Chl Content Research Articles

Unveiling Fatty Acid Profiles of the Parasitic Plants Orobanche foetida Poiret. and Orobanche crenata Forsk. and Modulation of Faba Bean (Vicia faba L.) Fatty Acid Composition in Response to Orobanche Infestation.

Broomrapes (Orobanche spp.) are root parasitic plants that threaten agricultural production in many parts of the world. In this study, the effect of two orobanche species, Orobanche crenata and O. foetida, on faba bean plants was studied in Tunisia. The two orobanche species inhibited both biomass production and pod formation, decreased the chlorophyll (Chl) content and total lipid (TL), and enhanced electrolyte leakage (EL) and lipid peroxidation. Concomitantly, orobanche parasitism induced a lower degree of fatty acid (FA) unsaturation due to a shift in the FA composition. On the other hand, with regard to orobanche seeds, oleic and linoleic acids were the predominant FA in the two orobanche species. After orobanche seed germination and penetration of host tissues, all the orobanche development stages showed a decrease in the TL content and changes in the FA composition in comparison to orobanche seeds. The level of TL was equal to or lower in all parasite development stages (except for S4) than that in the roots and leaves of healthy faba bean plants. These results suggest that the negative effect of orobanche infestation on faba bean development can be attributed to the reduced chlorophyll content and alteration in membrane stability attested by the reduced TL level and FA unsaturation.

Deep learning based soft-sensor for continuous chlorophyll estimation on decentralized data

Monitoring the concentration of pigments like chlorophyll (Chl) in water-bodies is a key task to contribute to their conservation. However, with the existing sensor technology, measurement in real-time and with enough frequency to ensure proper risk management is not completely feasible. In this work, with the concept of data-driven soft-sensing, three hydrophysical features are used together with three meteorological ones to estimate the concentration of Chl in two tributaries of the River Thames. Data driven models, specifically neural networks, are used with three learning approaches: individual, centralized and federated. Data reduction scenarios are proposed in order to analyze the performance of each approach when less data is available. The best results in the training are usually obtained with the individual approach. However, the federated learning provides better generalization ability. It was also observed that in most of the cases the results of the federated learning approach improve those of the centralized one.

Effects of Typhoon Chanthu on Marine Chlorophyll a, Temperature and Salinity

A typhoon is a severe weather process in tropical oceans. Typhoon transit is often accompanied by strong convective weather, such as gales and rainstorms, which threatens fishery, property, and human safety. In this study, the effects of typhoon Chanthu on chlorophyll a (Chl a), temperature, and ocean surface salinity are analyzed using remote sensing data. The results illustrate that before the transit of Chanthu (6–12 September), the mean concentration of Chl a and sea surface salinity (SSS) are low (0.74 mg/m3, 30.59 psu, respectively), while the mean sea surface temperature (SST) is high (29.01 °C). After the typhoon transits (13–30 September), the mean Chl a concentration and salinity increase (1.29 mg/m3, 30.87 psu respectively), while the mean SST decrease (27.43 °C). The Ekman pumping transports nutrients from the deep ocean to the surface layer, promotes the photosynthesis of surface phytoplankton, and increases the concentration of sea surface Chl a. Typhoon Chanthu causes the mixing and entrainment of the upper ocean, which causes the deep cold water of the ocean to rise into the mixed layer and cause the SST to decrease. Severe vertical mixing transports deep high-salt water to the surface, causing SSS to rise. The results of this study have important scientific significance and application value for developing coastal economy, aquaculture, and fishery.

Seasonal fluctuations in pigment content of macrophytes: implications for monitoring brownification

Seasonal variations of floating-leaved macrophyte Nuphar lutea chlorophyll content were studied in lakes with different water quality. The aim was to investigate whether chlorophyll content of the plants could be used as an indicator of brownification. The relationship between chlorophyll a and b (CHL a:b) of the petioles decreased with increasing water colour. The relationship between CHL a:b and turbidity was less clear. The sum concentration of chlorophyll a and b of the petioles did not respond to water colour consistently. The strong effect of water colour on petiole CHL a:b was probably due to the effect of colour on the attenuation of short-wavelength light. CHL b absorbs short-wavelength light more effectively than CHL a. To maximize the harvesting of short-wavelength light, macrophytes increase their CHL b concentration relative to CHL a. The results suggested that petiole CHL a:b of N. lutea can be used as an indicator of brownification. High phytoplankton biomass may, however, disturb the relationship between water colour and CHL a:b. Therefore, the most reliable results are obtained by sampling several times during the growing season. The floating leaves cannot be recommended as brownification indicators because the relationship between their CHL content and water colour is weak.

