Chlorophyll fluorescence imaging of plant–pathogen interactions

Abstract

Chlorophyll fluorescence imaging provides a noninvasive, non-destructive method with which to measure heterogenous changes in photosynthetic metabolism in plants infected by pathogens. The availability of commercial imaging fluorimeters has helped make this technique available to the wider scientific community, but considerable care is needed, both in experimental design and in the interpretation of results, to make the most of this powerful analytical tool. The origins of changes in chlorophyll fluorescence yield are discussed and the use of conventional and novel combinatorial imaging approaches explored, together with complementary techniques such as thermal imaging. This review examines the use of chlorophyll fluorescence imaging as a method for the early detection of viral, bacterial and fungal infection, before symptoms are visible by eye, and also as a means with which to probe underlying pathogen-induced changes in host physiology in both compatible and incompatible interactions. The use of chlorophyll fluorescence imaging to study host physiology is greatly enhanced when the atmosphere around the leaf is manipulated and simultaneous measurements of gas exchange made: The cost to the host plant of different resistance mechanisms can be calculated, the fate of the products of photosynthetic electron transport determined and localised alterations in the source-sink status of host tissue visualised.

Comparison of a compatible and an incompatible pepper-tobamovirus interaction by biochemical and non-invasive techniques: Chlorophyll a fluorescence, isothermal calorimetry and FT-Raman spectroscopy

“…The infected plants also showed a reduction in the efficiency of excitation capture in PSII by photoprotective thermal dissipation (Rahoutei et al, 2000). In recent years non-invasive chlorophyll fluorescence imaging techniques have been developed to continuously follow-up the physiological status and performance of plants, as well as to detect stress-induced deviations presymptomatically (Chaerle et al, 2007;Rolfe and Scholes, 2010). Modulation of photosynthetic activity can be revealed by measurements of chlorophyll a fluorescence emission.…”

Picturing pathogen infection in plants

“…Early detection of pathogens is essential to reduce disease spread and facilitate plant protection practices. Non-invasive techniques to image the patterns of multispectral fluorescence or leaf temperature across infected leaves have greatly increased our understanding of plant responses to biotic stress [1,2]. Visualization of the light signals emitted by plants can track the spreading of a pathogen through its host [3][4][5].…”

“…Furthermore, these techniques could be very useful for presymptomatic stress detection, depending on the extent in the changes in plants metabolism in response to pathogens. This early detection would allow appropriate measures at the right time, and can be used in the field, on the bench (microscopic or leaf level), as well as on canopy through remote sensing and in high-throughput plant phenotyping platforms [1,2,6,7].…”

Hyperspectral and Chlorophyll Fluorescence Imaging for Early Detection of Plant Diseases, with Special Reference to Fusarium spec. Infections on Wheat

“…Chlorophyll fluorescence analysis (CFA; e.g., [13,14] and chlorophyll fluorescence imaging (CFI; e.g., [15,16]) are well-established, effective tools for a comprehensive examination of development and effects of bacterial, fungal and viral infections on leaves of many cultivated plants [17][18][19][20]. It can be used for entire intact plants [21,22], detached leaves and also leaf disks punched out from infected plant material [23][24][25].…”

“…In addition, the potential maximum quantum yield of electron flow through completely open PSII, F v /F m [34] is often used for evaluation of microbial diseases [16,20,24]. F v /F m reflects the maximum photochemical efficiency and the interference with different environmental factors and may also indicate potential pathogen-related functional disturbance of the photosynthetic apparatus [13,14].…”