Computer Reconstruction of Plant Growth and Chlorophyll Fluorescence Emission in Three Spatial Dimensions

Plant leaves grow and change their orientation as well their emission of chlorophyll fluorescence in time. All these dynamic plant properties can be semi-automatically monitored by a 3D imaging system that generates plant models by the method of coded light illumination, fluorescence imaging and computer 3D reconstruction. Here, we describe the essentials of the method, as well as the system hardware. We show that the technique can reconstruct, with a high fidelity, the leaf size, the leaf angle and the plant height. The method fails with wilted plants when leaves overlap obscuring their true area. This effect, naturally, also interferes when the method is applied to measure plant growth under water stress. The method is, however, very potent in capturing the plant dynamics under mild stress and without stress. The 3D reconstruction is also highly effective in correcting geometrical factors that distort measurements of chlorophyll fluorescence emission of naturally positioned plant leaves

Response of grapevine leaves to Plasmopara viticola infection by means of measurement of reflectance and fluorescence signals

Response of grapevine leaf tissue naturally infected by Plasmopara viticola in field was measured by means of chlorophyll fluorescence and reflectance signals. Three susceptible grapevine varieties (Cabernet Sauvignon, Pinot Blanc and Pinot Gris) were used in this study. Since the infection impairs photosynthetic activity, distribution of FV/FM parameter (maximum quantum yield of Photosystem II) over the leaf was effective to discriminate healthy and naturally infected leaf tissue. FV/FM was reduced ~ 25% in all infected leaf parts. Infected leaf spots expressed significantly altered chlorophyll fluorescence induction kinetics expressing much slower electron transport rate both on donor and acceptor site of PSII. Vegetation reflectance indices followed the variations in pigment content after the fungal infection. R750/R700 (R2 = 0.877) and CRI (carotenoid reflectance index; R2 = 0.735) were the most potent to follow changes in chlorophylls and carotenoids contents, respectively. Infected leaf tissue exhibited decrease in chlorophyll a (~50 %) as well as carotenoids (~70%). We conclude that combination of chlorophyll fluorescence and reflectance measurements can be used as an effective non-invasive tool for an early detection of Plasmopara viticola in field as well as for estimation of the level of infection

Separation and Identification of Highly Fluorescent Compounds Derived from trans-Resveratrol in the Leaves of Vitis vinifera Infected by Plasmopara viticola

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Meta-analysis assessing potential of steady-state chlorophyll fluorescence for remote sensing detection of plant water, temperature and nitrogen stressplant

Many laboratory studies investigating chlorophyll fluorescence (F) of plants have provided sufficient evidence of the functional link between dynamic changes in photosynthetic activity and F emissions. Far fewer studies, however, have been devoted to detailed analysis of F emission under steady-state conditions, which may be amenable to measurement by passive spectroradiometers onboard airborne or satellite missions. Here, we provide a random-effects meta-analysis of studies using both passively (sun-induced) and actively (e.g. laser-induced) measured steady-state F for detecting stress reactions in terrestrial vegetation. Specifically, we review behaviour of F in red and far-red wavelengths, and also the red to far-red F ratio, for plants physiologically stressed by water deficit, temperature extremes, and nitrogen insufficiency. Results suggest that water stress is, in general, associated with a decline in red and far-red F signal intensity measured at both leaf and canopy levels, whereas the red to far-red F ratio displays an inconsistent behaviour. Chilling, for which only studies with active measurements at the leaf level are available, significantly increased red and far-red F, whereas heat stress produced a less convincing decrease in both F emissions, notably in canopies measured passively. The clearest indicator of temperature stress was the F ratio, which declined significantly and consistently. The F ratio was also the strongest indicator of nitrogen deficiency, revealing a nearly uniformly increasing pattern driven by predominantly declining far-red F. Although significant knowledge gaps were encountered for certain scales and F measurement techniques, the analyses indicate that future airborne or space-borne acquisitions of both red and far-red F signals would be beneficial for timely detection of plant stress events