Response of Dahlia Photosynthesis and Transpiration to High-Temperature Stress

The high temperature may cause difficult growth or bloom in the summer, which is the key problem limiting the cultivation and application of dahlia. The photosynthetic physiological mechanisms of dahlia under high temperature stress were studied to provide a theoretical basis for expanding the application range of cultivation and annual production. Two dahlia varieties, ‘Tampico’ and ‘Hypnotica Tropical Breeze’, were used as test materials and were treated for 1 d or 2 d at temperatures of 35/30 °C or 40/35 °C (day/night: 14 h/10 h) and then recovered at 25/20 °C for 7 d. A 25/20 °C treatment was used as the control. The results are as follows: (1) High-temperature stress resulted in the chlorophyll (Chl) content, Fv/Fm, transpiration rate (Tr), net photosynthetic rate (Pn), and water potential decreasing significantly, and the Chl content, Tr, and stomatal density of ‘Tampico’ were higher than those of ‘Hypnotica Tropical Breeze’ during the same period. (2) After the two dahlia varieties were treated with high-temperature stress and recovered at 25/20 °C for 7 d, the plant morphology and various physiological indices under the 35/30 °C treatment gradually returned to normal, with ‘Tampico’ in better condition than ‘Hypnotica Tropical Breeze’. (3) Both dahlia varieties could not withstand the stress of 40/35 °C for 2 days.

Physical mechanisms affecting phytoplankton variability along the Chilean coast

Chile has high phytoplankton production due to being a classic example of an Eastern Boundary Upwelling System. Monthly averaged chlorophyll-α (Chl) and physical parameters (sea surface temperature, precipitation rate, southerly and westerly winds) were studied off the Chilean coast from 2002 to 2018, in order to understand the primary production along this important ocean margin. The coastal margin was split into three zones and ten sub-sections. The Northern Zone had a low phytoplankton production with small seasonal variability, except in its north. This pattern is due to a narrow shelf, weak winds, lack of precipitation and relatively stable weather conditions driven by the Southeast Pacific Subtropical Anticyclone (SPSA). The Central Zone presented a seasonally varying production, with a high Chl concentration in summer and early spring. This is linked to the SPSA movement and sunlight reduction during the winter. A high Chl activity is seen in the Southern Zone despite this Zone being at the limits of the SPSA effect, leading to weak longshore winds only during the warm season. Overall, this study has demonstrated the importance of shelf width and the upwelling driven by the presence or absence of the SPSA for ocean primary production. Thus, the most productive region is from 35°S to 45°S owing to both variables being present.

Transcriptomic-metabolomic analysis of magnesium-stimulated in peel coloration of Satsuma mandarin

Magnesium (Mg) has been found to promote the color change citrus peel, but the underlying mechanism remains unclear. In this study, Mg application treatment significantly increased the Mg content in the peel of Satsuma mandarin fruit during the expansion stage (90–150 days after flowering). Mg fertilizer treatment was also found to significantly reduce chlorophyll (Chl) a content and increase β, β-xanthophyll (β-cryptoxanthin, zeaxanthin, neoxanthin), and abscisic acid (ABA) content in the flavedo during the key period of color change in Satsuma mandarin (165–195 days after flowering). Under Mg fertilizer treatment, Chl biosynthesis genes (CitGGDR, CitCHLH, CitCHLM, CitCHL27, and CitPORA) was down-regulated and that of Chl degradation genes (CitNYC, CitPPH, CitPAO, and CitRCCR) was up-regulated, which resulted in a lower Chl content in the flavedo than the control. Moreover, Mg fertilizer treatment up-regulated carotenoid biosynthesis genes (CitPSY, CitPDS, CitZDS, CitLCYb1, CitLCYb2, CitZEP, CitNCED2, and CitNCED3), leading to the accumulation of β, β-xanthophyll and ABA in the flavedo. Mg fertilizer treatment also promoted sugar (mainly fructose, glucose, and sucrose) accumulation in fruit flavedo, which showed significant negative correlations with Chl, α-carotene, lutein, and β-carotene, but positive correlations with β, β-xanthophyll compositions, and ABA in the flavedo. An analysis integrating transcriptome and metabolome data revealed that Mg may promote the color change of Satsuma mandarin fruit flavedo by regulating various metabolic pathways related to peel coloration, such as sugar accumulation, Chl degradation, carotenoid and ABA biosynthesis, and carbon fixation. The results can explain the regulatory pathways and networks of Mg-induced citrus peel coloration.

