With a PSR+ spectroradiometer a researcher can measure leaf reflectance and use the Photochemical Reflectance Index (PRI) to capture an accurate indication of a plant's ability to absorb and use energy efficiently. One of the 19 vegetation indices offered with DARWin SP Data Acquisition software and the PSR+ field spectroradiometer, PRI looks at the carotenoid pigments, especially the xanthophyll pigments absorbed by plants. The pigments can signify growth rate and biomass production. PRI uses the wavelengths of light from 400 to 700 nanometers and has a measurement range of -1 to 1 with healthy vegetation falling between the values of -0.2 to 0.2 in the PRI index.

In addition to PRI, the PSR+ with DARWin SP includes the Red/Green Index for growth cycle studies, stress detection of canopies, and prediction of potential crop yield. The Red/Green Index measures the expression of leaf redness caused by anthocyanin to the green caused by chlorophyll. It can be used as an indication of leaf production and/or stress. The means of the bands in the red range are divided by those in the green range. The typical range for green vegetation is 0.7 to 3.

The PSR+ is a high resolution, field portable spectroradiometer ideally suited for vegetation, canopy and crop studies. With its solid state design and three photodiode arrays, it provides a rugged and reliable way to measure plants in situ. Auto-shutter, auto-exposure and auto-dark correction deliver fast one-touch operation. Use with a range of direct attach lenses or fiber optic connection with FOV lenses or leaf clip, contact probe or pistol grip.

Every Spectral Evolution instrument includes DARWin SP Data Acquisition software with 19 built-in vegetation indices, including PRI and the Red/Green index.

The leaf clip includes a built-in white reference and is designed to keep the heat from the illumination away from your sample so that measurements can be accurate and non-destructive.