High Nitrogen Treatment Research Articles

Impact of nitrogen rates on biosynthesis pathways: A comparative study of diterpene synthases in clerodane diterpenoids and enzymes in benzylisoquinoline alkaloids

Tinospora sagittata is rich in secondary metabolites used in traditional medicine. However, environmental factors impact key enzymes in metabolite synthesis, highlighting the need for improved growth conditions. This study employs transcriptomics and metabolomics to assess nitrogen's impact on enzymes in secondary metabolites biosynthesis pathways. The gene expressions of berberine bridge enzymes (BBEs) like TsBBE2 had peak expression in low nitrogen treatments (A0 and A1) but were absent in higher nitrogen treatments (A2 and A3). Similar trends were observed for other enzymes such as (S)-scoulerine 9-O-methyltransferase (TsCMT3), Tetrahydroberberine oxidase (TsSTOX), and Columbamine O-methyltransferase (TsCoCOMT2-4) in response to nitrogen levels. In examining gene families related to diterpene synthases (diTPS), 1-deoxyxylulose 5-phosphate synthase (TsDXR1) expression increased with higher nitrogen fertilizer, while TsDXR2 peaked at maximal nitrogen levels. Geranylgeranyl diphosphate synthase (TsGGPP3 and TsGGPP5) decreased with nitrogen levels. (−)-kolavenyl diphosphate synthase (KPS) genes had higher expression in treatments, while ent-kaurene synthase (KSL) genes, especially TsKSL1 and TsKSL2, showed higher expression in control conditions with lower nitrogen fertilizer. Metabolite analysis confirmed more upregulated compounds in A3 compared to A0. These findings have practical implications for agriculture and pharmaceuticals, highlighting the link between nitrogen fertilization and specialized metabolism in medicinal plants.

Reinforcing Nitrogen Nutrition Through Partial Substitution with Organic Nitrogen Enhances the Properties of Natural Rubber

The partial substitution of chemical fertilizer with organic fertilizer is a crucial practice for enhancing crop production and quality, although its impact on natural rubber has rarely been explored. In this study, a two-year field experiment was conducted to investigate the impact of different nitrogen application rates and varying proportions of organic nitrogen substitution on dry rubber yield, nitrogen nutrition, and natural rubber properties. Regarding nitrogen application, the control treatment received no nitrogen amendment, while the low-nitrogen treatment was amended with 138 g·tree−1·year−1 of nitrogen. The medium-nitrogen treatment received 276 g·tree−1·year−1 of nitrogen, and the high-nitrogen treatment received 552 g·tree−1·year−1 of nitrogen. In addition, the low-organic-nitrogen substitution treatment and medium-organic-nitrogen substitution treatment were amended with 276 g·tree−1·year−1 of nitrogen each. The results demonstrated that the 50% organic nitrogen substitution treatment resulted in the highest dry rubber yield across all sampling periods, ranging from 46.43 to 94.65 g·tree−1. Additionally, this treatment exhibited superior soil total nitrogen (1067.69 mg·kg−1), available nitrogen (84.06 mg·kg−1), and nitrogen content in roots (1.08%), leaves (3.25%), fresh rubber latex (0.27%), and raw natural rubber (0.44%) compared with other treatments. In terms of the physical properties of natural rubber, the 50% organic nitrogen substitution treatment resulted in advantages in the weight-average molecular weight (1.57 × 106 g·mol−1), number-average molecular weight (0.36 × 106 g·mol−1), plasticity retention index (97.35%), Wallace plasticity (40.25), and Mooney viscosity (81.40). For mechanical properties, natural rubber from the substitution treatment exhibited higher tensile strength (19.84 MPa), greater elongation at break (834.75%), and increased tear strength (31.07 N·mm−1). Overall, the substitution of 50% chemical nitrogen fertilizer with organic nitrogen fertilizer improved nitrogen nutrition in rubber trees by introducing organic nitrogen input, resulting in remarkable enhancements in natural rubber properties. Therefore, the incorporation of organic fertilizer as a substitution for 50% of chemical fertilizer is demonstrated as an effective strategy for improving both the yield and properties of natural rubber.

Effects of Water and Nitrogen Regulation on Apple Tree Growth, Yield, Quality, and Their Water and Nitrogen Utilization Efficiency.

