Search Results (105)

We reexamined the critical importance of water motion in measuring algal growth and photosynthetic rates, addressing a significant limitation in traditional static incubation approaches. It presents a comprehensive framework for dynamic measurement methods that better simulate natural hydrodynamic conditions experienced by both macroalgae and other benthic autotrophs. We considered the barrier effects of the diffusion boundary layer surrounding the algae on the fluxes of gases and nutrients across the cellular membrane, and integrates findings demonstrating that flow-enhanced mass transfer of nutrients, inorganic carbon and O₂ across diffusion boundary layers can increase photosynthetic performance in macroalgae including the tested Sargassum, Porphyra and Macrocystis species. We provide quantitative comparisons demonstrating that increased velocities of water current can enhance photosynthetic and/or nutrient uptake rates compared to stagnant conditions. The comparative analysis highlights the advantages of flowing water systems in reducing diffusion limitations and better simulating natural environments against the technical simplicity of static methods. We detailed practical methodologies including flow-through system setup and sealed chamber with magnetic stirring techniques for macroalgae, and brush substrate for benthic diatoms. These approaches enable diurnal physiological tracking and reveal saturation responses to increasing water velocities. The methodological framework provides researchers with robust protocols for more accurate assessment of algal photosynthesis and primary productivity in both experimental and applied contexts such as aquaculture, carbon sequestration, and ecological monitoring. Full article

The application of biochar and magnesium (Mg) fertilizer can alleviate acidification, improve soil fertility, and enhance tea quality. However, the effects of different biochar application rates on soil properties, tea photosynthesis, and quality remain unclear. To elucidate their effects, a 90-day pot experiment was conducted with nine treatments: conventional fertilization (CK), improved conventional fertilization (CF), Mg fertilizer (MF), low/medium/high biochar (LBCF, MBCF, HBCF), and their combination with Mg (LBMF, MBMF, HBMF) in a controlled growth chamber, and soil properties, tea plant photosynthesis, and tea quality were measured. The results showed that higher application rates of biochar with Mg significantly alleviated soil acidification, increasing pH by 0.20–0.24 units. HBMF significantly enhanced key soil nutrients: total carbon (+198.11%), total nitrogen (+116.43%), and ammonium nitrogen (+73.89%). Ex-Mg increased with Mg addition and was further promoted by biochar, and photosynthetic rates increased by 71.69–101.41% in biochar and Mg application. These improvements increased free amino acids, caffeine, and soluble sugars in tea leaves by 39.56%, 46.88%, and 30.79% respectively under HBMF. Additionally, the relative contents of alcohols and esters increased by 93.29% and 62.20%, with marked rises in linalool and methyl salicylate. The increased tea quality is linked to higher activities of β-glucosidase and lipoxygenase observed in HBMF. In conclusion, the combined application of high biochar (2% of soil weight) and Mg fertilizer (15% of fertilizer weight) effectively improved soil quality, enhanced photosynthesis, and ultimately elevated both the taste and aroma quality of tea. Full article

Tropical maize often exhibits photoperiod sensitivity, which limits its adaptation to temperate regions. Understanding its proteomic dynamics under long-day conditions is therefore crucial for germplasm improvement. This study employed a Tandem Mass Tag (TMT)-based proteomic approach to investigate stage-specific protein expression patterns in the tropical maize inbred line QR273 under long-day conditions (16 h light/8 h dark). Seeds were cultivated in climate chambers, and leaves were collected at the four-leaf (P4) and nine-leaf (P9) stages. A total of 2881 differentially expressed proteins (DEPs) were quantified between the P4 and P9 stages, among which only 7 were upregulated and 2874 were downregulated at the P9 stage. Gene Ontology (GO) enrichment analysis revealed that these DEPs were significantly enriched in processes related to proteolysis, membrane components, and ATP binding. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed the enrichment of DEPs in amino acid biosynthesis, secondary metabolite biosynthesis, and aminoacyl-tRNA biosynthesis pathways. Protein–protein interaction (PPI) network analysis identified 60S ribosomal protein L12, adenosine 5′-phosphosulfate reductase, and RuvB helicase as core hub proteins. Based on functional annotation of representative DEPs, the DEPs were classified into four categories: 9 proteins related to storage material protection, 14 proteins related to protein modification, 12 proteins related to photosynthesis, and 25 proteins with other biological functions. Comparative analysis demonstrated a decrease in storage material protection, protein modification, and photosynthetic capacity at the P9 stage relative to the P4 stage. These findings provide insights into the proteomic dynamics underlying tropical maize development under long-day conditions and offer a theoretical basis for genetic improvement of tropical maize germplasm. Notably, inferences regarding nutrient reallocation based on DEP downregulation are derived solely from proteomic data and require further experimental validation. Full article

