Evaluating the relationship between leaf chlorophyll concentration and SPAD-502 chlorophyll meter readings

Abstract

Relationships between chlorophyll concentration ([chl]) and SPAD values were determined for birch, wheat, and potato. For all three species, the relationships were non-linear with an increasing slope with increasing SPAD. The relationships for birch and wheat were strong (r (2) approximately 0.9), while the potato relationship was comparatively weak (r (2) approximately 0.5). Birch and wheat had very similar relationships when the chlorophyll concentration was expressed per unit leaf area, but diverged when it was expressed per unit fresh weight. Furthermore, wheat showed similar SPAD-[chl] relationships for two different cultivars and during two different growing seasons. The curvilinear shape of the SPAD-[chl] relationships agreed well with the simulated effects of non-uniform chlorophyll distribution across the leaf surface and multiple scattering, causing deviations from linearity in the high and low SPAD range, respectively. The effect of non-uniformly distributed chlorophyll is likely to be more important in explaining the non-linearity in the empirical relationships, since the effect of scattering was predicted to be comparatively weak. The simulations were based on the algorithm for the calculation of SPAD-502 output values. We suggest that SPAD calibration curves should generally be parameterised as non-linear equations, and we hope that the relationships between [chl] and SPAD and the simulations of the present study can facilitate the interpretation of chlorophyll meter calibrations in relation to optical properties of leaves in future studies.

Use of a SPAD-502 meter to measure leaf chlorophyll concentration in Arabidopsis thaliana

“…By plotting these two datasets against each other, we assessed possible relationships between them. 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); R 2 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 thus significantly lower than those shown in Fig.…”

“…2, 3 and 4, it is apparent that the values determined using the SPAD meter differ from the conventionally acquired data by ~6%, on average, which for most purposes should be an acceptable margin of error. It is noteworthy that there is a strong linear relationship between readings of the SPAD-502 meter, employed here, and another popular chlorophyll meter, the N-Tester (Yara, Norway; formerly Hydro) (Levey and Wingler 2005;Uddling et al 2007). Thus, the conversion formulae derived here may also be useful in conjunction with data from that device.…”

“…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. These transmittance values are used by the device to derive a relative SPAD meter value (typically between 0.0 and 50.0) that is proportional to amount of chlorophyll in the sample (Uddling et al 2007). 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.…”

“…The relationship between SPAD values and chlorophyll concentration has been investigated in a variety of different species, and has been found to display considerable interspecific variation (Castelli et al 1996;Uddling et al 2007). This variability is presumed to be due to structural differences between the leaves of different species, causing different light reflection or scattering effects.…”

Estimating potato leaf chlorophyll content using ratio vegetation indices

“…LCC using a handheld chlorophyll metre (SPAD-502, Minolta Osaka Company Ltd., Japan) was measured per plant taking the average reading of three randomly selected leaves. SPAD measurements were converted to LCC (g m −2 ) using the potato-specific model by Uddling et al (2007).…”