Maximum Quantum Yield Of Photosystem Research Articles

Effects of clonal fragmentation on Pyrrosia nuda depend on growth stages in a rubber plantation.

Clonal fragmentation helps to assess clonal plants' growth resilience to human and environmental disturbance. Although clonal integration in epiphytes in tropical rubber plantations is important to understand their role in enhancing biodiversity and ecosystem services, research on this subject is limited. These plantations are typically monospecific economic forests that face increased anthropogenic disturbances. In this study, we selected the clonal fern Pyrrosia nuda to study its survival status, biomass, maximum quantum yield of photosystem II (Fv/Fm), and frond length in response to the level of clonal fragmentation in a tropical rubber plantation. The results showed that (1) clonal fragmentation significantly negatively affected the survival rate, biomass, and frond length of clonal plants, but with minimal effects on Fv/Fm at different growth stages; (2) the performance of a ramet (e.g., biomass or frond length) increased with ramet developmental ages and decreased with the number of ramets in a clonal fragment. The age-dependent impacts of clonal fragmentation provide insights into the biodiversity conservation of epiphytes and forest management in man-made plantations. Therefore, to better conserve the biodiversity in tropical forests, especially in environment-friendly rubber plantations, there is a need to reduce anthropogenic disturbances and alleviate the level of fragmentation.

Improvement of the Quality of Wild Rocket (Diplotaxis tenuifolia) with Respect to Health-Related Compounds by Enhanced Growth Irradiance.

For healthier human nutrition, it is desirable to provide food with a high content of nutraceuticals such as polyphenolics, vitamins, and carotenoids. We investigated to what extent high growth irradiance influences the content of phenolics, α-tocopherol and carotenoids, in wild rocket (Diplotaxis tenuifolia), which is increasingly used as a salad green. Potted plants were grown in a climate chamber with a 16 h day length at photosynthetic photon flux densities varying from 20 to 1250 μmol m-2 s-1. Measurements of the maximal quantum yield of photosystem II, FV/FM, and of the epoxidation state of the violaxanthin cycle (V-cycle) showed that the plants did not suffer from excessive light for photosynthesis. Contents of carotenoids belonging to the V-cycle, α-tocopherol and several quercetin derivatives, increased nearly linearly with irradiance. Nonintrusive measurements of chlorophyll fluorescence induced by UV-A and blue light relative to that induced by red light, indicating flavonoid and carotenoid content, allowed not only a semiquantitative measurement of both compounds but also allowed to follow their dynamic changes during reciprocal transfers between low and high growth irradiance. The results show that growth irradiance has a strong influence on the content of three different types of compounds with antioxidative properties and that it is possible to determine the contents of flavonoids and specific carotenoids in intact leaves using chlorophyll fluorescence. The results may be used for breeding to enhance healthy compounds in wild rocket leaves and to monitor their content for selection of appropriate genotypes.

Allelochemicals of Alexandrium tamarense and its algicidal mechanism for Prorocentrum donghaiense and Heterosigma akashiwo

The effects of culture filtrate of Alexandrium tamarense on Prorocentrum donghaiense and Heterosigma akashiwo were investigated, including determination of algal density, photosynthesis, intracellular enzyme content and activity. The filtrate of A. tamarense had a stronger inhibitory effect on P. donghaiense than H. akashiwo, and the inhibitory effect decreased with higher temperature treatment of the filtrate. Instantaneous fluorescence (Ft) and maximum quantum yield of photosystem II (Fv/Fm) values of both kinds of target algae were reduced as exposed to the filtrate of A. tamarense, which proved that allelopathy could inhibit the normal operation of photosynthetic system. The increase of Malondialdehyde (MDA) content of the two kinds of target algae indicated that the cell membrane was seriously damaged by allelochemicals released by A. tamarense. The different responses of Superoxide Dismutase (SOD) and Catalase (CAT) activity in two kinds of target algae demonstrated the complexity and diversity of allelopathic mechanism. The filtrate of A. tamarense also influenced the metabolic function (ATPases) of P. donghaiense and H. akashiwo, and the influence on P. donghaiense was greater. Liquid-liquid extraction was used to extract and isolate allelochemicals from the filtrate of A. tamarense. It was found that only component I with molecular weight of 424.2573 and 434.2857 could inhibit the growth of P. donghaiense by HPLC-MS.