Muskmelon (Cucumis melo) is a widely cultivated and economically important fruit crop that is severely affected by Fusarium wilt caused by Fusarium oxysporum f. sp. melonis (race 1.2) (Fom). Conventional management practices have shown limited effectiveness and pose environmental and health risks; therefore, sustainable and eco-friendly alternatives are required to manage this disease. In the present study, 23 endophytic fungal isolates belonging to eight genera were isolated from Ecballium elaterium and screened to determine antifungal potential against Fom using an in vitro antagonistic assay. Two endophytic isolates (Fusarium sp. EeR4 and Fusarium clavum EeR24) exhibited an inhibitory effect against Fom on quarter-strength PDA plates. In growth chamber experiments, F. clavum EeR24-colonized melon seedlings and significantly protected plants from wilting compared to non-colonized pathogen-challenged seedlings. Under greenhouse conditions, F. clavum EeR24 significantly improved morphological and physiological traits, including plant height, weight, number of leaves, membrane stability, photosynthesis, stomatal conductance, and transpiration, in Cucumis melo. Endophytic colonization improved catalase (56%), guaiacol peroxide (47%), and superoxide dismutase activity (25%), and increased flavonoid and phenolic content by 11–59% compared to non-colonized Fom-challenged plants. Lipid peroxidation significantly decreased by 37% and proline accumulation increased by 70% in colonized plants compared to non-colonized plants. Histochemical analysis also indicated that endophytic colonization considerably reduced the levels of H₂O₂, O₂⁻, malondialdehyde, and cell mortality in Fom-challenged plants. In addition, the culture filtrate and organic residues of F. clavum EeR24 inhibited the mycelial growth of Fom by 52–58%, respectively. Furthermore, a study on spatial colonization of the endophyte and the pathogen using GFP and RFP tagging indicated that both the endophyte and the pathogen simultaneously colonized the root tissues of C. melo; however, the endophyte significantly reduced the pathogenicity of Fom. These results suggest that endophytic F. clavum EeR24 may be developed as an effective biocontrol agent for the management of Fusarium wilt in melon plants under field conditions. Full article

Assimilated carbon allocation to belowground processes may influence soil respiration (Rs). Because Rs includes autotrophic respiration (Ra) and heterotrophic respiration (Rh), different root and microbial responses complicate the separation of these effects. In a temperate deciduous broadleaf forest, we used sap flux density and estimated photosynthesis as indicators of plant activity. Total soil respiration and heterotrophic respiration were measured using automated chambers, and autotrophic respiration was estimated as Rs minus Rh. We examined the overall responses and time lags of respiration components. Ra showed positive relationships with sap flux density and estimated photosynthesis (R² = 0.37 and 0.30, p < 0.05), whereas Rh showed weaker relationships (R² = 0.20 and 0.15, p < 0.05). In lagged cross-correlation analyses using high-resolution data, Rs and Ra showed maximum responses 13 h after plant activity changes, whereas Rh showed no lag response (p > 0.05). These results suggest that associations with plant activity were clearer for Ra than Rh, and that the detected lagged response of soil respiration was more consistent with partitioned Ra than Rh. However, because Ra was estimated as Rs minus Rh, these patterns should be interpreted cautiously. Considering the responses and time lags of respiration components may improve ecosystem carbon cycling predictions. Full article

