Net Quantum Research Articles

A nanophotonic structured resonators for GaInAsSb photocathodes with high electron collection rates

Abstract GaSb-based nanopillar arrays photocathodes have great potential in fields such as thermal photovoltaic systems, solar cells, and low light night vision due to their high long-wave sensitivity, good stability, and low cost. However, the characteristic that the electrons emitted from its side are easily to be captured by the adjacent units results in a generally low net quantum efficiency. We design a GaInAsSb NPAs photocathode with nanopillars and wafers made of the same material. By adjusting the height of the pillar, we can achieve changes in the cathode emitter, which can be directed to achieve high-efficiency photocathodes according to application scenarios. Using FDTD method, the influence of NPA surface density on the performance of different emitter cathodes was simulated. In addition, we investigated the effects of incident angle and external electric field on the emission performance of the cathode. The results indicate that there is an optimal incident angle that allows the wafer to achieve an EQE close to 18%, while the external electric field enhances the EQE of the nanopillar. The work improves the net efficiency of GaSb-based photocathodes, which has guiding significance for the research and development of high-efficiency infrared photocathodes.

Responses of Growth and Photosynthesis in Potted Radermachera hainanensis and R. sinica to Various Medium Water Contents

Abstract Radermachera hainanensis Merr. and R. sinica Hemsl. are woody ornamental plants commonly used for indoor or landscape purposes. However, there is currently a lack of information regarding their water management. Potted plants of these two species were subjected to four volumetric water content (VWC) treatments: 20% VWC (dry), 20%/60% VWC (dry/wet cycle), 40% VWC (moisture), and 70% VWC (waterlogging). Results revealed that both Radermachera species exhibited the poorest growth under the 20% VWC treatment, with the lowest stem diameter, leaf area, plant dry weight, net photosynthetic rate (Pn), stomatal conductance, and maximum quantum efficiency of photosystem II (Fv/Fm). The maximum stem diameter, leaf area, and root dry weight were recorded with the 40% VWC treatment. Stem diameter, leaf area, Pn, and Fv/Fm were higher in both Radermachera species with the 20%/60% VWC compared to the 20% VWC treatment. R. sinica exposed to 20%/60% VWC exhibited similar root dry weight and leaf drop as those with the 40% VWC treatment, while R. hainanensis showed lower root dry weight and higher leaf drop compared to the 40% VWC. Root dry weight, Pn, and Fv/Fm remained unchanged in R. sinica but reduced in R. hainanensis with the 70% VWC compared to the 40% VWC. Species used in this study: Golden jasmine tree, Radermachera hainanensis Merr.; China Doll, Radermachera sinica Hemsl.

Improving the frequency resolution of distribution of relaxation times by integrating elastic net regularization and quantum particle swarm optimization

The distribution of relaxation times (DRT) method is an efficient approach for analyzing electrochemical impedance spectroscopy (EIS) of fuel cells. However, facing electrochemical processes with close characteristic times/frequencies, low frequency resolution of DRT puts a damper on the analysis of results. To address this problem, a new DRT method integrating elastic net regularization and quantum particle swarm optimization (QPSO) algorithm is proposed in this study. Elastic net regularization combines the advantages of Lasso's feature selection and Tikhonov's coefficient shrinkage, thereby enhancing the frequency resolution of DRT. The use of the QPSO algorithm avoids the manual selection of parameters. A comprehensive evaluation of the developed method is conducted using both synthetic EIS and experimental EIS. The results show that the developed DRT method shows good performance and the reconstructed DRT functions exhibit high frequency resolution and accuracy. Overall, the proposed DRT method holds promise for advancing the characterization of fuel cells.

OsMGD1-Mediated Membrane Lipid Remodeling Improves Salt Tolerance in Rice.