Prioritization of Physio-Biochemical Selection Indices and Yield-Attributing Traits toward the Acquisition of Drought Tolerance in Chickpea (Cicer arietinum L.).

Chickpea is widely grown in rainfed areas of developing countries because of its nutritional abundance and adaptability. To overcome the environmental effect of drought on yield, a characteristic-linked selection strategy is proved as well-thought-out and advantageous for the development of drought-tolerant cultivars. To precisely understand the contribution of various physio-biochemical and yield-attributing traits toward drought tolerance in chickpea (Cicer arietinum L.), forty chickpea genotypes were evaluated in the years 2020-2021 and 2021-2022 under normal irrigated as well as drought-stressed conditions. Among the studied genotypes, genotype ICC4958 retained the highest chl content (0.55 mg g-1 FW), minimal electrolyte leakage, and superoxide dismutase (1.48 U/mg FW) and peroxidase (2.21 µmol/min/g FW) activities while cultivar JG11 maintained the maximum relative water content and proline accumulation. The principal-component-based biplots prioritized the physio-biochemical and yield-accrediting characteristics based on their association significance and contribution to terminal drought tolerance. Under drought stress, grain yield per plant was depicted to have a strongly positive association with canopy temperature depression, catalase, superoxide dismutase, and peroxidase activities as well as total soluble sugar, proline, and chlorophyll content, along with the numbers of pods and biological yield per plant. These identified physio-biochemical and yield-attributing traits can be further deployed to select drought-tolerant chickpea genotypes for the breeding of climate-smart chickpea genotypes.

Growth responses of tomato plants to different wavelength ratios of amber, red, and blue light

The differential effects of light quality and quantity are under scrutiny so that energy-efficient plant production may be optimized. This study aimed to determine the combined effects of amber (595 nm), red (635 nm), and blue (445 nm) wavelengths at different light intensities on tomato plant growth. Plants were treated for 12 days with combined light-emitting diode (LED) wavelengths, at a photosynthetic photon flux density (PPFD) ranging from 232 to 1660 μmol m−2s−1 with a 16 h d−1 photoperiod. Mean fresh mass of tomato plants treated with amber-red light (AR) was 22% greater than plants treated with blue-amber (BA) light and 67% greater than blue-red (BR) light. Plants treated with BA exhibited 36% greater fresh mass than plants treated with BR light. Mean dry mass of plants treated with AR light was 30% greater compared to BR light, and the dry mass of plants treated with BA and BR was statistically similar. Plants grown under BR had 28% and 35% smaller leaf area compared with those grown under BA and AR, respectively. Mean height of the plants treated with AR increased by 24 and 52% compared to plants grown under BA and BR lights, respectively. Maximum stem diameter was observed at 1000 μmol m−2s−1 for AR and BA, and 1200 μmol m−2s−1 for BR. Specific leaf area (SLA) decreased with the increase of PPFD levels up to 1000 μmol m−2s−1 for all the light treatments. A PPFD above 1000 μmol m−2s−1 showed an increase in SLA for plants cultivated with AR and AB. SLA for plants treated with RB was stable above 1000 μmol m−2s−1 PPFD levels. Plants treated with BR light had 25 and 38% higher chlorophyll content compared to plants treated with BA and AR light, respectively. Maximum yield and chlorophyll content data indicate that using Chl content to correlate full plant photosynthetic and growth potential is inappropriate. Findings suggest that a high percentage of amber light (>75%) in a full-spectrum LED regimen may augment controlled environment crop production.

Foliar-applied silicon and selenium nanoparticles modulated salinity stress through modifying yield, biochemical attribute, and fatty acid profile of Physalis alkekengiL.