In controlled environment agriculture (CEA), CO₂ enrichment can promote photosynthesis while simultaneously reducing evapotranspiration, but the optimal settings vary depending on crop type, growth stage, and microclimate. This study presents a near-field remote sensing framework that fuses RGB image features with environmental variables to predict the CO₂ uptake/respiration dynamics of five leafy vegetables grown in a hydroponic culture system and evaluate their impact on resource efficiency under CO₂ control. A hybrid deep model incorporating You Only Look Once version 11 (YOLOv11) and a Residual Network with 50 layers (ResNet50) extracts growth-related visual cues and integrates them with tabular features (CO₂, temperature, and light conditions) to predict chamber CO₂ dynamics. Performance was evaluated by Mean Absolute Error (MAE)/Mean Squared Error (MSE) on withheld data, and the system-level impacts on water use (ET), pumping energy, and relative yield were analyzed using a conventional greenhouse model. The model exhibited high accuracy (MAE = 0.95; MSE = 1.62). Scenario analysis results showed that increasing ambient CO₂ concentration from 400 to 1200 ppm reduced modeled water demand by approximately 11%, increased modeled yield by approximately 9%, and resulted in a corresponding reduction in pumping energy per unit area. Unlike conventional single-crop, table-based approaches, this study demonstrates multi-crop generalization and image-environment fusion for CO₂ dynamic prediction, establishing proximity sensing as a viable decision-making layer for CEA. While yield/ET results were simulated rather than measured in long-term trials, and leaf area normalization was not available, the proposed framework provides a viable path for data-driven CO₂ control in indoor farms by linking image-based monitoring with operational optimization. Full article

The sexual generation of Schlechtendalia chinensis (Bell) is pivotal for gallnut yield yet cannot feed due to mouthpart degeneration. Could respiratory metabolic rate (RMR) modulation compensate for nutritional deficits? We quantified the RMR across key developmental stages of sexual morphs (including parental sexuparae and progeny fundatrices) using an LI-6400XT portable photosynthesis system equipped with a customized insect respiration chamber (6400-89). All morphotypes exhibited significantly lower nocturnal RMRs compared to their diurnal rates (p < 0.05), while RMRs did not differ significantly between morning (9:00–12:00) and afternoon (14:00–17:00) (p > 0.05). Significant RMR variation occurred among morphotypes: females and sexuparae displayed the lowest rates, fundatrices were intermediate, and males exhibited remarkably elevated rates (2–3 times higher than those of females or sexuparae). Both sexes showed a characteristic RMR trajectory: elevated at birth and declining during early postnatal development, followed by a gradual resurgence that culminated in peak values on postnatal day 8, coinciding with mating. This physiological zenith was immediately succeeded by marked respiratory metabolic downregulation following copulation, with RMRs decreasing substantially during the post-copulatory phase. Our findings demonstrate significant intergenerational and intersexual RMR differentiation. This research addresses critical knowledge gaps in the respiratory metabolism of S. chinensis, is the first to elucidate a nutrient adaptation strategy through respiratory metabolic regulation under non-trophic conditions, and provides actionable insights for optimizing gallnut production in controlled cultivation systems. Full article

