G. (2015). Meta-analysis assessing potential of steadystate chlorophyll fluorescence for remote sensing detection of plant water, temperature and nitrogen stress. Remote Sensing of Environment: an interdisciplinary journal, 168 420-436.Meta-analysis assessing potential of steady-state chlorophyll fluorescence for remote sensing detection of plant water, temperature and nitrogen stress AbstractMany 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. laserinduced) 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. Disciplines Medicine and Health Sciences | Social and Behavioral Sciences Publication DetailsAc, A., Malenovky, Z., Olejnickova, J., Galle, A., Rascher, U. & Mohammed, G. (2015). Meta-analysis assessing potential of steady-state chlorophyll fluorescence for remote sensing detection of plant water, temperature and nitrogen stress. Here, we provide a random--effects meta--analysis of studies using both passively (sun--35 induced) and actively (e.g. laser--induced) measured steady--state F for detecting stress 36 reactions in terrestrial vegetation. Specifically, we review behaviour of F in red and far--37 red wavelengths, and also the red to far--red F ratio, for plants physiologically stressed 38 by water deficit, temperature extremes, and nitrogen insufficiency. Results suggest that 39 water stres...

Plasmopara viticola is an economically important pathogen of grapevine. Early detection of P. viticola infection can lead to improved fungicide treatment. Our study aimed to determine whether chlorophyll fluorescence (Chl-F) imaging can be used to reveal early stages of P. viticola infection under conditions similar to those occurring in commercial vineyards. Maximum (F(V)/F(M)) and effective quantum yield of photosystem II (I broken vertical bar(PSII)) were identified as the most sensitive reporters of the infection. Heterogeneous distribution of F(V)/F(M) and I broken vertical bar(PSII) in artificially inoculated leaves was associated with the presence of the developing mycelium 3 days before the occurrence of visible symptoms and 5 days before the release of spores. Significant changes of F(V)/F(M) and I broken vertical bar(PSII) were spatially coincident with localised spots of inoculation across the leaf lamina. Reduction of F(V)/F(M) was restricted to the leaf area that later yielded sporulation, while the area with significantly lower I broken vertical bar(PSII) was larger and probably reflected the leaf parts in which photosynthesis was impaired. Our results indicate that Chl-F can be used for the early detection of P. viticola infection. Because P. viticola does not expand systemically in the host tissues and the effects of infection are localised, Chl-F imaging at high resolution is necessary to reveal the disease in the field

Mature berries of Pinot Noir grapevines were sampled across a latitudinal gradient in Europe, from southern Spain to central Germany. Our aim was to study the influence of latitude-dependent environmental factors on the metabolite composition (mainly phenolic compounds) of berry skins. Solar radiation variables were positively correlated with flavonols and flavanonols and, to a lesser extent, with stilbenes and cinnamic acids. The daily means of global and erythematic UV solar radiation over long periods (bud break-veraison, bud break-harvest, and veraison-harvest), and the doses and daily means in shorter development periods (5-10 days before veraison and harvest) were the variables best correlated with the phenolic profile. The ratio between trihydroxylated and monohydroxylated flavonols, which was positively correlated with antioxidant capacity, was the berry skin variable best correlated with those radiation variables. Total flavanols and total anthocyanins did not show any correlation with radiation variables. Air temperature, degree days, rainfall, and aridity indices showed fewer correlations with metabolite contents than radiation. Moreover, the latter correlations were restricted to the period veraison-harvest, where radiation, temperature, and water availability variables were correlated, making it difficult to separate the possible individual effects of each type of variable. The data show that managing environmental factors, in particular global and UV radiation, through cultural practices during specific development periods, can be useful to promote the synthesis of valuable nutraceuticals and metabolites that influence wine quality.

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.