How can I convert chlorophyll content in plant leaves from SPAD unit values to mg per gram fresh weight?
Following the link below you can find a relevant discussion which can help you
https://www.researchgate.net/post/Does_anybody_know_how_we_can_calculate_the_chlorophyll_content_from_SPAD_readings/1
dehydration factor for vegetables, herbs and spices leaves = 7, you need to X7 (according to ESA)
I am asking about chlorophyll content value converted from SPAD unit to mg per g FW by using correct formula or equation.Accept my best regards
This is a common problem and a point of discussion when the chlorophyll content of native leaves are measured. The measured units can show a good correlation with the real chlorophyll content, for example, you van find a description here:
Photosynth Res. 2011 Feb;107(2):209-14. doi: 10.1007/s11120-010-9606-0. Epub 2010 Use of a SPAD-502 meter to measure leaf chlorophyll concentration in Arabidopsis thaliana. Ling Q, Huang W, Jarvis P.
This calculation is based on creating a calibration curve and it is valid for Arabidopsis.
A theoretical problem is, however, that the extinction coefficients of the native chlorophyll-protein complexes are unknown and the absorption spectrum of the leaves is very complex (i.e. the absorption bands of the chlorophyll-protein complexes strongly overlap). A practical problem is the variation of light scattering in case of different leaves. This scattering is influenced by the epidermis structure (hairs, cuticle, wax, the archetecture of the venation, etc.).
This means that a calibration curve should be created for each species and the validity of the regression should be tested.
Dear Ali
we can not use a single formula for all plants. It means we have to use a specific formula for each plant. For example,we can not use sugar beet formula for bean. But if you find a formula for wheat in the web , you can use it if your studied plant is wheat. If you did not find any formula for your under studied plant,you can first read your leaves with SPAD and then you measure chlorophyll content of the same leaves with spectrophotometer.Then you have to correlate them and find a formula(regression model). 20 leaves are enough.
regards
Dear Davood
I work with citrus species and root stocks i want to find a formula for these type of plants ( a regression model),but i don,t know if there are a formula used to convert reading of SPAD to mg per g FW so that i am asking my question.
regards
Hello, what you do depends on what you want! Is it a comparison of relative effects of treatments such as N supply, or an accurate measure of chlorophyll content? For the former using the SPAD readings may be enough. Using a published relationship may give an idea of chlorophyll but it is only going to be approximate, and open to question. Because it is unlikely that the SPAD/chlorophyll relationship is sufficiently constant across species, treatments etc very difficulty to use published equations to convert from SPAD values to actual Chl content, I would say that measurement of chlorophyll by standard methods would be best. Richardson et al ,"caution that differences in leaf structure may necessitate species-specific calibration". In work at Rothamsted we calibrated the SPAD carefully,
What formula can I use to convert chlorophyll concentration index to actual chlorophyll or relative SPAD units?
A standard calibration curve can be made between fresh weight and SPAD reading using the acetone extraction in spectrophotometric method.
standards equations may not be best suited for your crop and crop location, so the best possible way is to collect leaf samples from the target crop simultaneously with the SPAD readings. Use chemical methods to find out the chlorophyll content in mg/gm of leaf weight and then make a correlation (best-fit equation) between the SPAD units and chlorophyll content (mg/gm.) to generalize your results for a larger site and crop dataset. You may use Arnon's equations to calculate the chlorophyll content for the lab-based method.
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