by the future buds and by the leaves of these buds.
5.A/Case of Sinsemilla :
If there are not any seeds, the entirety of nitrogen goes into bracts and resources leaves, and can’t get out of them. It is mainly stored under the form of amino-acids and some Ammoniacal by-products.
In this case the sink strength is so important, even if the rest of the plant die, these parts will stay green.
The only way to push out this nitrogen is to increase temperature, to decrease hygrometry, and to severely flush the plant.
5.B/Case of seeded plants :
In this case the major part of nitrogen is transferred to the seeds with the Micropyle, and is stored under the form of amino-acids, HSP proteins, and stock proteins.
In this case it would be better to avoid flush cycle and to keep providing small amounts of nitrogen during all the blooming cycle.
5.C/Nitrogen use and senescence beginning :
During stretch cycle, the plant will stimulate its nitrogen absorption with its roots to create material stock to feed future seeds. During this period the plant has the maximum ability to absorb nutriments.
However that metabolism increase, leading to an over-activation of nitrogen and others nutriments anabolism, will seriously exhaust the roots of the plant.
This will consecutively lead to a COMPLETE deterioration of the roots’ nitrogen carriers and to a deterioration of 20% to 50% of others nutriments’ carriers.
Only the aquaporins (water passive carriers) will stay intact.
Following that, plant will store absorbed nitrogen in new material, and when stocks became empty, plant will destroy its old leaves to get back more nitrogen, leading to senescence.
Global mechanisms of senescence are genetically controlled, and will vary depending of the strain, about date of beginning, length and intensity.
A precocious senescence often results of a nitrogen feeding leak during the stretch cycle, and that is very difficult to regulate.
6/Nitrogen-blooming links :
Nitrogen plays two big roles with blooming:
- Beginning of the maximum vegetative post-grow floral multiplication (stretch).
Indeed the nitrogen amount stored in buffer areas will dictate the floral induction intensity, because only this nitrogen will be available to the plant, because of the loss of efficiency of the HATS with nitrogen of the soil.
Paradoxically this amount collected during this period will determinate the appearance date of the first reproductive organs, but also their future number (in the case where there are not any foliar exogenous feeding added).
So it is very important to not neglect the provisions of this nutriment during grow cycle, but during stretch cycle too.
- Beginning of senescence and maturation of flowers (bracts, trichomes, pistils...).
Senescence is the way whereby the nitrogen trapped in old adult leaves will be re-mobilized by an extremely strong sink strength from buds.
This senescence only happens when the plant has totally lost its ability to absorb nitrogen with its roots.
This is very important because this senescence produces foliar abscission of old leaves and material which became no essential.
Plant takes advantage of it and clears out a maximum of toxic elements which were stored in these parts (only these ones which are not affected by osmotic pressure).
Once these old parts of the plant have fallen down, sink strength will become extremely strong and the plant will be able to absorb anew others nutriments in optimal way (in spite of its roots weakness).
That fact, dictated by Nitrogen, will allow the plant to receive a runoff of nutriments (mainly P/K/S and citrate/maltate) which will induce a strong global maturation of the plant.
Maturation will start in areas with the most important sink strength, and so forth (from top to bottom and from main stem to extremities).
Last step, once sink strength is well balanced, the secondary compounds oxidation signal is sent (long-range protection of seeds carrying organs), leading to a maturation of these secondary metabolites (like THC and its by-products).
7/Nitrogen-Ethylene links
Cannabis is not a climacteric plant, so ethylene has no action on its maturation.
It’s a stress hormone, which can cause foliar abscission and the activity blocking of vegetative or floral meristems.
A nitrogen deficiency causes mineral negative stress, can stimulate ethylene production if coupled to a hydric stress.
In the same way, a nitrogen excess coupled to over- or under-watering will stimulate ethylene production, and cause abscisic acid synthesis, leading to chlorosis and to a loss of leaves.
8/Resources management :
8.A/Regeneration :
To regenerate a plant, nitrogen feeding is an essential element of growth revival, but depends on the roots system health.
Like we said before, NH3 is mainly deteriorated in the roots, so it is preferable to take care of Rhizogenesis first (AIA, AIB or rooting stimulators) before adding nitrogen, and preferably ammonium-nitric complexes, to have both an immediate and a more durable effect.
8.B/Nitrogen, leaves and photosynthesis :
We can make some links between nitrogen, leaves and photosynthesis…
Nitrogen -> leaves -> photosynthesis
Photosynthesis + nitrogen absorption -> leaves -> photosynthesis
Conclusion: Give a lot of nitrogen to your plants during growing cycle, and they will well give back to you…
8.c/Nitrogen removal :
To limit bad tastes, it can be interesting to remove a maximum of nitrogen from the plant, not too soon to not loose yield, but not too late to assure a better quality of final product.
General conclusion and improvements ways:
After these quite complex explanations, here is what we had to remember.
During growing cycle, nitrogen is very requested by the plant, but only at roots level, and every foliar addition will decrease nitrogen and other nutriments absorption by roots, so it will slow down the general development of the plant.
During stretch cycle, nitrogen absorption is very strong because this one is stored in buffer areas like stems and petioles.
A foliar feeding can be added at this time to allow the plant to express all its potential of reproduction organs. At this time the final mass of the buds is determined by the plant.
More the source potential of stock organs will be weak, more the architect genes responsible for the number, the size, and the density of Buds will be active.
Then in blooming cycle, plant lost between 70% and 95% of its ability to absorb Nitrogen with roots, and other elements which require an active carriage too.
