-
ICMag with help from Landrace Warden and The Vault is running a NEW contest in November! You can check it here. Prizes are seeds & forum premium access. Come join in!
Why go 24 hours lights on??
- Thread starter thcrefugee
- Start date
This must mean that the rest of the text had no clear definition, as did the discussion that generated the comment. Everything happens in a vacuum. That's not actually true, is it?
FWIW, the only acceptable mention of spelling happens when a SPELFLAIM is launched and is accompanied by a spelling error of its own.
...back to watching...
Simon
OsWiZzLe
Active member
This is a long thread, so I dont know if someone actually said you only get good results because of your strain, but nonetheless, you likely would get better results under 18/6 if other factors are ideal. Thats what Spurr has been trying to tell people all along.
Instead of people listening with an open mind, they defend their choices, and result to insults, drama, bullshit, etc, etc.
Your plants do look nice, but there's always room for improvement, and Spurr can give alot of tips if people are willing to listen. Unfortunately many people become attached to their plants as if they were kids, and well who wants to be told how to raise their kids?
OsWiZzLe
Active member
http://5e.plantphys.net/article.php?ch=e&id=480
In Vivo Measurement of Plant Respiration
August, 2010
Introduction
“Absentis est quos non anhelo”
“Dead is who does not respire”
Respiration is vital; it is the essence of life. Respiration is the mechanism by which energy obtained during the photosynthesis process is transformed into biochemical energy, in the form of ATP. This transformation of energy keeps all cells in all organisms alive. While energy conversion is the main function of respiration in animals, respiration has several other functions in plants. Among them, interactions with photosynthesis such as photorespiration and the production of carbon skeletons for the many compounds synthesized in plants (e.g., pigments, proteins and secondary metabolites). Therefore, it comes as no surprise that such a key role of respiration in plants promoted intense effort to investigate its regulation. Nevertheless, the interactions with other simultaneous processes make its measurement in plants very challenging. In animals, respiration can be simply measured as CO2 or O2 exchange with the atmosphere since there are no other processes performing similar gas exchange. In contrast, in plants, respiration produces CO2 and consumes O2 simultaneously with photorespiration. Moreover, photosynthesis performs the exact reverse process (Figure 1). The combined reaction can be described as:
Figure 1 Oxygen and carbon dioxide gas exchanges between the atmosphere and a leaf, in the light and in the dark (Modified from Hurry et al., 2005). PEPc, phosphoenolpyruvate carboxylase; GDC, glycine decarboxylase; TCA cycle, tricarboxylic acid cycle. (Click image to enlarge.)
General Aspects on How To Measure Respiration
Biochemically, respiration can be divided in three major parts: 1) glycolysis, 2) tricarboxylic acid (TCA) cycle, and 3) mitochondrial electron transport. The first series of reactions occur in the cellular cytosol, while the other two take place inside the mitochondria. Usual respiration measurements involve gas exchange, that is, O2 consumption and CO2 evolution rates. Gas exchange methods use either an open (comparison of inlet air of known composition with outlet air enriched in CO2 or depleted in O2) or a closed system (in which the CO2 raises or O2 decreases with time). Such a principle applies to dark-respiration. Other methods (e.g., isotopic measurements) are used in the light to distinguish CO2 and O2 fluxes caused by respiration from those due to photosynthesis or photorespiration.
During respiration, oxygen is consumed by terminal oxidases of the mitochondrial electron transport chain. In contrast to vertebrate animals, which only contain a single oxidase (the cytochrome oxidase), plants possess two terminal oxidases (the cytochrome oxidase and the alternative oxidase; McDonald 2008). Unlike the cytochrome oxidase, the alternative oxidase is resistant to cyanide (hence cyanide-resistant respiration) but is inhibited by salicylhydroxamic acid (SHAM). These two terminal oxidases compete to draw electrons from the ubiquinone pool to reduce oxygen to water. Unlike the cytochrome oxidase, the alternative oxidase is not linked to ATP synthesis (see Web topic 11.3) and the energy is released as heat, for example, to warm the floral ovens of thermogenic plants (see Web essay 11.6 and Watling et al 2006). The role played by the alternative oxidase in non thermogenic plants is an active research topic and specific methodologies (see below) are required to differentiate respiration via the two pathways.
