I want to know if there is any relationship between Fv/Fm, PI, total chlorophyll content and rate of photosynthesis.
Yes, the ratio Fv / Fm values indicates about the quantum efficiency of photosystem II, while the PI shows the efficiency of the two photosystems (I and II). Certainly the two variables is directly related to the total chlorophyll content.
Hello Tiago! Thanks! Does that mean if the Fv/Fm is high PI has to be high and the total chlorophyll concentration has to be high as well? If yes is there any paper?
HI Darshan,
Here is a paper regarding your question. Also for your SPAD correlation question.
Article Wheat cultivars selected for high F-v/F-m under heat stress ...
Fluorescence is collected relative to the best signal noise ratio for F0. This would indicate that all parameters are scaled to a relative value for photosynthesis, chlorophyll content and other characters are scaled to the relative 'optimal' value of flux. For understanding the principle you may think of green cells in a suspension at variable density. Remote sensing applies crop specific tables based on chlorophyll density from reflection ratios and photosynthesis from yield values of fluorescence, but the link is not scaled for photorespiration and night respiration
Hi there,
Fv/Fm gives you the quantum yield of your experiment subject PSII. In other words it tells you how many reaction centers (relative units) can do photochemistry when are exposed to light. The higher the better(
Guess that a confusion of terms is behind. Fluorescence depends on absorbed light Intensity, pigment concentration and yield. Yield is variable and the absolute flux of ellectrons requires an actinometer, a system that measures precisely the quanta that have been absorbed. It is not a cese that Butler Schreiber and Bjorkman use relative units for fluorescence. In other words if Fv/FM decreses it is expected a decrease in relative photon yield in photosynthesis, scaling it from an optimal value that depends on carbon cycle, oxxygen and other factors. In order to better understand you may follow http://spie.org/x92267.xml with careful reference to principles. Carbon flux is empirically linked to fluorescence by measuring both..
As mentioned by Tiago Massi Ferraz, the ratio Fv/Fm value indicates about the quantum efficiency of photosystem II, while the PI shows the efficiency of the two photosystems (I and II). Certainly the two variables are directly related to the total chlorophyll content. However, the quality of the pigment plays pivotal role.
I agree with Tiago’s answer. But if you are looking for an instrument for in-situ measurements of spectral characteristics and pigmentations to use in the field, this one might be of interest: http://cid-inc.com/products/spectroscopy/miniature-leaf-spectrometer
It comes pre-programmed with a number of indices related to chlorophyll taken from publications, like Chlorophyll Normalized Difference Vegetation Index (C NDVI), Normalized Pigment Chlorophyll Index (NPCI), and Greenness Index. The sources for all of the indices are included in the software, along with the actual spectral regions that it is analyzing. You can program the software with your own indices as well to target specific regions.
Can we conclude that if the net chlorophyll content is high then the Fv/Fm and PI should also be high?
Fv/Fm is a ratio (about 0.8 in unstressed photosynthesis) and does not depend on the chlorophyll content.
As such there is no relationship among Fv/Fm, PI and total chlorophyll content. Fv/Fm is a ratio, even under stress condition if both Fo and Fm decrease, plant shows stress symptom yet the Fv/Fm ratio may remain constant comparable to unstressed conditions. PI (performance index) in such condition may change dramatically depending on the susceptibility / tolerance nature of the plant. The decrease in PI and total chlorophyll due to any stress is obvious, however, PI is more sensitive compared to total chlorophyll content. If the stress is not so severe relationship between PI and Chlorophyll is not apparent. The relationship among Fv/Fm, PI and Chlorophyll content may come under severe stress when all the parameters decreases.
Greetings,
I join in this conversation because I'm planning to use Fv/Fm measurements to assess plant stress by drought in the field. I'm focused on mosses and pine needles, which represent additional challenges to perform the measurements.
Do you guys know whether measuring devices (as the one Megan suggests) can be rented?
I appreciate your comments,
Fv/Fm (on dark adapted samples) measures photonhibition. This may happen under chronical water stress on high lightened portions of vegetation butthe mechanics of dehydration between mosses and needles is different . Mosses are poikilohydric and absorb directly air humidity whereas needles take water from roots in the soil. You may combine Crop water stress index by rH and leaf temperature with fluorescence if you like Fv/Fm or use directly CWSI. http://link.springer.com/article/10.1007%2Fs00271-013-0415-z. instruments can be rented by local dealers of LiCor Walz or Campbell. Darl adaptation can be done by straps and aluminium foil.
Thank you for your answer and the suggested resources Guido,
I'll look for the dealers.
Greetings.
Very valuable information. Dear All am going to use FvFm value for willow plants in the Heavy metals contamianted soil if anyone has info regarding stress in willow (Salix).
Fv/fm is a ratio which at 0.8 show no stress to the system but the lower the ratio the more stressed the plant. Chlorophyll content could be one of the factors indirectly contributing to the stress.
Greeting
I enjoyed the discussion above, and these completely different ideas challenged me. I have a question, What do you think is the relationship between rate photosynthesis and chlorophyll fluorescence exactly? I don't mean their relationship to chlorophyll content, I mean other dependent parameters like NPQ.
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