Apple tree productivity is influenced by the quantity of water and nutrients that are supplied during planting. To enhance resource utilization efficiency and optimize yields, a suitable strategy for supplying water and nitrogen must be established. A field experiment was conducted using a randomized block group design on five-year-old apple trees in Ningxia, with two irrigation lower limit levels (55%FC (W1) and 75%FC (W2)) and four N application levels (0 (N1), 120 (N2), 240 (N3), and 360 (N4) kg·ha-1). Our findings showed that leaf N content increased with a higher irrigation lower limit, but the difference was not statistically significant. However, the leaf N content significantly increased with increasing N application. The growth pattern of new shoots followed logistic curve characteristics, with the maximum new shoot growth rate and time of new shoot growth being delayed under high water and high nitrogen treatments. Apple yield and yield components (weight per fruit and number of fruits per plant) were enhanced under N application compared to no N application. The maximum apple yields were 19,405.3 kg·ha-1 (2022) and 29,607 kg·ha-1 (2023) at the N3 level. A parabolic relationship was observed between apple yield and N application level, with the optimal range of N application being 230-260 kg⸱ha-1. Apple quality indicators were not significantly affected by the irrigation lower limit but were significantly influenced by N application levels. The lower limit of irrigation did not have a significant impact on the quality indicators of the apples. Water and N utilization efficiencies improved with the W2 treatment at the same N application level. A negative relationship was observed between the amount of nitrogen applied and the biased productivity of nitrogen fertilizer. The utilization of nitrogen fertilizer was 127.6 kg·kg-1 (2022) and 200.3 kg·kg-1 (2023) in the W2N2 treatment. The apple yield was sustained, the quality of the fruit improved, and a substantial increase in water productivity was achieved with the W2N3 treatment. The findings of this study can be used as a reference for accurate field irrigation.

Susceptibility of Zucchini Cultivars to Powdery Mildew (Podosphaera xanthii) Under High- and Low-Nitrogen Regimes

Powdery mildew, primarily caused by Podosphaera xanthii, threatens cucurbit crop yield and longevity. Fungicides and resistant cultivars cannot fully manage or prevent the disease. Previous work has shown that powdery mildew incidence and severity can increase under high soil nitrogen. This study was conducted in Kentucky to determine disease severity and yield using a split plot design with nitrogen fertility (high: 140 kg/ha; low: 84 kg/ha) and zucchini cultivar (Cash Machine, Cue Ball, Desert, Dunja, Eight Ball, Emerald Delight, Golden Glory, Mexicana, and Spineless Perfection) as the main plot and subplot factors, respectively. In year 1, powdery mildew severity was significantly higher in high soil nitrogen and varied significantly among cultivars. Yield was significantly lower in high soil nitrogen. Significant differences in fruit count, but not fruit weight, were observed among the cultivars. In year 2, nitrogen did not significantly affect disease severity, but fruit weight and count were significantly lower in the high soil nitrogen treatment. Golden Glory had significantly higher powdery mildew severity, while Mexicana and Eight Ball had significantly lower severity compared to all other cultivars. Spineless Perfection had the highest fruit weight and was significantly higher than all other cultivars except for Cue Ball and Eight Ball. Golden Glory had the highest fruit count and was significantly higher than all others except for Dunja. Nitrogen did not consistently affect disease severity throughout the study. The effects of powdery mildew on yield should be explored further, as heavily diseased plants did not always have low yield.

Nitrogen Addition Mitigates Drought by Promoting Soybean (Glycine Max (Linn.) Merr) Flowering and Podding and Affecting Related Enzyme Activities

Drought at the flower and pod stage, which is the most moisture-sensitive stage of soybean development, is the main cause of yield loss in soybean. Nitrogen is a vital nutrient for soybeans. The objective of this study was to assess the potential of post-drought nitrogen fertilization at the soybean (Heihe 45) pod stage to (1) reduce pod shedding and increase yield, and (2) elucidate the mechanisms by which nitrogen fertilization regulates soybean growth under drought stress. The pot experiment was designed with two moisture levels and three nitrogen levels, resulting in a total of six treatments. The results show that nitrogen reduces cellular oxidation by regulating key enzymes of sucrose metabolism, such as sucrose synthase and sucrose phosphate synthase; and regulates cellulase to reduce shedding and mitigate drought. Comparison of low and high nitrogen conditions under drought conditions showed that the number of flowers and pods in soybean increased by 30% and 32.94%, respectively, malondialdehyde content decreased by 24%, cellulase activity in flowers and pods decreased by 15.07% and 12.31%, respectively, and yields increased by 29.98% under high nitrogen conditions. The high nitrogen treatment performed optimally and the differences between treatments reached the significant level.

Effects of nitrogen application on ammonium assimilation and microenvironment in the rhizosphere of drip-irrigated sunflower under plastic mulch.

This study investigated the effect of nitrogen application on the rhizosphere soil microenvironment of sunflower and clarified the relationship between ammonium assimilation and the microenvironment. In a field experiment high (HN, 190 kg/hm2), medium (MN, 120 kg/hm2) and low nitrogen (CK, 50 kg/hm2) treatments were made to replicate plots of sunflowers using drip irrigation. Metagenomic sequencing was used to analyze the community structure and functional genes involved in the ammonium assimilation pathway in rhizosphere soil. The findings indicated that glnA and gltB played a crucial role in the ammonium assimilation pathway in sunflower rhizosphere soil, with Actinobacteria and Proteobacteria being the primary contributors. Compared with CK treatment, the relative abundance of Actinobacteria increased by 15.57% under MN treatment, while the relative abundance decreased at flowering and maturation stages. Conversely, the relative abundance of Proteobacteria was 28.57 and 61.26% higher in the MN treatment during anthesis and maturation period, respectively, compared with the CK. Furthermore, during the bud stage and anthesis, the abundance of Actinobacteria, Proteobacteria, and their dominant species were influenced mainly by rhizosphere soil EC, ammonium nitrogen (-N), and nitrate nitrogen (-N), whereas, at maturity, soil pH and -N played a more significant role in shaping the community of ammonium-assimilating microorganisms. The MN treatment increased the root length density, surface area density, and root volume density of sunflower at the bud, flowering, and maturity stages compared to the CK. Moreover, root exudates such as oxalate and malate were positively correlated with the dominant species of Actinobacteria and Proteobacteria during anthesis and the maturation period. Under drip irrigation, applying 120 kg/hm2 of nitrogen to sunflowers effectively promoted the community structure of ammonium-assimilating microorganisms in rhizosphere soil and had a positive influence on the rhizosphere soil microenvironment and sunflower root growth.