To compensate for a Nitrogen deficiency or any other nutriment deficiency except P & K, a foliar feeding will be the best way.
You also can, after 2 to 3 weeks of blooming induction, adding some calcium nitrate by foliar way, that will add nitrogen to increase the final mass and also add calcium which is the secondary messenger the most important for plants, this calcium will allow the plant to metabolize its resources to the maximum.
Author : exo
Trad : leMarcel
sources hysiologie végétale 2eme cycle, 6e édition de l'abrégé, DUNOD
nutrition- développement; R.Heller,R.Esnault,C.Lance
synthèse et mise en page par ER²
Source Malagoli et al 2004,2006,2006
SMRI pour l'analyse isotopique des mouvement d'azote par le rapport N13/N15 et N/C.
Diepenbrock W. 2000. Yield analysis of winter oilseed rape (Brassica
napus L.): a review. Field Crops Research 67: 35–49.
Dreccer MF, Schapendonk AHM, Slafer GA, Rabbinge R. 2000.
Comparative response of wheat and oilseed rape to nitrogen
supply: absorption and utilisation efficiency of radiation and nitrogen
during the reproductive stage determining yield. Plant and Soil 220:
189–205.
Gabrielle B, Denoroy P, Gosse G, Justes E, AndersonMN.1998.Amodel
of leaf area development and senescence of winter oilseed rape. Field
Crops Research 57: 209–222.
Habekotte´ B. 1997. Identification of strong and weak yield determining
components of winter oilseed rape compared with winter wheat.
European Journal of Agronomy 7: 315–321.
Hocking PJ, Randall PJ, DeMarco D. 1997. The response of dryland
canola to nitrogen fertilizer: partitioning and mobilization of dry matter
and nitrogen, and nitrogen effects on yield components. Field Crops
Research 54: 201–220.
Jensen LS, Christensen L, Mueller T, Nielsen NE. 1997. Turnover of
residual N-15-labelled fertilizer N in soil following harvest of oilseed
rape (Brassica napus L.). Plant and Soil 190: 193–202.
Laine´ P, Ourry A, Macduff JH, Boucaud J, Salette J. 1993. Kinetic
parameters of nitrate uptake by different catch crop species: effects
of low temperatures or previous nitrate starvation. Physiologia
Plantarum 88: 85–92.
Lawlor DW. 2002. Carbon and nitrogen assimilation in relation to yield:
mechanisms are the key to understanding production systems. Journal
of Experimental Botany 53: 773–787.
Leleu O, Vuylstecker C, Teˆtu JF, Degrande D, Champolivier L,
Rambour S. 2000. Effect of two contrasted N fertilisations on
rapeseed growth and nitrate metabolism. Plant Physiology and
Biochemistry 38: 639–645.
Lemaire G, Gastal F. 1997. N uptake and distribution in plant canopy. In:
Lemaire G, ed. Diagnosis of the nitrogen status in crops. Heidelberg:
Springer Verlag, 3–43.
Lemaire G, Onillon B, Gosse G, ChartierM,AllirandJM.1991. Nitrogen
distribution within lucerne canopy during regrowth: relation with
light distribution. Annals of Botany 68: 483–488.
Malagoli P, Laine´ P, Le Deunff E, Rossato L, Ney B, Ourry A. 2004.
Modeling N uptake in Brassica napus L. cv Capitol during a growth
cycle using influx kinetics of root nitrate transport systems and field
experimental data. Plant Physiology 134: 388–400.
Merrien A, Palleau JP, Maisonneuve C. 1988. Besoins en e´le´ments
mine´raux du colza cultive´ en France. In: Physiologie et e´laboration
du rendement du Colza. Paris: Cetiom Editions, 34–46.
Nanda R, Barghava SC, Rawson HM. 1995. Effect of sowing date on
rates of leaf appearance, final leaf numbers and areas in Brassica
campestris, B. juncea, B. napus and B. carinata. Field Crops Research
42: 125–134.
Rossato L, Laine´ P, Ourry A. 2001. Nitrogen storage and remobilisation in
Brassica napus L. during the growth cycle: nitrogen fluxes within the
plant and changes in soluble protein patterns. Journal of Experimental
Botany 52: 1655–1663.
Sanetra CM, Ito O, Virmani SM, Vlek PLG. 1998. Remobilisation of
nitrogen from senescing leaves of pigeonpea (Cajanus cajan (L.)
Milsp.): genotypic differences across maturity groups? Journal of
Experimental Botany 49: 853–862.
Schjoerring JK, Bock JGH, Gammelvind L, Jensen CR, Mogensen VO.
1995. Nitrogen incorporation and remobilisation in different shoot
components of field-grown winter oilseed rape (Brassica napus L.)
as affected by rate of nitrogen application and irrigation. Plant and Soil
177: 255–264.
Smith CJ, Whitfield DM, Gyles OA, Wright GC. 1989. Nitrogen fertilizer
balance of irrigated wheat grown on red-brown earth in southeastern
Australia. Field Crops Research 21: 265–275.
Tittonel ED, Chaput JP, Letoublon F, Bonnot O. 1988. Besoins
en e´le´ments mine´raux du colza cultive´ en France. In:
Physiologie et e´laboration du rendement du Colza. Paris: Cetiom
Editions, 68–72.
Triboı¨-Blondel AM. 1988. Mise en place et fonctionnement des
feuilles de colza d’hiver : relations azote-carbone et se´nescence. In:
Physiologie et e´laboration du rendement du Colza. Paris: Cetiom
Editions, 111–120.