Measuring Respiration in The Dark (Night Respiration)
In the absence of light, most of the CO2 production and O2 consumption is due to respiration. While CO2 is produced in the decarboxylation reactions (pyruvate decarboxylase and TCA cycle), oxygen is mostly consumed by the terminal oxidases of the mitochondrial electron transport chain. In order to avoid transient metabolic activities following darkening, known as Light Enhanced Dark Respiration, measurements of night respiration must be performed after 20-30 minutes acclimation to darkness. Carbon dioxide production can be measured with an Infra-Red Gas Analyzer (IRGA) in both open and closed systems. The advantage of this method is that the organ measured can remain attached to the whole plant. The main drawbacks of this method, especially for open systems, are its low sensitivity, as the CO2 gradient between the inlet and outlet air can fall within the noise/signal ratio of the measuring system (1-2 ppm), and possible leakage around the gaskets of the cuvettes (Hurry et al., 2005).
Measurements of oxygen consumption with oxygen electrodes (Clark et al., 1953) are good indicators of the total respiratory rate. This method is performed in a closed cuvette, either in liquid or gas phase and the main disadvantage is that it must be performed on detached tissues.
Since oxygen can be consumed by either the cytochrome or alternative oxidases, specific methodologies are required when we wish to measure the specific contribution of either pathway. Whilst the capacity of each of these two oxidases can be determined with the oxygen electrode after poisoning tissue with SHAM (cytochrome oxidase capacity) or KCN (alternative oxidase capacity), the actual contribution of each oxidase to total respiration can only be measured with the oxygen isotope fractionation technique (Guy et al., 1989).
The Oxygen Isotope Fractionation Technique
This oxygen isotope fractionation technique, based on Isotope Ratio Mass Spectrometry (IRMS), measures changes in the isotopic composition of oxygen molecules (18O/16O) during respiration in a closed system. Both oxidases favor 16O over 18O because it requires less energy to break the 16O=16O bond than the 18O=16O bond. Therefore, the proportion of 18O (18O/16O ratio) in the air remaining in a closed cuvette that contains a respiring tissue increases as oxygen is decreased due to respiration. The respiratory isotope fractionation is obtained from measurements of the oxygen isotope ratio (R=18O/16O) and the fraction of unreacted oxygen remaining in the respiration cuvette at different times during the course of the reaction.
A complete description of the calculations of the isotope fractionation (D) can be found in Guy et al. (1989). It results in the overall equation as follows:
Although both oxidases prefer to use 16O over 18O, their “degree of preference” differs, allowing the calculation of their relative contribution to the total mitochondrial oxygen consumption and electron transport. The two mitochondrial terminal oxidases have a different 18O/16O fractionation because they have different catalytic mechanisms to break the double bond of O2 (Hoefs, 1987). The alternative oxidase fractionates more against 18O than the cytochrome oxidase (Guy et al., 1989). Figure 2 shows a classical experiment in which fractionation by both cytochrome (Dc) and alternative oxidases (Da) is measured in the presence of the specific inhibitors SHAM and KCN, respectively. Once fractionation values for each respiratory pathway have been obtained, measurements of the fractionation in the absence of any inhibitors (Dn) give the electron partitioning through the alternative pathway (τa).
Figure 2 Calculation of the electron partitioning through the alternative oxidase(τa) using the oxygen isotope fractionation technique. This is an example of the lines expected in different situations where the participation of the alternative pathway (τa) would be approximately 90%, 60% and 30%. This could be the case for the floral receptacle of Nelumbo nucifera (Watling et al., 2006), cotyledons and leaves of Glycine max (Ribas-Carbo et al., 2005), respectively (Click image to enlarge.)