Genetic dissection of ten photosynthesis-related traits based on InDel- and SNP-GWAS in soybean.

A total of 416 InDels and 112 SNPs were significantly associated with soybean photosynthesis-related traits. GmIWS1 and GmCDC48 might be related to chlorophyll fluorescence and gas-exchange parameters, respectively. Photosynthesis is one of the main factors determining crop yield. A better understanding of the genetic architecture for photosynthesis is of great significance for soybean yield improvement. Our previous studies identified 5,410,112 single nucleotide polymorphisms (SNPs) from the resequencing data of 219 natural soybean accessions. Here, we identified 634,106 insertions and deletions (InDels) from these 219 accessions and used these InDel variations to perform principal component and linkage disequilibrium analysis of this population. The genome-wide association study (GWAS) were conducted on six chlorophyll fluorescence parameters (chlorophyll content, light energy absorbed per reaction center, quantum yield for electron transport, probability that a trapped exciton moves an electron into the electron transport chain beyond primary quinone acceptor, maximum quantum yield of photosystem II primary photochemistry in the dark-adapted state, performance index on absorption basis) and four gas-exchange parameters (intercellular carbon dioxide concentration, stomatal conductance, net photosynthesis rate, transpiration rate) and revealed 416 significant InDels and 112 significant SNPs. Based on GWAS results, GmIWS1 (encoding a transcription elongation factor) and GmCDC48 (encoding a cell division cycle protein) with the highest expression in the mapping region were determined as the candidate genes responsible for chlorophyll fluorescence and gas-exchange parameters, respectively. Further identification of favorable haplotypes with higher photosynthesis, seed weight and seed yield were carried out for GmIWS1 and GmCDC48. Overall, this study revealed the natural variations and candidate genes underlying the photosynthesis-related traits based on abundant phenotypic and genetic data, providing valuable insights into the genetic mechanisms controlling photosynthesis and yield in soybean.

Impact of treated wastewater on plant growth: leaf fluorescence, reflectance, and biomass-based assessment.

The study evaluated the impact of treated wastewater on plant growth through the use of hyperspectral and fluorescence-based techniques coupled with classical biomass analyses, and assessed the potential of reusing treated wastewater for irrigation without fertilizer application. Cherry tomato (Solanum lycopersicum) and cabbage (Brassica oleracea L.) were irrigated with tap water (Tap), secondary effluent (SE), and membrane effluent (ME). Maximum quantum yield of photosystem II (Fv/Fm) of tomato and cabbage was between 0.78 to 0.80 and 0.81 to 0.82, respectively, for all treatments. The performance index (PI) of Tap/SE/ME was 2.73, 2.85, and 2.48 for tomatoes and 4.25, 3.79, and 3.70 for cabbage, respectively. Both Fv/Fm and PI indicated that the treated wastewater did not have a significant adverse effect on the photosynthetic efficiency and plant vitality of the crops. Hyperspectral analysis showed higher chlorophyll and nitrogen content in leaves of recycled water-irrigated crops than tap water-irrigated crops. SE had 10.5% dry matter composition (tomato) and Tap had 10.7% (cabbage). Total leaf count of Tap/SE/ME was 86, 111, and 102 for tomato and 37, 40, and 42 for cabbage, respectively. In this study, the use of treated wastewater did not induce any photosynthetic-related or abiotic stress on the crops; instead, it promoted crop growth.

