Intercellular CO2 Concentration Research Articles

Metabolomics combined with physiology reveal how white clover (Trifolium repens L.) respond to 6PPD stress

As a ubiquitous tire antioxidant, N-(1,3-Dimethyl-butyl)-N′-phenyl-p-phenylene- diamine (6PPD) exists widely in various environmental media and has been detected at high levels in the environment. However, the effects of 6PPD on plants are still poorly understood. In this study, a hydroponic experiment was carried out to investigate the response of white clover (Trifolium repens L.) stressed by 6PPD on physiology and metabolomics. The results indicated that the length of stem and root, as well as biomass were significantly reduced after 500 μg L−1 6PPD treatment. Photosynthetic performances including photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci), transpiration rate (Tr) and chlorophyll content of leaves decreased in all treatments except 500 μg L−1 of 6PPD. The malondialdehyde (MDA) content in the shoot of white clover increased by 66.33 % when exposed to 500 μg L−1 of 6PPD compared to control group (CK). Hydrogen peroxide and superoxide anion presented a U-shape trend and began to increase at 500 μg L−1. Besides, peroxidase and catalase significantly decreased compared to CK after exposure to 500 μg L−1. Metabolic analysis of clover showed that 6PPD treatment induced changes in 10 metabolic pathways of white clover. Metabolites were significantly down-regulated after exposure to 500 μg L−1 in shoot, while significantly down-regulated in all treatment groups except 500 μg L−1 in root. These findings may provide a novel perspective for phytotoxicity assessment and phytoremediation of 6PPD.

Investigating the influence of varied ratios of red and far-red light on lettuce (Lactuca sativa): effects on growth, photosynthetic characteristics and chlorophyll fluorescence.

Far red photon flux accelerates photosynthetic electron transfer rates through photosynthetic pigments, influencing various biological processes. In this study, we investigated the impact of differing red and far-red light ratios on plant growth using LED lamps with different wavelengths and Ca1.8Mg1.2Al2Ge3O12:0.03Cr3+ phosphor materials. The control group (CK) consisted of a plant growth special lamp with 450 nm blue light + 650 nm red light. Four treatments were established: F1 (650 nm red light), F2 (CK + 730 nm far-red light in a 3:2 ratio), F3 (650 nm red light + 730 nm far-red light in a 3:2 ratio), and F4 (CK + phosphor-converted far-red LED in a 3:2 ratio). The study assessed changes in red and far-red light ratios and their impact on the growth morphology, photosynthetic characteristics, fluorescence characteristics, stomatal status, and nutritional quality of cream lettuce. The results revealed that the F3 light treatment exhibited superior growth characteristics and quality compared to the CK treatment. Notably, leaf area, aboveground fresh weight, vitamin C content, and total soluble sugar significantly increased. Additionally, the addition of far-red light resulted in an increase in stomatal density and size, and the F3 treatments were accompanied by increases in net photosynthetic rate (Pn), transpiration rate (Tr), intercellular CO2 concentration (Ci), and stomatal conductance (Gs). The results demonstrated that the F3 treatment, with its optimal red-to-far-red light ratio, promoted plant growth and photosynthetic characteristics. This indicates its suitability for supplementing artificial light sources in plant factories and greenhouses.

The Physiological Mechanism of Exogenous Melatonin on Improving Seed Germination and the Seedling Growth of Red Clover (Trifolium pretense L.) under Salt Stress.

Salt stress can affect various physiological processes in plants, ultimately hindering their growth and development. Melatonin (MT) can effectively resist multiple abiotic stresses, improving plant stress resistance. To analyze the mechanism of exogenous MT to enhance salt tolerance in red clover, we conducted a comprehensive study to examine the influence of exogenous MT on various parameters, including seed germination indices, seedling morphological traits, and physiological and photosynthetic indicators, using four distinct red clover varieties (H1, H2, H3, and H4). This investigation was performed under various salt stress conditions with differing pH values, specifically utilizing NaCl, Na2SO4, NaHCO3, and Na2CO3 as the salt stressors. The results showed that MT solution immersion significantly improved the germination indicators of red clover seeds under salt stress. The foliar spraying of 50 μM and 25 μM MT solution significantly increased SOD activity (21-127%), POD activity, soluble sugar content, proline content (22-117%), chlorophyll content (2-66%), and the net photosynthetic rate. It reduced the MDA content (14-55%) and intercellular CO2 concentration of red clover seedlings under salt stress. Gray correlation analysis and the Mantel test further verified that MT is a key factor in enhancing seed germination and seedling growth of red clover under salt stress; the most significant improvement was observed for NaHCO3 stress. MT is demonstrated to improve the salt tolerance of red clover through a variety of mechanisms, including an increase in antioxidant enzyme activity, osmoregulation ability, and cell membrane stability. Additionally, it improves photosynthetic efficiency and plant architecture, promoting energy production, growth, and optimal resource allocation. These mechanisms function synergistically, enabling red clover to sustain normal growth and development under salt stress.