Effects of Different Carbon and Nitrogen Ratios on Yield, Nutritional Value, and Amino Acid Contents of Flammulina velutipes.

The carbon-to-nitrogen (C/N) ratio in the cultivation medium significantly influences the growth rate, vigor of mycelium, yield of fruiting bodies, and their nutritional composition. Recently, agricultural and forestry wastes have been increasingly used in cultivating Flammulina velutipes. However, systematic research on how these materials affect the nutritional and functional properties of the fruiting bodies is lacking. This study investigated the effects of different C/N ratios on F. velutipes cultivation. We evaluated the agronomic traits, nutritional composition, and flavor compounds of the fruiting bodies. Our findings reveal that an optimal C/N ratio of 27:1 in the composted substrates enhances the total yield of fruiting bodies, with 25.1% soybean straw as the primary raw material. This ratio also significantly increases the levels of crude protein, total amino acids, and essential amino acids in the fruiting bodies (p < 0.05). Fruiting bodies from the high-nitrogen (HN) treatment showed the highest content of umami amino acids and equivalent umami concentration value. Additionally, we employed an untargeted liquid chromatography-mass spectrometry (LC-MS)-based metabolomics approach to analyze the metabolite profiles of fruiting bodies cultivated in high-nitrogen (HN), medium-nitrogen (MN), and low-nitrogen (LN) substrates. We found that the carbon-nitrogen ratio can affect the flavor and quality of fruiting bodies by regulating amino acid biosynthesis and metabolism and other related pathways. Our results suggest that a C/N ratio of 27:1 offers numerous benefits for the cultivation of F. velutipes with comprehensive analyses and has promising application prospects.

Interactions between halotolerant nitrogen-fixing bacteria and arbuscular mycorrhizal fungi under saline stress.

Soil salinity negatively affects crop development. Halotolerant nitrogen-fixing bacteria (HNFB) and arbuscular mycorrhizal fungi (AMF) are essential microorganisms that enhance crop nutrient availability and salt tolerance in saline soils. Studying the impact of HNFB on AMF communities and using HNFB in biofertilizers can help in selecting the optimal HNFB-AMF combinations to improve crop productivity in saline soils. We established three experimental groups comprising apple plants treated with low-nitrogen (0 mg N/kg, N0), normal-nitrogen (200 mg N/kg, N1), and high-nitrogen (300 mg N/kg, N2) fertilizer under salt stress without bacteria (CK, with the addition of 1,500 mL sterile water +2 g sterile diatomite), or with bacteria [BIO, with the addition of 1,500 mL sterile water +2 g mixed bacterial preparation (including Bacillus subtilis HG-15 and Bacillus velezensis JC-K3)]. HNFB inoculation significantly increased microbial biomass and the relative abundance of beta-glucosidase-related genes in the rhizosphere soil under identical nitrogen application levels (p < 0.05). High-nitrogen treatment significantly reduced AMF diversity and the relative abundance of beta-glucosidase, acid phosphatase, and urea-related genes. A two-way analysis of variance showed that combined nitrogen application and HNFB treatment could significantly affect soil physicochemical properties and rhizosphere AMF abundance (p < 0.05). Specifically, HNFB application resulted in a significantly higher relative abundance of Glomus-MO-G17-VTX00114 compared to that in the CK group at equal nitrogen levels. The impact of HNFB on the AMF community in apple rhizospheres is influenced by soil nitrogen levels. The study reveals how varying nitrogen levels mediate the relationship between exogenous HNFB, soil properties, and rhizosphere microbes.