Measuring Respiration In The Light (Day Respiration)
Measurement of respiration in the light is much more challenging than in the dark, because photorespiration and photosynthesis also occur, thereby masking the O2 and CO2 exchanges that are due to mitochondrial respiration. Moreover, there is evidence that the rate of mitochondrial O2/CO2 exchange is depressed in the presence of light as compared to the rate in darkness. Several methods have been proposed to estimate the rate of respiration in the light, some of which are briefly explained here but for detailed reviews of all methods see Hurry et al. (2005) and Tcherkez et al. (2005). For a proper understanding of these methods, it should be kept in mind that in the presence of light, leaf gas exchange can be described as:
AN = AG – PR – Rd,
where AN is the “net” photosynthesis (determined with a standard open gas exchange system), AG is gross CO2 assimilation, PR is photorespiration and Rd is respiratory CO2 evolution in the light. The first published method employed to measure respiration in the light was the so-called Kok method (Kok, 1948). It is based on the inhibitory effect of light on the rate of respiration, and it only requires the use of a commercial CO2 gas exchange system. It is based on a light-response curve performed at very low light intensity. Generally, the net CO2 assimilation rate shows an abrupt reduction in slope as light levels increase (Figure 3). The linear extrapolation to zero light from the gradual, “upper” slope indicates the rate of respiration in the light or “day” respiration (Rd) while the steeper part reaches the y axis (zero light) at the night respiration rate (Rn) (See Textbook Chapter 9 for more information on light and CO2 compensation points).
Figure 3 Kok method applied to detached leaves at 21°C in 21% O2 (typical graph redrawn from the dataset of Tcherkez et al. 2008). AN, Net photosynthesis; PAR, Photosynthetically active radiation; Rd, day respiration; Rn, night respiration. (Click image to enlarge.)
The Cornic method (Cornic 1973) is performed on an illuminated leaf placed in CO2-free air, in either N2 (0% O2) or 21% O2, and then darkened. The CO2-production rate in the light is denoted as LO (in 21% O2) or LN (in N2). When the leaf is darkened, refixation of (photo) respired CO2 vanishes and a peak of CO2 production, represented as p, can be seen. Under several simplifying assumptions, it can be shown that Rd = LO - LN - p + Rn.
Another commonly used technique is the Laisk method (Laisk 1977). This is based on the assumption that whilst light intensity alters the rates of photosynthesis and photorespiration, it does not affect the rate of mitochondrial respiration. Using a standard CO2 gas exchange system, assimilation response curves versus leaf intercellular CO2 concentration are performed at several different light levels (Figure 4). As light decreases both gross photosynthesis and photorespiration will decrease proportionally and so will the slope of the response of net photosynthesis. Therefore, if Rd does not to change with light intensity, all curves should converge to a single point which will correspond to the CO2 compensation point in the absence of day respiration (Γ*) on the X-axis and -Rd on the Y-axis (See Textbook Chapter 9 for more information on light and CO2 compensation points).
Figure 4 Laisk method. Net photosynthesis response to leaf internal CO2 (ci) at 200, 400 and 600 μmol m-2 s-1 (PAR) at 21°C in 21% O2 in french bean (Phaseolus vulgaris). In this example, the day respiration rate Rd is 0.51 μmol m-2 s-1. (Click image to enlarge.)
A more recent method uses stable isotopes of carbon to estimate the rate of respiration in the light (Loreto et al., 2001). This method takes advantage of the fact that “day” respiratory substrates turn over more slowly (half time in the order of minutes or more) than photorespiratory substrates (half-time in the order of seconds). That is, plants are grown under natural 12CO2-atmosphere and then placed in a 13CO2-atmosphere. The production of 12CO2 measured in a 13CO2-atmosphere indicates the “day” respiration rate Rd (with some corrections required to take into account refixation of respired 12CO2).
