Effective Quantum Yield Of Photosystem Research Articles

Antarctic benthic diatoms after 10 months of dark exposure: consequences for photosynthesis and cellular integrity.

Antarctic algae are exposed to prolonged periods of extreme darkness due to polar night, and coverage by ice and snow can extend such dark conditions to up to 10 months. A major group of microalgae in benthic habitats of Antarctica are diatoms, which are key primary producers in these regions. However, the effects of extremely prolonged dark exposure on their photosynthesis, cellular ultrastructure, and cell integrity remain unknown. Here we show that five strains of Antarctic benthic diatoms exhibit an active photosynthetic apparatus despite 10 months of dark-exposure. This was shown by a steady effective quantum yield of photosystem II (Y[II]) upon light exposure for up to 2.5 months, suggesting that Antarctic diatoms do not rely on metabolically inactive resting cells to survive prolonged darkness. While limnic strains performed better than their marine counterparts, Y(II) recovery to values commonly observed in diatoms occurred after 4-5 months of light exposure in all strains, suggesting long recovering times. Dark exposure for 10 months dramatically reduced the chloroplast ultrastructure, thylakoid stacking, and led to a higher proportion of cells with compromised membranes than in light-adapted cells. However, photosynthetic oxygen production was readily measurable after darkness and strong photoinhibition only occurred at high light levels (>800 µmol photons m-2 s-1). Our data suggest that Antarctic benthic diatoms are well adapted to long dark periods. However, prolonged darkness for several months followed by only few months of light and another dark period may prevent them to regain their full photosynthetic potential due to long recovery times, which might compromise long-term population survival.

Effects of light qualities on growth and physiological-biochemical traits of Scutellaria baicalensis.

Canopy spectral composition significantly affects growth and functional traits of understory plants. In this study, we explored the optimal light condition suitable for enhancing Scutellaria baicalensis's yield and quality, aiming to provide scientific reference for the exploitation and utilization of medicinal plant resources in the understory of forests. We measured the responses of growth, morphology, biomass allocation, physiological traits, and secon-dary metabolites of S. baicalensis to different light qualities. S. baicalensis was cultured under five LED-light treatments including full spectrum light (control), ultraviolet-A (UV-A) radiation, blue, green, and red light. Results showed that UV-A significantly reduced plant height, base diameter, leaf thickness, leaf area ratio, and biomass of each organ. Red light significantly reduced base diameter, biomass, effective quantum yield of photosystem Ⅱ (ФPSⅡ), and total flavonoid concentration. Under blue light, root length and total biomass of S. baicalensis significantly increased by 48.0% and 10.8%, respectively, while leaf number and chlorophyll content significantly decreased by 20.0% and 31.6%, respectively. The other physiological and biochemical traits were consistent with their responses in control. Our results suggested that blue light promoted photosynthesis, biomass accumulation, and secondary metabolite synthesis of S. baicalensis, while red light and UV-A radiation negatively affected physiological and biochemical metabolic processes. Therefore, the ratio of blue light could be appropriately increased to improve the yield and quality of S. baicalensis.

Micronutrient Fertiliser Reinforcement by Fulvate–Lignosulfonate Coating Improves Physiological Responses in Tomato

Micronutrients are essential to plants, and enhancing their availability is one of the agronomic challenges to improving crop quality and yield. This study, under controlled greenhouse conditions, compares tomato plants’ responses to two different micronutrient EDTA-chelated formulations, one of them including a newly developed fulvate–lignosulfonate coating. Growth, yield, and several physiological parameters, including photosynthetic gas exchange, water-use efficiency, leaf nutrient content, leaf greenness and the effective quantum yield of photosystem II, were measured to compare their efficiency. The results showed that the new coated formulation significantly improved growth and most of the determined physiological parameters. At the end of the experiment, higher foliar levels of Fe (2.4-fold) and Mn (2.9-fold) were measured, revealing increased availability of lignofulfonate-complexed micronutrients compared to the traditional fertiliser. Moreover, the photosynthesis rate and stomatal conductance were 9- and 20-fold higher, respectively, than when using the standard fertiliser. In conclusion, the new coated fulvate–lignosulfonated fertiliser provided a more suitable source of micronutrients for tomato plant fertilisation, allowing for higher yields, which correlated with a generally improved physiological response.

