Total Organic Nitrogen Content Research Articles

Promoting nitrogen conversion in aerobic biotransformation of swine slurry with the co-application of manganese sulfate and biochar

This study aimed to explore the co-application of MnSO4 (Mn) and biochar (BC) in nitrogen conversion during the composting process. A 70-day aerobic composting was conducted using swine slurry, supplemented with different levels of Mn (0, 0.25%, and 0.5%) and 5% BC. The results demonstrated that the treatment with 0.5MnBC had the highest levels of NH4+-N (3.07 g kg−1), TKN (29.90 g kg−1), and NO3−-N (1.94 g kg−1) among all treatments. Additionally, the 0.5MnBC treatment demonstrated higher urease, protease, nitrate reductase, and nitrite reductase activities than the other treatments, with the peak values of 18.12, 6.96, 3.57, and 15.14 mg g−1 d−1, respectively. The addition of Mn2+ increased the total organic nitrogen content by 29.59%–47.82%, the acid hydrolyzed ammonia nitrogen (AN) content by 13.84%–57.86% and the amino acid nitrogen (AAN) content by 55.38%–77.83%. The richness of Chloroflexi and Ascomycota was also enhanced by the simultaneous application of BC and Mn. Structural equation modeling analysis showed that Mn2+ can promote the conversion of Hydrolyzed Unknown Nitrogen (HUN) into AAN, and there is a positive association between urease and NH4+-N according to redundancy analysis. Firmicutes, Basidiomycota, and Mortierellomycota showed significant positive correlations with ASN, AN, and NH4+-N, indicating their crucial roles in nitrogen conversion. This study sheds light on promoting nitrogen conversion in swine slurry composting through the co-application of biochar and manganese sulfate.

Optimizing Nitrogen Application for Enhanced Barley Resilience: A Comprehensive Study on Drought Stress and Nitrogen Supply for Sustainable Agriculture

Soil water scarcity hinders crop productivity globally, emphasizing the imperative for sustainable agriculture. This study investigated the role of nitrogen in alleviating drought stress in barley. Parameters such as relative water content, photosynthetic rate, stomatal conductance, mesophyll concentration of CO2, total leaf nitrogen, grain yield, total organic nitrogen content, starch content, and macronutrient concentrations (N, P, K, Ca, Mg) were examined. The optimal grain yield (3.73 t·ha−1) was achieved with 1 g of nitrogen per container (near 200 kg N hectare−1) under ideal moisture conditions. However, under drought stress, nitrogen supply variants (1 g and 2 g per container) exhibited a significant decrease in photosynthetic rate (Pn), NRA activities, and a notable increase in Ci values. Stomatal conductance exhibited a substantial decrease by 84% in the early growth phase, especially with a 2 g dose of nitrogen supply. Nitrogen enhanced crude protein levels, yet both drought stress and nitrogen application reduced grain weight and starch content. Nitrogen effectively improved metabolic processes under drought, particularly in earlier growth stages (e.g., tillering). This research highlights the importance of sustainable agricultural practices related to the growth stage of barley, emphasizing nitrogen optimization to enhance crop resilience in water-scarce environments. The results underscore the intricate interplay between nitrogen fertilization, drought stress, and crop yield, indicating benefits during initial stress exposure but detrimental effects in subsequent growth stages.

Biochar-mediated remediation impacts on nitrogen cycling bacteria and ammonia monooxygenase activity in crude oil polluted soil

This study adopted an ecosystem services approach to pollution management by investigating the impact of biochar-mediated remediation on soil nitrogen, abundance of nitrogen cycling bacteria and the activity of ammonia monooxygenase (AMO) enzyme in petroleum-polluted soil using two biochar types applied at two treatment levels with monitoring over 15 weeks. The corn cob-derived biochar (CDB), generally, had a stronger restorative effect on soil ammonium nitrogen, nitrate and total organic nitrogen concentrations than the bone-derived biochar (BDB). Both biochar types had a more robust impact on restoration of Nitrosomonas, Nitrobacter and Azotobacter abundance (with the re-establishment of pre-pollution levels) than on Rhizobium and Pseudomonas aeruginosa. Biochar amendment restored the activity of AMO enzyme in the soil by week 15. The CDB (72.4% – 73.7%) showed more effective total petroleum hydrocarbon (TPH) elimination capacity than the BDB (51.1% – 57.7%). Biochar amendments exhibited great potential for restoration of nitrogen cycling while facilitating remediation of petroleum-polluted soils.