Salt stress severely reduces photosynthetic efficiency, resulting in adverse effects on crop growth and yield production. Two key thylakoid membrane lipid components, monogalactosyldiacylglycerol (MGDG) and digalactosyldiacylglycerol (DGDG), were perturbed under salt stress. MGDG synthase 1 (MGD1) is one of the key enzymes for the synthesis of these galactolipids. To investigate the function of OsMGD1 in response to salt stress, the OsMGD1 overexpression (OE) and RNA interference (Ri) rice lines, and a wild type (WT), were used. Compared with WT, the OE lines showed higher chlorophyll content and biomass under salt stress. Besides this, the OE plants showed improved photosynthetic performance, including light absorption, energy transfer, and carbon fixation. Notably, the net photosynthetic rate and effective quantum yield of photosystem II in the OE lines increased by 27.5% and 25.8%, respectively, compared to the WT. Further analysis showed that the overexpression of OsMGD1 alleviated the negative effects of salt stress on photosynthetic membranes and oxidative defense by adjusting membrane lipid composition and fatty acid levels. In summary, OsMGD1-mediated membrane lipid remodeling enhanced salt tolerance in rice by maintaining membrane stability and optimizing photosynthetic efficiency.

Photoinduced electron transfer across the polymer-capped CsPbBr3 interface in a polar medium.

In-situ polymer capping of cesium lead bromide (CsPbBr3) nanocrystals with polymethyl acrylate is an effective approach to improve the colloidal stability in the polar medium and thus extends their use in photocatalysis. The photoinduced electron transfer properties of polymethyl acrylate (PMA)-capped CsPbBr3 nanocrystals have been probed using surface-bound viologen molecules with different alkyl chains as electron acceptors. The apparent association constant (Kapp) obtained for the binding of viologen molecules with PMA-capped CsPbBr3 was 2.3 × 107 M-1, which is an order of magnitude greater than that obtained with oleic acid/oleylamine-capped CsPbBr3. Although the length of the alkyl chain of the viologen molecule did not show any impact on the electron transfer rate constant, it influenced the charge separation efficiency and net electron transfer quantum yield. Viologen moieties with a shorter alkyl chain length exhibited a charge separation efficiency of 72% compared with 50% for the longer chain alkyl chain length viologens. Implications of polymer-capped CsPbBr3 perovskite nanocrystals for carrying out photocatalytic reduction in the polar medium are discussed.

Baryon Number Transport, Strangeness Conservation and Ω-hadron Correlations

Although strange quarks are produced in ss¯ pairs, the ratio of Ω− to Ω¯+ is greater than one in heavy-ion collisions at lower RHIC energies. Thus the produced Ω hyperons must carry net baryon quantum numbers from the colliding nuclei. We present results of K-Ω correlations from AMPT model simulations of Au+Au collisions at √SNN = 14.6 GeV, to probe dynamics for baryon number transport to mid-rapidities at this beam energy. We use both the default and string-melting versions to illustrate how hadronization schemes of quark coalescence and string fragmentations could leave imprints on such correlations. Implications on the measurements of these correlations with the STAR experiment at RHIC will also be discussed.

Growth and photosynthetic performance of Nostoc linckia (formerly N. calcicola) cells grown in BG11 and BG110 media

The biotechnological potential of Nostoc linckia as a biofertilizer and source of bioactive compounds makes it important to study its growth physiology and productivity. Since nitrogen is a fundamental component of N. linckia biomass, we compared the growth and biochemical composition of cultures grown in BG11 (i.e., in the presence of nitrate) and BG110 (in the absence of nitrate). Cultures grown in BG11 accumulated more cell biomass reaching a dry weight of 1.65 ± 0.06 g L–1, compared to 0.92 ± 0.01 g L–1 in BG110 after 240 h of culture. Biomass productivity was higher in culture grown in BG11 medium (average 317 ± 38 mg L–1 day–1) compared to that attained in BG110 (average 262 ± 37 mg L–1 day–1). The chlorophyll content of cells grown in BG11 increased continuously up to (39.0 ± 1.3 mg L–1), while in BG110 it increased much more slowly (13.6 ± 0.8 mg L–1). Biomass grown in BG11 had higher protein and phycobilin contents. However, despite the differences in biochemical composition and pigment concentration, between BG11 and BG110 cultures, both their net photosynthetic rates and maximum quantum yields of the photosystem II resulted in similar.Graphical