Soil salinity is a major environmental problem owing to its negative impact on agricultural productivity and sustainability. Nanoparticles (NPs) have recently been highlighted for their ability to alleviate salinity stress. The current study aimed to alleviate salt stress by using silicon (Si) and selenium (Se) NPs on the growth and physiological attributes of Physalis alkekengi L. Plants were irrigated with saline water at 50, 100, and 200 mM NaCl, and Si NPs (200 mg L-1) and Se NPs (50 mg L-1) were sprayed on leaves three times in a pot experiment in 2022. Leaf chlorophyll (Chl) content, antioxidant capacity, and fatty acid (FA) profile of fruits were measured to find the effects of NPs and salinity in the plants. Salinity at 50 mM did not significantly differ from the control, but at 100-200 mM, salt stress had a substantial impact on the majority of traits. Compared with non-saline conditions, 200 mM NaCl led to decreases in shoot weight (40%), fruit weight (30%), Chl a (30%), Chl b (39%), anthocyanin (31%), ascorbic acid (16%), total phenolic content (TPC, 11%) but increases in total soluble solids (TSS, 79%), titration acidity (TA, 17%), and TSS/TA (52%) in plants without spraying the NPs. However, Si and Se NPs modulated salinity stress by increasing shoot and fruit weight, Chl content, anthocyanin, and TPC, and with decreasing TSS and TSS/TA. Salinity elevated polyunsaturated fatty acids (PUFAs) and lowered monounsaturated fatty acids (MUFAs). According to multivariate analysis, 50 mM and control were found to be in the same cluster, whereas 100 and 200 mM were shown to be in different clusters. Foliar application of Si and Se NPs at 200 and 50 mg L-1, respectively, can be recommended for mitigating salt stress at 100-200 mM NaCl inP. alkekengiL. Plants. Farmers can use the findings to increase the ability of Si and Se NPs to protect plants against salt.

Increase in cotton yield through improved leaf physiological functioning under the soil condition of reduced chemical fertilization compensated by the enhanced organic liquid fertilization.

Low agricultural nutrient input efficiency remains a significant impediment for crop production globally. To address this issue in cotton agroecosystems, there is a need to develop sustainable crop nutrient management strategies to achieve high crop yields. We hypothesized that organic liquid fertilizer (OF) combined with reduced chemical fertilizer (CF) would enhance cotton yield by improving leaf functioning and soil properties. However, the underlying mechanism and its related process is poorly understood. This study explored the effects of OF combined with reduced CF on cotton yield, physiology and soil properties. Treatments included a single application of CF (CF: N, P2O5 and K2O applied at 228, 131 and 95 kg ha-1) and combined applications of OF and CF (OF0.6-OF1.4) in the following ratios: OF0.6, OF+60% CF; OF0.8, OF+80% CF; OF1.0, OF+100% CF; OF1.2, OF+120% CF; OF1.4, OF+140% CF. The result showed that compared with CF, OF0.8, OF1.0 and OF1.2 increased soil organic matter (SOM) content by 9.9%, 16.3% and 23.7%, respectively. Compared with CF, the OF0.6, OF0.8, OF1.0, and OF1.2 treatments increased leaf area (LA) by 10.6-26.1%, chlorophyll content (Chl content) by 6.8-39.6%, and the efficiency of photosystem II (PSII) light energy (Y(II)), electron transfer rate of PSII (ETR) and photochemical quenching (qP) by 3.6-26.3%, 4.7-15.3% and 4.3-9.8%, respectively. The OF0.8 treatment increased net photosynthetic rate (P n), stomatal conductance (G s) and transpiration rate (E) by 22.0%, 27.4% and 26.8%, respectively, resulting in higher seed cotton yield. The seed cotton yield and economic coefficient were positively correlated with P n, E, G s and Y(II) from the full boll stage to the boll opening stage. In summary, the OF0.8 treatment can maintain a high SOM content and photosynthetic performance with reduced chemical fertilizer input without sacrificing yield. The integration of OF+80% CF (OF0.8) is a promising nutrient management strategy for highly efficient cotton production under mulch drip irrigation systems.