The suitable growth environment for quinoa is high-altitude areas. In recent years, quinoa is also gradually cultivated in other regions with high-temperature exposure. High-temperature stress poses a potential constraint on quinoa quality and yield by impacting pigments, photosynthesis, and metabolites. This study aimed to investigate the effect of exogenous melatonin (MT) in alleviating heat stress on quinoa in controllable conditions. Day/night temperatures were maintained at 35/25 °C in a climate chamber, and foliar spraying was performed using melatonin (MT) concentrations of 0, 50, 100, and 200 μmol L⁻¹. Day/night temperatures were maintained at 25/15 °C in another climate chamber as a comparative trial. Our results demonstrated that high temperature decreased the levels of photosynthetic pigments and the values of photosynthetic rate (P_n), stomatal conductance (g_s), and transpiration rate (T_r). Additionally, it also influenced the accumulation of polyphenols and altered polyphenol oxidase (PPO) activity in the red quinoa (RQ) cultivar. Obvious reductions in gas exchange parameters and metabolites including flavonoid, anthocyanin, and PPO were observed both in the BQ cultivar and the WQ cultivar. However, the application of 100 μmol L⁻¹ MT significantly increased the levels of photosynthetic pigments, the values of P_n, g_s, and T_r, and the PPO activity, as well as the contents of flavonoid and anthocyanin in the RQ cultivar. The application of 50 μmol L⁻¹ MT only led to an increase in the concentrations of Chl a, Chl (a + b), and flavonoids, as well as PPO activity, whereas 100 μmol L⁻¹ MT significantly enhanced the values of P_n, g_s, and T_r and the PPO activity. Additionally, 200 μmol L⁻¹ MT contributed to the synthesis of anthocyanins and polyphenols, and enhanced PPO activity in the BQ cultivar. The application of 50 μmol L⁻¹ MT limited the increase in the contents of total polyphenols, flavonoids, and anthocyanin, we all as PPO activity, in the WQ cultivar. The findings demonstrated that photosynthesis and metabolite synthesis in quinoa under high temperatures depends on an interactive response between cultivar and melatonin levels. The application of 100 μmol L⁻¹ MT was found to be optimal for alleviating the adverse effects of high temperature on photosynthesis and metabolites in the RQ cultivar during actual production. Full article

Regional increases in atmospheric O₃ are phytotoxic not only to major crops but also to root vegetables such as radish, and their effects can be further modulated by nitrogen (N) addition. To assess how cherry radish responds to elevated O₃ (eO₃) under N addition and to compare the dose–response relationships, we established six open-top chambers with two O₃ levels and two N treatments in Beijing, China, to examine gas exchange, growth, and biomass throughout the growing period. The results showed that: 1. eO₃ had a “priming effect” on photosynthesis rates (Pn) at the beginning of the experiment. N addition alleviated the O₃-induced Pn reduction at the end of the experiment by 6.76% but did not significantly influence the O₃-dose response to Pn; 2. stomatal conductance (gs) did not have a dose response to all treatments while evaporation rates (E) showed strong negative regression with AOT40; 3. N addition reduced the hypocotyl biomass (−47.70%), leaf biomass (−32.22%), and the whole plant biomass reduction caused by O₃ (−38.47%) at the end of the experiment, but N addition did not significantly influence O₃-dose response to biomass. In conclusion, N addition can alleviate O₃-induced reductions in Pn and biomass via non-stomatal mechanisms, but it is ineffective in altering long-term O₃ dose–response relationships. Soil N addition offers a short-term strategy to mitigate O₃ impacts on short-lived root vegetables such as cherry radish but does not influence key functional traits over the long term. This study highlights the potential of N addition to alleviate acute oxidative stress, while underscoring its limitations in mitigating the effects of prolonged O₃ exposure in root vegetables. Full article

Sugar beet is a nitrogen (N)-sensitive crop, and its N regulation and utilization are critical for enhancing productivity. Sugar beet seedlings at the two-true-leaf-pair stage were hydroponically grown in an artificial climate chamber. Leaves and roots from three seedlings per treatment were sampled at 10, 20, 25, and 30 days after exposure to N treatments (N5: 5 mmol/L, N10: 10 mmol/L, N15: 15 mmol/L, and N20: 20 mmol/L) to assess the effects of N supply level on growth, photosynthesis, and carbon and nitrogen metabolism. The results revealed a time-dependent dynamics in beet biomass accumulation, with N20 inducing chlorosis and necrosis symptoms by 10 days post-treatment (DPT), resulting in the lowest biomass. While N15 significantly promoted root biomass by 30 DPT, showing a 23.70% (root dry weight, RDW) increase over N20; chlorophyll content and gas exchange parameters-net photosynthetic rate (Pn), stomatal conductance (Gs), transpiration rate (Tr) exhibited significant N dependence, with N15 maintaining high chlorophyll level (0.78 mg/g) and photosynthetic rate (220.33 μmol/(m²·s). Nitrogen assimilation, as indicated by glutamine synthetase and glutamate synthetase activity (GS and GOGAT), was stronger under N15, promoting amino acid synthesis and root growth, whereas N20 inhibited enzyme activity. Carbon metabolism analysis revealed that N15-driven sucrose synthesis significantly increased root sucrose content, sucrose phosphate synthase and sucrose synthase activity (SPS and SS), optimizing source–sink allocation. Correlation analysis showed a positive relationship between leaf and root biomass (r = 0.91), and root sucrose content was positively correlated with GOGAT activity (r = 0.90), emphasizing the synergistic regulation of C/N metabolism. On the contrary, N20 led to disrupted C/N metabolic homeostasis, inhibited enzyme activity, and C/N distribution. These results indicated that the photosynthetic output, enzyme efficiency, and sucrose distribution were coordinated by nitrogen optimization, and the growth of sugar beet seedlings was optimized. Full article