Exogenous Melatonin Alleviates Osmotic Stress by Enhancing Antioxidant Metabolism, Photosynthetic Maintenance, and Hormone Homeostasis in Forage Oat (Avena sativa) Seedlings

Melatonin (MT) is a multifunctional hormone that enhances crop resilience against various abiotic stresses. However, its regulatory mechanism of osmotic tolerance in forage oats (Avena sativa) plants under water-limited scenarios is still unclear. This study aimed to delineate the impact of MT pretreatment on the morphological, physiological, and biochemical functions of oat seedlings under osmotic stress. Our findings demonstrated that exogenous treatment of MT noticeably elevated leaf area while decreasing the root/shoot ratio of oat seedlings subjected to osmotic stress. Osmotic-induced 38.22% or 48.37% decrease in relative water content could be significantly alleviated by MT pretreatment on day 7 or day 14, respectively. MT treatment also significantly mitigated osmotic-induced decreases in photosynthetic parameters including net photosynthetic rate, stomatic conductance, and intercellular CO2 concentration as well as various chlorophyll fluorescence parameters, which could contribute to enhanced accumulations of free proline and soluble sugars in seedlings after being subjected to a prolonged duration of osmotic stress. Furthermore, MT markedly improved antioxidant enzyme activities including superoxide dismutase, ascorbate peroxidase, catalase, and peroxidase along with the accumulation of ascorbic acid contributing to a significant reduction in reactive oxygen species under osmotic stress. In addition, the MT application induced a 978.12%, 33.54%, or 30.59% increase in endogenous MT, indole acetic acid, or gibberellic acid content under osmotic stress but did not affect the accumulation of abscisic acid. These findings suggest that an optimal concentration of MT (100 μmol·L−1) could relieve osmotic stress via improvement in osmotic adjustment, the enzymatic antioxidant defense system, and endogenous hormonal balance, thereby contributing to enhanced photosynthetic functions and growth of oat seedlings under water-limited conditions.

Stomatal response to VPD in C4 plants with different biochemical sub-pathways.

C4 NAD-malic enzyme (NAD-ME) species occurs in drier regions and exhibit different drought responses compared to C4 NADP-malic enzyme (NADP-ME) species. However, a physiological mechanism explaining the geographical discrepancies remains uncertain. This study examined gas exchange patterns that might explain different distributions observed between two subtypes of C4 photosynthesis. We measured the response of leaf gas exchange to vapour pressure deficit (VPD) and CO2 in plants from six distinct C4 clades having closely related NAD-ME and NADP-ME species using a Li-Cor 6400 gas exchange system. We found that NAD-ME species exhibited greater relative reductions in stomatal conductance with increases in VPD than NADP-ME species but observed no consistent subtype differences in C4 cycle activity as indicated by the initial slope of the A response to intercellular CO2 concentration. Based on these results, we hypothesise the greater response of gs to increasing VPD may enable NAD-ME plants to outperform NADP-ME plants in hot, dry environments where VPD is normally high.

Physiological and biochemical responses of the achachairu tree (Garcinia humilis) to prolonged flooding

Flooding and waterlogging create hypoxic or anoxic soil conditions that negatively affect the physiology of wild and cultivated tropical fruit trees. The achachairu (Garcinia humilis) is a slow-growing tropical fruit tree endemic to the Bolivian Amazon region. Like many tropical trees, G. humilis is increasingly affected by flooding events that may threaten its natural and cultivated areas, but its physiological and biochemical responses to prolonged flooding have not been reported. This study assessed the physiological, biochemical, and morphological responses of G. humilis to prolonged flooding of different durations for up to 30 d Physiological variables measured included leaf gas exchange [net CO2 assimilation (A), stomatal conductance of H2O (gs), and intercellular CO2 concentration (Ci)], leaf chlorophyll index (LCI), and the ratio of variable to maximum chlorophyll fluorescence (Fv/Fm). Antioxidant responses, such as superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), ascorbate peroxidase (APX), glutathione (GSH), glutathione reductase (GTR), dehydroascorbate reductase (DHAR), monodehydroascorbate reductase (MDAR), ascorbic acid (AsA), and glutathione (GSH); reactive oxygen species (ROS); and lipid peroxidation indicated by malondialdehyde (MDA) were also measured. Results indicate that G. humilis is very tolerant of flooding periods of at least 30 d, which causes approximately a 50 % reduction in net A but no measurable negative impact on other physiological variables, including LCI and Fv/Fm. Flooding caused an increase in ROS and malonaldehyde (MDA), which were countered by a robust antioxidant response that possibly contributed to improved flooding tolerance. Plants continued to grow during the flooding period, and A recovered to nearly pre-flooding levels 90 d after plants were unflooded.