Hydrogel-potassium humate composite alleviates cadmium toxicity of tobacco by regulating Cd bioavailability

Cadmium (Cd) removal from soil to reduce Cd accumulation in plants is essential for agroecology, food safety, and human health. Cd enters plants from soil and affects plant growth and development. Hydrogels can easily combine with Cd, thereby altering its bioavailability in soil. However, few studies have evaluated the effects of hydrogel on the complex phytotoxicity caused by Cd uptake in plants and the microbial community structure. Herein, a new poly (acrylic acid)-grafted starch and potassium humate composite (S/K/AA) hydrogel was added to soil to evaluate its impact on tobacco growth and the soil microenvironment. The results indicate that the addition of S/K/AA hydrogel can significantly improve the biomass, chlorophyll (Chl) content, and photosynthetic capacity of tobacco plants during Cd stress conditions, and decrease Cd concentration, probably by affecting Cd absorption through the expression of Cd absorption transporters (e.g., NRAMP5, NRAMP3, and IRT1). Moreover, the application of S/K/AA hydrogel not only reduced the accumulation of reactive oxygen species (ROS), but also reduced the antioxidant activities of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT), suggesting that S/K/AA hydrogel alleviates Cd toxicity via a non-antioxidant pathway. Notably, we further analyzed the effectiveness of the hydrogel on microbial communities in Cd-contaminated soil and found that it increased the Cd-tolerant microbial community (Arthrobacter, Massilia, Streptomyces), enhancing the remediation ability of Cd-contaminated soil and helping tobacco plants to alleviate Cd toxicity. Overall, our study provides primary insights into how S/K/AA hydrogel affects Cd bioavailability and alleviates Cd toxicity in plants.

The role of LAI and leaf chlorophyll on NDVI estimated by UAV in grapevine canopies

Despite the wide use of the Normalized Difference Vegetation Index (NDVI) in precision viticulture, there are no studies aimed at discriminating the contribution of plant biomass from that of leaf chlorophyll on canopy NDVI. Leaf area index (LAI) and leaf chlorophyll (Chl) were concomitantly monitored by ground measurements and projected canopy area (PCA), canopy volume (CV) and NDVI by high resolution UAV multispectral images in fully productive “Sangiovese” grapevines either grown in containers or in the field and subjected to different irrigation regimes over two consecutive years. NDVI values calculated from only vine canopy pixels (NDVIUAV) and NDVI obtained from mixed ground-canopy pixels (simulated Satellite NDVI, NDVISAT) were both evaluated as potential predictor of LAI and leaf Chl concentration.The seasonal patterns of LAI and leaf Chl concentration were affected by irrigation, showing differences depending on field vs container-grown conditions. In situations where a decoupling between LAI and leaf Chl occurred, NDVIUAV and NDVISAT showed different responses: NDVIUAV patterns strictly followed the leaf Chl ones, whereas NDVISAT was more affected by LAI. The coefficient of determination between NDVIUAV and leaf Chl ranged between 0.51 and 0.78, that between NDVIUAV and leaf Chl from 0.01 to 0.76, depending on the irrigation-growing conditions combination. NDVISAT was a better predictor of LAI (R2=0.69) than NDVIUAV (R2=0.42). In field-grown vines the relationships between NDVI (both UAV and SAT) and LAI was stronger than in potted ones. The relationships between LAI and PCA (R2=0.44) or LAI and canopy volume (R2=0.77) were both significant. The results allowed to confirm the two main hypotheses behind this experiment: i) leaf Chl concentration had a greater impact than LAI on NDVI values obtained from vine canopy pixels (NDVIUAV), whereas NDVISAT was more affected by LAI; ii) The canopy volume from UAV images was a better predictor of LAI than NDVI and the resulting relationship showed a better temporal stability.

Overexpression of chloroplastic Zea mays NADP-malic enzyme (ZmNADP-ME) confers tolerance to salt stress in Arabidopsis thaliana.

The C4 plants photosynthesize better than C3 plants especially in arid environment. As an attempt to genetically convert C3 plant to C4, the cDNA of decarboxylating C4 type NADP-malic enzyme from Zea mays (ZmNADP-ME) that has lower Km for malate and NADP than its C3 isoforms, was overexpressed in Arabidopsis thaliana under the control of 35S promoter. Due to increased activity of NADP-ME in the transgenics the malate decarboxylation increased that resulted in loss of carbon skeletons needed for amino acid and protein synthesis. Consequently, amino acid and protein content of the transgenics declined. Therefore, the Chl content, photosynthetic efficiency (Fv/Fm), electron transport rate (ETR), the quantum yield of photosynthetic CO2 assimilation, rosette diameter, and biomass were lower in the transgenics. However, in salt stress (150mM NaCl), the overexpressers had higher Chl, protein content, Fv/Fm, ETR, and biomass than the vector control. NADPH generated in the transgenics due to increased malate decarboxylation, contributed to augmented synthesis of proline, the osmoprotectant required to alleviate the reactive oxygen species-mediated membrane damage and oxidative stress. Consequently, the glutathione peroxidase activity increased and H2O2 content decreased in the salt-stressed transgenics. The reduced membrane lipid peroxidation and lower malondialdehyde production resulted in better preservation, of thylakoid integrity and membrane architecture in the transgenics under saline environment. Our results clearly demonstrate that overexpression of C4 chloroplastic ZmNADP-ME in the C3 Arabidopsis thaliana, although decrease their photosynthetic efficiency, protects the transgenics from salinity stress.