Nutrient enrichment alters phytoplankton biomass and composition via silicon limitation

Despite management efforts, anthropogenic nutrient enrichments continue to enhance phytoplankton blooms worldwide. Release of nitrogen and phosphorus compounds not only provides surplus of nutrients but also disbalances their stoichiometry. Declines in the relative availability of dissolved silicon might induce limitation in diatoms, major primary producers with silicified shells. We studied experimentally how nutrient enrichment and resulting decline in dissolved silicon to nitrogen ratios (Si:N) affect the structure and functioning of natural plankton communities. Nitrate was added to create a range of Si:N ratios and phosphate was supplied in Redfield ratio to nitrogen. We also manipulated copepod abundance to understand the top-down effects on communities experiencing nutrient enrichment. Nitrogen and phosphorus additions resulted in a steep phytoplankton biomass increase, followed by a post-bloom decline. Phytoplankton bloom biomass was higher in high nitrogen treatments but during the post-bloom period this trend switched. Biomass was sustained longer in high Si:N treatments, indicating that silicon limitation terminates the bloom. Many diatom species did not benefit from nitrogen and phosphorus enrichment and diatom dominance ceased below Si:N of 0.4:1. Under high grazing pressure, silicate was taken up faster suggesting that silicification is important in diatom defense. Copepods shaped plankton communities via feeding on dinoflagellates, chlorophytes and the diatom Skeletonema costatum but there was no significant effect of nitrogen and phosphorus enrichment on copepod abundance. Our results, combined with previous studies, show that while nutrient concentrations define the total phytoplankton bloom biomass, resource ratios are important in sustaining biomass and determining community structure and composition.

Response of soil microbial community structure to temperature and nitrogen fertilizer in three different provenances of Pennisetum alopecuroides.

Soil microorganisms are key indicators of soil health, and it is crucial to investigate the structure and interactions of soil microbial communities among three different provenances of Pennisetum alopecuroides under varying nitrogen fertilizer and temperature levels in Northwest China. This study aims to provide theoretical support for the sustainable use of artificial grassland in this region. Employing a two-factor pot-control experiment with three nitrogen fertilizer treatments and three temperature treatments, a total of all treatments was utilized to examine the composition and abundance of soil microbial communities associated with Pennisetum alopecuroides using high-throughput sequencing, PCR technology, and molecular ecological network analysis. The results revealed that Proteobacteria was the dominant bacterial phylum while Ascomycota was the dominant fungal phylum in the soil samples from three provenances of Pennisetum. Specifically, Proteobacteria exhibited higher abundance in the N3T2 treatment compared to other treatments under N3T2 (25-30°C, 3 g/pot) treatment conditions in Shaanxi and Gansu provinces; similarly, Proteobacteria was more abundant in the N1T2 (25-30°C, 1 g/pot) treatment in Inner Mongolia under N1T2. Moreover, Ascomycota displayed higher abundance than other treatments in both Inner Mongolia and Gansu provinces. Additionally, Pennisetum Ascomycota demonstrated greater prevalence under (25-30°C, 3 g/pot) treatment compared to other treatments; furthermore, Shaanxi's Pennisetum Ascomycota exhibited increased prevalence under N3T1 (18-23°C, 3 g/pot) treatment compared to other treatments. The richness and diversity of soil microbial communities were significantly influenced by nitrogen fertilizer and temperature changes, leading to notable alterations in their structure. Molecular ecological network analyses revealed strong collaborative relationships among microbial species in Shaanxi Pennisetum and Inner Mongolia Pennisetum under high nitrogen and high temperature treatments, while competitive relationships were observed among microbial species in Gansu Pennisetum under similar conditions. Redundancy analysis indicated that soil pH, total potassium, and total phosphorus were the primary environmental factors influencing microorganisms. In summary, this study offers a theoretical foundation for assessing the sustainable utilization of Pennisetum artificial grasslands in Northwest China by investigating the shifts in soil microbial communities and the driving factors under varying nitrogen fertilizer and temperature levels.

Mechanistic insights into nitrogen-induced changes in pasting characteristics of rice during storage based on proteomics analysis

Nitrogen application delays rice quality deterioration due to changes in its pasting characteristics; however, the underlying mechanisms remain unclear. Using a label-free quantitative proteomics approach, we identified differentially expressed proteins (DEPs) during storage in paddy rice treated with different nitrogen levels. On combining the changes in physiological indicators, high-nitrogen treatment was found to downregulate β-1,3-glucanase, reduce the decomposition of cell wall components, downregulate three proteins involved in starch metabolism, decrease the range of the amylose content and increase the range of the amylopectin, upregulate three proteins related to the lysosomal pathway, and enhance glutelin degradation. In addition, it upregulated three proteins related to flavonoid synthesis, which enhanced the stress response ability of rice, thereby contributing to the stability of biological macromolecules. The discovery of these key DEPs provides potential targets for further control over the deterioration of crop seed storage quality.

Effects of nitrogen addition on species composition and diversity of early spring herbs in a Korean pine plantation.

