I am conducting a variety trial of 60 tomato cultivars and I want to determine leaf chlorophyll content of each tomato cultivar by using SPAD 502. Some calibration equation I have found mostly valid only for one cultivar or a specific condition. I am wondering if there is an equation or other means which is suitable for many cultivars of tomato?
ist u can work out by using the spectrophotometer than draw a standard curve against the values
The Spad works on trasmitted light in red relative to far red. This is fairly accurate but often chlorophyll content is unaffected is leaf age and nutrients are kept in a physiological range. You may eventually use a paper puncher on some leaf and check chlorophyll content by the method of Porra et al. http://www.chem.ucla.edu/dept/Faculty/merchant/pdf/Porra_1989.pdf or check variants in leaf area and apply nutrient stress
With my previous work using the SPAD meter, I have used the formula Dr. Markwell's team established 20 years ago. Here are the citation and the pdf file of the paper (as attachment) for your reference:
Markwell, J., J. C. Osterman, and J. L. Mitchell, 1995. Calibration of the Minolta SPAD-502 leaf chlorophyll meter. Photosynthesis Research 46: 467-472.
I hope this is helpful to you, in addition to the three answers you have received previously. Please feel free to contact me if you have any questions.
Would only suggest that any Spad calibration is sensitive to specific leaf weight variations. Then you should rank samples in the same slw range befor using spad readings or just take Spad/slw reading.
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