Structural, DFT calculations and photophysical and photochemical characteristics of 1-((E)-2-phenylethenyl)-2-(4-(2-((E)-2-phenylethenyl) phenoxy) butoxy) benzene (PPPBB)

X-ray single crystal structure and spectroscopic and photophysical parameters of the titled compound were studied. The titled compound shows thermal stability prior to melting at 126.17 °C with Δ H value of 109.991 J g−1. Photophysical parameters include singlet electronic absorption, molar absorption coefficient, oscillator strength, and dipole moment of electronic transition, fluorescence spectra, excited state lifetime, and fluorescence quantum yield for 1-((E)-2-phenylethenyl)-2-(4-(2-((E)-2-phenylethenyl) phenoxy) butoxy) (PPPBB) in different solvents. PPPBB displays a little change in maximum absorption and emission spectra with solvent polarity, indicating a slight change in dipole moment of dye molecules upon excitation. The dipole moments' (Δ μ) difference between the excited and ground states was obtained from the Lippert–Mataga method. Ground and electronic excited states' geometric optimization was performed using density functional theory (DFT) and time-dependent density functional theory (time dependent-DFT), complemented with spectral findings. A good agreement between theoretical data and experimental observations was found. The net photochemical quantum yield (φc) of PPPBB dye was calculated in various solvents.

Dissecting the below- and aboveground specific responses of two waterlogging-tolerant arbor species to nutrient supply under waterlogging conditions.

Although environmental factors affecting adventitious root (AR) formation have been examined, how nutrient status affects ARs under waterlogging conditions remains unclear. In this study, plants' performance in responding to AR regulation based on nutrient supply was investigated in terms of plant morphology, physiology and AR traits. Results indicated that Cleistocalyx operculatus possesses higher waterlogging tolerance than Syzygium cumini according to the waterlogging tolerance coefficient, mainly because of the higher fresh weight, porosity and length of AR in C. operculatus. Nutrient supply treatment under a waterlogging condition significantly decreased the fresh weight, length, number, porosity, cortex area of AR and the ratio of cortex-to-stele area in both species relative to those in the waterlogging treatment, but significantly increased the activities and stele areas of AR, and leaf nutrient content. This result showed that nutrient supply caused variations in the morphological and anatomical structures of AR that were more beneficial to improve nutrient transportation than oxygen absorption under waterlogging conditions, supporting the nutrient-priority hypothesis. Moreover, nutrient supply under waterlogging conditions induced greater increase in stele area of ARs, fresh weight of the whole plant, total leaf area, leaf nitrogen level, total chlorophyll content, net photosynthesis rate and maximum photochemical quantum yield of PSII in S. cumini than in C. operculatus, suggesting that S. cumini can transport more nutrients and easily adapts to increase in nutrient supply under waterlogging conditions. Thus, S. cumini have better performance in extracting and utilizing nutrients in the water for plant growth. The findings showed that terrestrial arbor plants have physiological and microstructural mechanisms that respond to nutrient supply under waterlogging conditions and provide novel insights into the phytoremediation of eutrophic water bodies in wetland systems.

Effects of Chromium Toxicity on Physiological Performance and Nutrient Uptake in Two Grapevine Cultivars (Vitis vinifera L.) Growing on Own Roots or Grafted onto Different Rootstocks