Elevated CO2 and Nitrogen Supply Boost N Use Efficiency and Wheat (T. aestivum cv. Yunmai) Growth and Differentiate Soil Microbial Communities Related to Ammonia Oxidization.

Elevated CO2 levels (eCO2) pose challenges to wheat (Triticum aestivum L.) growth, potentially leading to a decline in quality and productivity. This study addresses the effects of two ambient CO2 concentrations (aCO2, daytime/nighttime = 410/450 ± 30 ppm and eCO2, 550/600 ± 30 ppm) and two nitrogen (N) supplements (without N supply-N0 and with 100 mg N supply as urea per kg soil-N100) on wheat (T. aestivum cv. Yunmai) growth, N accumulation, and soil microbial communities related to ammonia oxidization. The data showed that the N supply effectively mitigated the negative impacts of eCO2 on wheat growth by reducing intercellular CO2 concentrations while enhancing photosynthesis parameters. Notably, the N supply significantly increased N concentrations in wheat tissues and biomass production, thereby boosting N accumulation in seeds, shoots, and roots. eCO2 increased the agronomic efficiency of applied N (AEN) and the physiological efficiency of applied N (PEN) under N supply. Plant tissue N concentrations and accumulations are positively related to plant biomass production and soil NO3--N. Additionally, the N supply increased the richness and evenness of the soil microbial community, particularly Nitrososphaeraceae, Nitrosospira, and Nitrosomonas, which responded differently to N availability under both aCO2 and eCO2. These results underscore the importance and complexity of optimizing N supply and eCO2 for enhancing crop tissue N accumulation and yield production as well as activating nitrification-related microbial activities for soil inorganic N availability under future global environment change scenarios.

Ascorbic acid-mediated enhancement of antioxidants and photosynthetic efficiency: A strategy for enhancing canola yield under salt stress

Ascorbic acid (AsA), a water-soluble antioxidant, act as cofactor for enzymes that regulate photosynthesis, hormonal and antioxidant biosynthesis that enables the plants to alleviate the harmful effects of salinity stress. The study was aimed to investigate the ameliorative role of foliar application of 200 ppm ascorbic acid (AsA) in improving growth by changing antioxidant response, photosynthetic capacity and mineral nutrient status of two canola varieties (Dunkled and Cyclone) under salinity stress (200 mM NaCl). Salt stress reduced plant biomass, photosynthetic activity, and accumulation of macro and micronutrients such as K+, Ca2+and Zn2+ in both canola varieties, on the other hand accumulation of Na+ and Cl−was increased. The salinity-induced oxidative stress (H2O2 and MDA) caused photoinhibition of PSII at the donor and acceptor ends. The salinity-induced reduction in efficiency of electron donation to PSII (Fv/Fo) and electron transport through PSII (Fm/Fo), especially in Cyclone, significantly reduced ETRII thus enhancing CEF around PSI and NPQ in both canola varieties that has been considered as photo-protective mechanism of plants. In addition, salt stress enhanced CEF around PSI. However, application of AsA improved the structural stability of PSII, linear electron transport and reduced donor end limitation of PSI activity by improving electron transfer from PSII to PSI. The application of AsA improved the stomatal conductance, inter-cellular CO2 concentration and net CO2 assimilation rate thereby resulting in improved consumption of extra-electrons in CO2 fixation generated by photosynthetic electron transport. Exogenous AsA application reduced the oxidative stress and improved the antioxidant potential by managing extra-electrons produced in CO2 fixation. All these physiological and biochemical changes due to AsA application helped the canola plants to improve growth and yield under salinity. Thus, the application of ascorbic acid has the potential to ameliorate the detrimental effects of NaCl stress on canola plants.

