A flash-lamp chlorophyll (Chl) fluorescence imaging system (FL-FIS) is described that allows to screen and image the photosynthetic activity of several thousand leaf points (pixels) of intact leaves in a non-destructive way within a few seconds. This includes also the registration of several thousand leaf point images of the four natural fluorescence bands of plants in the blue (440 nm) and green (520 nm) regions as well as the red (near 690 nm) and far-red (near 740 nm) Chl fluorescence. The latest components of this Karlsruhe FL-FIS are presented as well as its advantage as compared to the classical single leaf point measurements where only the fluorescence information of one leaf point is sensed per each measurement. Moreover, using the conventional He-Ne-laser induced two-wavelengths Chl fluorometer LITWaF, we demonstrated that the photosynthetic activity of leaves can be determined measuring the Chl fluorescence decrease ratio, R Fd (defined as Chl fluorescence decrease F d from maximum to steady state fluorescence F s : F d /F s ), that is determined by the Chl fluorescence induction kinetics (Kautsky effect). The height of the values of the Chl fluorescence decrease ratio R Fd is linearly correlated to the net photosynthetic CO 2 fixation rate P N as is indicated here for sun and shade leaves of various trees that considerably differ in their P N . Imaging the R Fd -ratio of intact leaves permitted the detection of considerable gradients in photosynthetic capacity across the leaf area as well as the spatial heterogeneity and patchiness of photosynthetic quantum conversion within the control leaf and the stressed plants. The higher photosynthetic capacity of sun versus shade leaves was screened by Chl fluorescence imaging. Profile analysis of fluoresence signals (along a line across the leaf area) and histograms (the signal frequency distribution of the fluorescence information of all measured leaf pixels) of Chl fluorescence yield and Chl fluorescence ratios allow, with a high statistical significance, the quantification of the differences in photosynthetic activity between various areas of the leaf as well as between control leaves and water stressed leaves. The progressive uptake and transfer of the herbicide diuron via the petiole into the leaf of an intact plant and the concomitant loss of photosynthetic quantum conversion was followed with high precision by imaging the increase of the red Chl fluorescence F 690 . Differences in the availability and absorption of soil nitrogen of crop plants can be documented via this flash-lamp fluorescence imaging technique by imaging the blue/red ratio image F 440 /F 690 , whereas differences in Chl content are detected by collecting images of the fluorescence ratio red/far-red, F 690 /F 740 .Additional key words: blue-green fluorescence; chlorophyll fluorescence decrease ratio; diuron absorption; flash light pulses; nitrogen supply; R Fd -ratio; sun and shade leaves, water stress.

Images taken at different spectral bands are increasingly used for characterizing plants and their health status. In contrast to conventional point measurements, imaging detects the distribution and quantity of signals and thus improves the interpretation of fluorescence and reflectance signatures. In multispectral fluorescence and reflectance set-ups, images are separately acquired for the fluorescence in the blue, green, red, and far red, as well as for the reflectance in the green and in the near infrared regions. In addition, 'reference' colour images are taken with an RGB (red, green, blue) camera. Examples of imaging for the detection of photosynthetic activity, UV screening caused by UV-absorbing substances, fruit quality, leaf tissue structure, and disease symptoms are introduced. Subsequently, the different instrumentations used for multispectral fluorescence and reflectance imaging of leaves and fruits are discussed. Various types of irradiation and excitation light sources, detectors, and components for image acquisition and image processing are outlined. The acquired images (or image sequences) can be analysed either directly for each spectral range (wherein they were captured) or after calculating ratios of the different spectral bands. This analysis can be carried out for different regions of interest selected manually or (semi)-automatically. Fluorescence and reflectance imaging in different spectral bands represents a promising tool for non-destructive plant monitoring and a 'road' to a broad range of identification tasks.

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There is an urgent quest for room-temperature qubits in nanometer-sized, ultrasmall nanocrystals for quantum biosensing, hyperpolarization of biomolecules, and quantum information processing. Thus far, the preparation of such qubits at the nanoscale has remained futile. Here, we present a synthesis method that avoids any interaction of the solid with high-energy particles and uses self-propagated high-temperature synthesis with a subsequent electrochemical method, the no-photon exciton generation chemistry to produce room-temperature qubits in ultrasmall nanocrystals of sizes down to 3 nm with high yield. We first create the host silicon carbide (SiC) crystallites by high-temperature synthesis and then apply wet chemical etching, which results in ultrasmall SiC nanocrystals and facilitates the creation of thermally stable defect qubits in the material. We demonstrate room-temperature optically detected magnetic resonance signal of divacancy qubits with 3.5% contrast from these nanoparticles with emission wavelengths falling in the second biological window (1000− 1380 nm). These results constitute the formation of nonperturbative bioagents for quantum sensing and efficient hyperpolarization.

Agricultural production is limited by a wide range of abiotic (e.g. drought, waterlogging) and biotic (pests, diseases and weeds) stresses. The impact of these stresses can be minimized by appropriate management actions such as irrigation or chemical pesticide application. However, further optimization requires the ability to diagnose and quantify the different stresses at an early stage. Particularly valuable information of plant stress responses is provided by plant imaging, i.e. non-contact sensing with spatial resolving power: (i) thermal imaging, detecting changes in transpiration rate and (ii) fluorescence imaging monitoring alterations in photosynthesis and other physiological processes. These can be supplemented by conventional video imagery for study of growth. An efficient early warning system would need to discriminate between different stressors. Given the wide range of sensors, and the association of specific plant physiological responses with changes at particular wavelengths, this goal seems within reach. This is based on the organization of the individual sensor results in a matrix that identifies specific signatures for multiple stress types. In this report, we first review the diagnostic effectiveness of different individual imaging techniques and then extend this to the multi-sensor stress-identification approach.

The effect of high irradiance (HI) during desiccation and subsequent rehydration of the homoiochlorophyllous desiccation-tolerant shade plant Haberlea rhodopensis was investigated. Plants were irradiated with a high quantum fluence rate (HI; 350 μmol m -2 s -1 compared to ca. 30 μmol m -2 s -1 at the natural rock habitat below trees) and subjected either to fast desiccation (tufts dehydrated with naturally occurring thin soil layers) or slow desiccation (tufts planted in pots in peat-soil dehydrated by withholding irrigation). Leaf water content was 5 % of the control after 4 d of fast and 19 d of slow desiccation. Haberlea was very sensitive to HI under all conditions. After 19 d at HI, even in well-watered plants there was a strong reduction of rates of net photosynthesis and transpiration, contents of chlorophyll (Chl) and carotenoids, as well as photosystem 2 activity (detected by the Chl fluorescence ratio R Fd ). Simultaneously, the blue/red and green/red fluorescence ratios increased considerably suggesting increased synthesis of polyphenolic compounds. Desiccation of plants in HI induced irreversible changes in the photosynthetic apparatus and leaves did not recover after rehydration regardless of fast or slow desiccation. Only young leaves survived desiccation.Additional key words: carotenoids; chlorophyll fluorescence; desiccation tolerant plant; drought stress; fluorescence imaging; leaf area; net photosynthetic rate; transpiration rate; water use efficiency.

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