Lipid peroxidation and chlorophyll fluorescence of photosystem ii performance during drought and heat stress is associated with the antioxidant capacities of C3 sunflower and C4 maize varieties

Agricultural production is predicted to be adversely affected by an increase in drought and heatwaves. Drought and heat damage cellular membranes, such as the thylakoid membranes where photosystem II occurs (PSII). We investigated the chlorophyll fluorescence (ChlF) of PSII, photosynthetic pigments, membrane damage, and the activity of protective antioxidants in drought-tolerant and -sensitive varieties of C3 sunflower and C4 maize grown at 20/25 and 30/35 °C. Drought-tolerant varieties retained PSII electron transport at lower levels of water availability at both temperatures. Drought and heat stress, in combination and isolation, had a more pronounced effect on the ChlF of the C3 species. For phenotyping, the maximum fluorescence was the most effective ChlF measure in characterizing varietal variation in the response of both species to drought and heat. The drought-tolerant sunflower and maize showed lower lipid peroxidation under drought and heat stress. The greater retention of PSII function in the drought-tolerant sunflower and maize at higher temperatures was associated with an increase in the activities of antioxidants (glutathione reductase, superoxide dismutase, catalase, peroxidase, and ascorbate peroxidase), whereas antioxidant activity declined in the drought-sensitive varieties. Antioxidant activity should play a key role in the development of drought- and heat-tolerant crops for future food security

Strain-induced Evolution of Electronic Band Structures in a Twisted Graphene Bilayer

Here we study the evolution of local electronic properties of a twisted graphene bilayer induced by a strain and a high curvature. The strain and curvature strongly affect the local band structures of the twisted graphene bilayer; the energy difference of the two low-energy van Hove singularities decreases with increasing the lattice deformations and the states condensed into well-defined pseudo-Landau levels, which mimic the quantization of massive Dirac fermions in a magnetic field of about 100 T, along a graphene wrinkle. The joint effect of strain and out-of-plane distortion in the graphene wrinkle also results in a valley polarization with a significant gap, i.e., the eight-fold degenerate Landau level at the charge neutrality point is splitted into two four-fold degenerate quartets polarized on each layer. These results suggest that strained graphene bilayer could be an ideal platform to realize the high-temperature zero-field quantum valley Hall effect.Comment: 4 figure

Gauging the mass of metals in the gas phase of galaxies from the Local Universe to the Epoch of Reionization

The chemical enrichment of dust and metals are vital processes in constraining the star formation history of the universe. Previously, the dust masses of high-redshift star-forming galaxies have been determined through their far-infrared continuum, however, equivalent, and potentially simpler, approaches to determining the metal masses have yet to be explored at $z\gtrsim 2$. Here, we present a new method of inferring the metal mass in the interstellar medium (ISM) of galaxies out to $z\approx 8$, using the far-infrared [CII]$-158\mu$m emission line as a proxy. We calibrated the [CII]-to-$M_{\rm Z,ISM}$ conversion factor based on a benchmark observational sample at $z\approx 0$, in addition to gamma-ray burst sightlines at $z>2$ and cosmological hydrodynamical simulations of galaxies at $z\approx 0$ and $z\approx 6$. We found a universal scaling across redshifts of $\log (M_{\rm Z,ISM}/M_\odot) = \log (L_{\rm [CII]}/L_\odot) - 0.45,$ with a 0.4 dex scatter, which is constant over more than two orders of magnitude in metallicity. We applied this scaling to recent surveys for [CII] in galaxies at $z\gtrsim 2$ and determined the fraction of metals retained in the gas-phase ISM, $M_{\rm Z,ISM} / M_\star$, as a function of redshift showing that an increasing fraction of metals reside in the ISM of galaxies at higher redshifts. We place further constraints on the cosmic metal mass density in the ISM ($\Omega_{\rm Z,ISM}$) at $z\approx 5$ and $\approx 7$, yielding $\Omega_{\rm Z,ISM} = 6.6^{+13}_{-4.3}\times 10^{-7}\,M_\odot\, {\rm Mpc}^{-3}$ ($z\approx 5$) and $\Omega_{\rm Z,ISM} = 2.0^{+3.5}_{-1.3}\times 10^{-7}\,M_\odot\, {\rm Mpc}^{-3}$ ($z\approx 7$). These results are consistent with the expected metal yields from the integrated star formation history at the respective redshifts. This suggests that the majority of metals produced at $z\gtrsim 5$ are confined to the ISM of galaxies.Comment: Accepted in A&A, abstract abridge

Ecophysiology of urban trees in a perspective of climate change

The current ecological condition of cities in respect to the surrounding countryside (higher temperatures and CO, levels, drought, photochemical pressure and particulate matter pollutants), may anticipate the effects of climate change at a broader scale. However, the condition of urban trees can be exacerbated by some specific factors within cities, such as mismanagement and the direct impact of human activities. The acclimation and adaptation strategies shown by urban tree species may be similar to those already known for climate change, including the substitution of the current tree species with better adapted genotypes (native or not native) and the adoption of techniques aimed at improving stress resistance. In this paper, we review the main ecological factors affecting the physiology of urban trees, with a special reference to Mediterranean conditions. We summarise the criteria to select the most suitable trees, such as phenotyping and the identification of functional traits associated with stress resistance, physiological functionality and ecosystem services. The role of tree diversity in maximising ecosystem stability and services is introduced

New frontiers: Adult to adult living donor liver transplantation, single center experience from Turkey

2001: A Transplant Odyssey Congress -- 2001 -- ISTANBUL, TURKEYWOS: 000173143600173PubMed ID: 11750480Novarti

Photosynthetic and morphological responses of oak species to temperature and [CO2] increased to levels predicted for 2050

Urban forests are environmentally, climatically, socially and economically important. An understanding of the response of urban trees to future climate change is crucial to the maintenance of urban forests and the ecosystem services they support. We conducted a controlled environment pot-experiment on four-year-old Mediterranean oak species: the evergreen Quercus ilex and the deciduous Quercus cerris, to investigate the combined impact of elevated CO2 and temperature on growth and leaf physiology to levels predicted for 2050 in urban areas of central Italy. Quercus cerris initially increased net-photosynthesis (PN) under elevated 2050 conditions (EC) compared to present ambient conditions (AC), before PN declined, possibly indicative of down-regulation of photosynthetic physiology. Quercus ilex PN was not influenced by EC throughout the 70 days duration of the study. Levels of PN and stomatal conductance (Gs) were generally lower in Q. ilex than Q. cerris. Quercus ilex also reduced Gs during growth at EC. This reduced transpirative water-loss caused a significant increase in the water use efficiency (WUE) of Q. ilex. This reduction in Gs may have been associated with the observed reduction in stomatal density in Q. ilex grown under EC, while the number of stomata on leaves developed under the experimental conditions were unaffected by the EC treatment in Q. cerris. Over the course of the experiment, above (stem dry weight: SDW) and below-ground biomass (root dry weight: RDW) and foliar starch increased in Q. cerris (in both EC and AC equally) but not Q. ilex. Chlorophyll a fluorescence (ChlF); Prompt Fluorescence (PF), Delayed Fluorescence (DF) and Modulated Reflectance (MR) also indicated that a greater resilience of photochemistry to growth under EC was more apparent in Q. ilex than Q. cerris. In particular, the reduction of the quantum yield efficiency (FV/FM) in Q. ilex may also be considered functional to maintain constant PN levels in elevated temperature and [CO2]. The results of this study suggest that Q. ilex exhibits greater plasticity and adaptation to EC, and may therefore perform more favourably under future 2050 climatic condition