Temporal and spatial changes in parameters of fast chlorophyll fluorescence kinetics (ground fluorescence, Fo and maximal fluorescence, Fm) and red/NIR reflectance were assessed with a Pulse-Amplitude-Modulated (PAM)-Imaging system on a daily basis over a period of 2 weeks following inoculation of wheat leaves with powdery mildew and leaf rust. The early detection of these infections by means of fluorescence imaging was possible 2-3 days before visual symptoms or significant changes in normalised-differenced-vegetation index (NDVI) became apparent. The initial infection of both fungi caused an increase in Fo and decrease in photochemical efficiency (Fv/Fm, Fv/Fo). The appearance and development of fungal pustules was accompanied by reduction in Fo and Fm. This resulted mainly from lower absorption of fluorescence exciting light by the leaf mesophyll due to the shielding effect of fungal mycelium, and to lesser extent from the chlorophyll breakdown underneath pustules. Among the evaluated fluorescence parameters, Fv/Fo displayed the most pronounced response to both kinds of infection. Mildew infection influenced chlorophyll fluorescence neither in the direct vicinity of mycelium nor in the apparently healthy leaf regions. Rust infected plants, in contrast, displayed significantly reduced photochemical efficiency Fv/Fm and Fv/Fo in chlorotic tissue around pustules. The same, but less pronounced tendency was found in the apparently healthy regions of rust infected leaves in the last days of the experiment. Dark adaptation of leaves proved to be necessary for accurate detection of both pathogen infections by means of fluorescence imaging. Additional experiments are needed to estimate the potential of this technique for remote sensing under field conditions.

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Summary• The aim of the work was to compare autumnal photosynthesis and remobilization processes in apple ( Malus domestica ) trees harvested either at commercial harvest date or 6 wk later (delayed harvest).• Apple leaf photosynthesis, measured by porometry, remained large at 8 -14 µmol CO 2 m − 2 s − 1 and was not limited by stomatal function after the commercial harvest date. The autumnal reduction both in photosynthesis and in vivo RUBISCO activity was less pronounced in apple trees with a delayed harvest. Maximum photochemical efficiency ( F v : F m ) of apple leaves also remained large at 0.80 for 3 wk after the commercial harvest date. The subsequent decreases in both maximum photochemical efficiency ( F v : F m ) and chlorophyll content were delayed by 2 wk in trees harvested 6 wk later.• Long shoot leaves developed red-blue anthocyanin colouration 2 wk after harvest, accompanied by greater leaf carbohydrate content. This was by marked contrast to long shoot leaves of still-fruiting apple trees, which lacked this anthocyanin colouration. Potassium, phosphorus and nitrogen declined more rapidly in the leaves of apple trees harvested at the commercial date, an indication of earlier remobilization.• In conclusion, fruit harvest accelerated leaf senescence, indicated by chlorophyll breakdown and remobilization of nutrients in both spur and long shoot leaves, and, additionally, by commencing anthocyanin synthesis in long shoot leaves.

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