The estimation of the health status of plants and fruit by fluorescence approaches: a short review

The use of non-invasive optical techniques to assess the health status of plant material, such as crops in agriculture and horticulture, has been improved much during the last decades. One can use laboratory designed instruments and or transportable-portable field equipment. The first group includes for instance spectrophotometric techniques such as absorption (UV-VIS), fluorescence and infrared spectroscopy and chlorophyll fluorescence methods. Each technique has its specific characteristics and will deliver specific information on the material examined. Field designed instruments are mostly less complicated and should be portable or at least transportable and battery operated. In this group, several techniques based on fluorescence (chlorophyll, metabolic compounds) and or hyperspectral characteristics of the plant material are available. Due to technical restrictions, most of these instruments can perform only so called point measurements whereby obtaining spatial information is quite hard. The development of imaging systems, including remote systems, and imaging processing techniques has made major contributions in the field of the non-destructive assessment of the physiological status of plants and crops. In this paper a short overview of the state of the art will be given. More specifically, a few examples in which several fluorescence measurements (such as fluorescence spectroscopy, determination of the photochemical efficiencies, chlorophyll fluorescence quenching analysis, imaging) of leaves and fruits under different conditions ('preharvest - postharvest') will be presented.