Investigating the phytotoxic potential of Carlina acaulis essential oil against the weed Bidens pilosa through a physiological and metabolomic approach

Essential oils (EOs) are widely studied as possible candidates for new eco-friendly herbicides for weed management due to their phytotoxicity. In this study we tested the phytotoxic potential of the EO obtained from the roots of Carlina acaulis L. (Apiaceae) against the weed Bidens pilosa L. This EO, containing 98% of the polyacetylene carlina oxide, showed strong phytotoxic effects on the plant metabolism, such as leaf necrosis, reduction of relative water content and total leaf area, and an increase in the dry weight/fresh weight ratio, suggesting a water status alteration. The EO also damaged the photosynthetic machinery, as evidenced by the significant reduction of the effective quantum yield of photosystem II (ΦII) and the maximum quantum yield of photosystem II (Fv/Fm). In addition, the non-photochemical quenching (ΦNPQ) significantly increased after spraying with C. acaulis EO. Damage to photosystem II was further demonstrated through the reduction of manganese and calcium concentrations, possibly due to an alteration in the correct functionality of the Mn4Ca cluster of the PSII. Metabolomics analysis revealed an accumulation of branched-chain amino acids, such as isoleucine and valine, which is commonly related to osmotic alterations under drought stress situations and a general reduction in sugar content (fructose, glucose, mannose, among others), suggesting reduction of the photosynthetic efficiency too. Overall, these findings suggest C. acaulis EO as a promising natural product with phytotoxic potential against weeds that deserves further investigation.

Chlorophyll fluorescence parameter as a predictor of tomato growth and yield under CO2 enrichment in protective cultivation

Greenhouse crops production has been improved by CO2 enrichment commercially. The impact of a threshold level of elevated CO2 (e[CO2]) on the effective quantum yield of photosystem II (ФPSII, chlorophyll fluorescence parameter), which is linked to crop yield, crop growth and fruit quality, is still uncertain. Many previous studies cultivated C3 crops under 550–700 µmol·mol-1, not beyond this range. Hence, tomato plants were grown under ambient CO2 (a[CO2], 500 µmol·mol-1) and e[CO2] (700, 850, and 1000 µmol·mol-1): named as EC700, EC850, and EC1000, respectively, under uniform environmental conditions for two growing seasons to investigate the response of ФPSII along with four photosynthetically active radiation intensities and plant growth to continuous CO2 concentration [CO2]. Under four constant PAR intensities during autumn-winter 2020 and spring-summer 2021, the order of mean ФPSII values under e[CO2] were explored as EC700 > EC1000 > EC850 > a[CO2] and EC700 > EC850 > EC1000 > a[CO2], respectively. The optimum total fruit yield was stimulated under EC700 by 74.04% and 55.86% during autumn-winter 2020 and spring-summer 2021, respectively, as compared to a[CO2]. The results showed that water use efficiency related to yield (WUEy) were enhanced by reducing the stomatal conductance under e[CO2] as compared to a[CO2]. Optimum WUEy was enhanced by 55.91–210.87% under EC700 compared to a[CO2]. The principal component analysis showed strong correlation of ФPSII with plant height, yield and water use efficiency in autumn-winter 2020 and spring-summer 2021, LAI in spring-summer 2021, weak correlation with stem diamter in autumn-winter 2020 and spring-summer 2021, indicated the strong effect of ФPSII on plant growth and yield under e[CO2]. The EC1000 in autumn-winter 2020 and EC700 in spring-summer 2021 were found more influential by the analytic hierarchy process to get optimum crop production, no significant difference between the ranking scores of EC1000 and EC700 during autumn-winter 2020 was found. Thus, the overall optimum impact of e[CO2] on tomato growth was explored under EC700. The findings of this study are beneficial to greenhouses crops production commercially and could be used as references for validating the climate change impact modelling.