Mechanistic insight into the impact of polystyrene microparticle on submerged plant during asexual propagules germination to seedling: Internalization in functional organs and alterations of physiological phenotypes

Asexual reproduction is one of the most important propagations in aquatic plants. However, there is a lack of information about the growth-limiting mechanisms induced by microplastics on the submerged plant during asexual propagule germination to seedling. Hence, we investigated the effects of two sizes (2 µm, 0.2 µm) and three concentrations (0.5 mg/L, 5 mg/L, and 50 mg/L) of polystyrene microplastics (PSMPs) on Potamogeton crispus turion germination and seedling growth. Both PSMPs sizes were found in P. crispus seedling tissues. Metabolic profile alterations were observed in leaves, particularly affecting secondary metabolic pathways and ATP-binding cassette transporters. Metal elements are indispensable cofactors for photosynthesis; however, alterations in the metabolic profile led to varying degrees of reduced concentrations in magnesium, iron, copper, and zinc within P. crispus. Therefore, the maximum quantum yield of photosystem II significantly decreased in all concentrations with 0.2 µm-PSMPs, and at 50 mg/L with 2 µm-PSMPs. These findings reveal that internalization of microplastics, nutrient absorption inhibition, and metabolic changes contribute to the negative impact on P. crispus seedlings.

Interplay among photoreceptors determines the strategy of coping with excess light in tomato.

This study investigates photoreceptor's role in the adaption of photosynthetic apparatus to high light (HL) intensity by examining the response of tomato wild type (WT) (Solanum lycopersicum L. cv. Moneymaker) and tomato mutants (phyA, phyB1, phyB2, cry1) plants to HL. Our results showed a photoreceptor-dependent effect of HL on the maximum quantum yield of photosystem II (Fv /Fm ) with phyB1 exhibiting a decrease, while phyB2 exhibiting an increase in Fv /Fm . HL resulted in an increase in the efficient quantum yield of photosystem II (ΦPSII ) and a decrease in the non-photochemical quantum yields (ΦNPQ and ΦN0 ) solely in phyA. Under HL, phyA showed a significant decrease in the energy-dependent quenching component of NPQ (qE ), while phyB2 mutants showed an increase in the state transition (qT ) component. Furthermore, ΔΔFv /Fm revealed that PHYB1 compensates for the deficit of PHYA in phyA mutants. PHYA signaling likely emerges as the dominant effector of PHYB1 and PHYB2 signaling within the HL-induced signaling network. In addition, PHYB1 compensates for the role of CRY1 in regulating Fv /Fm in cry1 mutants. Overall, the results of this research provide valuable insights into the unique role of each photoreceptor and their interplay in balancing photon energy and photoprotection under HL condition.

The acute and chronic low-temperature stress responses in Porites lutea from a relatively high-latitude coral reef of the South China Sea

Relatively high-latitude coral reefs could be potential “refuges” for corals under climate change. One of the most important aspects limiting their availability as refuges is low-temperature stress. However, the mechanisms underlying the response of coral holobionts to low-temperature stress is unclear. In this study, we aimed to explore the underlying mechanisms by recording the maximum quantum yields of photosystem II (Fv/Fm) and transcriptome responses of Porites lutea under acute (1–2 weeks) and chronic (6–12 weeks) low-temperature stress at 20°C and 14°C. The P. lutea samples were collected from a relatively high-latitude coral reef in the South China Sea (109°00′–109°15′E and 21°00′–21°10′ N). The study suggested that: (1) Under acute low-temperature stress, the Fv/Fm of Symbiodiniaceae dropped by 64%, which was significantly higher than the 49% observed under chronic stress. Low-temperature stress inhibited photosystem II(PSII) functioning, with greater inhibition under acute stress. (2) Downregulation of sugar metabolism-related genes under low-temperature stress implied that the decrease in energy was due to obstruction of PSII. (3) Under low-temperature stress, calcification-related genes were downregulated in coral hosts, possibly because of energy deprivation caused by inhibited photosynthesis, Symbiodiniaceae expulsion, and oxidative phosphorylation uncoupling in mitochondria. (4) Acute low-temperature stress induced the upregulation of genes related to the TNF signaling pathway and endoplasmic reticulum stress, promoting apoptosis and coral bleaching. However, these phenomena were not observed during chronic stress, suggesting acclimation to chronic low-temperature stress and a greater survival pressure of acute low-temperature stress on coral holobionts. In conclusion, low-temperature stress inhibits Symbiodiniaceae PSII functioning, reducing energy production and affecting calcification in coral holobionts. Acute low-temperature stress is more threatening to coral holobionts than chronic stress.

