Hi Darshan, I agree with David that the reader should now more about the conditions at which the experiments have been conducted. However I we assume that all experiments have been done after dark acclimation and at the same actinic intensity, then a system analysis of the OIJIP curves  (see for example my paper in  Biosystems 103: 2011, 1138-151) could be very helpful. Globally I would expect  from your data that such analysis will point to a strong effect of the treatment on the pmf generated by the proton pumps. A decrease of their activity leads to a decrease in the rate and extent at which the variable fluorescence changes in the J-I- and IP phase. The effect on PSII is expected to be much less. 

Wim Vredenberg

Darshan,

If PSII efficiency is desired you have to get fluorescent transient curve in light adapted sample. F0', Fv ', Fm' notations are used. If dark adapted then F0, Fv, Fm etc. Fs is steady state fluorescence.

Fq' = Fm' - Fs

Fq'/Fm'  gives PSII efficiency.

Fv/F0 gives parameter related to maximum quantum yield of PSII.

A review article by Kalkaji et al (2014) Photosynth Res 122:121-158 may be helpful.

Thanks sir 

Hi Darshan, There is too little information from your figures to know what is going on. How was the experiment conducted? Under background light? After dark acclimation?  Why do you use OJIP. The approach is complex and the interpretation is often uncertain. It sound like you just want photochemical efficiency, so why not use the Fv/FM' approach? What kinds of instruments do you have?

Dave

Hi Darshan, I agree with David that the reader should now more about the conditions at which the experiments have been conducted. However I we assume that all experiments have been done after dark acclimation and at the same actinic intensity, then a system analysis of the OIJIP curves  (see for example my paper in  Biosystems 103: 2011, 1138-151) could be very helpful. Globally I would expect  from your data that such analysis will point to a strong effect of the treatment on the pmf generated by the proton pumps. A decrease of their activity leads to a decrease in the rate and extent at which the variable fluorescence changes in the J-I- and IP phase. The effect on PSII is expected to be much less. 

Wim Vredenberg

Hey Wim!

I agree that there is a lot of information in the OJIP curves...

...but it is important for the poster to know that, if the experiment was performed in dark-adapted material, it would not be possible to extract the actual "efficiency" of PSII.

Anyway, great to hear from you!

Dave

Hi David,

Thanks for your remark. I had not discovered yet  that we could exchange ideas via Research Gate.  But it is highly welcome.

..contrary to what you see as an impossibility, I would say that, if an experiment on OJIP is  performed in dark-adapted material, it will be possible to extract the “actual efficiency” (φPP)  of PSII. In our paper ‘The analysis of PSII photochemical activity using single and multi-tornover excitation’ (in J. Photochem. Photobiol.-B 107:2012, 45-54) we have argued  that ‘….the maximal variable fluorescence Fm induced by a multiple‐turnover, fluorescence‐saturating pulse (SP), is associated with the release of photochemical and photoelectrochemical quenching, and . …that the OJIPMT‐ or Kautsky induction curve of variable chlorophyll fluorescence in the 0 – 100 s time range is the reflection of the release of photochemical quenching supplemented with a temporary Photosystem I (PSI)‐dependent photoelectric stimulation and transient release of photoelectrochemical

quenching of radiative energy loss in the Photosystem II (PSII) antennas, rather than solely of a decrease in PSII photochemical activity as is usually concluded.

If the FIA algorithm (Biosystems 103: 2011, 138-1510 is applied to the data in the figures of Dasha, one can estimate φPP like it has been done for algae and leaves in the J.Photochem.Photobiol.(B)-paper.

I will be in Maastricht on Wednesday 10 Aug.. I look forward to meet you there.

Wim

Dear Darshan,

I am answering from a practical point of view only, using my own expertise in the field and many years analysing hundreds of thousands fluorescence curves... I will avoid scientific polemics and technical terms as much as possible, to help you understand what's going on with those curves, and what they tell you about your plants... ok?