Effects of irradiance and nitrate on photosynthesis in the seagrass Cymodocea nodosa

The effects of temperature, irradiance, and other environmental variables on photosynthesis in seagrasses are well understood. However, little information is available regarding the effects of the nitrate concentration in seawater on the photosynthetic characteristics of marine vegetation. Thus, the aim of this study was to determine the effect of the nitrate concentration in seawater on the effective quantum yield of the seagrass Cymodocea nodosa. Cymodocea nodosa shoots were incubated under different irradiance levels and with different nitrate concentrations. In contrast, a decrease in transmittance and an exponential increase in the absorptance of the shoots were observed as a function of increasing nitrate levels. Furthermore, the effective quantum yield of photosystem II (ΦPSII) in C. nodosa shoots increased exponentially as the nitrate concentration in the media increased. The ΦPSII values in the shoots decreased as irradiance increased and reached minimum values at solar noon or 2 h afterward. However, the decrease of ΦPSII values was 4-fold greater in shoots incubated under full solar radiation (100% natural incident irradiance, Eo) compared to those of shoots incubated with 20% Eo. The ΦPSII values decreased to almost zero in shoots pre-incubated with no nitrate (0 μM NO3–), whereas ΦPSII values in shoots pre incubated with 25 and 100 μM NO3– decreased by approximately 25% of their initial values. Collectively, these results indicate that nitrogen levels in seawater regulate the effective quantum yield values of C. nodosa, which suggests that the photosynthetic characteristics of this seagrass might be regulated by fluctuating nitrate levels in the water column such as those that are observed in upwelling regions.

Kaolin, boron, and zinc increase photosynthetic activity and mitigate the effects of light stress in heliconia grown under semi-arid conditions

Tropical flowers species of high commercial importance such as heliconia, if grown in semi-arid regions, can have their photosynthesis compromised and, consequently, flower production, due to high irradiation. Foliar applications of kaolin and the mineral nutrients boron and zinc may be an alternative for reducing the harmful effects of light stress. Thus, the objective of this study was to evaluate the effects of the application of these mitigating substances on physiological aspects in two species of heliconia grown under semi-arid conditions. The experimental design was randomized blocks in split-plot scheme, with four repetitions and four plants per replication. The plots consisted of two species of heliconias (H. psittacorum cv. Red Opal and H. bihai cv. Lobster Claw Two) and the subplots corresponded to three light stress mitigating substances (kaolin, boron + zinc, and control). The species H. psittacorum showed higher chlorophyll indexes, photosynthesis rate, stomatal conductance, and transpiration rate than the species H. bihai. The applications of kaolin and the mineral nutrients boron + zinc caused increases in the chlorophyll a and total chlorophyll indices, photosynthesis rate, carboxylation efficiency, effective quantum yield of photosystem II, leaf temperature, and vapor pressure deficit in plants of H. bihai and H. psittacorum. It is concluded that the foliar application of kaolin and the minerals boron and zinc reduce the harmful effects caused by high luminosity, with emphasis on the kaolin particle film, which promoted better photosynthetic performance and reduced the effects of non-stomatic limitation of photosynthesis, being a promising strategy for the cultivation of heliconia in semi-arid conditions. In addition, both kaolin and the minerals boron and zinc promote the production of flowering stems of heliconia with better quality and post-harvest durability.

Galactoglucomannan oligosaccharides alleviate cadmium toxicity by improving physiological processes in maize

Phosphate fertilisers and past mining activity are significant source of cadmium (Cd) pollution; thus, the concentration of Cd in agricultural soils has been substantially rising. Various substances have been tested for their potential to alleviate the toxicity of Cd and stimulate the accumulation of Cd in plant organs. This study brought new insight of the impact of galactoglucomannan oligosaccharides (GGMOs) on the maize plants grown under/in Cd stress. The application of GGMOs reduced concentration of Cd in the maize leaves and thus GGMOs increased their growth (by 24%), concentration of photosynthetic pigments (up to 39.4%), effective quantum yield of photosystem II (up to 29.6%), and net photosynthetic rate (up to 19.6%). The concentrations of stress markers increased in the Cd and Cd + GGMOs treatment; however, significantly lower concentration was detected in the Cd + GGMOs treatment (malondialdehyde by 21.7%, hydrogen peroxide by 13%). The concentration of auxin increased almost by two-fold in the Cd + GGMOs treatment compared to the Cd treatment. The recovered auxin level and enhanced nutrient uptake are proposed mechanisms of GGMOs’ action during stress. GGMOs are molecules with biostimulant potential that could support vitality of maize plants in Cd stress.