The Influence of Applying Foliar Micronutrients at Nodulation and the Physiological Properties of Common Soybean Plants

Legumes, due to their symbiosis with papillary bacteria, can receive nitrogen from the air. The remaining nutrients must be supplied in fertilisers, either soil or foliar. In the pot experiment, we recorded the responses of two soybean cultivars (Annushka, Pompei) to the foliar application of micronutrients (control, Zn, Fe, Cu, Mn, B, or Mo). The physiological properties were expressed as net photosynthetic rate (PN), intercellular CO2 concentration (Ci), transpiration rate (E), stomatal conductance (gs), maximum quantum yield of photosystem II (Fv/Fm), maximum quantum yield of primary photochemistry (Fv/F0), photosynthetic performance index (PI), and the development of soil plant analyses (SPAD), which were analysed. The effects of individual micronutrients on nodulation, plant growth, and condition were also investigated. Micronutrient fertilisation had a positive effect on plant fresh weight and no negative effect on plant condition. It was shown that elements such as B, Fe, and Mo had the most beneficial effect on nodulation compared to the control, regardless of the cultivar analysed. The application of single-component foliar fertilisers improved the physiological parameters of the plants. The relative chlorophyll content was most favourably affected by the application of Mn, B, and Mo in the Annushka cultivar, and Fe, Mn, and Mo in the Pompei cultivar. Similarly, in the case of chlorophyll fluorescence, the most stimulating effect was found for Mn and B, regardless of the cultivar. In the case of gas exchange, the application of Fe, Mo, and B for the Annushka cultivar and Cu for the Pompei cultivar had the most favourable effect on physiological measurements. The results obtained indicate that the foliar application of the evaluated micronutrients is justified in soybean cultivation and does not disturb the nodulation process.

Photochemical activity in developing pea (Pisum sativum L.) cotyledons depends on the light transmittance of covering tissues and the spectral composition of light.

Many crops require not only leaf photosynthesis for their seed development but also the photochemical reactions that occur in the seeds. The purpose of this work was a comparative analysis of light transmittance and photochemical activity in the leaves of Pisum sativum L. and its pericarp, seed coat, and cotyledons at the early, middle, and late maturation stages. The spectral composition of light was measured using a spectroradiometer in the range of 390-760 nm. We assessed the light transmittance of plant tissues by placing the plant tissue between the light source and the spectroradiometer's sensor. PAM fluorometry was used to quantify the photochemical activity in plant tissues: this technique is handy for evaluating the efficiency of converting light energy into chemical energy through the analysis of the kinetics of chlorophyll fluorescence excitation and quenching. On average, a photochemically active green leaf of pea transmitted 15 % of solar radiation in the 390-760 nm, blue light was delayed entirely, and the transmitted red light never exceeded 5 %. Photochemically active radiation passing through the pericarp and coat and reaching the cotyledons at the early and middle seed maturation stages manifested a high proportion of green and far-red light; there was no blue light, and the percentage of red light was about 2 %. However, the cotyledons were photochemically active regardless of low irradiance and spectral ranges untypical of leaf photosynthesis. At the early and middle maturation stages, the maximum quantum yield of photosystem II (Fv/Fm) averaged 0.5 at the periphery of cotyledons and 0.3 at their center. Since the intensity of embryonic photochemical reactions significantly affects the efficiency of reserve nutrient accumulation, this parameter is a promising marker in pea breeding for seeds with improved nutritional qualities.

