Citrate test

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Rick,

I got a small citric acid sample from a vendor. If I wanted to try a test and modify the K-lite I'm using, about how much would you suggest I add?

I had thought, based upon some of your comments, that about the same as the citric acid it already contains might be OK.
 
Ray said:
Rick,

I got a small citric acid sample from a vendor. If I wanted to try a test and modify the K-lite I'm using, about how much would you suggest I add?

I had thought, based upon some of your comments, that about the same as the citric acid it already contains might be OK.
Click to expand...

Gazania rigens study (Rick's message #33) used 100 and 300 mg/l (ppm) for foliar spray. Malate or citrate at 300ppm was the best most of the time (increase in the root dry mass and root/shoot ratio). Maybe a good starting point? Interestingly G. riggers is a C4 plant. Malate is a transport acid of carbon in C4 pathway. So it would be relevant in CAM plants (they use C4 pathway), too. Maybe early morning foliar spray of malate to CAM might be effective (Paphs are C3, though).

citrate and malate are easily available and cheap.

This one uses malate and citrate foliar spray on lily (closer to orchids than Gazania). They use 750 and 1500ppm + a couple drops of tween-20 (soap) per 500ml + 0.1% glycerin.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3355684/
An interesting part is that Malate did increase the chlorophyll contents slightly (statistically significant, but not dramatic effect), consistent with Rick's original observation. I couldn't get the exact time frame of acid application and chlorophyll measurement, but I'm guessing that the response was relatively quick in the lily. Another interesting part is that citrate reduced the weight of bulbil (asexual reproductive structure at the base of leaves). So it is influencing the resource allocation pattern.
 
1. I saw an article that showed a toxic effect to leaves of some types of plants with citrate at a high concentration. What I can't do is get from say 300 mg/mL of citrate or malate to an amount of lemon juice to add because I can't find a clear reference giving even a range of either citrate or malate concentrations in lemon juice.

2. An interesting other issue is that I saw that lemon juice is a "good" source of potassium, but I don't know whether that is meaningful with the mounts of lemon juice we are talking about. It may make K-Lite a good partner because we start from a lower base. IF the only beneficial substances in lemon juice are the citrate and malate and these are cheap and easy to deal with as an additive AND come as non-potassium salts, I can see wanting to get the pure substances to add rather than lemon juice. But, maybe like kelp extracts, there are various magical substances in lemon juice.
 
I confirm your math! It would take about 5 teaspoons (1.67 tablespoons) per gallon to get to the 300 ppm (or mg)/L you mentioned. I won't do the metric conversions, but it doesn't make Rick's initial 1 tablespoon per gallon look at all excessive.

For me, the pH lowering effect of the lemon juice is essential because I have a potting mix that is on the alkaline side to begin with. A more acid fertigation solution might help with nutrient availability for a few things at least. I think that I now know the safe range of lemon juice to play with and can now focus on the pour-through pH result after fertilizing with different strengths as my target. Makes more sense to me than phosphoric acid.


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naoki said:
Gazania rigens study (Rick's message #33) used 100 and 300 mg/l (ppm) for foliar spray. Malate or citrate at 300ppm was the best most of the time (increase in the root dry mass and root/shoot ratio). Maybe a good starting point? Interestingly G. riggers is a C4 plant. Malate is a transport acid of carbon in C4 pathway. So it would be relevant in CAM plants (they use C4 pathway), too. Maybe early morning foliar spray of malate to CAM might be effective (Paphs are C3, though).

citrate and malate are easily available and cheap.

This one uses malate and citrate foliar spray on lily (closer to orchids than Gazania). They use 750 and 1500ppm + a couple drops of tween-20 (soap) per 500ml + 0.1% glycerin.
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3355684/
An interesting part is that Malate did increase the chlorophyll contents slightly (statistically significant, but not dramatic effect), consistent with Rick's original observation. I couldn't get the exact time frame of acid application and chlorophyll measurement, but I'm guessing that the response was relatively quick in the lily. Another interesting part is that citrate reduced the weight of bulbil (asexual reproductive structure at the base of leaves). So it is influencing the resource allocation pattern.
Click to expand...

Thanks for the link Naoki.
I found some other papers that indicate that malic acid can increase and/or preserve the chlorophyll content of cut flowers post harvest (i.e. not preharvest treatment). Succinic acid can have the same effect for some plants.

http://scialert.net/fulltext/?doi=ajpp.2011.167.175&org=10
http://www.idosi.org/wasj/wasj12(9)/37b.pdf
 
terryros said:
1. I saw an article that showed a toxic effect to leaves of some types of plants with citrate at a high concentration. What I can't do is get from say 300 mg/mL of citrate or malate to an amount of lemon juice to add because I can't find a clear reference giving even a range of either citrate or malate concentrations in lemon juice.