Under the background of global nitrogen deposition, temperate forest ecosystems are suffering increasing threats, and species diversity is gradually decreasing. In this study, nitrogen addition experiments were conducted on Korean pine (Pinus koraiensis) plantations in Northeast China to explore the effect of long-term nitrogen addition on herb species diversity to test the following hypothesis: long-term nitrogen addition further reduced plant species diversity by affecting plant growth, which may be due to soil acidification caused by excessive nitrogen addition. Experimental nitrogen addition was conducted from 2014 to 2021, and the nitrogen treatment levels were as follows: N0 (control treatment, 0/(kg N ha-1 year-1)), N20 (low nitrogen treatment, 20/(kg N ha-1 year-1)), N40 (medium nitrogen treatment, 40/(kg N ha-1 year-1)) and N80 (high nitrogen treatment, 80/(kg N ha-1 year-1)). A herb community survey was conducted in the region from 2015 to 2021. The results showed that long-term nitrogen addition decreased soil pH, changed the species and composition of herbaceous plants, and decreased the species diversity of understory herbaceous plants. With the increase in nitrogen application years, middle- and high-nitrogen treatments significantly reduced the diversity of early-spring flowering herbs and early-spring foliating herbs, and their diversity decreased with the decrease in soil pH, indicating that soil acidification caused by long-term nitrogen addition may lead to the decrease of plant diversity. However, for early-spring growing herbs, adequate nitrogen addition may promote their growth. Our results show that plants have evolved different life-history strategies based on their adaptation mechanisms to the environment, and different life-history strategies have different responses to long-term nitrogen addition. However, for most plants, long-term nitrogen application will have a negative impact on the growth and diversity of herbs in temperate forests.

Effects of Water and Nitrogen Coupling on Yield, Quality, Water and Nitrogen Use Efficiencies of Greenhouse Muskmelon

The proficient supply of water and nitrogen is a key factor in facility agriculture. In order to pursue high yields, most farmers blindly irrigate and fertilize, leading to yield reduction, quality decline, soil salinization, and fertility destruction. A successive two-year greenhouse experiment was carried out on fruit quality, yield, irrigation water use efficiency (IWUE), and nitrogen use efficiency (NUE) of greenhouse muskmelon (Cucumis melo L.) under drip fertigation, which can provide a scientific basis for local muskmelon intensive production in Southeast China. The experiments were conducted in 2020 and 2021, with three irrigation levels 80% (W1), 100% (W2), and 120% (W3) of ETc and three N levels 60 (N1), 95 (N2), and 130 (N3) kg N ha−1. The amount of drip irrigation water was determined every 5 days based on crop evapotranspiration (ETc). The seasonal irrigation amount ranged from 209.77 mm to 298.86 mm in 2020 and from 201.22 mm to 286.04 mm in 2021. The highest muskmelon yield was obtained in the treatment of W3N3 with an average of 27.38 t ha−1 in 2020 and 27.10 t ha−1 in 2021. Although the yield was improved by increasing nitrogen supply, there was no significant difference between N2 and N3 treatment in two years under the irrigation level of W2 and W3. The highest irrigation water use efficiency was observed in the W1N3 treatment in 2020 and 2021. The NUE increased with decreasing N rates at the same irrigation level. Under the same nitrogen application level, TSS and Vc under low water (W1) were higher than that under medium water (W2) and high water (W3) treatment. The highest content of nitrate in low water and high nitrogen (W1N3) treatment was 55.41 µg/g in 2020 and 52.50 µg/g in 2021, respectively. The yield and quality of muskmelon are often incompatible, for instance, W2N2 treatment can obtain a higher yield, but W1N2 treatment maximizes Vc, TSS of muskmelon quality. Our findings suggest that the irrigation level of 1.0 ETc, nitrogen level of 95 N ha−1, and 3500 kg·ha−1 of decomposed organic fertilizer was recommended as the best combination, which can improve the yield, quality, IWUE, NUE of muskmelon under drip fertigation with soil mulching in the experimental site.

HIGH NPK SOLUTION AND PGP IMPROVED EOS PROPERTIES OF ROSE GROWN IN COCOPEAT

This research was carried out at Research Station , Department of Horticulture and Landscape Engineering , College of Agricultural Engineering Sciences , University of Baghdad during fall season of 2020, it was aimed to improve flower productivity, quantity and quality of essential oils with increasing the concentration of N, P , K elements in the nutrient solution, and foliar app `lication of Plant growth promoters (PGP) on Rosa Damascene grown on a soilless culture system with coco peat substrate bags. A factorial experimental design was carried out according to (RCBD)with three replication. Results indicated the superiority of a high nitrogen treatment and 1.5 g of PGP (N2S2 ), of the flowers number, dry matter%, flower diameter, oil quantity and all physical and the anatomical characteristics, represented by the diameter of the head diameter of the glandular capillaries. Petals number increased significantly with a high potassium nutrient solution and PGP 1 g (N4S1).The high phosphorous solution, which was not treated with growth stimulator, showed superiority in the length of glandular capillaries.

