Magnetic field protects plants against high light by slowing down production of singlet oxygen

Recombination of the primary radical pair of photosystem II (PSII) of photosynthesis may produce the triplet state of the primary donor of PSII. Triplet formation is potentially harmful because chlorophyll triplets can react with molecular oxygen to produce the reactive singlet oxygen (1O(2)). The yield of 1O(2) is expected to be directly proportional to the triplet yield and the triplet yield of charge recombination can be lowered with a magnetic field of 100-300 mT. In this study, we illuminated intact pumpkin leaves with strong light in the presence and absence of a magnetic field and found that the magnetic field protects against photoinhibition of PSII. The result suggests that radical pair recombination is responsible for significant part of 1O(2) production in the chloroplast. The magnetic field effect vanished if leaves were illuminated in the presence of lincomycin, an inhibitor of chloroplast protein synthesis, or if isolated thylakoid membranes were exposed to light. These data, in turn, indicate that 1O(2) produced by the recombination of the primary charge pair is not directly involved in photoinactivation of PSII but instead damages PSII by inhibiting the repair of photoinhibited PSII. We also found that an Arabidopsis thaliana mutant lacking alpha-tocopherol, a scavenger of 1O(2), is more sensitive to photoinhibition than the wild-type in the absence but not in the presence of lincomycin, confirming that the target of 1O(2) is the repair mechanism

Global maps of soil temperature

Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km2 resolution for 0\u20135 and 5\u201315 cm soil depth. These maps were created by calculating the difference (i.e. offset) between in situ soil temperature measurements, based on time series from over 1200 1-km2 pixels (summarized from 8519 unique temperature sensors) across all the world's major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10\ub0C (mean = 3.0 \ub1 2.1\ub0C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6 \ub1 2.3\ub0C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler ( 120.7 \ub1 2.3\ub0C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications

Global maps of soil temperature

Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km² resolution for 0–5 and 5–15 cm soil depth. These maps were created by calculating the difference (i.e., offset) between in-situ soil temperature measurements, based on time series from over 1200 1-km² pixels (summarized from 8500 unique temperature sensors) across all the world’s major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean = 3.0 ± 2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6 ± 2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (-0.7 ± 2.3°C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in-situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications

Global maps of soil temperature.

Research in global change ecology relies heavily on global climatic grids derived from estimates of air temperature in open areas at around 2 m above the ground. These climatic grids do not reflect conditions below vegetation canopies and near the ground surface, where critical ecosystem functions occur and most terrestrial species reside. Here, we provide global maps of soil temperature and bioclimatic variables at a 1-km2 resolution for 0-5 and 5-15 cm soil depth. These maps were created by calculating the difference (i.e. offset) between in situ soil temperature measurements, based on time series from over 1200 1-km2 pixels (summarized from 8519 unique temperature sensors) across all the world's major terrestrial biomes, and coarse-grained air temperature estimates from ERA5-Land (an atmospheric reanalysis by the European Centre for Medium-Range Weather Forecasts). We show that mean annual soil temperature differs markedly from the corresponding gridded air temperature, by up to 10°C (mean = 3.0 ± 2.1°C), with substantial variation across biomes and seasons. Over the year, soils in cold and/or dry biomes are substantially warmer (+3.6 ± 2.3°C) than gridded air temperature, whereas soils in warm and humid environments are on average slightly cooler (-0.7 ± 2.3°C). The observed substantial and biome-specific offsets emphasize that the projected impacts of climate and climate change on near-surface biodiversity and ecosystem functioning are inaccurately assessed when air rather than soil temperature is used, especially in cold environments. The global soil-related bioclimatic variables provided here are an important step forward for any application in ecology and related disciplines. Nevertheless, we highlight the need to fill remaining geographic gaps by collecting more in situ measurements of microclimate conditions to further enhance the spatiotemporal resolution of global soil temperature products for ecological applications

A Mutation in the D-de Loop of D1 Modifies the Stability of the S2QA- and S2QB- States in Photosystem II.