From the Kautsky curves you've measured (OJIP fluorescence induction kinetics) on Swarna varieties (A, swarna control or SC) and Swarna Sub1 (B or SS), after 1, 3, 5 and 7 days of full submergence we can observe:

1) no differences between SC0 and SS0 (0 means Chl a fluorescence measured at  start of submergence experiment or day 0),

2) no differences between SC1 and SS1 (day 1),

3) Slightly differences between SC3 and SS3 start to appear... (day 3),

4) Chl a Fluorescence of the SS5 plants shows a SS plant doing better than the control SC5 (day 5),

5) Chl a Fluorescence of the SS7 shows a plant doing much better than the control SC7 (day 7).

I suggest to use Biolyzer software for making a double normalisation plot of fluorescence between F=20 us and F=Fmax for each group of curves. You can calculate the JIP test parameters in order to compare PI(ABS) for each case. Usually, those curves represented in your figure should correspond to an average curve for each case. The average curve should be estimated in advance, after doing a pre-evaluation of statistical variability of Kautsky curves.

Ideally, in order to compare both samples, light, temperature and any other conditions should be the same for both populations. Well, I assume, it is difficult to keep same temperature and light conditions on both, control and submerged Swarna plants. Possibly, a slightly more "optimal" photosynthesis in SS plants can be explained by differences in the ambient temperature, because, from what I see in those curves, light/temperature conditions were higher in control plants compared to submerged plants. Possibly foliage in control plants is less than in submerged plants? In any case, it seems like SS submerged plants were able to cope better with light/temperature changes than control plants. Also, seems like submerged plants are more "green" and happy than control plants. You should measure Chlorophyll content using a SPAD machine for example... I would not be surprised if you tell me that SS is a genetically modified variety of plants developed for coping with flooding... we can see that also from those curves...

Please, check the double normalisation and show us the pictures. Then we can talk about PSII efficiency. But in any case, when using JIP test ideas  and OJIP curves, PSII efficiency is a relative, steady and overall parameter. It is like energy, an absolute magnitude, but we can not measure absolute energy, nobody did until now, however we can measure changes in temperature and then we can calculate state changes in energetic content... beside that, PSII efficiency is by definition a ratio, therefore, it is a relative magnitude, that's why we speak of comparing the "efficiency" of a plant with the efficiency of a "reference" control plant... 

Kind regards,

Ronald

Hello David,

from the curves, it is clearly and evident that they were measured with a Handypea ((UK Hansatech's) machine. There are a few fluorometer manufacturers in the world able to measure OJIP curves, and the lab made will not show this kind of log stepped transients with so nice "zero noise" clean signals... it needs some programming of the ADC system in order to get the data at specific time intervals only... from all of the commercially available fluorometers I know, the Optisciences, the Czech PSI, the Hansatech ones, the Walz also and I can tell each of these machines have their own characteristic way of measuring and showing those Kaustky curves. And this one is definitely a Hansatech's Handypea machine.

Well, it is impossible to obtain so low Fo values if you haven't previously dark-adapted your plants, so yes, the plants were definitely dark-adapted using a clip and for at least 15-20 minutes. Anybody that ever used a Handypea machine knows it is not useful to make measurements enabling background natural illumination go inside the measuring cone, because of the method itself. That's one of the difference between PAM and direct methods... Even if there is a high quality 720-740 optical pass filter in the head cone of the Handypea, the background light will be so strong that will bleach the photometer chip cell in the measuring head of the machine.  In a word, yes, it's evident  that those measurements were done with a clip directly connected to the measuring head of the fluorometer to avoid any background external light, and applying only good old nice actinic light as excitation source.

Moreover, looking at those curves, we clearly see that no far red preflash has been applied. Just look at the Fo's values...

Finally, can the "Fv/Fm" parameter be used with OJIP Kautsky curves as a "safe method" to measure absolute PSII efficiency? I see behind a nearly 60 years old scientific debate... Actually, the signal is much rich than an overall good guess, Maybe the path is as important as the departing and the arriving points...

All the best,

Ronald

Dear Darshan Panda

ϕPo = TR0/ABS = [1 − FO/FM)] = FV/FM is maximum quantum yield of primary PSII photochemistry and in more paper had more correlation with PSII efficiency. You can use from your parameter data of yourself study for more information about PSII efficiency.

Please find attached files.

Regards,

Ramin Lotfi

Its possible to calculate F at 300µs based on other OJIP parameters?