Chromium toxicity is considered within the most severe and dangerous nutritional disorders, and it can often be observed in crops grown in industrial areas. The present study aims to determine the effects of Cr(VI) toxicity on the growth, nutrition, and physiological performance of grapevines. In a pot hydroponic experiment, own-rooted Merlot and Cabernet Franc grapevine cultivars or cultivars grafted onto 1103P and 101-14 Mgt rootstocks were exposed to 120 μM Cr(VI). Leaf interveinal chlorosis appeared after forty-five days of treatment. Overall leaf chlorosis and brown root coloration after sixty days was reported. A significant effect on the majority of the measured parameters due to the Cr(VI) treatment was observed. Chromium stress increased the total Cr concentrations in all parts of the vines, i.e., leaves, shoots, roots, and trunks. When comparing between the studied plant sections, the roots presented the highest Cr concentrations, ranging from 396 to 868 mg kg−1 d. w., and then, in descending order, the Cr concentrations ranged from 41 to 102 mg kg−1 d. w. in the trunks, from 2.0 to 3.3 mg kg−1 d. w. in the leaves, and from 1.9 to 3.0 mg kg−1 d. w. in the shoots. Between the assessed rootstocks, 1103P was identified to be a better excluder of Cr concentration in the roots and other aerial parts of the vines. Additionally, chromium toxicity negatively affected the concentrations and compartmentalization of the most important nutrients. Leaf chlorophyll (Chl) concentration decreased down to approximately 53% after sixty days of Cr stress. Chromium toxicity significantly reduced the stem water potential (SWP), net CO2 assimilation rate (A), stomatal conductance (gs), and PSII maximum quantum yield in all the cases of grafted or own-rooted vines. At this stage, chromium stress increased the leaf total phenolic content from 46.14% in Merlot vines to 75.91% in Cabernet Franc vines.

Gas exchange and chlorophyll fluorescence in spearmint (Mentha spicata L.) leaves influenced by mineral nutrition

The production of export-quality spearmint is limited in Colombia because of low production volumes, poor compliance with good agricultural practices, nutrient availability, and fertilization management. This study aimed to identify how NPK fertilization influences photosynthesis and photochemistry in Mentha plants during vegetative growth in a mesh house. Increasing doses of chemical fertilization were evaluated with a 10-30-10 (N-P-K) formula at 0, 60, 90, 120, and 180 kg ha-1. The evaluated variables were net photosynthesis (A), transpiration (E), stomatal conductance (gs), leaf temperature (Tleaf), quantum yield (Qy), Non-photochemical quenching (NPQ), photochemical quenching (qP), and dry matter (Dm). The highest A, Qy, E, and gs values were in the plants treated with high NPK doses; the NPQ and qP increased in the plants with low NPK doses. These findings elucidated the influence of NPK on photosynthesis and other physiological parameters in the growth and development of spearmint.

CuZn and ZnO Nanoflowers as Nano-Fungicides against Botrytis cinerea and Sclerotinia sclerotiorum: Phytoprotection, Translocation, and Impact after Foliar Application.

Inorganic nanoparticles (INPs) have dynamically emerged in plant protection. The uptake of INPs by plants mostly depends on the size, chemical composition, morphology, and the type of coating on their surface. Herein, hybrid ensembles of glycol-coated bimetallic CuZn and ZnO nanoparticles (NPs) have been solvothermally synthesized in the presence of DEG and PEG, physicochemically characterized, and tested as nano-fungicides. Particularly, nanoflowers (NFs) of CuZn@DEG and ZnO@PEG have been isolated with crystallite sizes 40 and 15 nm, respectively. Organic coating DEG and PEG (23% and 63%, respectively) was found to protect the NFs formation effectively. The CuZn@DEG and ZnO@PEG NFs revealed a growth inhibition of phytopathogenic fungi Botrytis cinerea and Sclerotinia sclerotiorum in a dose-dependent manner with CuZn@DEG NFs being more efficient against both fungi with EC50 values of 418 and 311 μg/mL respectively. Lettuce (Lactuca sativa) plants inoculated with S. sclerotiorum were treated with the NFs, and their antifungal effect was evaluated based on a disease index. Plants sprayed with ZnO@PEG NFs showed a relatively higher net photosynthetic (4.70 μmol CO2 m−2s−1) and quantum yield rate (0.72) than with CuZn@DEG NFs (3.00 μmol CO2 m−2s−1 and 0.68). Furthermore, the penetration of Alizarin Red S-labeled NFs in plants was investigated. The translocation from leaves to roots through the stem was evident, while ZnO@PEG NFs were mainly trapped on the leaves. In all cases, no phytotoxicity was observed in the lettuce plants after treatment with the NFs.