Coordination of leaf photosynthetic traits and chloroplast relocation of the C4 plant Setaria palmifolia

Setaria palmifolia (Poaceae), an NADP-malic enzyme type C4 grass, is distributed from the understory to the margins of forests. To reveal how this C4 plant acclimates to habitats with contrasting light regimes, we documented the behavior of chloroplast relocation and determined patterns of chloroplast relocation and photosynthetic characteristics in response to the light of S. palmifolia grown under different light regimes. Through the observation of leaf sections and measurement of leaf transmittance (T), we confirmed that mesophyll (M) cells of S. palmifolia performed avoidance and accumulation responses, resulting in an increase and decrease in T, respectively. Measurements of gas exchange revealed that the leaf photosynthetic characteristics of S. palmifolia were modulated by growth light. Shade-grown plants significantly increased dry-weight-based chlorophyll (Chl) contents and specific leaf area (SLA), indicating increased light capture. These plants, however, displayed a reduced light-saturated photosynthetic rate (Pmax) and light saturation point (LSP) compared to unshaded plants. The patterns of chloroplast relocation were closely aligned with the photosynthetic response. Shade-grown plants displayed significantly faster kinetics, a greater extent of chloroplast relocation, and lower incident light for the induction of the avoidance response than unshaded plants. The coordination patterns of chloroplast relocation and photosynthetic response suggest that chloroplast relocation in S. palmifolia complements its leaf photosynthetic responses to light availability. The ability to adjust its photosynthetic behavior and perform chloroplast relocation may enable this C4 species to thrive in habitats with various light conditions.

Effects of the nitrate and ammonium ratio on plant characteristics and Erythropalum scandens Bl. substrates.

Erythropalum scandens Bl. is a woody vegetable with high nitrogen demand that inhabits southern China. Ammonium and nitrate are the two main forms of inorganic nitrogen that plants directly absorb. A pot experiment was performed to determine the growth, physiological responses, and preferences of 12-month-old E. scandens seedlings for ammonium and nitrate. Aboveground and underground growth indexes, biomass, physiological and biochemical indexes (chlorophyll [Chl], soluble sugar, soluble protein and free proline contents), and substrate pH and nitrogen contents were determined under different nitrate and ammonium ratios (0 NO3-: 100 NH4+, 25 NO3-: 75 NH4+, 50 NO3-: 50 NH4+, 75 NO3-: 25 NH4+, and 100 NO3-: 0 NH4+), and the control (0 NO3-: 0 NH4+). The results showed that ammonium and nitrate improved the growth and physiological status of E. scandens seedlings in most of the treatments compared to the control. The aboveground growth status and biomass accumulation of E. scandens seedlings were significantly better under the 0 NO3-: 100 NH4+ treatment during fertilization compared with all other treatments. However, the growth status of the underground parts was not significantly different among treatments. Significant differences in osmoregulator content, except for soluble sugars, and Chl content were observed. Soluble sugars and soluble proteins were highest under the 0 NO3-: 100 NH4+ treatment at the end of fertilization (day 175). However, free proline accumulated during fertilization and the increase in NO3- indicated that excessive use of NO3- had a negative effect on the E. scandens seedlings. The order of accumulating nitrogen content was leaves > roots > stems. The highest N accumulation occurred in the aboveground parts under the 0 NO3-: 100 NH4+ treatment, whereas the highest N accumulation occurred in the underground parts under the 50 NO3-: 50 NH4+ treatment. Substrate pH increased at the end of fertilization (day 175) compared with the middle stage (day 75), while total nitrogen, ammonium, and nitrate were highly significantly different among the treatments. Total nitrogen and NH4+ content were the highest under the 0 NO3-: 100 NH4+ treatment, while NO3- content was the highest under the 100 NO3-: 0 NH4+ treatment. In conclusion, 12-month-old E. scandens seedlings grew best, and had better physiological conditions in NH4+ than NO3-. The 0 NO3-:100 NH4+ treatment (ammonium chloride 3.82 g/plant) resulted in the best growth and physiological conditions. Most of the growth and physiological indexes were inhibited with the increase in nitrate.