Recent warming and increasing CO2 stimulate growth of dominant trees under no water limitation in South Korea.

Increases in temperatures and atmospheric CO2 concentration influence the growth performance of trees worldwide. The direction and intensity of tree growth and physiological responses to changing climate do, however, vary according to environmental conditions. Here we present complex, long-term, tree-physiological responses to unprecedented temperature increase in East Asia. For this purpose, we studied radial growth and isotopic (δ13C and δ18O) variations using tree-ring data for the past 100yr of dominant Quercus mongolica trees from the cool-temperate forests from Hallasan, South Korea. Overall, we found that tree stem basal area increment, intercellular CO2 concentration and intrinsic water-use efficiency significantly increased over the last century. We observed, however, short-term variability in the trends of these variables among four periods identified by change point analysis. In comparison, δ18O did not show significant changes over time, suggesting no major hydrological changes in this precipitation-rich area. The strength and direction of growth-climate relationships also varied during the past 100yr. Basal area increment (BAI) did not show significant relationships with the climate over the 1924-1949 and 1975-1999 periods. However, over 1950-1974, BAI was negatively affected by both temperature and precipitation, while after 2000, a temperature stimulus was observed. Finally, over the past two decades, the increase in Q. mongolica tree growth accelerated and was associated with high spring-summer temperatures and atmospheric CO2 concentrations and decreasing intrinsic water-use efficiency, δ18O and vapour pressure deficit, suggesting that the photosynthetic rate continued increasing under no water limitations. Our results indicate that the performance of dominant trees of one of the most widely distributed species in East Asia has benefited from recent global changes, mainly over the past two decades. Such findings are essential for projections of forest dynamics and carbon sequestration under climate change.

Effects of different water stresses under subsurface infiltration irrigation on eggplant growth and water productivity

Soil moisture deficiency limits eggplant growth and affects the yield and quality. Identifying an appropriate deficit irrigation strategy to enhance irrigation water productivity is an urgent task. Additionally, the dynamic response of eggplants to water stress at various phenological stages needs further clarification. In this study, eggplants were used as experimental materials, with field capacity (FC) (Senyigit et al.) serving as the irrigation standard. Two levels of deficit irrigation treatments (60 % FC and 50 % FC) were applied at three key phenological stages of eggplant (seedling stage, flowering and fruiting, and prime fruit stage). A randomized block design was used with non-deficit irrigation (80 % FC) during the phenological stages as the control (W1), resulting in seven treatments, each with three replicates. The results showed that at the same phenological stage, plant height, stem diameter, leaf area index (LAI), dry matter accumulation, total fresh root weight, total root length, total root surface area, and total root volume decreased as the irrigation threshold was lowered. The content of vitamin C, soluble sugars, souble proteins, and crude fiber increased as the irrigation threshold decreased. Leaf photosynthetic parameters (photosynthetic rate (Pn), transpiration rate (Tr), stomatal conductance (Gs), and intercellular CO2 concentration (Ci)) were positively correlated with the irrigation threshold. The W1 treatment had the highest yield (89.1 t·ha−1 in 2018; 88.8 t·ha−1 in 2019), followed by the W2 treatment (86.1 t·ha−1 in 2018; 85.6 t·ha−1 in 2019). Water deficit during the prime fruit stage (W6, W7) had the most significant impact on yield. W1 had the highest water productivity (19.4 kg·m−3 in 2018; 19.2 kg·m−3 in 2019), with no significant difference from W2 (19.4 kg·m−3 in 2018; 19.0 kg·m−3 in 2019). Using the Jensen function, the water sensitivity of eggplants at different phenological stages was ranked as follows:prime fruit stage > flowering and fruiting stage > seedling stage. Path analysis indicated that dry matter accumulation, single fruit weight, and single plant yield were important indicators affecting yield. Considering irrigation amount, eggplant growth, fruit yield and quality, and water productivity, the optimal deficit irrigation thresholds for eggplants in arid regions are determined to be 60 % FC during the seedling stage, 60 % FC during the flowering and fruiting stage, and 80 % FC during the prime fruit stage. The findings of this study offer valuable insights for precision agricultural irrigation practices.