These methods have contrasting advantages and disadvantages: for example, both the Kok and the Laisk methods are performed at low light intensities and, consequently, plants present small assimilation rates, causing large measurement variability. In addition, the Laisk method requires measurements at several light levels and it is plausible that “day” respiration varies with light.
To summarize, measuring respiration is a very challenging task, especially in the light, when substrates and products are interchanged by different and opposing reactions that operate simultaneously. In the dark, respiration consumes oxygen by two different oxidases that act simultaneously and, consequently, can only be differentiated using stable isotope techniques. Moreover, the recent discovery of the alternative oxidase in other phylogenetic groups means that microbiologists and invertebrate physiologists will also have to reassess their methodologies for measuring respiration and will have much to learn from plant physiologists.
In Vivo Measurement of Plant Respiration
August, 2010
Introduction
“Absentis est quos non anhelo”
“Dead is who does not respire”
Respiration is vital; it is the essence of life. Respiration is the mechanism by which energy obtained during the photosynthesis process is transformed into biochemical energy, in the form of ATP. This transformation of energy keeps all cells in all organisms alive. While energy conversion is the main function of respiration in animals, respiration has several other functions in plants. Among them, interactions with photosynthesis such as photorespiration and the production of carbon skeletons for the many compounds synthesized in plants (e.g., pigments, proteins and secondary metabolites). Therefore, it comes as no surprise that such a key role of respiration in plants promoted intense effort to investigate its regulation. Nevertheless, the interactions with other simultaneous processes make its measurement in plants very challenging. In animals, respiration can be simply measured as CO2 or O2 exchange with the atmosphere since there are no other processes performing similar gas exchange. In contrast, in plants, respiration produces CO2 and consumes O2 simultaneously with photorespiration. Moreover, photosynthesis performs the exact reverse process (Figure 1). The combined reaction can be described as:
Figure 1 Oxygen and carbon dioxide gas exchanges between the atmosphere and a leaf, in the light and in the dark (Modified from Hurry et al., 2005). PEPc, phosphoenolpyruvate carboxylase; GDC, glycine decarboxylase; TCA cycle, tricarboxylic acid cycle. (Click image to enlarge.)
General Aspects on How To Measure Respiration
Biochemically, respiration can be divided in three major parts: 1) glycolysis, 2) tricarboxylic acid (TCA) cycle, and 3) mitochondrial electron transport. The first series of reactions occur in the cellular cytosol, while the other two take place inside the mitochondria. Usual respiration measurements involve gas exchange, that is, O2 consumption and CO2 evolution rates. Gas exchange methods use either an open (comparison of inlet air of known composition with outlet air enriched in CO2 or depleted in O2) or a closed system (in which the CO2 raises or O2 decreases with time). Such a principle applies to dark-respiration. Other methods (e.g., isotopic measurements) are used in the light to distinguish CO2 and O2 fluxes caused by respiration from those due to photosynthesis or photorespiration.
During respiration, oxygen is consumed by terminal oxidases of the mitochondrial electron transport chain. In contrast to vertebrate animals, which only contain a single oxidase (the cytochrome oxidase), plants possess two terminal oxidases (the cytochrome oxidase and the alternative oxidase; McDonald 2008). Unlike the cytochrome oxidase, the alternative oxidase is resistant to cyanide (hence cyanide-resistant respiration) but is inhibited by salicylhydroxamic acid (SHAM). These two terminal oxidases compete to draw electrons from the ubiquinone pool to reduce oxygen to water. Unlike the cytochrome oxidase, the alternative oxidase is not linked to ATP synthesis (see Web topic 11.3) and the energy is released as heat, for example, to warm the floral ovens of thermogenic plants (see Web essay 11.6 and Watling et al 2006). The role played by the alternative oxidase in non thermogenic plants is an active research topic and specific methodologies (see below) are required to differentiate respiration via the two pathways.