2. An interesting other issue is that I saw that lemon juice is a "good" source of potassium, but I don't know whether that is meaningful with the mounts of lemon juice we are talking about. It may make K-Lite a good partner because we start from a lower base. IF the only beneficial substances in lemon juice are the citrate and malate and these are cheap and easy to deal with as an additive AND come as non-potassium salts, I can see wanting to get the pure substances to add rather than lemon juice. But, maybe like kelp extracts, there are various magical substances in lemon juice.
Click to expand...

For those thinking of experimenting with malic acid, please be aware that it is chiral (unlike citric acid), and is most commonly available as the DL racemic mix, meaning that 50% is the unnatural D form. This commercial DL malic acid mixture is used as an acidulent / taste modifier in commercially produced beverages and acidic desserts and is considered to be food safe, although it's use is not permitted for organic product certification in the USA. Pure L-malic acid (as found in fruits) is more expensive to manufacture, but it is this natural L-malic acid that will have been used in most published experiments. If it's inexpensive and doesn't specify that it's L-malic acid then it will almost certainly be the DL mixture.

Whether the D-form would have any toxic effect on plants I don't know and I have been unable to find an answer to this question. I did find out that D-malic acid is metabolised by the E.coli in our gut to pyruvic acid, but I could not find any references about D-malic acid and plant metabolism. The D isomers of some amino acids are toxic to plants and so I've decided to err on the side of caution and avoid using the DL mix on plants.

I bought some malic acid from an online (local) supplier that claimed it was " the pure natural L-form " (in bold print no less), but it was not labelled as such on the container I recieved. When I tracked down the original manufacturer's specification it turned out to be the DL mixture after all. If you really want to be sure about malic acid, use natural fruit juice or be prepared to spend a lot more by buying it from a scientific supply company. There is a US supplier that apparently does sell genuine L-malic acid (food supplement/detox market) at a reasonable price but I didn't get around to inquiring whether they ship to the UK.

As for fruits, apples have high malic acid content. A popular English cooking apple, the Bramley, has between 0.8 and 1.2 % malic acid (w/v of juice) and other tart cooking apples will also also have high concentrations. Sweet raw-eating apples come in around 0.4% and the more tart ones like Granny Smith's about 0.6-0.7%.
 
Interesting point, myxodex. According to this:
http://www.plantphysiol.org/content/69/2/456.short
The uptake rate of L-malate by vacuoles gets drastically reduced with the excess of D-malate in CAM plants. CAM plants open stomata at night and stores CO2 in the form of malate, which moves into the vacuoles. Then the CO2 get released from malate during the day time, so that photosynthesis can work without opening the stomata. The paper didn't give the details or interpretation of the results, but it seems that D- form could interfere with this process. So it is probably better to stick with L- form.
 
terryros said:
I confirm your math! It would take about 5 teaspoons (1.67 tablespoons) per gallon to get to the 300 ppm (or mg)/L you mentioned. I won't do the metric conversions, but it doesn't make Rick's initial 1 tablespoon per gallon look at all excessive.
Click to expand...
I am curious to know the Ph of a solution 20 ppm N from KLite at which 100 ppm of citric acid has been added. Using RO or rain water of course. Don't forget also that the degradation of citric acid will also decrease the Ph of the substrate.
 
terryros said:
1. I saw an article that showed a toxic effect to leaves of some types of plants with citrate at a high concentration. What I can't do is get from say 300 mg/mL of citrate or malate to an amount of lemon juice to add because I can't find a clear reference giving even a range of either citrate or malate concentrations in lemon juice.

2. An interesting other issue is that I saw that lemon juice is a "good" source of potassium, but I don't know whether that is meaningful with the mounts of lemon juice we are talking about. It may make K-Lite a good partner because we start from a lower base. IF the only beneficial substances in lemon juice are the citrate and malate and these are cheap and easy to deal with as an additive AND come as non-potassium salts, I can see wanting to get the pure substances to add rather than lemon juice. But, maybe like kelp extracts, there are various magical substances in lemon juice.
Click to expand...

Brabantia said:
I am curious to know the Ph of a solution 20 ppm N from KLite at which 100 ppm of citric acid has been added. Using RO or rain water of course. Don't forget also that the degradation of citric acid will also decrease the Ph of the substrate.
Click to expand...

I personally would use caustion watering my Paphs/Phrags at 300mg. I'm currently using N at 10 ppm with the addition of citric acid to adjust the feed rain water to pH 5.6. It takes approx. 1.5 tbp in 55 gals of rain water to reach pH 5.6. I think serious root damage at the min if 1.5 tbp per gal was used.
 
I have found that 10 mL/gallon of lemon juice (which is under 100 ppm citrate) reduces my fertilization solution pH such that the pour-through pH after feeding is about 6.6, right where I would like it. I don't need it any lower. However, the fertilization solution with this amount of lemon juice is about 4.3 for me, with a TDS of about 250 (EC 0.5). I think this is about where I would like things to be. I wouldn't push the citrate beyond this.


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