Photosystem II electron transfer, charge stabilization, and photoinhibition were studied in three site-specific mutants of the D1 polypeptide of Synechocystis PCC 6803: E243K, E229D, and CA1 (deletion of three glutamates 242-244 and a substitution, glutamine-241 to histidine). The phenotypes of the E229D and E243K mutants were similar to that of the control strain (AR) in all of the studied aspects. The characteristics of CA1 were very different. Formate, which inhibits the QA- to QB- reaction, was severalfold less effective in CA1 than in AR. The S2QA- and S2QB- states were stabilized in CA1. It was previously shown that the electron transfer between QA- and QB was modified in CA1 (P Maenpaa, T. Kallio, P. Mulo, G. Salih, E.-M. Aro, E. Tyystjarvi, C. Jansson [1993] Plant Mol Biol 22: 1-12). A change in the redox potential of the QA/QA- couple, which renders the reoxidation of QA- by back or forward reactions more difficult, could explain the phenotype of CA1. Although the rates of photoinhibition measured as inhibition of oxygen evolution, Chl fluorescence quenching, and decrease of thermoluminescence B and Q bands were similar in AR and CA1, the CA1 strain more quickly reached a state from which the cells were unable to recover their activity. The results described in this paper suggest that a modification in the structure of the D-de loop of D1 could influence the properties of the couple QA/QA- in D2 and the mechanism of recovery from photoinhibition

Potential of carbon nanotubes in algal biotechnology

A critical mass of knowledge is emerging on the interactions between plant cells and engineered nanomaterials, revealing the potential of plant nanobiotechnology to promote and support novel solutions for the development of a competitive bioeconomy. This knowledge can foster the adoption of new methodological strategies to empower the large-scale production of biomass from commercially important microalgae. The present review focuses on the potential of carbon nanotubes (CNTs) to enhance photosynthetic performance of microalgae by (i) widening the spectral region available for the energy conversion reactions and (ii) increasing the tolerance of microalgae towards unfavourable conditions occurring in mass production. To this end, current understanding on the mechanisms of uptake and localization of CNTs in plant cells is discussed. The available ecotoxicological data were used in an attempt to assess the feasibility of CNT-based applications in algal biotechnology, by critically correlating the experimental conditions with the observed adverse effects. Furthermore, main structural and physicochemical properties of single- and multi-walled CNTs and common approaches for the functionalization and characterization of CNTs in biological environment are presented. Here, we explore the potential that nanotechnology can offer to enhance functions of algae, paving the way for a more efficient use of photosynthetic algal systems in the sustainable production of energy, biomass and high-value compounds

Fluorescence as a tool to understand changes in photosynthetic electron flow regulation

International audienceThe physiological state of a chloroplast is stronglyinfluenced by both biotic and abiotic conditions.Unfavourable growth conditions lead to photosyntheticstress. Chlorophyll a fluorescence is a widelyused probe of photosynthetic activity (specificallyPSII), and therefore stress which specifically targetsthe electron transport pathway and associated alternativeelectron cycling pathways. By manipulating theprocesses that control photosynthesis, affecting thechlorophyll a fluorescence, yields detailed insight intothe biochemicalpathways. Light that is captured by achlorophyll molecule can be utilised in three competingprocesses; electron transport, energy dissipation(via heat) and chlorophyll a fluorescence emission.Electrons produced by water-splitting are not alwaysused in carbon fixation; if the incident irradiancegeneratesmore electrons than the dark reactionscan use in carbon fixation, damage will occur to the photosynthetic apparatus. If carbon fixation is inhibitedby temperature or reduced inorganic carbon (Ci), ATPor NADPH availability, then the photosystem dynamicallyadjusts and uses alternate sinks for electrons, suchas molecular oxygen (water-water cycle or Mehler ascorbateperoxidase reaction). The process of stress acclimationleads to a number of photoprotective pathwaysand we describe how inhibitors can be used to identifythese particular processes. In this chapter, we describethe processes controlling electron transport as influencedby light-induced stress