Mulberry (Morus alba L.), a species of significant ecological and economic importance, is widely cultivated for sericulture, soil conservation, and environmental restoration. Despite its remarkable resilience to environmental stresses, the combined impact of elevated CO₂ (eCO₂) and drought stress on aboveground–root–soil interactions remains poorly understood, particularly in the context of global climate change. Here, we investigated the effects of eCO₂ and drought on physiological leaf and root indicators, nutrient absorption and allocation, and soil properties in mulberry seedlings. Mulberry seedlings were grown in environmentally auto-controlled growth chambers under ambient CO₂ (420/470 ppm, day/night) or eCO₂ (710/760 ppm) and well-watered (75–85% soil relative water content, RWC), moderate-drought (55–65% RWC), or severe-drought (35–45% RWC) conditions. Results showed that both above- and below-ground plant biomass production were significantly promoted by eCO₂, particularly by 36% and 15% under severe drought, respectively. This could be attributed to several factors. Firstly, eCO₂ improved leaf photosynthesis by 25–37% and water use efficiency by 104–163% under drought stresses while reducing negative effects of drought on the effective quantum yield of PSII photochemistry and the photochemical quenching coefficient. Secondly, eCO₂ significantly decreased proline accumulation while increasing soluble sugar contents, as well as peroxidase and superoxide dismutase activities, in both leaves and roots under drought stress. Lastly, eCO₂ promoted soil sucrase, urease, and phosphatase activities, as well as plant nitrogen, phosphorus and potassium uptake while facilitating their allocation into roots under drought stress. These findings demonstrate that eCO₂ enhanced the drought tolerance of mulberry plants through improvements in photosystem II efficiency, water use efficiency, antioxidative defense capacity, and nutrient uptake and allocation, providing critical insights for sustainable mulberry plantation management under future climate change scenarios. Full article

There are many factors affecting rice yield and quality during cultivation, including temperature, light, water, and fertilization, among which high temperature (HT) is one of the main factors affecting rice yield and quality. However, less is known about the effects and potential mechanisms of different durations of HT stress during the grain filling stage on grain quality. In this study, the differences in rice quality and starch rapid viscosity analyzer (RVA) characteristics of eight indica rice varieties under different high-temperature treatment times were studied by simulating high temperature in an artificial climate chamber. The prolonged duration of HT leads to an overall deterioration in the milling quality, appearance quality, and cooking quality of rice. The impact of HT duration on the starch RVA characteristics of rice is more complex and is mainly related to the varieties. Among them, the starch RVA characteristics of R313 were more stable. It is worth noting that there is a significant difference in the sensitivity of the appearance quality of 8XR274 and 5W0076 to HT duration, with 8XR272 being more sensitive and 5W0076 being the opposite. We selected these two varieties for transcriptome analysis after 14 days of HT treatment and found that the number of differentially expressed genes (DEGs) in 8XR274 was significantly less than that in 5W0076. The DEGs of 8XR274 were mainly enriched in pathways related to carbohydrates, while 5W0076 was mainly enriched in pathways related to photosynthesis. Our study provides a new perspective on the molecular response and related genes of different rice varieties under high temperature, as well as the high-quality rice breeding under high temperature. Full article