Effects of Nitrogen Application in Recovery Period after Different High Temperature Stress on Plant Growth of Greenhouse Tomato at Flowering and Fruiting Stages

High temperatures have become a severe factor limiting growth and yield for tomatoes (Lycopersicon esculentum Mill.) due to unfavorable, above-optimum temperatures. Temperature and nitrogen application were the main regulatory factors in tomato plant cultivation. This research was undertaken to evaluate the effects of nitrogen application and high temperature on tomato morphology, dry matter accumulation and distribution, root vitality and nitrogen content of the above ground. Tomato variety “Jinfen No. 1” was planted and exposed to 4 day/night temperature levels (25 °C/15 °C as control CKT; 30 °C/20 °C, lightly high-temperature LHT; 35 °C/25 °C, moderate high-temperature MHT; 40 °C/30 °C, severe high temperature SHT) for 7 days after five nitrogen supply levels (N1–N5: 0, 1.3, 1.95, 2.6 and 3.75 g/plant, respectively; 2.6 g/plant is the recommended nitrogen-application rate, as control CKTN4). Within conditions, there was an extremely significant difference (p &lt; 0.01) in all tomato plant parameters and an extremely significant interaction (p &lt; 0.01) between high temperatures and nitrogen supply levels, except for plant height sampling on the 1st day in the recovery period. Dry matter accumulation decreased, and the accumulation rate slowed down. Dry matter accumulation under low nitrogen treatment was higher than in high nitrogen treatment. The proportion of dry matter in leaves decreased, the proportion of dry matter in stems increased and the difference in dry matter accumulation and proportion of dry matter between different nitrogen treatments decreased. Under LHT, the root activity of the tomato was increased under all nitrogen levels, while under MHT and SHT, high nitrogen and low nitrogen supply significantly inhibited root activity. Lightly high-temperature stress can increase root activity, and LHTN4 can increase by 5.15% compared with CKTN4. Appropriate nitrogen application can alleviate the damage caused by high-temperature stress on tomato plants and enhance the resistance of tomato plants, while excessive nitrogen application will aggravate the damage degree of tomato plants. In this study, the optimal nitrogen application rates under CKT-SHT treatment were 2.6, 2.6, 1.95 and 1.3 g/plant, respectively.

Effects of Simulated Nitrogen Deposition on Soil Microbial Community Structure in Temperate Forest Based on PLFA Method

Soil microorganisms play a crucial role in the biogeochemical cycling of terrestrial ecosystems. However, previous studies on the effects of nitrogen deposition on microorganisms have primarily focused on nitrogen-sensitive tropical forest ecosystems. This study focused on soil in a temperate Korean pine plantation and conducted a field simulated nitrogen deposition experiment. The effects of different nitrogen application rates on the microbial community structure were analyzed using the phospholipid fatty acid (PLFA) method. The experiment included four nitrogen application rates: control (CK: 0 kg N ha−1 yr−1), low nitrogen treatment (LN: 20 kg N ha−1 yr−1), medium nitrogen treatment (MN: 40 kg N ha−1 yr−1), and high nitrogen treatment (HN: 80 kg N ha−1 yr−1). After seven years of continuous application of ammonium nitrate solution, the soil microbial community structure was determined using the PLFA method. The results showed that all nitrogen application rates significantly reduced the PLFA concentration of fungi and AM fungi (P &lt; 0.05), while bacterial biomass significantly decreased in the high nitrogen treatment group. The biomass of Gram-positive bacteria, Gram-negative bacteria (G-), and actinomycetes also significantly decreased in the HN treatment group. Furthermore, long-term application of high nitrogen concentration (80 kg N ha−1 yr−1) significantly reduced soil microbial biomass and changed the fungal to bacterial ratio, thus affecting the soil microbial community structure. Redundancy analysis (RDA) of soil microbial and soil chemical properties found that the long-term simulated nitrogen deposition experiment affected the soil microbial community structure by changing the content of soil N, P elements, and soil pH values. In summary, long-term simulated N deposition can negatively affect soil microbial biomass and its community structure, and the main reason for this analysis is related to long-term N application leading to soil acidification and changes in the conversion of soil N and P elements.

Mesophyll conductance and N allocation co-explained the variation in photosynthesis in two canola genotypes under contrasting nitrogen supply.

The application of nitrogen fertilizer within a normal range has been found to increase the leaf nitrogen content and photosynthetic rate of canola plants (Brassica napus L.). Despite numerous studies on the separate effects of CO2 diffusion limitation and nitrogen allocation trade-off on photosynthetic rate, few have examined both these factors in relation to the photosynthetic rate of canola. In this study, two genotypes of canola with varying leaf nitrogen content were analyzed to determine the impact of nitrogen supply on leaf photosynthesis, mesophyll conductance, and nitrogen partitioning. The results showed that the CO2 assimilation rate (A), mesophyll conductance (g m), and photosynthetic nitrogen content (N psn) increased with an increase in nitrogen supply in both genotypes. The relationship between nitrogen content and A followed a linear-plateau regression, while A had linear relationships with both photosynthetic nitrogen content and g m, indicating that the key to enhancing A is increasing the distribution of leaf nitrogen into the photosynthetic apparatus and g m, rather than just increasing nitrogen content. Under high nitrogen treatment, the genotype (QZ) with high nitrogen content had 50.7% more nitrogen than the other genotype (ZY21), but had similar A, which was primarily due to ZY21's higher photosynthetic nitrogen distribution ratio and stomatal conductance (g sw). On the other hand, QZ showed a higher A than ZY21 under low nitrogen treatment as QZ had higher N psn and g m compared to ZY21. Our results indicate that, in selecting high PNUE rapeseed varieties, it is important to consider the higher photosynthetic nitrogen distribution ratio and CO2 diffusion conductance.