Morphological and Physiological Response of Maize (Zea mays L.) to Drought Stress during Reproductive Stage

Maize is among the most significant crops in the world regarding production and yield, but it is highly sensitive to drought, which reduces the growth, photosynthetic efficiency, grain quality, and yield production of a plant. Quantum yield efficiency of photosystem II is a critical photosynthetic component that is susceptible to drought stress. This study intended to investigate the effects of drought stress on growth and morpho-physiological parameters using three maize hybrids (‘P-3011w’, ‘P-3092’ and ‘iku20’) with contrasting soil moisture contents (100%, 40%) at the pre-flowering stage. The stress treatment (40%) was initiated at stage V7, for a period of 15 days; the experimental units were established in a completely randomized design with split-plot arrangement along with three repetitions in 42 L pots using a substrate of peat moss, black soil and poultry manure (1:2:1). The morphological, growth-related and physiological parameters were assessed, including chlorophyll fluorescence (Fv/Fm), which was measured using a LiCor-6400-40 fluorometer. The results showed that all morphological, growth-related and physiological variables decreased under drought stress during the reproductive stage, with the exception of leaf temperature and intercellular CO2 concentration, which increased by 12% and 54%, respectively. Drought stress significantly reduced the photosynthetic chlorophyll fluorescence (43%), due to damage to photosystem II. The lowest percentage of damage to photosystem II (34%) was observed in the iku20 genotype. In contrast, P-3011w and P-3092 had the highest levels of significantly similar damage (49% and 46%, respectively). The correlation analysis showed a highly positive interaction of chlorophyll fluorescence (Fv/Fm) with net photosynthetic rate and stomatal conductance under drought conditions, and multiple regression analysis revealed that the maximum effect on net photosynthetic rate under drought was due to the damage it caused to photosystem II. Thus, iku20 might have a tendency to be able to withstand drought stress in the dry northeast region of Mexico. Overall, we concluded that the photosystem II was negatively impacted by drought stress thus causing a reduction in all physiological, morphological and growth-related variables.

Doses of N in the Morphological and Physiological Characteristics of African Mahogany Seedling

Purpose: To analyse the growth of African mahogany (Khaya senegalensis) seedlings, regarding their morphology and physiology, in soil fertilized with different doses of N, from the application of ammonium sulphate. Theoretical framework: Based on scientific articles found on search engines and books in the area of ​​soil fertility and plant nutrition. To support the explanation of how the physiological characteristics of seedlings are related to the nutrition they receive from fertilization. Therefore, the application of different doses to the soil can provide different physiological responses, resulting in greater or lesser growth and dry mass production of plants. Method: The experiment was carried out in a completely randomized design with five doses of N and five replications, using ammonium sulphate as the source. The doses tested were: T0 – without fertilization; T1 – 50 mg dm-3; T2 – 100 mg dm-3; T3 – 150 mg dm-3; T4 – 200 mg dm-3. The seedlings were produced and then transplanted to the definitive container, when it received nitrogen fertilization. These seedlings went through an adaptation process and, at the end of 90 days, the morphological characteristics were evaluated: height, diameter, leaf dry mass, stem dry mass, root dry mass and; physiological characteristics: net photosynthetic rate, transpiration rate, stomatal conductance, intercellular CO2 concentration, vapor pressure deficit and transpiration rate. Results and conclusion: Nitrogen fertilization influenced the morphological and physiological characteristics of African mahogany seedlings. The greatest growth and production of dry mass was observed at doses of 100 and 150 mg dm-3 of N. These results were related to the increase in the net photosynthetic rate, stomatal conductance, transpiration and CO2 concentration. Recommending the most economical dose of 100 mg dm-3 of N. Research implications: These results indicate that nitrogen fertilization is essential for the quality growth of African mahogany seedlings, and the dose to be applied is essential for this to happen, since values ​​lower than this dose may not allow the plant to perform at its maximum. growth potential. Meanwhile, higher doses do not guarantee greater growth and will result in unnecessary expenses and, probably, loss of growth due to toxicity. Originality/value: Using nitrogen fertilizers, in the correct dose for the species, increases its growth potential and guarantees the production of quality seedlings within the nursery.

Alfalfa Mosaic Virus and White Clover Mosaic Virus Combined Infection Leads to Chloroplast Destruction and Alterations in Photosynthetic Characteristics of Nicotiana benthamiana.