Effect of different levels of EDTA on phytoextraction of heavy metal and growth of Brassica juncea L.

Heavy metal pollution of soil is a major concern due to its non-biodegradable nature, bioaccumulation, and persistence in the environment. To explore the probable function of EDTA in ameliorating heavy metal toxicity and achieve the sustainable development goal (SDG), Brassica juncea L. seedlings were treated with different concentrations of EDTA (0, 1.0, 2.0, 3.0, and 4.0 mM Kg-1) in heavy metal-polluted soil. Plant samples were collected 60 days after sowing; photosynthetic pigments, H2O2, monoaldehyde (MDA), antioxidant enzymes, and ascorbic acid content, as well as plant biomass, were estimated in plants. Soil and plant samples were also examined for the concentrations of Cd, Cr, Pb, and Hg. Moreover, values of the phytoremediation factor were utilized to assess the accumulation capacity of heavy metals by B. juncea under EDTA treatments. In the absence of EDTA, B. juncea seedlings accrued heavy metals in their roots and shoots in a concentration-dependent manner. However, the highest biomass of plants (roots and shoots) was recorded with the application of 2 mM kg-1 EDTA. Moreover, high levels (above 3 mM kg-1) of EDTA concentration have reduced the biomass of plants (roots and shoots), photosynthetic area, and chlorophyll content. The effect of EDTA levels on photosynthetic pigments (chlorophyll a and b) revealed that with an increment in EDTA concentration, accumulation of heavy metals was also increased in the plant, subsequently decreasing the chlorophyll a and b concentration in the plant. TLF was found to be in the order Pb> Hg> Zn> and >Ni, while TF was found to be in the order Hg>Zn>Ni>Pb, and the best dose was 3 mM kg-1 EDTA for Hg and 4 mM kg-1 for Pb, Ni, and Zn. Furthermore, hyperaccumulation of heavy metals enhanced the generation of hydrogen peroxide (H2O2), superoxide anions (O2•-), and lipid peroxidation. It also interrupts mechanisms of the antioxidant defense system. Furthermore, heavy metal stress reduced plant growth, biomass, and chlorophyll (chl) content. These findings suggest that the exogenous addition of EDTA to the heavy metal-treated seedlings increases the bioavailability of heavy metals for phytoextraction and decreases heavy metal-induced oxidative injuries by restricting heavy metal uptake and components of their antioxidant defense systems.

Synergistic effects of warming and low salinity enhanced the production of Gracilariopsis lemaneiformis in the warming drainage zone of Tianwan Nuclear Power Plant, China

Tianwan Nuclear Power Plant in China is the world's largest coastal nuclear power plant in terms of its total installed capacity both in operation and under construction. Its operations create a warming drainage zone that is potentially beneficial to the large-scale cultivation of macroalgae. Moreover, natural freshwater river flow and ocean acidification caused by increasing levels of atmospheric CO2 bring new uncertainties to the growth and photophysiology of commercial macroalgae. In this study, two CO2 concentrations (LC, 400 μatm; HC, 1000 μatm), two salinity levels (LS, 20 ppt; HS, 30 ppt), and two temperatures (LT, 20 °C; HT, 26 °C) were tested to examine the synergistic effects of warming and salinity on the economically important macroalga Gracilariopsis lemaneiformis under ocean acidification. The results showed that the synergistic effect of LS and HT treatments significantly promoted the growth of G. lemaneiformis under LC treatment, but this promotion effect was more obvious under HC treatment. In contrast, HSLT conditions inhibited G. lemaneiformis growth under both LC and HC conditions. Under HC treatment, warming and low salinity together increased the maximum photosynthetic rate and the maximum electron transport rate of G. lemaneiformis. Photosynthetic pigment analysis revealed that LS had a significantly negative effect on the contents of chlorophyll a (Chl a) and carotenoids (Car.), and HT had an obviously adverse influence on the contents of Chl a, Car., phycoerythrin, and phycocyanin. Moreover, the dual limitation of LSHT conditions significantly reduced the contents of Chl a and Car. under HC and LC conditions. These findings suggested that warming and low salinity synergically improved the growth and photosynthetic performance of G. lemaneiformis, especially under ocean acidification. The results provide a scientific basis for macroalgal cultivation as part of environmental restoration around nuclear power plants generally and year-round cultivation of G. lemaneiformis in northern China specifically.