Impacts of Returning Straw and Nitrogen Application on the Nitrification and Mineralization of Nitrogen in Saline Soil

In order to discuss the problems of the transformation of soil nitrogen and nitrogen leaching in saline farmland, this study carried out a split-plot experiment with returning straw and various nitrogen application rates. The main treatment of the experiment was returning corn straw, at quantities of 0.64 g (C1) and 0 g (C0), and the secondary treatment was nitrogen fertilizer (urea) at the quantities of 0 g (N0), 0.015 g (N1) and 0.03 g (N2). The results showed that, firstly, with the extension of the incubation time, the nitrogen nitrification rate of saline soil in each treatment decreased gradually until it stabilized without straw. For Days 0–7 of incubation, the nitrogen mineralization rate of saline soil decreased rapidly, and the mineralization rates of C0N0, C0N1 and C0N2 decreased by 86.91%, 89.26% and 83.64%, respectively. The nitrification rate of nitrogen in saline soil was C0N0 &gt; C0N1 &gt; C0N2, which decreased by 68.01%, 67.42% and 60.52%, respectively. Secondly, under the condition of returning straw to the field, the nitrogen mineralization rate of saline soil in each treatment decreased gradually and became stable with the extension of the incubation time. The nitrogen mineralization rate of saline soil in each nitrogen application treatment was C1N2 &gt; C1N1 &gt; C1N0 within 0–3 days of incubation, which decreased by 87.46%, 87.20% and 81.83%, respectively. The nitrification rate of saline soil under different nitrogen treatments was C1N2 &gt; C1N0 &gt; C1N1, and the nitrification rates of C1N0, C1N1 and C1N2 decreased by 66.62%, 62.54% and 47.21%, respectively. Thirdly, during the incubation period, returning straw slowed down nitrogen mineralization and nitrification in saline soil under the reduced nitrogen and no-nitrogen fertilizer treatments, but it enhanced nitrogen mineralization and nitrification in saline soil under the high nitrogen treatment. In conclusion, returning straw and reducing the application of nitrogen fertilizer to saline soil can retain more ammonium nitrogen, thus inhibiting nitrification of the soil nitrogen, reducing the environmental pollution risk of nitrate leaching and reducing nitrogen losses, all of which are of great significance for environmental pollution.