Reduced quantum defect in a Yb-doped fiber laser by balanced dual-wavelength excitation

Two color optical pumping, both above (anti-Stokes pump or ASP) and below (Stokes pump) the lasing wavelength, was adopted to reduce the net quantum defect (QD) in a solid-state Yb-doped fiber laser. The reduction in QD was achieved by converting a substantial portion of the gain medium's phonons directly into useful photons through a dual-wavelength excitation (DWE) mechanism. Since this is achieved through the usual processes of absorption and stimulated emission associated with lasing, high efficiency can be maintained. Both time domain and power measurements are presented, demonstrating a 13.2% reduction of the system's net QD and a 13.8% reduction in the lasing threshold power. These values were limited only by the available ASP power. Laser slope efficiency, with respect to launched ASP power, was found to be as high as 38.3%. A finite difference time domain model, developed to elucidate the role of both pumps in populating the upper states, corroborated the experimental findings. The DWE concept proposed here opens the door to an “excitation-balanced” type of self-cooled fiber laser. Simulation results also suggest that the technique is scalable and conceptually applicable to other solid-state laser systems.

Effects of Soil Nitrogen Addition on Crown CO2 Exchange of Fraxinus mandshurica Rupr. Saplings

The impact of atmospheric nitrogen deposition on carbon exchange between forest and atmosphere is one of the research hotspots of global change ecology, past researchers have extensively studied the impacts on leaf level, while the impacts on crown CO2 exchange are still unclear. Therefore, we explored the impacts of different nitrogen addition levels on crown CO2 exchange of Fraxinus mandshurica saplings and their responses to the changes of major meteorological factors (photosynthetically active radiation, PAR; vapor pressure deficiency, VPD; and air temperature, Tair) with a novel automated chamber system. There are four levels of nitrogen addition treatments: control (no nitrogen addition, CK), 23 (low nitrogen addition, LN), 46 (medium nitrogen addition, MN), and 69 kgN·hm−2·a−1 (high nitrogen addition, HN). Our results showed that all nitrogen addition treatments increased daily average and accumulated gross primary production (GPP), crown respiration (R), and net crown CO2 exchange (Ne), especially at medium and high nitrogen levels. Similarly, maximum net photosynthetic rate (Nemax) and apparent quantum efficiency (α) were promoted. The change of Ne with PAR, Tair, and VPD showed that nitrogen addition postponed the appearance of photosynthesis midday depression. In addition, the monthly accumulation of R with all nitrogen addition treatments showed an increasing trend (June to July), and then decreased (July to September) during the growing season, while the Ne and GPP decreased gradually with seasonal vegetation senescence. Finally, the crown shifted from carbon sink to carbon source at the end of the growing season, however, the change under high nitrogen treatment occurred 3 days later. The crown CO2 exchange measurements provide a new perspective to better understand the response of forest ecosystem CO2 exchange to elevated nitrogen deposition and provide a basis for related carbon model parameter correction under the influence of nitrogen deposition.

ROS-Scavenging Enzymes as an Antioxidant Response to High Concentration of Anthracene in the Liverwort Marchantia polymorpha L.

Marchantia polymorpha L. responds to environmental changes using a myriad set of physiological responses, some unique to the lineage related to the lack of a vascular- and root-system. This study investigates the physiological response of M. polymorpha to high doses of anthracene analysing the antioxidant enzymes and their relationship with the photosynthetic processes, as well as their transcriptomic response. We found an anthracene dose-dependent response reducing plant biomass and associated to an alteration of the ultrastructure of a 23.6% of chloroplasts. Despite a reduction in total thallus-chlorophyll of 31.6% of Chl a and 38.4% of Chl b, this was not accompanied by a significant change in the net photosynthesis rate and maximum quantum efficiency (Fv/Fm). However, we found an increase in the activity of main ROS-detoxifying enzymes of 34.09% of peroxidase and 692% of ascorbate peroxidase, supported at transcriptional level with the upregulation of ROS-related detoxifying responses. Finally, we found that M. polymorpha tolerated anthracene-stress under the lowest concentration used and can suffer physiological alterations under higher concentrations tested related to the accumulation of anthracene within plant tissues. Our results show that M. polymorpha under PAH stress condition activated two complementary physiological responses including the activation of antioxidant mechanisms and the accumulation of the pollutant within plant tissues to mitigate the damage to the photosynthetic apparatus.

