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Soil nitrogen drives inverse acclimation of xylem growth cessation to rising temperature in Northern Hemisphere conifers
Controlled experiments suggest that the seasonal build-up of nitrogen (N) limitation constrains the responses of forest autumn phenology to elevated temperatures. Therefore, rising soil N is expected to increase the delaying effects of elevated temperature on the end of the season, i.e., leaf senescence. However, the interactive effects of temperature, soil N, and aridity on xylem autumn phenology remain unknown. We conducted a wide spatial analysis from 75 conifer sites in the Northern Hemisphere and found that rising soil N increases the delaying effects of elevated temperature on the end of xylem cell wall thickening but reduced the delaying effects on the cessation of cell enlargement, especially in humid regions. The contrasting effects of elevated soil N on cell enlargement versus cell wall thickening could affect xylem cell anatomy, thereby induce changes in wood density, and induce a decoupling of stem size growth from photosynthate production. These analyses extend previous findings on forest autumn phenology by systematically investigating the spatial variation in the interactive effects of temperature and soil N on xylem autumn phenology at the cellular scale
Early stress detection in forest trees using a nanobody-functionalized electrochemical biosensor for ascorbate peroxidase
Forest environments are exposed to multiple stressful factors of both abiotic and biotic nature such as heavy metal contamination, drought, or pest infestations which may lead to their massive decline. We designed a comprehensive approach for isolating, producing and functionalizing reagents suitable for the affordable detection of forest plant stress biomarkers with the aim to provide quantitative data to assess plant stress fluctuation and, possibly, to design mitigation strategies. We first optimized a panning protocol to recover nanobodies targeting shared sequences that could cross-react with both Pisum sativum and Populus nigra ascorbate peroxidase (APX). After their production as recombinant constructs and their extensive biophysical and biochemical characterization, such reagents were exploited as the immunocapture element of an electrochemical biosensor conceived as a potential point-of-care device. Such biosensor could detect both pea and poplar APX in leaf extracts and could be used to clearly discriminate between control and heavy metal-stressed poplar plants based on their APX activity, even before the appearance of any phenotypic symptom. The combination of fast and inexpensive reagent production with the development of portable diagnostics opens the opportunity for large-scale, on-site surveys of forest trees