Measuring Respiration in The Dark (Night Respiration)
In the absence of light, most of the CO2 production and O2 consumption is due to respiration. While CO2 is produced in the decarboxylation reactions (pyruvate decarboxylase and TCA cycle), oxygen is mostly consumed by the terminal oxidases of the mitochondrial electron transport chain. In order to avoid transient metabolic activities following darkening, known as Light Enhanced Dark Respiration, measurements of night respiration must be performed after 20-30 minutes acclimation to darkness. Carbon dioxide production can be measured with an Infra-Red Gas Analyzer (IRGA) in both open and closed systems. The advantage of this method is that the organ measured can remain attached to the whole plant. The main drawbacks of this method, especially for open systems, are its low sensitivity, as the CO2 gradient between the inlet and outlet air can fall within the noise/signal ratio of the measuring system (1-2 ppm), and possible leakage around the gaskets of the cuvettes (Hurry et al., 2005).
Measurements of oxygen consumption with oxygen electrodes (Clark et al., 1953) are good indicators of the total respiratory rate. This method is performed in a closed cuvette, either in liquid or gas phase and the main disadvantage is that it must be performed on detached tissues.
Since oxygen can be consumed by either the cytochrome or alternative oxidases, specific methodologies are required when we wish to measure the specific contribution of either pathway. Whilst the capacity of each of these two oxidases can be determined with the oxygen electrode after poisoning tissue with SHAM (cytochrome oxidase capacity) or KCN (alternative oxidase capacity), the actual contribution of each oxidase to total respiration can only be measured with the oxygen isotope fractionation technique (Guy et al., 1989).
The Oxygen Isotope Fractionation Technique
This oxygen isotope fractionation technique, based on Isotope Ratio Mass Spectrometry (IRMS), measures changes in the isotopic composition of oxygen molecules (18O/16O) during respiration in a closed system. Both oxidases favor 16O over 18O because it requires less energy to break the 16O=16O bond than the 18O=16O bond. Therefore, the proportion of 18O (18O/16O ratio) in the air remaining in a closed cuvette that contains a respiring tissue increases as oxygen is decreased due to respiration. The respiratory isotope fractionation is obtained from measurements of the oxygen isotope ratio (R=18O/16O) and the fraction of unreacted oxygen remaining in the respiration cuvette at different times during the course of the reaction.
A complete description of the calculations of the isotope fractionation (D) can be found in Guy et al. (1989). It results in the overall equation as follows:
Although both oxidases prefer to use 16O over 18O, their “degree of preference” differs, allowing the calculation of their relative contribution to the total mitochondrial oxygen consumption and electron transport. The two mitochondrial terminal oxidases have a different 18O/16O fractionation because they have different catalytic mechanisms to break the double bond of O2 (Hoefs, 1987). The alternative oxidase fractionates more against 18O than the cytochrome oxidase (Guy et al., 1989). Figure 2 shows a classical experiment in which fractionation by both cytochrome (Dc) and alternative oxidases (Da) is measured in the presence of the specific inhibitors SHAM and KCN, respectively. Once fractionation values for each respiratory pathway have been obtained, measurements of the fractionation in the absence of any inhibitors (Dn) give the electron partitioning through the alternative pathway (τa).
Figure 2 Calculation of the electron partitioning through the alternative oxidase(τa) using the oxygen isotope fractionation technique. This is an example of the lines expected in different situations where the participation of the alternative pathway (τa) would be approximately 90%, 60% and 30%. This could be the case for the floral receptacle of Nelumbo nucifera (Watling et al., 2006), cotyledons and leaves of Glycine max (Ribas-Carbo et al., 2005), respectively (Click image to enlarge.)