Alfalfa mosaic virus (AMV) is one of the most widely distributed viruses; it often exhibits combined infection with white clover mosaic virus (WCMV). Even so, little is known about the effects of co-infection with AMV and WCMV on plants. To determine whether there is a synergistic effect of AMV and WCMV co-infection, virus co-infection was studied by electron microscopy, the double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA), and real-time fluorescence quantitative PCR (RT-qPCR) of AMV and WCMV co-infection in Nicotiana benthamiana. Meanwhile, measurements were carried out on the photosynthetic pigments, photosynthetic gas exchange parameters, and chlorophyll fluorescence parameters. The results showed that the most severe disease development was induced by AMV and WCMV co-infection, and the disease grade was scale 7. N. benthamiana leaves induced mottled yellow-green alternating patterns, leaf wrinkling, and chlorosis, and chloroplasts were observed to be on the verge of disintegration. The relative accumulation of AMV CP and WCMV CP was significantly increased by 15.44-fold and 10.04-fold upon co-infection compared to that with AMV and WCMV single infection at 21 dpi. In addition, chlorophyll a, chlorophyll b, total chlorophyll, the net photosynthetic rate, the water use efficiency, the apparent electron transport rate, the PSII maximum photochemical efficiency, the actual photochemical quantum yield, and photochemical quenching were significantly reduced in leaves co-infected with AMV and WCMV compared to AMV- or WCMV-infected leaves and CK. On the contrary, the carotenoid content, transpiration rate, stomatal conductance, intercellular CO2 concentration, minimal fluorescence value, and non-photochemical quenching were significantly increased. These findings suggest that there was a synergistic effect between AMV and WCMV, and AMV and WCMV co-infection severely impacted the normal function of photosynthesis in N. benthamiana.

Effects of Low-Temperature Stress on Cold Resistance Biochemical Characteristics of Dali and Siqiu Tea Seedlings

Cold stress causes considerable damage to tender tea seedlings. Previous studies have explored changes in the physiological and biochemical factors of tea in response to cold stress; however, the mechanisms of cold resistance in ancient tea tree plants are unclear. The aim of this study was to analyze the effects of 0 °C cold stress for 15 days and 24 °C ambient temperature recovery for 5 days on the physiological and biochemical characteristics of two representative old tea varieties: Dali tea and Siqiu tea. The results revealed significant changes in antioxidant, photosynthetic efficiency, and physiological and biochemical indicators in response to cold stress, with the two species exhibiting different patterns. Cold stress decreased chlorophyll and carotene content, Fv/Fm, Y(II), non-photochemical quenching coefficient, photochemical quenching, and superoxide dismutase (SOD) activity, and increased intercellular CO2 concentration and ascorbate peroxidase activity. Siqiu tea showed a higher increase in soluble sugar content and antioxidant enzyme activity and a lower accumulation of malondialdehyde and minimal fluorescence (F0) than Dali, indicating a greater tolerance to cold stress. Based on partial least-squares discriminant analysis, six key differential physiological indicators of cold resistance—water-soluble sugar, F0, peroxidase, catalase, SOD, and gas conductance—were identified. Our findings provide technical support for identifying ways to protect ancient tea trees from extreme weather conditions.

Fluctuating ozone exposures caused trade-offs between vegetative growth and reproduction of two Chinese bean cultivars and ethylenediurea alleviated ozone phytotoxicities

Ozone (O3) pollution has elevated in China, threatening plants and crop production. Ethylenediurea (EDU) is a chemical alleviating O3-induced phytotoxicities. This study aimed at revealing fluctuating O3 exposures effects on Youxian No 3 (Phaseolus vulgaris) and Sukui No 4 (Vigna angularis), two widely grown Chinese bean cultivars, and EDU role in mediating these effects. Plants were periodically treated with EDU (400 mg/L) or water and exposed to charcoal-filtered air (CF) or non-filtered ambient air enriched with an additional targeted O3 concentration of 40 ppb (NF40) with subsequent ambient or NF40 exposures. A 10-day exposure to NF40 increased photosynthetic rate (A) while decreasing the leaf intercellular CO2 concentration (Ci), but this effect was absent after moving plants to ambient air for two weeks. Moving previously CF-exposed plants to ambient air for two weeks also increased A, which was not linked with Ci but more related to stomatal conductance (gs). Following two one-week and two-week sequential exposures of all plants to NF40, with an intermediate exposure to ambient air, elevated O3 reduced chlorophylls (SPAD), A, gs, Ci, and transpiration and decoupled A-gs response. More O3 effects were observed in plants treated with NF40 during each O3-treatment cycle, compared to those exposed to CF during the first cycle. The former plants exhibited significantly decreased biomass and water content of leaves and stems but increased flowers biomass and water content. Some of the effects were cultivar-dependent, with Youxian showing more apparent trade-offs between vegetative growth and reproduction. EDU alleviated various negative O3 effects.