Tuning the redox potential of tyrosine-histidine bioinspired assemblies.

Photosynthesis powers our planet and is a source of inspiration for developing artificial constructs mimicking many aspects of the natural energy transducing process. In the complex machinery of photosystem II (PSII), the redox activity of the tyrosine Z (Tyrz) hydrogen-bonded to histidine 190 (His190) is essential for its functions. For example, the Tyrz-His190 pair provides a proton-coupled electron transfer (PCET) pathway that effectively competes against the back-electron transfer reaction and tunes the redox potential of the phenoxyl radical/phenol redox couple ensuring a high net quantum yield of photoinduced charge separation in PSII. Herein, artificial assemblies mimicking both the structural and redox properties of the Tyrz-His190 pair are described. The bioinspired constructs contain a phenol (Tyrz model) covalently linked to a benzimidazole (His190 model) featuring an intramolecular hydrogen bond which closely emulates the one observed in the natural counterpart. Incorporation of electron-withdrawing groups in the benzimidazole moiety systematically changes the intramolecular hydrogen bond strength and modifies the potential of the phenoxyl radical/phenol redox couple over a range of ~ 250mV. Infrared spectroelectrochemistry (IRSEC) demonstrates the associated one-electron, one-proton transfer (E1PT) process upon electrochemical oxidation of the phenol. The present contribution provides insight regarding the factors controlling the redox potential of the phenol and highlights strategies for the design of futures constructs capable of transporting protons across longer distances while maintaining a high potential of the phenoxyl radical/phenol redox couple.

Mid-infrared quantum optics in silicon.

Applied quantum optics stands to revolutionise many aspects of information technology, provided performance can be maintained when scaled up. Silicon quantum photonics satisfies the scaling requirements of miniaturisation and manufacturability, but at 1.55 µm it suffers from problematic linear and nonlinear loss. Here we show that, by translating silicon quantum photonics to the mid-infrared, a new quantum optics platform is created which can simultaneously maximise manufacturability and miniaturisation, while reducing loss. We demonstrate the necessary platform components: photon-pair generation, single-photon detection, and high-visibility quantum interference, all at wavelengths beyond 2 µm. Across various regimes, we observe a maximum net coincidence rate of 448 ± 12 Hz, a coincidence-to-accidental ratio of 25.7 ± 1.1, and, a net two-photon quantum interference visibility of 0.993 ± 0.017. Mid-infrared silicon quantum photonics will bring new quantum applications within reach.

Interaction of zinc and IAA alleviate aluminum-induced damage on photosystems via promoting proton motive force and reducing proton gradient in alfalfa

BackgroundIn acidic soils, aluminum (Al) competing with Zn results in Zn deficiency in plants. Zn is essential for auxin biosynthesis. Zn-mediated alleviation of Al toxicity has been rarely studied, the mechanism of Zn alleviation on Al-induced photoinhibition in photosystems remains unclear. The objective of this study was to investigate the effects of Zn and IAA on photosystems of Al-stressed alfalfa. Alfalfa seedlings with or without apical buds were exposed to 0 or100 μM AlCl3 combined with 0 or 50 μM ZnCl2, and then foliar spray with water or 6 mg L− 1 IAA.ResultsOur results showed that Al stress significantly decreased plant growth rate, net photosynthetic rate (Pn), quantum yields and electron transfer rates of PSI and PSII. Exogenous application of Zn and IAA significantly alleviated the Al-induced negative effects on photosynthetic machinery, and an interaction of Zn and IAA played an important role in the alleviative effects. After removing apical buds of Al-stressed alfalfa seedlings, the values of pmf, gH+ and Y(II) under exogenous spraying IAA were significantly higher, and ΔpHpmf was significantly lower in Zn addition than Al treatment alone, but the changes did not occur under none spraying IAA. The interaction of Zn and IAA directly increased Y(I), Y(II), ETRI and ETRII, and decreased O2− content of Al-stressed seedlings. In addition, the transcriptome analysis showed that fourteen functionally noted genes classified into functional category of energy production and conversion were differentially expressed in leaves of alfalfa seedlings with and without apical buds.ConclusionOur results suggest that the interaction of zinc and IAA alleviate aluminum-induced damage on photosystems via increasing pmf and decreasing ΔpHpmf between lumen and stroma.