Measuring Respiration In The Light (Day Respiration)
Measurement of respiration in the light is much more challenging than in the dark, because photorespiration and photosynthesis also occur, thereby masking the O2 and CO2 exchanges that are due to mitochondrial respiration. Moreover, there is evidence that the rate of mitochondrial O2/CO2 exchange is depressed in the presence of light as compared to the rate in darkness. Several methods have been proposed to estimate the rate of respiration in the light, some of which are briefly explained here but for detailed reviews of all methods see Hurry et al. (2005) and Tcherkez et al. (2005). For a proper understanding of these methods, it should be kept in mind that in the presence of light, leaf gas exchange can be described as:
AN = AG – PR – Rd,
where AN is the “net” photosynthesis (determined with a standard open gas exchange system), AG is gross CO2 assimilation, PR is photorespiration and Rd is respiratory CO2 evolution in the light. The first published method employed to measure respiration in the light was the so-called Kok method (Kok, 1948). It is based on the inhibitory effect of light on the rate of respiration, and it only requires the use of a commercial CO2 gas exchange system. It is based on a light-response curve performed at very low light intensity. Generally, the net CO2 assimilation rate shows an abrupt reduction in slope as light levels increase (Figure 3). The linear extrapolation to zero light from the gradual, “upper” slope indicates the rate of respiration in the light or “day” respiration (Rd) while the steeper part reaches the y axis (zero light) at the night respiration rate (Rn) (See Textbook Chapter 9 for more information on light and CO2 compensation points).
Figure 3 Kok method applied to detached leaves at 21°C in 21% O2 (typical graph redrawn from the dataset of Tcherkez et al. 2008). AN, Net photosynthesis; PAR, Photosynthetically active radiation; Rd, day respiration; Rn, night respiration. (Click image to enlarge.)
The Cornic method (Cornic 1973) is performed on an illuminated leaf placed in CO2-free air, in either N2 (0% O2) or 21% O2, and then darkened. The CO2-production rate in the light is denoted as LO (in 21% O2) or LN (in N2). When the leaf is darkened, refixation of (photo) respired CO2 vanishes and a peak of CO2 production, represented as p, can be seen. Under several simplifying assumptions, it can be shown that Rd = LO - LN - p + Rn.
Another commonly used technique is the Laisk method (Laisk 1977). This is based on the assumption that whilst light intensity alters the rates of photosynthesis and photorespiration, it does not affect the rate of mitochondrial respiration. Using a standard CO2 gas exchange system, assimilation response curves versus leaf intercellular CO2 concentration are performed at several different light levels (Figure 4). As light decreases both gross photosynthesis and photorespiration will decrease proportionally and so will the slope of the response of net photosynthesis. Therefore, if Rd does not to change with light intensity, all curves should converge to a single point which will correspond to the CO2 compensation point in the absence of day respiration (Γ*) on the X-axis and -Rd on the Y-axis (See Textbook Chapter 9 for more information on light and CO2 compensation points).
Figure 4 Laisk method. Net photosynthesis response to leaf internal CO2 (ci) at 200, 400 and 600 μmol m-2 s-1 (PAR) at 21°C in 21% O2 in french bean (Phaseolus vulgaris). In this example, the day respiration rate Rd is 0.51 μmol m-2 s-1. (Click image to enlarge.)
A more recent method uses stable isotopes of carbon to estimate the rate of respiration in the light (Loreto et al., 2001). This method takes advantage of the fact that “day” respiratory substrates turn over more slowly (half time in the order of minutes or more) than photorespiratory substrates (half-time in the order of seconds). That is, plants are grown under natural 12CO2-atmosphere and then placed in a 13CO2-atmosphere. The production of 12CO2 measured in a 13CO2-atmosphere indicates the “day” respiration rate Rd (with some corrections required to take into account refixation of respired 12CO2).
These methods have contrasting advantages and disadvantages: for example, both the Kok and the Laisk methods are performed at low light intensities and, consequently, plants present small assimilation rates, causing large measurement variability. In addition, the Laisk method requires measurements at several light levels and it is plausible that “day” respiration varies with light.