Eucalyptus urograndis physiological and hormonal changes under drought conditions in response to trinexapac-ethyl

Previous studies have reported that trinexapac-ethyl (TE) stimulates growth of well-watered (WW) eucalypt plants. However, the physiological and hormonal changes in response to this chemical remain unclear. Furthermore, there are reports that this chemical attenuates drought responses in grasses. This research investigated the hormonal and physiological response of Eucalyptus urograndis (Clone 1407) plants treated with TE, cultivated under WW and drought conditions. The experiment was carried out in a greenhouse up to 42 days after application of 0, 90 and 150 g ha−1 of TE. Eucalypt growth, hormone concentration, gas exchange, maximum quantum yield of photosystem II and total relative chlorophyll content were evaluated. TE increased growth of WW plants by up to 65%. Drought restricted the stimulatory effects of TE on eucalypt growth, despite an increase of at least 102% in gibberellin A4 (GA4), trans-zeatin (tZ) and N6-isopentenyladenine (iP) concentrations after application. GA4 stood out as an indicator of drought stress as it increased almost 6-fold compared to WW eucalypt. TE caused a hormonal imbalance in eucalypt up to 42 days after application, increasing GA1 concentration as a short-term effect (8 days) and GA8 as a medium-term effect (42 days). Gibberellin homeostasis was not reestablished until 42 days after TE treatment. These results provide insights into eucalypt hormonal response to TE. Future research should be conducted under field conditions to understand how long such positive effects would be detected over time in short-rotation eucalypt plantations.

Exploring salt tolerance and indicator traits across four temperate lineages of the common wetland plant, Phragmites australis

Common reed (Phragmites australis) is a widely utilized plant for wetland restoration and construction, facing challenges posed by high salinity as a stressor. Among the diverse P. australis lineages, functional traits variation provides a valuable genetic resource for identifying salt-tolerant individuals. However, previous investigations on P. australis salt tolerance have been restricted to regional scales, hindering the identification of key functional traits associated with salt tolerance in natural habitats. To address this gap, we conducted a greenhouse experiment to assess and compare the salt tolerance of four major temperate P. australis lineages worldwide. We utilized the maximum quantum yield of photosystem II (Fv/Fm) as a health indicator, while final biomass and wilt status served as indicators of salt tolerance across lineages. Our findings revealed significant differentiation in plant functional traits among different lineages, but no significant effect of interaction between salinity and lineage on most traits. Correlation analyses between salt-tolerance indicators and functional traits in the control group indicated that biomass, leaf width, and relative leaf water content are potential predictors of salt tolerance. However, ecological strategies, physiological traits, and latitudinal origin did not exhibit significant correlations with salt tolerance. Our study provides valuable indicator traits for effectively screening salinity-tolerant genotypes of P. australis in field settings, and holds significant potential for enhancing wetland construction and biomass production in marginal lands.

Growth, photosynthetic function, and stomatal characteristics of Persian walnut explants in vitro under different light spectra.

Light plays a crucial role in photosynthesis, which is an essential process for plantlets produced during in vitro tissue culture practices and ex vitro acclimatization. LED lights are an appropriate technology for in vitro lighting but their effect on propagation and photosynthesis under in vitro condition is not well understood. This study aimed to investigate the impact of different light spectra on growth, photosynthetic functionality, and stomatal characteristics of micropropagated shoots of Persian walnut (cv. Chandler). Tissue-cultured walnut nodal shoots were grown under different light qualities including white, blue, red, far-red, green, combination of red and blue (70:30), combination of red and far-red (70:30), and fluorescent light as the control. Results showed that the best growth and vegetative characteristics of in vitro explants of Persian walnut were achieved under combination of red and blue light. The biggest size of stomata was detected under white and blue lights. Red light stimulated stomatal closure, while stomatal opening was induced under blue and white lights. Although the red and far-red light spectra resulted in the formation of elongated explants with more lateral shoots and anthocyanin content, they significantly reduced the photosynthetic functionality. Highest soluble carbohydrate content and maximum quantum yield of photosystem II were detected in explants grown under blue and white light spectra. In conclusion, growing walnut explants under combination of red and blue lights leads to better growth, photosynthesis functionality, and the emergence of functional stomata in in vitro explants of Persian walnuts.

