Photochemical Reflectance Index (PRI)

The Photochemical Reflectance Index is a measure of the light-use efficiency of foliage and thus is primarily used as an indicator of water stress and for the assessment of carbon-dioxide uptake by plants.

 

                                                                

 

It is sensitive to the variations in the carotenoid pigments (for example, xanthophyll) in the leaves. These carotenoid pigments are involved in converting the absorbed photosynthetic radiation into fixed carbon.