Nitrogen burial characteristics of Quaternary sediments and its controls on high ammonium groundwater in the Central Yangtze River Basin

As the strata sedimentary process proceeds, considerable amounts of nitrogen (N) is buried in sediments, which controls the sources and fate of N in the “groundwater-sediment” system. However, there is little concern regarding N burial characteristics in continuous sediment profiles from surface layer to deep aquifer thus far. In this study, lithology, grain size, geochronology, exchangeable N contents and geochemical proxies of sediments were analyzed to reveal the controlling mechanisms of N burial characteristics in Quaternary sediments and to interpret the enrichment of N in groundwater of central Yangtze River Basin. The results demonstrated a similar distribution trend for buried N in two sedimentary cores, which were high in the surface layer and decreased to stable in the deep aquifer. Excessive exchangeable N (EX-N) contents in sediments were mainly attributed to geologic origin. The N burial characteristics were controlled by the evolution of depositional environment: sedimentary facies determined the concentrations of total organic nitrogen (TON), further affecting the mineralization capacity of sediments; while paleoclimate regulated the intensity of the N transformation processes, ultimately influencing the actual concentrations of EX-N in sediments. In addition, due to the fast accumulation of alluvial deposits after Last Glacial Maximum and rapid development of Jianghan Lake Groups during Holocene, abundant organic matter (with high TON contents) was buried in sediments, which were still able to produce more ammonium or nitrate, and further posing continuous threats to groundwater quality. This study provided a new interpretation for the formation of high-ammonium aquifer in terms of depositional evolution.

Conversion effects of farmland to Zanthoxylum bungeanum plantations on soil organic carbon mineralization in the arid valley of the upper reaches of Yangtze River, China.

Farmland conversion to forest is considered to be one of the effective measures to mitigate climate change. However, the impact of farmland conversion to forest land or grassland on soil CO2 emission in arid areas is unclear due to the lack of comparative information on soil organic carbon (SOC) mineralization of different conversion types. The SOC mineralization in 0–100 cm soil layer in farmland (FL), abandoned land (AL) and different ages (including 8, 15, 20 and 28 years) of Zanthoxylum bungeanum plantations were measured by laboratory incubation. The size and decomposition rate of fast pool (Cf) and slow pool (Cs) in different land-use types and soil layers were estimated by double exponential model. The results showed that: 1) Farmland conversion increased the cumulative CO2-C release (Cmin) and SOC mineralization efficiency, and those indexes in AL were higher than that in Z. bungeanum plantations. The Cmin and SOC mineralization efficiency of 0–100 cm soil increased with the ages of Z. bungeanum plantation. Both Cmin and SOC mineralization efficiency decreased with the increase of soil depth; 2) Both soil Cf and Cs increased after farmland converted to Z. bungeanum plantations and AL. The Cs in the same soil layer increased with the ages of Z. bungeanum plantation, and the Cf showed a “V” type with the increased ages of Z. bungeanum plantation. The Cf and Cs decreased with the increase of soil depth in all land-use types; 3) Farmland conversion increased the decomposition rate of Cf (k1) in all soil layer by 0.008–0.143 d−1 and 0.082–0.148 d−1 in Z. bungeanum plantations and AL, respectively. The k1 was obviously higher in the 0−20 cm soil layer than that in other soil layers, while the decomposition rate of Cs (k2) was not affected by FL conversion and soil depth; and 4) The initial soil chemical properties and enzyme activity affected SOC mineralization, especially the concentrations of total organic nitrogen (TON), SOC, easily oxidizable organic carbon (EOC) and microbial biomass carbon (MBC). It indicated that the conversion of farmland to Z. bungeanum plantations and AL increases SOC mineralization, especially in deeper soils, and it increased with the ages. The conversion of farmland to Z. bungeanum plantation is the optimal measure when the potential C sequestration of plant-soil system were taken in consideration.

Enzymatic Activity as New Moorsh-Forming Process Indicators of Peatlands

The aim of this study is to comprehensively assess the change in oxidoreductive enzyme activities, due to the potential in catalyzing oxidation and reduction reactions, as the basic processes on undrained and drained peat soils. On undrained peatlands, a significant decrease of enzyme activities was observed such as xanthine oxidase, urate oxidase, phenol oxidase, and peroxidase with an increase in depth. It was connected with significantly higher porosity values, hot water extractable organic carbon, and total organic nitrogen contents, ammonium and nitrate ions concentrations, and significantly lower ash and bulk density values in the upper layers. On drained peatlands, a significant increase of enzyme activities in depth was measured. Enzyme activities such as xanthine, urate, phenol oxidase, and peroxidase were documented to be effective as new indicators and tools for changes of the moorsh-forming process in association with the oscillation of the water table caused by the drainage of the peatlands.

