Abstract
The SPAD-502 meter is a hand-held device that is widely used for the rapid, accurate and non-destructive measurement of leaf chlorophyll concentrations. It has been employed extensively in both research and agricultural applications, with a range of different plant species. However, its utility has not been fully exploited in relation to the most intensively studied model organism for plant science research, Arabidopsis thaliana. Measurements with the SPAD-502 meter produce relative SPAD meter values that are proportional to the amount of chlorophyll present in the leaf. In order to convert these values into absolute units of chlorophyll concentration, calibration curves must be derived and utilized. Here, we present calibration equations for Arabidopsis that can be used to convert SPAD values into total chlorophyll per unit leaf area (nmol/cm(2); R(2) = 0.9960) or per unit fresh weight of leaf tissue (nmol/mg; R(2) = 0.9809). These relationships were derived using a series of Arabidopsis chloroplast biogenesis mutants that exhibit chlorophyll deficiencies of varying severity, and were verified by the subsequent analysis of senescent or light-stressed leaves. Our results revealed that the converted SPAD values differ from photometric measurements of solvent-extracted chlorophyll by just ~6% on average.
Highlights
Ling et al, page 3 of 13Leaf chlorophyll concentration is an important parameter that is frequently measured as an indicator of chloroplast development, photosynthetic capacity, leaf nitrogen content, or general plant health
In order to derive useful relationships between SPAD meter readings and chlorophyll content, it is necessary to study plants that have a variety of different pigmentation levels
While linear and exponential relationships between SPAD values and chlorophyll concentrations have previously been proposed (Uddling et al 2007), we observed a much stronger fit using second-order polynomial functions (Fig. 1, b and c); R2 values for linear and exponential relationships were, respectively, 0.979 and 0.973 for the data in b, and 0.959 and 0.972 for the data in c, and significantly lower than those shown in Fig. 1 for the selected polynomial functions
Summary
Leaf chlorophyll concentration is an important parameter that is frequently measured as an indicator of chloroplast development, photosynthetic capacity, leaf nitrogen content, or general plant health In the laboratory, it is commonly determined photometrically following extraction of the pigments using an organic solvent, such as acetone or dimethyl formamide (Arnon 1949; Porra et al 1989). The SPAD-502 meter (Konica-Minolta, Japan) provides an alternative method for the measurement of relative leaf chlorophyll levels that overcomes these disadvantages It is an inexpensive, hand-held device based on two light-emitting diodes and a silicon photodiode receptor, that measures leaf transmittance in the red (650 nm; the measuring wavelength) and infrared (940 nm; a reference wavelength used to adjust for non-specific differences between samples) regions of the electromagnetic spectrum. The meter has been used extensively in both research and agricultural settings, and there are many publications in the scientific literature that describe its use
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