The principles of quantum optics have yielded a plethora of ideas to surpass the classical limitations of sensitivity and resolution in optical microscopy. While some ideas have been applied in proof-of-principle experiments, imaging a biological sample has remained challenging mainly due to the inherently weak signal measured and the fragility of quantum states of light. In principle, however, these quantum protocols can add new information without sacrificing the classical information and can therefore enhance the capabilities of existing super-resolution techniques. Image scanning microscopy (ISM), a recent addition to the family of super-resolution methods, generates a robust resolution enhancement without sacrificing the signal level. Here we introduce quantum image scanning microscopy (Q-ISM): combining ISM with the measurement of quantum photon correlation allows increasing the resolution of ISM up to two-fold, four times beyond the diffraction limit. We introduce the Q-ISM principle and obtain super-resolved optical images of a biological sample stained with fluorescent quantum dots using photon antibunching, a quantum effect, as a resolution enhancing contrast mechanism. Main TextThe diffraction limit, as formulated by Abbe, sets the attainable resolution in far-field optical microscopy to about half of the visible wavelength 1 , hindering its applicability in life science studies at very small scales. Over the past two decades, several super-resolution methods have successfully overcome the diffraction limit, including emission depletion microscopy, localization microscopy and structured illumination microscopy 2-6 . The continuous and rapid improvement in detector technology has enabled two more recent developments in the field of super-resolution microscopy, which are the center of this work: quantum super-resolution microscopy and image scanning microscopy (ISM). As for the first, a surge of interest in super-resolution imaging based on quantum optics concepts 7-13 , inspired and facilitated by the progress in high temporal resolution imagers, resulted in a few successful proof-of-principle demonstrations 7,8,14 . The second, ISM, relies on a small array of fast detector and offers a two-fold enhancement of resolution 15,16 . Since ISM is compatible with a standard confocal microscope architecture it has already been integrated into commercial products.While all super-resolution modalities violate at least one of the basic assumptions of the Abbe theory, many rely on breaking more than one. For instance, stimulated emission depletion (STED) and saturated structured illumination microscopy (SSIM) breach both the assumption of a linear response of a fluorophore to the excitation light and that of a uniform illumination field 17,18 . In contrast, the few demonstrations of quantum super-resolution microscopy 7,8,14 relied solely on violating the implicit assumption, underlying Abbe's derivation, that light behaves as waves rather than particles. ISM, as well, depends on violating a single assumption, a u...

trees are adapted to diverse environments and have some of the highest rates of photosynthesis among trees. leaves can deposit one or more of the three major mineral types found in leaves: amorphous calcium carbonate cystoliths, calcium oxalates, and silica phytoliths. In order to better understand the functions of these minerals and the control that the leaf exerts over mineral deposition, we investigated leaves from 10 species from vastly different environments (Rehovot, Israel; Bologna, Italy; Issa Valley, Tanzania; and Ngogo, Uganda). We identified the mineral locations in the soft tissues, the relative distributions of the minerals, and mineral volume contents using microcomputed tomography. Each species is characterized by a unique 3D mineral distribution that is preserved in different environments. The mineral distribution patterns are generally different on the adaxial and abaxial sides of the leaf. All species examined have abundant calcium oxalate deposits around the veins. We used micromodulated fluorimetry to examine the effect of cystoliths on photosynthetic efficiency in two species having cystoliths abaxially and adaxially () or only abaxially (). In , both adaxial and abaxial cystoliths efficiently contributed to light redistribution inside the leaf and, hence, increased photosynthetic efficiency, whereas in, the abaxial cystoliths did not increase photosynthetic efficiency.

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The manner in which leaves adapt to different light intensities is key for enabling plants to survive in diverse environments and in constantly changing conditions. Many studies have addressed this subject, but little attention has been given to the effect that mineral deposits in leaves can have on photosynthesis.Here we study 6 species of Ficus and investigate how different cystolith configurations affect photosynthesis in both non-saturating and saturating light. We quantified the effect of light scattering by cystoliths on light absorption by measuring chlorophyll fluorescence intensity using microfluorimetry. We complement this by carbon assimilation measurements to directly estimate how light scattering by cystoliths affects the overall photosynthetic process.We show that light waste is reduced when irradiance is on a cystolith compared to cystolith free tissue. Moreover, light is channeled into the center of the leaf where photosynthesis occurs more efficiently than in the outer layers. This, in turn, leads to more efficient CO2 assimilation.We conclude that cystoliths contribute to photosynthesis optimization under saturating light. Cystoliths reduce the wasted portion of absorbed light under saturating irradiance by scattering light into the light-deprived leaf center. The increased efficiency may well provide important benefits to plants that form mineral scatterers.