Isotope ratios of tree-ring cellulose are a prominent tool to reconstruct paleoclimate and plant responses to environmental variation. Current models for cellulose isotope ratios assume a transfer of ...the environmental signals recorded in bulk leaf water to carbohydrates and ultimately into stem cellulose. However, the isotopic signal of carbohydrates exported from leaf to branch may deviate from mean leaf values if spatial heterogeneity in isotope ratios exists in the leaf. We tested whether the isotopic heterogeneity previously observed along the length of a ponderosa pine (Pinus ponderosa) leaf water was preserved in photosynthetic products. We observed an increase in both sugar and bulk tissue delta.sup.18O values along the needle, but the increase in carbohydrate delta.sup.18O values was dampened relative to the trend observed in leaf water. In contrast, delta.sup.13C values of both sugar and bulk organic matter were invariant along the needle. Phloem-exported sugar measured in the branch below the needles did not match whole-needle values of delta.sup.18O or delta.sup.13C. Instead, there was a near-constant offset observed between the branch and needle sugar delta.sup.13C values, while branch delta.sup.18O values were most similar to delta.sup.18O values observed for sugar at the base of the needle. The observed offset between the branch and needle sugar delta.sup.18O values likely arises from partial isotope oxygen exchange between sugars and water during phloem loading and transport. An improved understanding of the conditions producing differential delta.sup.13C and delta.sup.18O isotope effects between branch phloem and needle sugars could improve tree-ring-based climate reconstructions.
In memory of Vladimir Anatolievich Shuvalov Vasilieva, Lyudmila G; Kaminskaya, Olga P; Yakovlev, Andrei G ...
Photosynthesis research,
11/2022, Letnik:
154, Številka:
2
Journal Article
Increasing the speed of breeding to enhance crop productivity and adaptation to abiotic stresses is urgently needed. The perception that a second Green Revolution should be implemented is widely ...established within the scientific community and among stakeholders. In recent decades, different alternatives have been proposed for increasing crop yield through manipulation of leaf photosynthetic efficiency. However, none of these has delivered practical or relevant outputs. Indeed, the actual increases in photosynthetic rates are not expected to translate into yield increases beyond 10-15%. Furthermore, instantaneous rates of leaf photosynthesis are not necessarily the reference target for research. Yield is the result of canopy photosynthesis, understood as the contribution of laminar and non-laminar organs over time, within which concepts such as canopy architecture, stay-green, or non-laminar photosynthesis need to be taken into account. Moreover, retrospective studies show that photosynthetic improvements have been more common at the canopy level. Nevertheless, it is crucial to place canopy photosynthesis in the context of whole-plant functioning, which includes sink-source balance and transport of photoassimilates, and the availability and uptake of nutrients, such as nitrogen in particular. Overcoming this challenge will only be feasible if a multiscale crop focus combined with a multidisciplinary scientific approach is adopted.
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•This review summarizes the research trends of natural, semi-artificial and artificial photosynthesis in terms of concepts, design, and examples.•Biohydrogen production via ...photosynthesis and direct energy production, and production of hydrogen in natural systems in vivo.•Semi-artificial system in vitro and the ways of producing biohydrogen in semi-artificial devices.•Relations between structures and photoinduced reactivities of the reported artificial photosynthetic donor-acceptor systems are discussed in relation to the efficiency.•Photocatalytic production of hydrogen peroxide as a more promising solar fuel than hydrogen is discussed in relation with the natural photosynthesis.
Solar energy has a great potential as a clean, cheap, renewable and sustainable energy source, but it must be captured and transformed into useful forms of energy as plants do. An especially attractive approach is to store solar energy in the form of chemical bonds as performed in natural photosynthesis. Therefore, there is a challenge in the last decades to construct semi-artificial and artificial photosynthetic systems, which are able to efficiently capture and convert solar energy and then store it in the form of chemical bonds of solar fuels such as hydrogen or hydrogen peroxide, while at the time producing oxygen from water. Here, we review the molecular level details of the natural photosynthesis, particularly the mechanism of light dependent reactions in oxygen evolving organisms, absorption efficiency of solar energy and direct energy production. We then demonstrate the concept and examples of the semi-artificial photosynthesis in vitro. Finally we demonstrate the artificial photosynthesis, which is composed of light harvesting and charge-separation units together with catalytic units of water oxidation and reduction as well as CO2 reduction. The reported photosynthetic molecular and supramolecular systems have been designed and examined in order to mimic functions of the antenna-reaction center of the natural process. The relations between structures and photochemical behaviors of these artificial photosynthetic systems are discussed in relation to the rates and efficiencies of charge-separation and charge-recombination processes by utilizing the laser flash photolysis technique, as well as other complementary techniques. Finally the photocatalytic production of hydrogen peroxide as a more promising solar fuel is discussed in relation with the natural photosynthesis, which also produces hydrogen peroxide in addition to NADPH.
