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estimation of vegetation photochemical processes: an application of the photochemical reflectance index at the san rossore test site | 量子荧光|微型光纤光谱仪-ag贵宾会

estimation of vegetation photochemical processes: an application of the photochemical reflectance index at the san rossore test site
【摘要】: 

the photochemical reflectance index (pri) has been proposed as a tool for the estimation of leaf and canopy light-use efficiency and photosynthesis from remote-sensing data. the application of the index is based on more than fifteen years of spectroscopic studies at the leaf level, which support it with a sound physiological basis. in the present study, the correlation between pri and instantaneous light-use efficiency was estimated across a range of vegetation types in the san rossore regional park, a chris-proba core site. the relationship was also tested over an entire season for a pine forest in the park where carbon fluxes have been monitored by eddy-covariance over the last five years. seasonal changes in photosynthetic potential were also monitored at the site, in order to test the correlation with pri reported in the literature. in september 2004, estimates of canopy pri from chris images were compared with leaf-level measurements from 13 plots corresponding to different vegetation types. the results were used to extrapolate leaf-level information to the entire scene.

when exposed to an excess of irradiation, plants cannot use all the absorbed energy and as a photoprotective process increase both fluorescence and thermal energy dissipation without evident damage to the photosynthetic apparatus. such a dissipation is the result of xanthophyll deepoxidation under conditions of low lumen ph, from violaxanthin via antheraxanthin to zeaxanthin (demmig-adams 1990). even under unstressed conditions, however, the daily decline of photosynthesis efficiency can also be the result of photoinibition resulting in a reduction in maximum photosynthetic capacity.

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