Genotype‐dependent Strategies to “Overcome” Excessive Light: Insights into Non‐Photochemical Quenching under High Light Intensity

AbstractHigh light (HL) intensities have a significant impact on energy flux and distribution within photosynthetic apparatus. To understand the effect of high light intensity (HL) on the HL tolerance mechanisms in tomatoes, we examined the response of the photosynthesis apparatus of 12 tomato genotypes to HL. A reduced electron transfer per reaction center (ET0/RC), an increased energy dissipation (DI0/RC) and non‐photochemical quenching (NPQ), along with a reduced maximum quantum yield of photosystem II (FV/FM), and performance index per absorbed photon (PIABS) were common HL‐induced responses among genotypes; however, the magnitude of those responses was highly genotype‐dependent. Tolerant and sensitive genotypes were distinguished based on chlorophyll fluorescence and energy‐quenching responses to HL. Tolerant genotypes alleviated excess light through energy‐dependent quenching (qE), resulting in smaller photoinhibitory quenching (qI) compared to sensitive genotypes. Quantum yield components also shifted under HL, favoring the quantum yield of NPQ (ՓNPQ) and the quantum yield of basal energy loss (ՓN0), while reducing the efficient quantum yield of PSII (ՓPSII). The impact of HL on tolerant genotypes was less pronounced. While the energy partitioning ratio did not differ significantly between sensitive and tolerant genotypes, the ratio of NPQ components, especially qI, affected plant resilience against HL. These findings provide insights into different patterns of HL‐induced NPQ components in tolerant and sensitive genotypes, aiding the development of resilient crops for heterogeneous light conditions.

Possible Contribution of Corticular Photosynthesis to Grapevine Winter Hardiness

Numerous studies show that photosynthesis in non-foliar tissues contributes to plant productivity. Here, we demonstrate that in chlorenchyma tissues of lignified branches of grape vines, photosynthetic activity is maintained during winter and provide evidence that corticular photosynthesis could contribute to the plant’s freeze tolerance. In a collection of grape varieties that varied noticeably in freeze tolerance, a positive correlation between the maximum quantum yield of photosystem II in the wintering vines and the ability to survive harsh winter temperatures was observed. A more detailed comparison of two grapevine varieties differing in freeze tolerance showed that the vines of the more tolerant variety have more abundant corticular chlorenchyma with chloroplasts containing a better developed network of photosynthetic membranes, characterized by a higher photosynthetic pigments content, higher efficiency of both photosystems, and higher mobility of antennae complexes under the changing light intensity. In addition, we found that freezing temperatures induced more damage in vine samples when they were preliminarily treated with a specific inhibitor of photosynthetic electron transfer. The data obtained could be useful in the generation of freeze-tolerant grape varieties.

Phenotypic plasticity in Pinus canariensis seedlings growing at chilling and freezing temperatures

Global change is affecting the frequency and temporal distribution of frost events. We can expect damage caused by low temperatures to increase specially at the upper limit of a species’ elevation range. Here, we assessed how Pinus canariensis two-year old seedlings from different islands and elevations responded differently to chilling and freezing temperatures. Seedlings from six populations were grown either in a greenhouse (tmin = 5 ̊C, chilling conditions) or outdoors (tmin = −3.3 ̊C, freezing conditions) for 104 days in winter. Seedlings from one of these populations belonged to three half-sib families. Maximum quantum yield of Photosystem II and evapotranspiration (ETP) were determined four times throughout the study. All populations suffered photoinhibition under freezing but not under chilling conditions. We measured the lowest ETP in the population from the warmest and driest environment and lowest elevation (250 m) both under chilling and freezing conditions. The three populations from the higher elevations reached the highest ETP under chilling, a likely adaptation to the shortening of the vegetative period. The effect of elevation remained elusive for other parameters, which could be partly attributed to high intrapopulation variability. Epicuticular wax concentration increased and needle water content decreased in plants growing outdoors. All populations except the one most affected by cold dehydration showed osmotic adjustment and a simultaneous decrease in tissue elasticity under freezing. This response was stronger in the population from the highest elevation (2,241 m). Our results highlight the coexistence of adaptive processes, genetic variation and plasticity conditioning the response to low temperatures in this species.