Potential of halophytic plant Atriplex hortensis for phytoremediation of metal-contaminated soils in the mine of Tamra

ABSTRACT Contamination by metals from anthropogenic activities has significant consequences for ecosystems and human health. Indeed, these elements, by nature are non-biodegradable, have a high ecotoxicity, and could be involved in many pathologies. The genus Atriplex is well adapted to extreme environmental conditions and exhibits heavy metal accumulation properties. This study aimed to examine the response of halophytic plant (Atriplex hortensis) in soil polluted with toxic elements. To address this, we measured plant growth parameters, chlorophyll fluorescence parameters of optimal (Fv/Fm), PSII quantum yield (ϕPSII), and stomatal conductance (gS). By applying this metallic stress to the A. hortensis plant during 2 months of growth, morphological analyses show no reduction in the leaf area, elongation of the stems and roots, and dry matter compared to controls grown on sand. Biochemical and physiological analyses show a slight decrease in the content of foliar chlorophyll pigments (chlorophyll total) and carotenoids as a function of time in soil contaminated with heavy metals. In these experiments, we investigated the photosynthetic rate and chlorophyll fluorescence parameters; the results indicated that on polluted and sandy soil, the values of chlorophyll fluorescence parameters of optimal (Fv/Fm), effective quantum yield of photosystem II photochemistry (ϕPSII) and stomatal conductance (gS) have no significant difference. The results obtained in our study show that A. hortensis can grow in environments heavily polluted by metals, such as zinc, lead, and cadmium. As a result, the cultivation of these species, often recommended for the phytostabilization of sites polluted by metals, could be established. The results obtained are in favor of the involvement of Atriplex hortensis in a phytoremediation project to clean up contaminated soils.

Phytostimulator Application after Cold Stress for Better Maize (Zea mays L.) Plant Recovery

Phytostimulators are attracting considerable attention for replacing mineral fertilizers, which are of environmental concern, being especially forbidden in organic farming. The benefit of applying such products based on microorganisms (e.g., algae extract) or minerals of nano-meter-sized particle (e.g., nanofertilizers) is that plants can uptake them faster than soil fertilizers, targeting plant growth by regulating their phytohormones, as well as improving plant tolerance to unfavorable environmental conditions (e.g., cold stress). The aim of this study was to test and evaluate the effects of three commercial phytostimulators, called biostimulants (a seaweed-based extract—Kelpak®, mineral nanoparticles—Nano Active®, zinc nanoparticles—Dynamic Cresco®) on yield, chlorophyll content, level of CO2 assimilation and the effectiveness of PSII under cold stress. The values of all chlorophyll fluorescence and photosynthetic parameters significantly decreased under cold, which indicated a strong inhibition of light-phase photosynthesis in maize leaves. Predicted by the regression analysis minimum, 20 days was enough for maize plants to recover from the inhibition caused by stress damages in their photosynthetic apparatus. At the final measurement in maize growth stage BBCH 65, all the tested phytostimulators showed significant effects in increased values of effective quantum yield of photosystem II, maximum photosynthetic efficiency of PSII and electron transport rate. At this stage, Dynamic Cresco® and Nano Active® treatment significantly increased the value of maximum net photosynthetic rate (15.37% and 18.85%, respectively) and leaf chlorophyll content (7.8% and 8.7%, respectively). The application of Dynamic Cresco® significantly promoted total dry weight by 43.4% in comparison to control under stress growth conditions with cold. These phytostimulators can be used to enhance yield and physiological status of plants after abiotic stress (such as cold) to improve crop productivity, especially in organic farming.

