Example of Application

Miniature Spectrometer MINI-SPEC
Measuring Spectra of PAR, Reflectance and Fluorescence

Miniature Spectrometer MINI-SPEC is a compact and robust outdoor instrument for gathering spectral information of the light environment and the sample.

Figures 1 to 3 illustrate types and signal quality of PAR spectra as well as of reflectance and fluorescence spectra.

Figure 1

Absorption of light by water affects the spectral properties of radiation available for aquatic photosynthesizers. The MINI-SPEC measures PAR in air or in water and, thus, adds spectral information on light to PAM fluorometry. The spectra in Figure 1 are recorded above and below canopy and demonstrate how markedly the intensity ratios visible/far red are affected by leaf absorption.

Figure 2

Reflectance spectra contain information on light absorbed by a sample. Typically, troughs in reflectance spectra correspond to absorption peaks of photosynthetic pigment-protein complexes. Reflectance spectra can also reveal the screening function of non-photosynthetic pigments. Figure 2 shows how light screening anthocyanins mask the reflectance peak around 550 nm observed in a green leaf.

Figure 3

The shape of fluorescence emission spectra is affected by the chlorophyll content of a leaf (Buschmann C (2007) Photosynth Res 92, 261–271). Reabsorption of fluorescence at wavelength < 700 is the major factor determining the ratio of short to long-wavelength emission peaks. Figure 3 illustrates how this ratio decreases with increasing chlorophyll content in ivy leaves.