Integrated physiological and omics analyses reveal the mechanism of beneficial fungal Trichoderma sp. alleviating cadmium toxicity in tobacco (Nicotiana tabacum L.)

Cadmium (Cd) is a highly toxic heavy metal and readily accumulates in tobacco, which imperils public health via Cd exposure from smoking. Beneficial microbes have a pivotal role in promoting plant growth, especially under environmental stresses such as heavy metal stresses. In this study, we introduced a novel fungal strain Trichoderma nigricans T32781, and investigated its capacity to alleviate Cd-induced stress in tobacco plants through comprehensive physiological and omics analyses. Our findings revealed that T32781 inoculation in soil leads to a substantial reduction in Cd-induced growth inhibition. This was evidenced by increased plant height, enhanced biomass accumulation, and improved photosynthesis, as indicated by higher values of key photosynthetic parameters, including the maximum quantum yield of photosystem Ⅱ (Fv/Fm), stomatal conductance (Gs), photosynthetic rate (Pn) and transpiration rate (Tr). Furthermore, element analysis demonstrated that T. nigricans T32781 inoculation resulted in a remarkable reduction of Cd uptake by 62.2% and a 37.8% decrease in available soil Cd compared to Cd-stressed plants without inoculation. The protective role of T32781 extended to mitigating Cd-induced oxidative stress by improving antioxidant enzyme activities of superoxide dismutase (SOD), peroxidase (POD), and ascorbate peroxidase (APX). Metabolic profiling of tobacco roots identified 43 key metabolites, with notable contributions from compounds like nicotinic acid, succinic acid, and fumaric acid in reducing Cd toxicity in T32781-inoculated plants. Additionally, rhizosphere microbiome analysis highlighted the promotion of beneficial microbes, including Gemmatimonas and Sphingomonas, by T32781 inoculation, which potentially contributed to the restoration of plant growth under Cd exposure. In summary, our study demonstrated that T. nigricans T32781 effectively alleviated Cd stress in tobacco plants by reducing Cd uptake, alleviating Cd-induced oxidative stress, influencing plant metabolite and modulating the microbial composition in the rhizosphere. These findings offer a novel perspective and a promising candidate strain for enhancing Cd tolerance and prohibiting its accumulation in plants to reduce health risks associated with exposure to Cd-contaminated plants.

Physiological Responses of Pak Choi (Brassica rapa Subsp. Chinensis) Genotypes to Salt Tolerance

Salinity stress poses a significant challenge to Pak Choi (Brassica rapa subsp. Chinensis) production. To address this limitation, we conducted an evaluation of 24 Korean native Pak Choi species to identify genotypes with resistance to salt stress. Through cluster analysis of electrolyte leakage data, we discovered ‘IT262109’, ‘IT279432’, and ‘IT185735’ as native accessions displaying the strongest salt tolerance. Additionally, our assessment of the maximum quantum yield of photosystem II revealed a 3.7% reduction in seaweed yield in the highly salt-tolerant system compared with the control group, while the weak salt-tolerant system experienced a substantial reduction rate of 45.7% to 49.4%. Notably, salt stress had a significant impact on Pak Choi growth, but the salt-tolerant genotype exhibited less growth reduction compared with the salt-sensitive genotype. Based on the electrolyte leakage and maximum quantum yield data, it was evident that ‘IT185735’ demonstrated poorer growth compared with ‘IT262109’ and ‘IT279432’. Consequently, ‘IT262109’ and ‘IT279432’ show great potential as parent varieties for enhancing salt tolerance in Pak Choi.