Influence of Salicylic and Succinic Acids on the Indicators of Growth and Photosynthesis and the Content of Chlorophyll in Wheat Plants Grown under Water Deficiency

In the conditions of climate warming, the frequency and intensity of droughts have increased, therefore, the development of methods that increase the resistance of crops to water scarcity is of great importance. The aim of the work is to study the effect of salicylic and succinic acids on growth indicators, photosynthetic activity indicators and on the content of pigments in the leaves of plants grown under conditions of irrigation and water scarcity. Wheat plants were grown under laboratory conditions. The seeds were pre-soaked in distilled water (control), in a solution of 0.05 mM salicylic acid or in a solution of 0.05 mM succinic acid. After the appearance of the first roots on the 3rd day, the germinated seeds were transferred to 200 ml vegetative vessels filled with soil and grown at 22-24C in natural light and daily watering. On day 5, the plants were divided into groups watering and water shortage. The water shortage group was stopped watering until the end of the experiment. On day 11, the indicators of the maximum and effective quantum yield of photosystem II, photochemical and non-photochemical quenching and electron flux density were determined using a FRAME-fluorimeter. On the 16th day of growing plants, the quantitative content of chlorophyll a and b and carotenoids was determined, the relative water content in shoots and roots was calculated. The relative water content in plants hardly changed when treated with acids under irrigation conditions, but in case of water deficiency, treatment with succinic acid reduced the water content in the root by 6%. In conditions of lack of moisture, acid treatment increased the effective quantum yield of photosystem II, the photochemical quenching coefficient of chlorophyll and the electron flux density by an average of 17-20%. Under irrigation conditions, treatment with salicylic and succinic acids caused a decrease in the content of chlorophyll a (by 11 and 32%, respectively), carotenoids (by 57 and 32%) and an increase in the content of chlorophyll b (by 49 and 23%). When treated with succinic acid, the total content of chlorophyll a + b decreased by 14%. In conditions of water deficiency, treatment with salicylic acid increased the relative content of chlorophylls and carotenoids by an average of 2.6 and 3.3 times, when treated with amber - by 3.5 and 2.0 times, respectively, compared with the control in terms of raw weight. The use of the studied acids can be recommended for potential use in agriculture.

Ray-tracing analysis on the far-red induced light-capturing ability of kale

Far-red (FR, 700–800 nm) light has recently been used to regulate phytochrome-mediated morphological responses in vertical farms. Long-term morphological changes in different FR intensities are well known, but changes in photosynthetic capacity have not been sufficiently investigated. The objectives of this study were to quantitatively analyze the growth, photosynthetic responses, and light interception of kale (Brassica oleracea L. var. acephala) depending on the FR fraction. The plants were cultivated at a photosynthetic photon flux density (PPFD) of 240 μmol m−2 s−1 under red and white LEDs with FR LED (peak at 730 nm) for 16 h. The FR fractions determined as FR/R+FR were FR0.07 (control), FR0.28, FR0.60, and FR0.72. To evaluate the morphological and physiological responses in each FR fraction, the growth, chlorophyll content, chlorophyll fluorescence, P700 absorbance change, and photosynthetic rate were measured. Light interception was quantitatively calculated using 3D-scanned plant models with physiological changes and ray-tracing simulations. The dry weight of shoot and root, total petiole length, and leaf area increased with increasing FR fractions. As a result of ray-tracing analysis, the light interception and canopy photosynthetic rate increased with high FR fraction treatment. As the FR fraction increased, the effective quantum yield of photosystem II [Y(II)], the parameters of the JIP test that is related to quantum yield and efficiency for electron transport in photosystem II and photosystem performance indices decreased. Despite the decreased electron transport efficiency, the canopy photosynthetic rate increased in relation to the FR fraction. In conclusion, the increase in the FR fraction increased the yield of kale because of the synergistic improvement in morphological change and canopy photosynthesis.

Xanthophyll cycle-related non-photochemical quenching protects Sargassum thunbergii from high light-induced photoinhibition

