In situ plant peel spectral attenuation of chlorophyll fluorescence excitation as a tool in precision agriculture and photobiology studies

Abstract

Polyphenols are important compounds of the plant secondary metabolism, being involved in the plant response to abiotic and biotic stresses and conferring quality properties to fruits and vegetables. Their determination provides valuable information to be used in precision agriculture and in plant physiology studies. Non-destructive evaluation of polyphenols, present in leaf epidermises and fruit skins, can be determined indirectly by multispectral measurements of the chlorophyll fluorescence from the underlying cell layers. This technique, called the chlorophyll fluorescence excitation screening (ChlFES) method, is based on the spectral attenuation by superficial compounds of the incoming radiation impinging on chlorophyll molecules. Examples of the non-destructive monitoring of plant flavonoids response to different UV radiation regimes are reported. Application of the ChlFES to apples, olives, kiwifruits, plums and mainly wine grape to detect flavonoids and anthocyanins was aimed to select fruits with the highest nutraceutical value. In field appliance of the technique by portable fluorescence sensors allowed the control of the wine grape phenolic maturity during the season and the mapping of the grape phenolic content in the vineyard to perform selective harvest and then the production of top quality wines. Furthermore, the estimate of the plant nutrient status as proximal sensing of the leaf nitrogen content was proved on different crops and proposed to drive precision fertilization.