Powdery mildew pathogen [Erysiphe necator (Schw.) Burrill.] induced physiological and biochemical alterations in leaf tissue of grapevines (Vitis spp.)

Grapevine serves as a host for an array of pathogenic agents, among which powdery mildew (PM), a fungal disease, stands as a major threat under changing climate and erratic weather patterns. The study aimed to examine the physiological, biochemical responses and microscopic examinations of diverse grapevine genotypes including the 42 Vitis species to powdery mildew infection caused by Erysiphe necator (Schw.) Burrill. Significant reductions were observed in leaf gas exchange parameters like net photosynthetic rate (33.09 %) and transpiration rate (32.36 %) in the infected leaves of susceptible genotypes compared to resistant and moderate genotype groups. Susceptible genotypes had higher intercellular CO2 concentration (4.01 %). Chlorophyll fluorescence analysis revealed a decrease in the maximum quantum efficiency of photosystem-II in PM-infected leaves across the genotype groups. Furthermore, PM infection led to a decrease in chlorophyll content, particularly in susceptible plants, along with a notable reduction in total chlorophyll (25.86 %) and total carotenoids (3.58 %) contents. The ascorbic acid/dehydroascorbic ascorbic acid ratio was observed to be increased by 50 % in the susceptible genotypes due to PM infection. The higher potassium content was registered in healthy leaves of resistant genotypes compared to PM infection stage. This clearly demonstrated the genotype-specific ability to withstand biotic stress. Antioxidant enzyme activities, including glutathione reductase (1.27-fold), polyphenol oxidase (1.15-fold), phenylalanine ammonia-lyase (1.02-fold) and peroxidase (1.21-fold), were enhanced in PM infected plants, suggesting the activation of different defence mechanisms against oxidative stress induced due to pathogen. Scanning electron microscopy revealed prominent differences in fungal hyphae growth between susceptible and resistant genotypes, which showed restricted tissue growth and host cell necrosis.

Changes in the growth and physiological property of tea tree after aviation mutagenesis and screening and functional verification of its characteristic hormones.

Aerospace breeding is a breeding technique that utilizes a spacecraft to position plants in a space environment for mutagenesis, which is conducive to rapid mutagenesis for the screening of superior plant varieties. In this study, tea trees with aviation mutagenesis (TM) and those without aviation mutagenesis (CK) were selected as research subjects to analyze the effects of aviation mutagenesis on the growth, physiological properties, and hormone metabolism of tea trees, and to further screen the characteristic hormones and validate their functions. The results showed that the leaf length, leaf width, and leaf area of TM tea trees were significantly larger than those of CK. The growth indexes, the photosynthetic physiological indexes (i.e., chlorophyll content, intercellular CO2 concentration, stomatal conductance, transpiration rate, and photosynthetic rate), and the resistance physiological indexes (i.e., superoxide dismutase, peroxidase, catalase, and soluble sugar) were significantly higher in TM than in CK. Hormone metabolome analysis showed that four characteristic hormones distinguished CK from TM, namely, l-tryptophan, indole, salicylic acid, and salicylic acid 2-O-β-glucoside, all of which were significantly more abundant in TM than in CK. These four characteristic hormones were significantly and positively correlated with the growth indexes, tea yield, and the photosynthetic and resistance physiological indexes of tea trees. The leaf area, chlorophyll content, photosynthetic rate, and superoxide dismutase activity of tea tree seedlings after spraying with the four characteristic hormones were significantly increased, in which salicylic acid and salicylic acid 2-O-β-glucoside were more favorable to increase the leaf area and superoxide dismutase activity, while l-tryptophan and indole were more favorable to increase the leaf chlorophyll content and photosynthetic rate. It can be observed that aviation mutagenesis improves the accumulation of the characteristic hormones of tea trees, enhances their photosynthetic capacity, improves their resistance, promotes their growth, and then improves the tea yield.

Two Carya Species, Carya hunanensis and Carya illinoinensis, Used as Rootstocks Point to Improvements in the Heat Resistance of Carya cathayensis.

