We compared by chlorophyll (Chl) fluorescence imaging the effects of two strains of the same virus (Italian and Spanish strains of the Pepper mild mottle virus - PMMoV-I and-S, respectively) in the host plant Nicotiana benthamiana. The infection was visualized either using conventional Chl fluorescence parameters or by an advanced statistical approach, yielding a combinatorial set of images that enhances the contrast between control and PMMoV-infected plants in the early infection steps. Among the conventional Chl fluorescence parameters, the non-photochemical quenching parameter NPQ was found to be an effective PMMoV infection reporter in asymptomatic leaves of N. benthamiana, detecting an intermediate infection phase. The combinatorial imaging revealed the infection earlier than any of the standard Chl fluorescence parameters, detecting the PMMoV-S infection as soon as 4 d post-inoculation (dpi), and PMMoV-I infection at 6 dpi; the delay correlates with the lower virulence of the last viral strain. and M. Pineda ... [et al.].
To quantify photosynthetic response of wheat to the combination of a fungal brown rust infection and a post-infection drought, four treatments were compared: no stress (control), fungal stress (FS), water stress (WS), and twofold stress (WS×FS). Predawn leaf water potential (Ψwp) was similar in FS and WS treatments over a 3-week period. In the WS treatment, net photosynthetic rate (PN) and stomata CO2 conductance (gs) diminished concomitantly with a constant intercellular CO2 concentration (Ci) close to 200 µmol mol-1. In the FS treatment, a reduction of PN occurred with an increase in respiration rate (doubling of the CO2 compensation concentration) and in Ci but with no water loss modification. Healthy leaves of infected plants (FS) showed a reduction of PN as well, with constant gs and increased Ci. In the twofold stress treatment (WS×FS), leaves showed reduced PN in relation to the lower Ψwp. Deleterious effects of both drought and fungal infection on the final area of leaves and dry matter were additive. and O. Bethenod, L. Huber, H. Slimi.
Changes of chlorophyll (Chl) a fluorescence and photosynthetic pigment contents were analysed in galled leaves (visibly damaged and undamaged parts) and intact leaves. The values of minimal fluorescence of the dark-adapted state, maximal quantum yield of PSII photochemistry, effective quantum yield of PSII photochemical conversion, and photochemical quenching coefficient decreased in Ulmus pumila L. leaves galled by Tetraneura ulmi (L.) and in U. glabra Huds. galled by Eriosoma ulmi (L.). Colopha compressa (Koch.) feeding affected these parameters only in damaged parts of U. laevis Pall. galled leaves. The increasing number of T. ulmi galls progressively decreased photosynthetic performance. In gall tissues of all analysed aphid species, the lowest photosynthetic pigment content was found, indicating that the photosynthetic capacity must have been low in galls. Significant reduction of Chl and carotenoid contents were observed in damaged and undamaged portions of galled leaves only in the case of T. ulmi feeding., K. Kmieć, K. Rubinowska, W. Michałek, H. Sytykiewicz., and Obsahuje bibliografii