Cucumber cultivation suffers from severe yield and quality decline due to cold damage. Cucurbita ficifolia is used as a rootstock for grafting cucumber to improve resistance due to its excellent resistance. This study used Yunnan C. ficifolia as the rootstock and Jingyan Xiamei 2 cucumber as the scion, simulating common low-temperature stress of 15 °C, 10 °C, and 5 °C in an artificial climate chamber, to study the mechanism of cucumber-grafted seedlings responding to low temperatures in terms of growth and development, photosynthesis, osmotic regulation substances, antioxidant system, and gene expression. The results showed that the growth and development of grafted seedlings of C. ficifolia was less inhibited, the chlorophyll content was less reduced, and the content of osmoregulatory substances was significantly increased under low-temperature stress. The activity of antioxidant enzymes in grafted seedlings of C. ficifolia was significantly upregulated at low temperatures, and the expression of antioxidant enzyme genes was consistently higher in grafted seedlings of C. ficifolia. These results confirmed that C. ficifolia as a rootstock could improve the cold resistance of cucumber. Collectively, this study provides the basis for revealing the physiological and molecular mechanism of grafting seedlings to improve cucumber’s low temperature tolerance. Full article

Gross primary productivity (GPP), the primary driver of carbon accumulation, governs the sequestration of atmospheric CO₂ into biomass. However, GPP cannot be measured directly, as photosynthesis and respiration are simultaneous. At canopy level in plot-scale studies, GPP can be estimated through the closed chamber-based measurements of net ecosystem exchange (NEE) and ecosystem respiration (Reco). This technique is cost-effective and widely used in small-scale studies with short vegetation, but measurements are periodic-based and require temporal interpolations. The rectangular hyperbolic model (RH) was the basis of this study, developing two temperature-dependent factors following a linear and exponential shift in GPP when the temperature oscillates from the optimum for vegetation performance. Additionally, a water table depth (WTD)-dependent model and an exponential model were tested. In the peak season, modified RH models showed the best performance, while for the rest of the year, the best model varied for each subplot. The statistical results demonstrate the limitations of assuming the light-use efficiency as a fixed shape mechanism (using only one model). Therefore, a multi-model approach with the best performance model selected for each period is proposed to improve GPP estimations for peatlands. Full article

The present work aimed to investigate the effect of increasing CO₂ concentration on the growth, productivity, grain quality, and biochemical changes in quinoa and amaranth plants. An experiment was conducted in open chambers (OTCs) to evaluate the responses of these species to different levels of CO₂ {a[CO₂] = 400 ± 50 μmol mol⁻¹ CO₂ for ambient CO₂ concentration, e[CO₂] = 700 ± 50 μmol mol⁻¹ CO₂ for the elevated CO₂ concentration}. Growth parameters and photosynthetic pigments reflected changes in gas exchange, saccharolytic enzymes, and carbohydrate metabolism when plants were grown under e[CO₂]. Furthermore, both species maintained most of the parameters related to gas exchange, demonstrating that the antioxidant system was efficient in supporting the primary metabolism of plants under e[CO₂] conditions. Both species were taller and had longer roots and a greater dry weight of roots and shoots when under e[CO₂]. On the other hand, the panicle was shorter under the same situation, indicating that the plants invested energy, nutrients, and all mechanisms in their growth to mitigate stress in expense of yield. This led to a reduction on panicle size and, ultimately, reducing quinoa grain yield. Although e[CO₂] altered the plant’s metabolic parameters for amaranth, the plants managed to maintain their development without affecting grain yield. Protein levels in grains were reduced in both species under e[CO₂] in the average of two harvests. Therefore, for amaranth, the increase in CO₂ mainly contributes to lowering the protein content of the grains. As for quinoa, its yield performance is also affected, in addition to its protein content. These findings provide new insights into how plants C3 (amaranth) and C4 (quinoa) respond to e[CO₂], significantly increasing photosynthesis and its growth but ultimately reducing yield for quinoa and protein content in both species. This result ultimately underscore the critical need to breed plants that can adapt to e[CO₂] as means to mitigate its negative effects and to ensure sustainable and nutritious crop production in future environmental conditions. Full article