Grafting as a crucial horticultural technique has been widely used in the cultivation of Carya cathayensis (Chinese hickory), which is a unique and important economic tree in the northeast of Zhejiang Province and the south of Anhui Province. However, the existing literature lacks research on the potential impact of various rootstocks on the thermal tolerance of Chinese hickory. The objectives of this study were to evaluate heat tolerance in four distinct groups of Chinese hickory, including C. cathayensis grafted onto Carya hunanensis and Carya illinoinensis, one self-grafted group (C. cathayensis grafted onto C. cathayensis), and one non-grafted group (C. cathayensis). We examined photosynthesis parameters, phytohormones, and differentially expressed genes in the four various hickory groups subjected to 25 °C, 35 °C, and 40 °C heat stress (HS). The results demonstrated that grafting onto C. hunanensis and C. illinoinensis exhibited a higher net photosynthetic rate and stomatal conductance, lower intercellular CO2 concentration, and smaller changes in plant hormone content compared to self-grafted and non-grafted group under HS. The transcriptome results revealed that the majority of differentially expressed genes (DEGs) associated with photosynthetic pathways exhibited downregulation under HS, while the degree of variation in grafted groups using C. hunanensis and C. illinoinensis as rootstocks was comparatively lower than that observed in self-grafted and non-grafted groups. The alteration in the expression patterns of DEGs involved in plant hormone synthesis and metabolism under HS corresponded to changes in plant hormone contents. Overall, Chinese hickory grafted onto C. hunanensis and C. illinoinensis exhibited enhanced resistance to high-temperature stress at the juvenile stage.

Combining Desulfurisation Gypsum and Polyacrylamide to Reduce Soil Salinity and Promote Buckwheat Photosynthesis

ABSTRACTSoil salinisation poses a significant threat to global agricultural production and food security. China is among the countries most severely impacted by soil salinisation. To investigate the improvement technology for saline–alkali stress in buckwheat, a typical multigrain crop in northwest China, a coupling regulation study using desulfurisation gypsum and polyacrylamide (PAM) was conducted in 2019 and 2020. Desulfurisation gypsum was applied at 0, 5.5, 11, 16.5 and 22 kg·ha−1, while PAM was applied at 0, 15, 30, 45 and 60 kg·ha−1. The results demonstrated that applying 11 t·ha−1 desulfurisation gypsum and 30 kg·ha−1 PAM effectively reduces soil salinity and pH, averaging 81.79% and 6.07%, respectively. Furthermore, it did not cause soil heavy metal pollution and created the best soil environment for buckwheat growth. Among the models tested, the nonrectangular hyperbolic model was the most accurate in describing buckwheat's photosynthetic light response. The optimal treatment for achieving the best photosynthetic performance—measured by apparent quantum efficiency, maximum net photosynthetic rate, light compensation point, light saturation point, dark respiration rate, stomatal conductance, intercellular CO2 concentration, transpiration rate, leaf water use efficiency and yield—was achieved through applying 11 t·ha−1 desulfurisation gypsum and 30 kg·ha−1 PAM. Therefore, desulfurised gypsum and PAM should be applied at 11 t·ha−1 and 30 kg·ha−1, respectively, to improve buckwheat's adaptability to different light intensities while promoting its photosynthetic response in saline–alkali soils. This study provides an effective technical scheme for reducing salt and promoting the growth of crops under salinity stress, which is of great significance for improving salinity land in arid areas.

Overexpression of RpKTI2 from Robinia pseudoacacia Affects the Photosynthetic Physiology and Endogenous Hormones of Tobacco.

Kunitz trypsin inhibitor genes play important roles in stress resistance. In this study, we investigated RpKTI2 cloned from Robinia pseudoacacia and its effect on tobacco. RpKTI2 was introduced into the tobacco cultivar NC89 using Agrobacterium-mediated transformation. Six RpKTI2-overexpressing lines were obtained. Transgenic and wild-type tobacco plants were then compared for photosynthetic characteristics and endogenous hormone levels. Transgenic tobacco showed minor changes in chlorophyll content, fluorescence, and photosynthetic functions. However, the maximum photochemical efficiency (Fv/Fm) increased significantly while intercellular CO2 concentration (Ci) decreased significantly. Stomatal size and hormone content (indole-3-acetic acid, zeatin riboside, gibberellin, and indole-3-propionic acid) were reduced, while brassinosteroid content increased. Random forest regression revealed that RpKTI2 overexpression had the biggest impact on carotenoid content, initial fluorescence, Ci, stomatal area, and indole-3-acetic acid. Overall, RpKTI2 overexpression minimally affected chlorophyll synthesis and photosynthetic system characteristics but influenced stomatal development and likely enhanced the antioxidant capacity of tobacco. These findings provide a basis for future in-depth research on RpKTI2.