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Detection of grassland canopy chlorophyll fluorescence (Chl-F) conducted with an imaging spectroradiometer provided evidence of potential remote sensing estimation of steady-state Chl-F (Chl-F s ). Daily near-nadir views of extremely high spatial resolution hyperspectral images were acquired from a distance of 4 m for temperate montane grassland in the Czech Republic. Simultaneously, measurements of Chl-F and total chlorophyll content (Chl a + b ) were made on a single leaf at ground level were collected. A specifically designed 'shade removal' experiment revealed the influence of dynamic physiological plant processes on hyperspectral reflectance of three wavelengths: 532, 686 and 740 nm. Based on this information, the vegetation indexes R 686 /R 630 , R 740 /R 800 and PRI calculated as (R 532 -R 570 )/(R 532 +R 570 ) were tested for statistical significance with directly measured Chl-F parameters (maximum fluorescence yield, F v /F m ; steady-state chlorophyll fluorescence, Chl-F s and actual quantum yield, Ф II ). The grassland species under investigation were: Festuca rubra agg. (L.), Hieracium sp., Plantago sp., Nardus stricta (L.) and Jacea pseudophrygia (C.A. Meyer). The coefficients of determination (R 2 ) for best-fit relationships between PRI-Ф II and PRI-Chl-F s , measured in the daily course, show a high variability of 0.23-0.78 and 0.20-0.65, respectively. Similarly, R 2 for the R 686 /R 630 -Ф II and R 686 /R 630 -Chl-F s relationships varied between 0.20-0.73 and 0.41-0.70, respectively. The highest average R 2 values were found between PRI and Chl a + b (0.63) and R 686 /R 630 and Chl a + b (0.72). The ratio R 740 /R 800 did not yield a statistically significant relation with Chl-F parameters.

Near-distance imaging spectroscopy investigating chlorophyll fluorescence and photosynthetic activity of grassland in the daily course