The atmospheric CO.sub.2 concentration CO.sub.2 has been increasing markedly since the industrial revolution and is predicted to reach 500-1,000 µmol mol.sup.-1 by the end of this century. Although ...the short-term and acclimatory responses to elevated CO.sub.2 have been well studied, much less is understood about evolutionary responses to high CO.sub.2. We studied phenotypic and genetic differences in Plantago asiatica populations around a natural CO.sub.2 spring, where CO.sub.2 has been consistently high over an evolutionary time scale. Our common-garden experiment revealed that plants transferred from habitats with higher CO.sub.2 had higher relative growth rates, greater leaf to root ratios, lower photosynthetic rates, and lower stomatal conductance. The habitat-dependent differences were partly heritable because a similar trend of leaf to root ratio was found among their offsprings. Genetic analyses indicated that selfing or biparental inbreeding might promote local adaptation in areas with high CO.sub.2 despite substantial gene flow across the CO.sub.2 gradient. These results indicate that phenotypic and genetic differences have occurred between high and normal CO.sub.2 populations.
CAM photosynthesis: the acid test Winter, Klaus; Smith, J. Andrew C.
New phytologist,
January 2022, Letnik:
233, Številka:
2
Journal Article
Recenzirano
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Summary
There is currently considerable interest in the prospects for bioengineering crassulacean acid metabolism (CAM) photosynthesis – or key elements associated with it, such as increased ...water‐use efficiency – into C3 plants. Resolving how CAM photosynthesis evolved from the ancestral C3 pathway could provide valuable insights into the targets for such bioengineering efforts. It has been proposed that the ability to accumulate organic acids at night may be common among C3 plants, and that the transition to CAM might simply require enhancement of pre‐existing fluxes, without the need for changes in circadian or diurnal regulation. We show, in a survey encompassing 40 families of vascular plants, that nocturnal acidification is a feature entirely restricted to CAM species. Although many C3 species can synthesize malate during the light period, we argue that the switch to night‐time malic acid accumulation requires a fundamental metabolic reprogramming that couples glycolytic breakdown of storage carbohydrate to the process of net dark CO2 fixation. This central element of the CAM pathway, even when expressed at a low level, represents a biochemical capability not seen in C3 plants, and so is better regarded as a discrete evolutionary innovation than as part of a metabolic continuum between C3 and CAM.
A ternary nanocomposite structure of TiO.sub.2-Cu.sub.2O-Au was successfully synthesized by the hydrothermal method to explore the light trapping mechanism of Au nanoparticles in photoelectrochemical ...water splitting. The photocurrent curve of TiO.sub.2-Cu.sub.2O-Au quickly arrived at saturation and increased to 1044 muA/cm.sup.2 at 1.23 V (vs RHE), which was 10.4 times higher than the TiO.sub.2 only. This attributed to the positive synergistic effect of Au plasmon and TiO.sub.2-Cu.sub.2O heterojunction, in which Au act as a light absorber extended the optical path while Cu.sub.2O promoted the separation of photogenerated electron-hole pairs in semiconductors. These intriguing results expanded the comprehensive understanding of the plasmon-assisted photocatalyic reactions and gave a better manipulation in the design of efficient artificial photosynthesis systems.
The Surface Urban Energy and Water Balance Scheme (SUEWS) has recently been introduced to include a bottom-up approach to modeling carbon dioxide (CO.sub.2) emissions and uptake in urban areas. In ...this study, SUEWS is evaluated against the measured eddy covariance (EC) turbulent fluxes of sensible heat (Q.sub.H ), latent heat (Q.sub.E ), and CO.sub.2 (F.sub.C) in a densely built neighborhood in Beijing. The model sensitivity to maximum conductance (g.sub.max) and leaf area index (LAI) is examined. Site-specific g.sub.max is obtained from observations over local vegetation species, and LAI parameters are extracted by optimization with remotely sensed LAI obtained from a Landsat 7 data product. For the simulation of anthropogenic CO.sub.2 components, local traffic and population data are collected. In the model evaluation, the mismatch between the measurement source area and simulation domain is also considered.
Elevated atmospheric CO.sub.2 concentration increases the performance of invasive plants relative to natives when grown in monoculture, but it is unclear how that will affect the relative competitive ...abilities per se of invasive and native grasses grown together. We tested competitive outcomes for four native and four invasive perennial C3 and C4 grasses under ambient (390 ppm) and elevated (700 or 1000 ppm) CO.sub.2 concentrations in the greenhouse with non-limiting water and nutrients. We predicted that elevated CO.sub.2 would increase the competitive suppression of native grasses by invasive grasses. To test this, we determined the relative interaction intensity of biomass allocation for natives grown alone vs. those grown in native-invasive species pairs. We also measured photosynthetic traits that contribute to plant invasiveness and may be affected by elevated CO.sub.2 concentrations for species pairs in mixture to determine native-invasive relative performance. We found no effect of CO.sub.2 for the aboveground biomass and tiller production measures of interaction intensity or for relative performance for most of the measured photosynthetic traits. In competition, the invaders nearly always outperform natives in biomass and tiller production, regardless of CO.sub.2 level. The results suggest that increasing CO.sub.2 concentration alone has little effect on grass competitive outcomes under controlled conditions.
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