增温和氮添加对杉木不同序级细根形态和化学性状的影响

PDF HTML阅读 XML下载 导出引用 引用提醒 增温和氮添加对杉木不同序级细根形态和化学性状的影响 DOI: 10.5846/stxb202204291200 作者: 作者单位: 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金重点项目（31830014）；国家重点研发计划项目课题项目（2021YFD2200403） Effects of soil warming and nitrogen addition on the morphological and chemical characteristics of fine roots in different order classes of the Chinese fir Author: Affiliation: Fund Project: National Natural Science Foundation of China(31830014);Topics of state key R & D projects（2021YFD2200403） 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:全球气候变暖与氮（N）沉降是两个同时存在的全球变化主要因素，但目前关于二者的研究多以单因子为主。细根形态和化学性状等功能性状在促进植物养分获取和森林生物地球化学循环方面起着关键作用，但目前气候变暖、N沉降以及两者交互对细根形态和化学性状的影响尚不清楚。在福建三明森林生态系统国家野外科学观测研究站陈大观测点开展土壤增温与N添加双因子试验，包括对照（无增温，无氮添加）、低氮（+4gN m-2 a-1）、高氮（+8gN m-2 a-1）、增温（+5℃）、增温+低氮（+5℃，+4gN m-2 a-1）、增温+高氮（+5℃，+8gN m-2 a-1）六个处理，探讨增温与N添加对杉木（Cunninghamia Lanceolata）细根形态和化学性状的影响。结果表明：（1）增温显著增加了细根直径（D）。增温和N添加的交互作用对细根比根长（SRL）、比表面积（SRA）及组织密度（RTD）均存在显著影响，与对照相比，增温处理及增温+高氮处理均降低了细根SRL和SRA；不同处理间细根RTD无显著差异。N添加与序级交互作用对细根SRA存在显著影响，仅低氮添加显著增加了1级根SRA。（2）增温和N添加交互作用对细根碳（C）含量存在显著影响，与对照相比，仅增温+高氮处理显著增加了细根C含量。N添加与序级交互作用对细根C含量存在显著影响，仅在1级细根中，高氮添加的细根C含量要显著高于低氮添加。增温、N添加以及序级三者交互作用对细根N含量及碳氮比（C ： N）存在显著影响，与对照相比，低氮和高氮处理对细根N含量及C ： N影响因序级而异；增温处理、增温+低氮处理以及增温+高氮处理均显著提高了细根N含量，降低了细根C ： N；与高阶根相比，低阶根N含量和C ： N对单独增温处理及增温+低氮处理响应要更为敏感。以上结果表明，不同细根功能性状对增温、N添加及两者交互的响应存在差异，这种差异主要与细根序级和N添加水平有关；增温和N添加抑制了细根SRL和SRA，但促进了细根N含量并降低了细根C ： N，这将有助于理解亚热带地区森林地下养分循环以及C固存对全球环境变化的响应。 Abstract:Global warming and nitrogen deposition are two main global change drivers, often occurring simultaneously. However, most of related studies referred to only single factor. Fine root functional traits such as morphology and chemical properties play a key role in promoting plant nutrient acquisition and forest biogeochemistry cycling. The effects of climate warming, N deposition and their interactions on fine root morphology and chemical properties remain unclear. To explore the effects of warming and N addition on the morphological and chemical characteristics of fine roots of Cunninghamia Lanceolata. We conducted a two-factor experiment of soil warming and nitrogen addition, which consisted control (CT), low nitrogen treatment (LN), high nitrogen treatment (HN), warming treatment (W), warming and low nitrogen treatment (WLN), warming and high nitrogen treatment (WHN), at the Forest Ecosystem and Global Change Research Station of Fujian Normal University, Chenda, Sanming, Fujian Province. The results showed that:(1) the warming significantly increased fine root diameter (D). The interaction of warming and N addition had significant effects on the specific root length (SRL), specific surface area (SRA) and root tissue density (RTD) of fine roots. Compared with CT, the W and WHN reduced fine root SRL and SRA; there was no significant difference in RTD of fine roots among different treatments. The interaction of N addition and order had significant effects on fine root SRA. Low nitrogen addition only increased SRA of first order root significantly. (2) The interaction of warming and N addition had a significant effect on fine root C concentration, and only WHN significantly increased fine root C concentration. The interaction of N addition and order had significant effects on fine root concentration. The fine root C concentration of high N addition was significantly higher than that of low N addition. The interaction of warming, N addition and order had significant effects on fine root N concentration and C:N. Compared with CT, the effects of LN and HN on fine root N content and C:N varied with the order; The W, WLN and WHN significantly increased the fine root N concentration and decreased the fine root C:N. Compared with high-order root, low-order root N concentration and C:N were more sensitive to the effects of W and WLN. The results showed that the responses of fine root morphology and chemical characteristics to warming, N addition and their interaction were different, and the differences were mainly regulated by fine root branch order and N addition level; The warming and N addition promoted fine root N concentration and decreased fine root C:N, which would contribute to understand the subsurface nutrient cycling and the response of C sequestration to global environmental change in subtropical forests. 参考文献 相似文献 引证文献

Production of Primary Metabolites by Rhizopus stolonifer, Causal Agent of Almond Hull Rot Disease.

Species in the fungal genus Rhizopus are able to convert simple sugars into primary metabolites such as fumaric acid, lactic acid, citric acid, and, to a lesser extent, malic acid in the presence of specific carbon and nitrogen sources. This ability has been linked to plant pathogenicity. Rhizopus stolonifer causes hull rot disease in almonds, symptoms of which have been previously associated with the fungus's production of fumaric acid. Six isolates of R. stolonifer taken from infected almond hulls were grown in artificial media amended with one of four carbon sources (glucose, fructose, sucrose, and xylose) and two nitrogen sources (asparagine and ammonium sulphate) chosen based on almond hull composition and used in industry. Proton nuclear magnetic resonance (1H NMR)-based metabolomics identified that R. stolonifer could metabolise glucose, fructose, sucrose, and to a lesser extent xylose, and both nitrogen sources, to produce three metabolites, i.e., fumaric acid, lactic acid, and ethanol, under in vitro conditions. Sugar metabolisation and acid production were significantly influenced by sugar source and isolates, with five isolates depleting glucose most rapidly, followed by fructose, sucrose, and then xylose. The maximum amounts of metabolites were produced when glucose was the carbon source, with fumaric acid produced in higher amounts than lactic acid. Isolate 19A-0069, however, preferred sucrose as the carbon source, and Isolate 19A-0030 produced higher amounts of lactic acid than fumaric acid. This is the first report, to our knowledge, of R. stolonifer producing lactic acid in preference to fumaric acid. Additionally, R. stolonifer isolate 19-0030 was inoculated into Nonpareil almond fruit on trees grown under high- and low-nitrogen and water treatments, and hull compositions of infected and uninfected fruit were analysed using 1H NMR-based metabolomics. Glucose and asparagine content of uninfected hulls was influenced by the nitrogen and water treatments provided to the trees, being higher in the high-nitrogen and water treatments. In infected hulls, glucose and fructose were significantly reduced but not sucrose or xylose. Large amounts of both fumaric and lactic acid were produced, particularly under high-nitrogen treatments. Moreover, almond shoots placed in dilute solutions of fumaric acid or lactic acid developed leaf symptoms very similar to the 'strike' symptoms seen in hull rot disease in the field, suggesting both acids are involved in causing disease.