Production of ice-nucleating particles (INPs) by fast-growing phytoplankton

Abstract. Sea spray aerosol contains ice-nucleating particles (INPs), which affect the formation and properties of clouds. Here, we show that aerosols emitted from fast-growing marine phytoplankton produce effective immersion INPs, which nucleate at temperatures significantly warmer than the atmospheric homogeneous freezing (−38.0 ∘C) of pure water. Aerosol sampled over phytoplankton cultures grown in a Marine Aerosol Reference Tank (MART) induced nucleation and freezing at temperatures as high as −15.0 ∘C during exponential phytoplankton growth. This was observed in monospecific cultures representative of two major groups of phytoplankton, namely a cyanobacterium (Synechococcus elongatus) and a diatom (Thalassiosira weissflogii). Ice nucleation occurred at colder temperatures (−28.5 ∘C and below), which were not different from the freezing temperatures of procedural blanks, when the cultures were in the stationary or death phases of growth. Ice nucleation at warmer temperatures was associated with relatively high values of the maximum quantum yield of photosystem II (ΦPSII), an indicator of the physiological status of phytoplankton. High values of ΦPSII indicate the presence of cells with efficient photochemistry and greater potential for photosynthesis. For comparison, field measurements in the North Atlantic Ocean showed that high net growth rates of natural phytoplankton assemblages were associated with marine aerosol that acted as effective immersion INPs at relatively warm temperatures. Data were collected over 4 d at a sampling station maintained in the same water mass as the water column stabilized after deep mixing by a storm. Phytoplankton biomass and net phytoplankton growth rate (0.56 d−1) were greatest over the 24 h preceding the warmest mean ice nucleation temperature (−25.5 ∘C). Collectively, our laboratory and field observations indicate that phytoplankton physiological status is a useful predictor of effective INPs and more reliable than biomass or taxonomic affiliation. Ocean regions associated with fast phytoplankton growth, such as the North Atlantic during the annual spring bloom, may be significant sources of atmospheric INPs.

Exploring the tropical acclimation of European and American hop cultivars (Humulus lupulus L.): Focus on physiology, productivity, and chemical composition

Hop (Humulus lupulus L.) cones are widely used by the beer industry to provide flavor, aroma, and bitterness due to the presence of α-acids, β-acids, and volatile oil components. Although the brewing sector plays an important role in Brazil’s economy, hops are entirely imported. In this study, we aimed to investigate the physiological acclimation potential, productivity, and chemical composition of four hop cultivars in a warm tropical region of Brazil. For this purpose, three North American-bred hop cultivars (‘Cascade’, ‘Chinook’ and ‘Triple Pearl’) and one European hop cultivar (‘Saaz’) that grew under tropical ambient conditions for two consecutive years were used. ‘Saaz’ and ‘Triple Pearl’ showed higher mortality and smaller photosynthetic rates, while ‘Cascade’ and ‘Chinook’ cultivars showed the best physiological and growth performance under a tropical-type climate. With a few exceptions, maximum quantum yield of photosystem II (PSII), chlorophyll content, and antioxidant enzymes activity were very similar between these two cultivars. A higher dry mass of cones was observed in ‘Chinook’ and ‘Cascade’, however, with a higher variability within each cultivar. Both cultivars increased the production of the dry mass of cones in the second year. The average concentration of bitter acids in ‘Cascade’ and ‘Chinook’ was below the expected values, but there was a considerable increase in the volatile oil content between the first and second year of cultivation. We concluded that 'Cascade' and 'Chinook', American cultivars, showed better development and lower mortality compared to 'Triple Pearl' (American cultivar) and 'Saaz' (European cultivar) under tropical climate conditions in Brazil. Although the concentration of bitter acids was lower than expected in the first two years, the concentration may increase with plant maturity.