To summarize, measuring respiration is a very challenging task, especially in the light, when substrates and products are interchanged by different and opposing reactions that operate simultaneously. In the dark, respiration consumes oxygen by two different oxidases that act simultaneously and, consequently, can only be differentiated using stable isotope techniques. Moreover, the recent discovery of the alternative oxidase in other phylogenetic groups means that microbiologists and invertebrate physiologists will also have to reassess their methodologies for measuring respiration and will have much to learn from plant physiologists.
OsWiZzLe
Active member
http://www.ncbi.nlm.nih.gov/pubmed/20966153
Targeting mitochondrial metabolism and machinery as a means to enhance photosynthesis.
Abstract
It has long been recognised that photosynthesis and respiration in the plant cell must be intimately linked given that they share carbon dioxide and oxygen as substrate and product or product and substrate, respectively (for a review see Siedow and Day, 2000). Whilst the core reaction schemes of the pathways of photosynthesis, respiration and the associated process of photorespiration are well defined, it is only since the advent and widespread adoption of reverse genetic strategies that the high level of interaction between them has begun to be fully realised (Bauwe et al., 2010; Sweetlove et al., 2010). However, the exact contribution of each pathway to energy status is dependent on cell type and fundamental questions such as the degree of inhibition of the tricarboxylic acid (TCA) cycle in the light remain somewhat controversial. Here we will outline current understanding of the influence of mitochondrial function, focussing almost exclusively on the illuminated leaf of C3 plants and taking the majority of our case studies from tomato (Solanum lycopersicum) and Arabidopsis. We contest that, having achieved a more comprehensive understanding of the interaction between photosynthesis and respiration (and indeed also photorespiration), the manipulation of mitochondrial metabolism and machinery has recently emerged as a novel potential means to enhance photosynthesis.
Targeting mitochondrial metabolism and machinery as a means to enhance photosynthesis.
Abstract
It has long been recognised that photosynthesis and respiration in the plant cell must be intimately linked given that they share carbon dioxide and oxygen as substrate and product or product and substrate, respectively (for a review see Siedow and Day, 2000). Whilst the core reaction schemes of the pathways of photosynthesis, respiration and the associated process of photorespiration are well defined, it is only since the advent and widespread adoption of reverse genetic strategies that the high level of interaction between them has begun to be fully realised (Bauwe et al., 2010; Sweetlove et al., 2010). However, the exact contribution of each pathway to energy status is dependent on cell type and fundamental questions such as the degree of inhibition of the tricarboxylic acid (TCA) cycle in the light remain somewhat controversial. Here we will outline current understanding of the influence of mitochondrial function, focussing almost exclusively on the illuminated leaf of C3 plants and taking the majority of our case studies from tomato (Solanum lycopersicum) and Arabidopsis. We contest that, having achieved a more comprehensive understanding of the interaction between photosynthesis and respiration (and indeed also photorespiration), the manipulation of mitochondrial metabolism and machinery has recently emerged as a novel potential means to enhance photosynthesis.
There's some that are so prone to auto flower that going less than 24/0 is not an option at all. One strain right off could name is a BlackBerry Kush that many hav been growing out in nor cal ...
Holy shyte , the mothers of this cut would go into flower even under 24hrs when they got even slightly rootbound & lighting too low . Then there was the problem of the clones themselves going into flower . Plant/strain was overrated with to much rudy in her ....pretty to look at can see her over here
https://www.icmag.com/ic/showthread.php?t=182727&page=8
just one run of her & found, she was just
too autflower prone & it was :
bye bye baby
personally ive learnt a lot from this thread so thanks to everyone who contributed constructively
Can I please ask everyone to stop direct personal attacks for the sake of keeping this thread open? We have been warned already, please, just let bygones be bygones. Not only would this thread be locked, but it was threatened to be binned, and that would be a real shame because this thread stands out amongst the many threads of its ilk. This one uses science, whereas most others I have seen (here and at all other forums) uses conjuncture and hearsay and calls it fact.
Please, lets keep this thread open.
I have more papers to upload about PPFD and cannabis, and I would like to have the chance to do so.