As a common macroalga living in the intertidal zone, Sargassum thunbergii (Sargassaceae, Phaeophyta) is often exposed to drastic changes in solar photosynthetically active radiation during a diurnal cycle; thus, the potential photosynthetic adaptation processes deserve attention. In this work, we examined the photosynthetic performance and xanthophyll cycle activity of this alga in response to high light (1,200 μmol photons m–2 s–1, the average in-situ light intensity at noon) by using chlorophyll fluorescence and high-performance liquid chromatography (HPLC). On exposure to high light, a rapid decrease in the effective quantum yield of photosystem II (PSII) (Y(II)) occurred, indicating down-regulation of PSII activity; a corresponding increase in non-photochemical quenching (NPQ) indicated the existence of energy-dissipating cycles. After turning off the light, Y(II) gradually increased to 0.7, accompanied by a decrease in NPQ. However, no complete recovery of NPQ was observed, and its value remained at ≈4, even after an 80-min dark treatment. The size of the xanthophyll cycle pigments pool was quantified using HPLC and was found to be ≈16 mol mol−1 Chl a × 100. The activity of the xanthophyll cycle, characterized by a de-epoxidation state (DPS), could reach up to ≈0.5. Such a large pigments pool and rapid accumulation of zeaxanthin may allow S. thunbergii to induce high values of NPQ (≈10). These results were further complemented by inhibitor (dithiothreitol, DTT) and pre-illumination experiments showing that (1) both NPQ and the xanthophyll cycle could be inhibited by DTT, and there was always a strong positive correlation between NPQ and DPS; (2) the previously formed antheraxanthin exhibited a long retention time and a slow epoxidation; and (3) the long retention of antheraxanthin contributed to a rapid accumulation of zeaxanthin. In conclusion, our present study demonstrated that xanthophyll cycle-induced NPQ can significantly protect S. thunbergii from light fluctuations in the intertidal zone.

Nghiên cứu ảnh hưởng của hạt nano cobalt hoá trị 0 lên hàm lượng chlorophyll A và các thông số quang hợp của cây đậu tương Glycine max (L). Merrill “DT96”

The application of nanotechnology in agriculture is a promising way to increase crop production and yield, reduce the amount of fertilizer, increase the storage time of the productions and protect the environmental sustainability. Soybean is one of the four important crops of Vietnam's agriculture and a source of food for humans and domestic animals. In this study, the effect of zerovalent cobalt nanoparticles with different concentrations (0; 0.17; 0.33 and 100 mg/kg seed) on chlorophyll a content and photosynthesis parameters of soybean plant Glycine max (L). Merr. DT96 which was planted in the autumn-winter crop in Xuan Hoa, Phuc Yen, Vinh Phuc were carried out. The obtained results showed that zerovalent cobalt nanoparticles had a positive effect on the photosynthetic parameters of soybean plants. At the used concentration of 0.33 mg cobalt/kg seed, the chlorophyll a content and photosynthetic parameters of soybean were the highest and there was a statistically significant difference compared with control. The chlorophyll a content tends to increase gradually and reaches the maximum value of 1.77 ± 0.05 mg/g fresh leaves after 40 days of sowing. The parameters related to chlorophyll fluorescence such as Fo (initial fluorescence), Fm (maximal fluorescence), Fv/Fm (maximal photochemical efficiency), effective quantum yield of photosystem II (FPSII), photosynthetic electron transport rate (ETR), Pn (net photosynthetic rate) of soybean seedlings which were treated by cobalt nanoparticles were higher than the control (except at the concentration of 100 mg/kg). The soybean seeds treated by cobalt nanoparticles had increased the chlorophyll a content of leaves and photosynthetic efficiency, leading to improve productivity of soybean.

Suppression of leaf growth and photosynthetic capacity as an acclimation strategy to nitrogen deficiency in a nitrogen-sensitive and shade-tolerant plant Panax notoginseng

ABSTRACT Photosynthesis is susceptible in response to nitrogen (N) deficiency. However, the acclimation of shade-tolerant and high-N sensitive species to N deficiency is unclear. Leaf morpho-physiological traits, photosynthetic performance related parameters were examined in a shade-tolerant and high-N sensitive species P. notoginseng grown under different N levels. Lower N content and Chl content were recorded in the N0-grown P. notoginseng. The maximum values of leaf morpho-physiological traits, photosynthetic rate, and photosynthetic N use efficiency (PNUE) were obtained in the N15-grown P. notoginseng. Coefficients for leaf N allocation into the carboxylation and light-harvesting system components in the N0-grown plants were significantly higher than others. N0 and N7.5 plants showed higher K phase. N addition decreased the absorption and capture of the light energy per unit area (ABS/RC and TRO/RC) and non-photochemical quenching (NPQ). Photochemical quenching (qP), electron transport rate (ETR), and effective quantum yield of photosystem II (ϕPSII) were reduced in the N0-grown plants. The reduction of light-harvesting and utilization capacity not only leads to a decrease in PNUE, but also induces the damage of PSII reaction center. Overall, the inhibition of leaf growth and photosynthetic capacity is an essential strategy for high-N sensitive and shade-tolerant plants in response to N deficiency.