The Alleviative Effects of Salicylic Acid on Physiological Indices and Defense Mechanisms of Maize (Zea Mays L. Giza 2) Stressed with Cadmium

The present study evaluated the physiological and biochemical mechanisms through which exogenous salicylic acid (SA) mitigates cadmium (Cd) stress in maize. The different concentrations of Cd included 0, 5, 10 µM CdCl2.3H2O. Half of plants received salicylic acid as a soil drench. Results showed that Cd exposure reduced chlorophyll contents, chlorophyll fluorescence, photosynthetic rate and activity of catalase (CAT). However, Cd stress enhanced non-photochemical quenching (NPQ), the production of malondialdehyde (MDA) and activities of key antioxidant enzymes superoxide dismutase (SOD), ascorbate peroxidase (APX), guaiacol peroxidase (POD). The increased activities of antioxidant enzymes and concentration of MDA were reduced by exogenous application of SA as a soil drench. Our research proves that SA, as a novel endogenous plant hormone exerts beneficial physiological effects on plants as it has a dual role in scavenging active oxygen species (AOS) and modulating redox balance to enhance photosynthetic performance in cadmium-stressed maize plants. It was concluded that SA improved plant tolerance under Cd contamination and may have alleviated the inhibitory effect of Cd on photosynthesis by protecting maize plants against oxidative damage as indicated by the marked decline in net photosynthetic rates, quantum yield and chlorophyll content as well as alteration of antioxidants activity and accumulation of MDA. Collectively, results of the present study provide an insight into the alleviative role of SA in Cd-stressed maize and propose SA as a potential candidate in mitigating Cd toxicity.

Increased irradiance availability mitigates the physiological performance of species of the calcifying green macroalga Halimeda in response to ocean acidification

Although negative responses of tropical calcifying organisms to ocean acidification have been widely reported, the modulating potential of irradiance combined with elevated pCO2 has not been well studied. In this study, the interactive effects of elevated pCO2 and irradiance availability on the physiology of calcifying macroalgae Halimeda cylindracea and Halimeda lacunalis were investigated using a fully factorial, 28-day aquaria coupling experiment. The results of the present study demonstrate that elevated pCO2 negatively influences growth, photosynthesis, calcification and other physiological processes of both Halimeda species. However, these negative effects could be mitigated to some extent by increased irradiance availability. Specific growth rate (SGR), net calcification rates (Gnet) and maximum quantum yield (Fv/Fm) decreased significantly by 6.84%–86.70%, 51.78%–62.29% and 2.37%–28.91% in elevated pCO2 treatments. However, SGR, Gnet and Fv/Fm increased by 3.39%–84.78%, 29.61%–40.68% and 1.68%–6.92% in high irradiance conditions, respectively. Chl-a in elevated pCO2 treatments was 7.75%–61.25% lower than ambient pCO2 conditions, while the carotenoid content increased by 12.12%–57.45% in low irradiance conditions from day 20–28. Malondialdehyde (MDA) content was higher in elevated pCO2 treatments. However, there was also a two- to four-fold increase in proline content in elevated pCO2 treatments. Tissue total organic carbon (TCorg) and nitrogen (TN) were positively correlated to CO2 enrichment. The results of the current study suggested that elevated pCO2 negatively influenced the physiological responses of Halimeda, while increased irradiance availability may enhance the metabolic performance in response to ocean acidification.