Using Isotopes to Identify the Sources of Organic Carbon and Nitrogen in Surface Sediment in Shallow Lakes Alongside Poyang Lake

Water exchange in shallow lakes alongside Poyang Lake is weak because of sluggish water flow, and thus these lakes are susceptible to the effects of human activities and nutrient oversupply. Therefore, it is meaningful to study the sources of organic matter in these lakes, which is supposed to provide theoretical basis for the control of eutrophication of the lakes. The sources of organic matter in surface sediment in shallow lakes (Bang, Sha, Dahuchi, and Zhu lakes) alongside Poyang Lake and urban lakes (Qingshan and Xiang lakes) in Nanchang City were investigated by measuring the δ15N and δ13C values, total organic carbon and total organic nitrogen contents, and C/N ratios of sedimented organic matter (SOM). The δ15N, δ13C, and C/N ratios indicated that SOM in Sha and Dahuchi lakes mostly originated in phytoplankton, SOM in Bang and Zhu lakes was supplied by phytoplankton and soil organic matter, SOM in Qingshan Lake was strongly affected by sewage organic matter, and SOM in Xiang Lake mainly came from aquatic macrophytes. The results demonstrate that stable isotopes in SOM in lakes can be used to discriminate between different sources of organic material.

Temporal and Spatial Variations of Microbial Carbon Utilization in Water Bodies from the Dajiuhu Peatland, Central China

To investigate the microbial utilization of organic carbon in peatland ecosystem, water samples were collected from the Dajiuhu Peatland and nearby lakes, central China across the year of 2014. The acridine orange (AO) staining and Biolog Eco microplates were used to numerate microbial counts and determine the carbon utilization of microbial communities. Meanwhile, physicochemical characteristics were measured for subsequent analysis of the correlation between microbial carbon utilization and environmental factors. Results indicated that total microbial counts were between 106–107 cells/L. Microbial diversities and carbon utilization rates showed a similar pattern, highest in September and lowest in November. Microbial communities in the peat pore waters preferred to utilize N-bearing carbon sources such as amines and amino acids compared with microbial communities in lakes. The network analysis of microbial utilization of 31 carbon substrates clearly distinguished microbial communities from peat pore waters and those from lakes. Redundancy analysis (RDA) showed the total organic nitrogen content (P=0.03, F=2.5) and daily average temperature (P=0.034, F=2.4) significantly controlled microbial carbon utilization throughout the sampling period. Our report is the first one to address the temporal and spatial variations of carbon utilization of microbial communities which are closely related to the decomposition of organic matter in the Dajiuhu Peatland in context of climate warming.

Time-lapse effect of ancient plant coal biochar on some soil agrochemical parameters and soil characteristics.

Biochar is a solid material obtained from reductive, oxygen-free processes, i.e. the thermo-chemical conversion of biomass in oxygen-limited environment. The obtained products have high carbon sequestration potential and strong nutrient-water absorption capacities because of the enlarged carbon surfaces. It is not yet clear how carbon stimulates agrochemical parameters in soil and how those characteristics are developing as time goes on a long-term basis. Samples of ancient (25, 35, 80years old) plant coal-affected soils were collected in a temperate deciduous forest site located in the south part of the Bükk Mountains (in North Eastern Hungary). Physical-chemical soil characteristics, such as soil pH, cation exchange capacity (CEC), the organic and inorganic nitrogen (NH4+, NH3-) and the available nutrients (P2O5 and K2O), were estimated beside organic matter (SOM) content, measured by two different methods. Levels of polycyclic aromatic hydrocarbon (PAH) compounds in soil and in various biochar samples were assessed in relation with permissible limit values and potential toxicity. Positive correlation was found between the amount of available nutrients, total organic nitrogen content, cation exchange capacity and the age of plant coal-affected soils. The sample soils were exposed to continuous plant coal biochar effect for 25years, during which macronutrients absorbed and accumulated in the plant coal surfaces. After this period, the degradation of carbon developed simultaneously with the reduction of the amount of available nutrients, till the end of the studied 80-year-affecting period. Measured CEC level indicated positive correlation with nutrient availability and the age of biochar-affected soils. Our results support the hypothesis that biochar in soil can improve its general agrochemical characteristics in relation with its persistence in a specific soil-plant system. Potential PAH content and toxicity of biochar products are key issues of developing proper application rates in sustainable agricultural practices.

