I had communicated a paper to a peer reviewed journal of Elsevier where one of the reviewer has made a statement "The plant growth regulators (PGRs) were evaluated using 'mg/l' which make comparison among the selected PGR illogical. Given the difference in the molecular mass of the tested PGRs, 1 mg/ml BAP is not equivalent to 1 mg/ml mT or 1 mg/ml TDZ. ". Actually I had used far lesser concentration of mettopolinin comparison to BAP/TDZ as metatoplin gives fantastic results in lesser amount. The range of BAP was in (1-4 mg/l) whereas in case of metatopolin I used in range of 0.5 to 2mg/l. I have seen various papers where they take this approach, but I am not able to frame the right reasoning statement to defend my experiment.If you people can please help me, it will be great.
I think what the reviewer is getting at is that you should express your concentrations in moles, and compare molar equivalents of each of the PGRs rather than mass. If you are comparing the potency of different PGRs, then expressing and comparing your concentrations in moles is the correct way to do so. While other published papers may have used the mass approach, this is the reviewer you have to get it past, so you will have to compare and present your data using the molar concentration of the PGRs.
Bu there are so many micropropagation papers getting published in journals like PCTOC/APP where still the concentration getting used is in mg/l.
While there are many papers who use mg/l, they may not necessarily be comparing the potency of different PGRs. If they are, then the comparison is not strictly correct from a biochemical point of view as it is the number of PGR molecules (i.e. moles) it takes to elicit a response of a certain magnitude from their receptor/target that is the best measure of potency.
At the end of the day, to publish in the journal you want, you have to satisfy the requirements of the reviewers. If you want to publish in this journal, you will have to convert your concentrations into mole/l and then compare their potency.
It is just a way of expressing a concentration - for the more biochemistry oriented person moles does make more sense while to others mg/l is more easier to comprehend - you can very easly convert mg/l to mole - you should go for it - strict reviewers would want you to do it and there is no harm in complying - it is actually scientifically more sound as Hutchins has already pointed out.
Statement of your reviewer is correct.
The concentrations of growth regulators are commonly used in mg/l.However for correct analysis ,they should be mention in molar concentration.Because molar concentration is the correct reflection of the actual number of molecules of the growth regulators per unit volume of the media.
But i have carried all my experiments in mg/l. So how can i convert them?
Hi Paromik,
If you know the material's molecular weight (M.W.), you can convert mg/L into molar concentration. A solution of concentration 1 mol/L is also denoted as 1 molar (1 M).
I think that there are two points of view. The first is specifically scientific, in relation to the opportunity to use of the concentration unit or the molecular mass. A second is exclusively a publishing matter, depending on the guidelines fixed by the editor.
Following example may be help you for conversion
Conversion of 4.0mg BAP into molar
Molecular Wt of BAP=225.2
1molar=molecular Wt in 1000 ml
1molar BAP=225.2g in 1000ml
1molar=1000mM
1mM BAP=225.2mg/1000ml or 1micromolar=225.2microgram/1000ml
1mg =1000microgram
1mgBAP(999.888microgram)=4.44micromolar
4mgBAP(3999.552microgram)=4 x 4.44=17.763micromolar
To further satisfy the referee, you can draw a line graph of the trend of response rather than a bar graph. Then you can compare millimolar concentrations of different PGR.
Dr. A. Shajahan, your example is very helpful. thanks for that. i normally get annoyed with ppm and molar concentration published in tissue culture research paper hence used mg/l all the time. your example going to make my life easy.
thanks alot.
Thank you Mr.Sujit.If this discussion is really helpful for you,the credits will goes to all researchers those involved in this discussion including Mr.Paromika,Prof.Pathirama,Prof.Yuan-yeu Yau,Dr.Chakraborthy,Dr.Daniel and Dr.Maurizio.My special thanks to all for make this discussion into useful.
As has already been alluded to, molar concentrations reflect the number of molecules therefore is easier to compare effects of particular phytohormone. The mg/l concentrations have traditionally used (in earlier publications), but has been discouraged later on - for ease of comparison, again.
You don't have to redo your experiments, you can just convert your concentrations from mg/l to micromolar concentrations (as suggested by Dr. Shajahan) and use them in your paper.
Hope this helps.
A Dr Shajahan I am not understanding the last steps of the conversion:
1mgBAP(999.888microgram)=4.44micromolar
4mgBAP(3999.552microgram)=4 x 4.44=17.763micromolar
U mentioned 1mg is 10000microgram
Now 1mg of BAP should be 225.2 multiplied by 1000 but here I can see u have multiplied the both sides with 4.44. why so? I am getting confused with the last steps. can you please explain.
Dear Paromic
The second last step is : 1mg (999.888 microgram = rounded up/down to 1000 microgram) divided by 225.2 (microgram required for 1 micromolar) gives you 4.44 micromolar.
In the last step, if you have 4 mg BAP (instead of 1 mg), then you multiply (4.44) by 4 to get 17.763 micromolar.
Or in other words, 1mg/l BAP is equivalent to 4.44 micromolar, and 4 mg/l is equivalent to 17.76 micromolar.
Hope this helps.
Dear Paromic.. this is a problem we generally encounter. For the ease of calculations and experiment, we do use mg/l concentration. As someone above has rightly pointed that in old references we do find mg/l unit, but now Molar units are more accepted.
Now, as for as the referees comments are concerned, just convert the mg/l into micro Molar or Molar as the case may be. You can write the reviewer that originally the experiment was conducted using mg/l concentrations, but as per his suggestion you are now converting all the concentrations into more accepted unit (Molar).
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