Revegetation of mining-impacted sites with a tropical native grass: Constraints of climate seasonality and trace-element accumulation

The iron ore mining activity results in considerable waste production and impacts on surrounding ecosystems. Natural recovery of impacted areas is absent or occurs slowly, especially when associated with prolonged dry seasons in tropical regions. The objective of this work was to unveil the mechanisms of Paspalum densum (Poir.) grass to overcome the periods of seasonal drought and its metal accumulation in areas impacted by iron mining, a tailings storage facilities and surrounding ferruginous grassland in Brazil. Lower mortality was observed among individuals in the tailings storage facilities, with a 74.3% survival rate. In contrast, after the beginning of the dry season, all individuals died in the ferruginous grassland. The plants in the tailings deposits showed better nutrition, with a higher concentration of P, Cu, Fe, Zn, Mn and greater capacity to accumulate Pb and Cd over time. Pb was the element with highest bioconcetration factor (BCF) and bioaccumulation coefficient (BAC), while Mn was the one with the highest translocation factor (TF). The dry season resulted in reduced chlorophyll a, b and total and effective quantum yield of photosystem II (PSII) of P. densum individuals. However, the plants in the tailings storage facilities showed adjustments to overcome the effects of drought, with an increase in the concentration of proline in leaves and reduction of oxidative damage (MDA and H2O2) at the end of the dry season. The grass P. densum showed rapid acclimatization in the tailings storage facilities and resistance to drought through antioxidant and photosynthetic adjustments and was still able to bioaccumulate and translocate in plant tissues some metals present in the iron ore impacted sites.

Chromosome 3A harbors several pleiotropic and stable drought-responsive alleles for photosynthetic efficiency selected through wheat breeding.

Water deficit is the most severe stress factor in crop production threatening global food security. In this study, we evaluated the genetic variation in photosynthetic traits among 200 wheat cultivars evaluated under drought and rainfed conditions. Significant genotypic, treatments, and their interaction effects were detected for chlorophyll content and chlorophyll fluorescence parameters. Drought stress reduced the effective quantum yield of photosystem II (YII) from the anthesis growth stage on. Leaf chlorophyll content measured at anthesis growth stages was significantly correlated with YII and non‐photochemical quenching under drought conditions, suggesting that high throughput chlorophyll content screening can serve as a good indicator of plant drought tolerance status in wheat. Breeding significantly increased the photosynthetic efficiency as newer released genotypes had higher YII and chlorophyll content than the older ones. GWAS identified a stable drought‐responsive QTL on chromosome 3A for YII, while under rainfed conditions, it detected another QTL on chromosome 7A for chlorophyll content across both growing seasons. Molecular analysis revealed that the associated alleles of AX‐158576783 (515.889 Mbp) on 3A co‐segregates with the NADH‐ubiquinone oxidoreductase (TraesCS3A02G287600) gene involved in ATP synthesis coupled electron transport and is proximal to WKRY transcription factor locus. This allele on 3A has been positively selected through breeding and has contributed to increasing the grain yield.

24-Epibrassinolide Simultaneously Stimulates Photosynthetic Machinery and Biomass Accumulation in Tomato Plants under Lead Stress: Essential Contributions Connected to the Antioxidant System and Anatomical Structures