The influences of phenology, spatial distribution, and nitrogen form on Long Island Sound phytoplankton biomass and taxonomic composition

Long Island Sound (LIS), USA, is an urban estuary that receives excessive nitrogen (N) inputs resulting in ecosystem impairments, such as hypoxia and algal blooms. Despite established linkages between N concentrations and algal blooms worldwide, connections between N forms and phytoplankton assemblages within LIS remain less characterized, representing a critical information gap for water quality management. This study assessed the spatio-temporal distributions of phytoplankton biomass and abundances, N, and other key water quality parameters Mar-2020 to Oct-2021 in Western (WLIS), Central (CLIS), and Eastern LIS (ELIS). During both study years, mean dissolved inorganic N (DIN) concentrations were significantly higher during fall than other seasons (ANOVA: p < 0.004), coincident with diatom blooms. Diatoms were abundant throughout the study, though WLIS flagellate numbers rose during Jul and Aug both years. Smaller (<5 μm diameter) cells generally contributed most to overall chlorophyll a (Chl a) and with significantly higher summer biomass in WLIS and CLIS than other seasons (ANOVA; WLIS: p < 0.004; CLIS: p < 0.006). Across LIS, there was a clear west to east decline in levels of Chl a, DIN, and the proportional contribution of picoplankton to overall phytoplankton biomass; however, seasonal mean concentrations of Chl a, nutrients, and other water quality parameters did not significantly differ between sampling (0.5 and 2 m) depths except for ELIS summer temperature and Chl a (T-test; both p = 0.002). Given climate change challenges, such as warmer temperatures enhancing blooms particularly in systems enriched with anthropogenic N, findings indicate that N-management strategies should re-evaluate targets spanning LIS. Study results are likely applicable to other eutrophic urban estuaries worldwide.

Effects of hydrogen sulfide on the growth and physiological characteristics of Miscanthus sacchariflorus seedlings under cadmium stress

As a gas signal molecule, hydrogen sulfide (H2S) can participate in many physiological and biochemical processes such as seed germination and photosynthesis regulation. In order to explore the regulatory effect of H2S on the growth of Miscanthus sacchariflorus under Cd stress and to provide sufficient theoretical basis for the complex action of H2S and energy plants to remediate soil pollution. In this experiment, the effects of different concentrations of H2S (10, 25, 50, 100, 300, 400, 500 μmol·L−1 (μM)) pretreatment on the growth index, lipid peroxidation degree, chlorophyll (Chl) content, osmoregulation substance content, antioxidant enzyme activity and non-enzymatic antioxidant content of M. sacchariflorus under Cd stress (50 μM) were studied. The results showed that under Cd stress, the reactive oxygen species (ROS) content in the body of M. sacchariflorus was unbalanced, and the growth were severely inhibited, the activities of antioxidant enzymes, such as catalase (CAT) and superoxide dismutase (SOD) significantly decreased, and the content of osmoregulation substance, ascorbic acid (AsA) and glutathione (GSH) significantly increased. With the increase of H2S concentration, its effect on resisting Cd stress can be shown as "low concentration promotes, high concentration inhibits". When the concentration of H2S ≤ 300 μM, although there was no significant difference in Cd content compared with Cd treatment alone, it can regulate the activities of peroxidase (POD), SOD, glutathione reductase (GR) and monodehydroascorbate reductase (MDHAR), increase the content of osmoregulation substances, oxidized glutathione (GSSG), and the transformation rate of AsA and dehydroascorbic acid (DHA) to reduce the oxidative damage and improve the growth and photosynthetic indicators of plants; when the concentration of H2S ≥ 400 μM, Cd content in the ground and root decreased significantly, but the transport factor increased significantly, the growth status of M. sacchariflorus were more severely inhibited by the combined stress of H2S and Cd. In this experiment, it was found that the concentration of H2S pretreatment ≤ 300 μM could regulate the growth of M. sacchariflorus under Cd stress to normal level, and when the treatment concentration was 50 μM, the effect was the best. It will provide a new idea for the treatment of contaminated soil by energy plants.