Yes, that.
No, not that. There are more than enough of those threads, I have seen well over a dozen at lots of forums. If that is all you want, then take your pick, you dont' need to re-hash the same old-same old here, yet again. A two sentence post about what someone does because so-and-so told them to is not the best way to figure out the 'truth'...science is the way.
Please, lets keep this thread open.
I have more papers to upload about PPFD and cannabis, and I would like to have the chance to do so.
THCrefugee said:
Yes, that.
THCrefugee said:
No, not that. There are more than enough of those threads, I have seen well over a dozen at lots of forums. If that is all you want, then take your pick, you dont' need to re-hash the same old-same old here, yet again. A two sentence post about what someone does because so-and-so told them to is not the best way to figure out the 'truth'...science is the way.
Is that rhetorical? I am not sure what you mean.
Grams per watt is a poor measure because it doesn't take time into consideration. That is why grams per kilowatt-hour is a better measure. This topic of 'garden efficiency' has been written about before here. Garden X that yields 2 lbs in 70 days is more efficient than garden Y that yields 2 lbs in 80 days.
And considering the thread topic, a very simple example is garden A that yields 2 lbs using 18/6 (in veg) in 70 days is more efficient than garden B that yields 2 lbs using 24/0 (in veg) in 70 days. Another example is Garden C that yields 2 lbs using 18/6 (in veg) in 75 could be more efficient than garden D that yeilds 2 lbs using 24/0 in 70 days (depending upon electricity cost of running the lamps by kilowatt-hour).
DirtDoctor
Member
Thanks for the great information Spurr.
Grams per watt per kilowatt hr x harvest cycle has "always" been the formula for folks that actually knew what they were doin....
That`s why separate areas are allocated for bloom rooms runnin 24/7 flippin every 12 hrs a month +/- apart in age for perpetual harvey`s that maximizes the gpw`s per room , per cycle , per yr......
Of late the question on "grams per cubic ft" per KWH , per cycle , per yr , has come about with 50 watts per sq ft minimum on a horizontal grow equating to 20 watts per sq ft sideways with bare bulbs on shelves of plants on 4 walls....
Said I wouldn`t post here again , but wanted to clear some things up .........first hand experience wise.......
Science may be the way for you Gojo , but all you seek has come to pass yrs ago......Folks did every combination of lights on and off times for the optimum results using actual grow time to see results .....It`s not rocket science.....Even I muddled through it for yrs and yrs.......
K.I.S.S.
Peace...DHF......
Do you realize that science advances, and that not everything people believe is true actually is?
How many people actually back then even heard of DLI when testing out different light schedules? Most likely zero.
DLI is of vital importance to the Floriculture industry and rightly so as it effects their profits, yet alot of people in this thread are extremely adverse to it, and I dont understand why. If your growing Marijuana, there's a good chance that you are making money off of it. Even if you only grow for personal smoke, its still worth learning about. Why wouldn't you want to be well educated in all aspects of growing and ultimately increase your yield????
Spurr isn't just making this shit up as some of you believe.
Here is a link about DLI written by an assistant professor at Clemson University. Its a good read, and you'll learn alot about DLI and how it affects your plants. Even if you dont want to read it, check out the pictures. Maybe someone will pick up something from it.
U~know~who
New member
U~know~who
New member
Thanks for the great information Spurr.
Tell me one thing you are going to change or do in your garden based on the info.
U~know~who
New member
So now that you know did you yield go up?
Tell me one thing you are going to change or do in your garden based on the info.
Though you didn't ask me, I'll respond as this thread relates to my own needs. After reading the material and taking a little more time to digest the info, I increased the light intensity in my veg room and lengthened the dark period. It's one of my bread and butter strains that I've been working with for 4+ years. The plans are scheduled to be flowered this coming Monday, as the veg period has stayed consistent over the life of the strain, but I doubt they'll make it to the weekend. They grew faster. It's as simple as that.
Simon