Several toxic pollutants are released into the atmosphere through human activities. Among these pollutants, lead (Pb) is a non-biodegradable element that can cause reduced cell division, impact negatively on the biosynthesis of photosynthetic pigments, and lower biomass accumulation, which can lead to plant death. 24-epibrassinolide (EBR) is a plant growth regulator with broad benefits on physiological functions and biochemical responses, conferring tolerance to plants against several biotic and abiotic stresses. The experiment was randomized with four treatments, two lead concentrations (0 and 200 µM Pb, described as −Pb and +Pb, respectively) and two EBR (0 and 100 nM EBR, described as −EBR and +EBR, respectively). We detected a negative impact of Pb stress in tomato plants; however, the exogenous application of EBR induced protection on leaf anatomy and photosynthetic apparatus, mitigating the Pb impacts on growth. This steroid enhances the root and leaf structures (in root tissue, the epidermis thickness; and in the leaf, palisade parenchyma, and spongy parenchyma), improving the membrane selectivity, light energy absorption, and CO2 fixation. Applying 200 µM Pb and 100 nM EBR caused an increase in superoxide dismutase, catalase, ascorbate peroxidase, and peroxidase activity (by 26%, 18%, 25%, and 20%, respectively). Moreover, the improvements obtained on photosynthetic pigments, electron transport rate, the effective quantum yield of photosystem II photochemistry, and net photosynthetic rate prove the benefits and protection of photosynthetic apparatus, resulting in increased biomass accumulation, with increases of 95%, 115%, 74%, and 92% in leaf, root, stem, and the whole plant, respectively. Taken together, our findings confirm that EBR alleviates the damages provoked by Pb stress in tomatoes.

Effect of microplastics on silty loam soil properties and radish growth

Abstract Microplastics (particles of plastics <5 mm) affect the physical, biological and hydrological properties of agricultural soil, as well as crop growth. We investigated the effect of the addition of three microplastics (high-density polyethylene (HDPE), polyvinyl chloride (PVC), and polystyrene (PS)) at a concentration of 5% (w/w) to a silty loam soil on selected soil properties and growth of radish (Raphanus sativus L. var. sativus). Changes in the soil properties and radish growth in three microplastic treatments were compared with the control. Soil properties (bulk density, hydraulic conductivity, sorptivity, water repellency) were estimated for each treatment at the beginning and at the end of the radish growing period (GP). The bulk density was significantly lower in the HDPE and PVC treatments compared to the control within the measurement at the beginning of the GP and in all microplastic treatments compared to the control at the end of the GP. The values of hydraulic conductivity and water sorptivity did not show significant differences between any treatments within the measurement at the beginning of GP, but they were significantly higher in the HDPE treatment compared to the control at the end of the GP. The growth of radish was characterized by the plant biomass and effective quantum yield of Photosystem II (Y (II)). We did not find a statistically significant difference in the total biomass of radish between any of the experimental treatments, maybe due to used concentration of microplastics. The mean value of Y (II) was significantly higher in all microplastic treatments compared to control only within the last measurement at the end of the GP. A statistically significant change of Y(II) in all microplastic treatments may indicate functional shift in soil properties; however, the measured values of the soil characteristics have not shown the significant changes (except for the bulk density values in all microplastic treatments and hydraulic conductivity together with sorptivity in HDPE treatment within the measurement at the end of GP).

Repeated colonization of alpine habitats by Arabidopsis arenosa viewed through freezing resistance and ice management strategies.

Success or failure of plants to cope with freezing temperatures can critically influence plant distribution and adaptation to new habitats. Especially in alpine environments, frost is a likely major selective force driving adaptation. In Arabidopsis arenosa (L.) Lawalrée, alpine populations have evolved independently in different mountain ranges, enabling studying mechanisms of acclimation and adaptation to alpine environments. We tested for heritable, parallel differentiation in freezing resistance, cold acclimation potential and ice management strategies using eight alpine and eight foothill populations. Plants from three European mountain ranges (Niedere Tauern, Făgăraș and Tatra Mountains) were grown from seeds of tetraploid populations in four common gardens, together with diploid populations from the Tatra Mountains. Freezing resistance was assessed using controlled freezing treatments and measuring effective quantum yield of photosystem II, and ice management strategies by infrared video thermography and cryomicroscopy. The alpine ecotype had a higher cold acclimation potential than the foothill ecotype, whereby this differentiation was more pronounced in tetraploid than diploid populations. However, no ecotypic differentiation was found in one region (Făgăraș), where the ancient lineage had a different evolutionary history. Upon freezing, an ice lens within a lacuna between the palisade and spongy parenchyma tissues was formed by separation of leaf tissues, a mechanism not previously reported for herbaceous species. The dynamic adjustment of freezing resistance to temperature conditions may be particularly important in alpine environments characterized by large temperature fluctuations. Furthermore, the formation of an extracellular ice lens may be a useful strategy to avoid tissue damage during freezing.