Antioxidant compounds of organically and conventionally fertilized jambu (Acmella oleracea)

Acmella oleracea (jambu), native to the Amazonas region (Brazil), has cosmetic and pharmacological properties, many of which are due to chemical components with antioxidant activity. Since organic cultivation has been reported to induce an increase in metabolic antioxidant components, this study aimed to determine the content of phenolic compounds, carotenoids, vitamin C, and polyamines, and the activity of peroxidase in two cultivars of jambu, Jambuarana, and Nazareth. Furthermore, leaves and inflorescences were studied to estimate the relative contribution of these tissues to the antioxidant potential of jambu. Organic farming induced higher levels of total phenolics and carotenoids in Jambuarana leaves and of spermidine and spermine in leaves and flowers of both the cultivars than conventional cultivation. Conventional fertilization led to nitrate accumulation in inflorescences and vitamin C in leaves, and to a higher total organic nitrogen content in jambu leaves and flowers than in organic cultivated plants. The fertilization procedures did not affect the activity of the enzyme peroxidase, but differences were observed between cultivars.

长江口及东海夏季小型底栖动物的丰度和生物量及近十年的变化

PDF HTML阅读 XML下载 导出引用 引用提醒 长江口及东海夏季小型底栖动物丰度和生物量变化 DOI: 10.5846/stxb201309112249 作者: 作者单位: 中国科学院海洋研究所,中国科学院大学;中国科学院海洋研究所,中国科学院大学;中国科学院海洋研究所 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点基础研究发展计划(973) (2011CB403604); 中国科学院知识创新工程重要方向(KSCX2-EW-Z-5) Abundance and biomass of meiofauna in the Yangtze Estuary and East China Sea in summer, with special reference to changes over the past ten years Author: Affiliation: Institute of Oceanology, Chinese Academy of Sciences,,Institute of Oceanology, Chinese Academy of Sciences Fund Project: 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:2012年7月,对长江口及东海海域的小型底栖动物类群组成、丰度、生物量的空间分布及其与沉积环境的关系进行了调查研究。该研究海域夏季小型底栖动物的丰度和生物量总体上自北向南递减,在长江口以东的海域由近岸向外海增加,至约45 m等深线达到最高,然后向深水区减少。其小型底栖动物的丰度和生物量分别为(1203±191) 个/10 cm2和(723±171) μg 干重/10 cm2,略高于同一海域春季和秋冬季的数量,但明显低于以往夏季的数量,这可能与本年度该海域沉积物中叶绿素a含量明显偏低有关。在小型底栖动物11个主要类群中,自由生线虫在丰度上占绝对优势(94.1%),其次是桡足类(2.7%)和涡虫类(1.2%)。线虫在生物量上也是最优势类群(62.1%),其次是多毛类(18.8%)、桡足类(8.3%)和涡虫类(6.1%)。Spearman相关分析表明,小型底栖动物的生物量、桡足类和涡虫的丰度均与沉积物中有机氮含量呈负相关;多毛类的丰度与盐度、叶绿素a呈显著正相关;而线虫与所测环境因子未见任何相关关系。BIOENV分析显示,与小型底栖动物各类群的丰度相关性最高的环境因子组合为盐度、沉积物含水量和有机氮含量。研究发现,近10年该海域小型底栖动物的丰度呈总体下降趋势;而且,小型底栖动物的垂直分布随时间推移趋向于向沉积物表层聚集,一定程度上显示沉积环境趋于恶化。通过对近岸和外海两个站位的702条线虫生物体积的测算,获得两个站位线虫的平均个体干重分别为0.186 μg/个体和0.281 μg/个体,两站位平均为0.214 μg/个体,与2009年秋冬季相邻两站位的0.213 μg/个体非常接近,但各站位的线虫个体干重变化相对较大。该结果一方面反映了我国当前普遍采用的0.4 μg/个体系数高估了线虫的生物量,另一方面显示季节和站位差异影响了线虫个体的大小。 Abstract:The assemblage composition and distribution of meiofauna in the Yangtze Estuary and East China Sea were investigated using samples collected from 16 stations (from 26°N to 32°N, 121°E to 126°E) in July 2012. Generally, both the abundance and biomass of meiofauna decreased from the northern to the southern sea area, increased from the inshore to the offshore area, peaked along the about 45 m isobathymetric line, and then decreased to the offshore area. The meiofaunal abundance amounted to (1206±189) ind/10 cm2, and the biomass reached (729±170) μg dwt/10 cm2. The standing crops of meiofauna were slightly higher in the summer season than those from the same area in spring and in winter, but distinctly lower than those in summer (June 2003). The low standing crops were likely associated with the low food supply, as indicated by the low sediment chlorophyll-a concentration, though no close relationship was observed. Among the eleven main meiofaunal groups sorted, nematodes represented the most abundant group, accounting for 94.1% of the total abundance, followed by copepods (2.7%) and turbellarians (1.2%). In terms of biomass, nematodes and polychaetes accounted for 62.1% and 18.8%, respectively, followed by copepods (8.3%) and turbellarians (6.1%). Spearman correlation analysis showed that the biomass of meiofauna and the abundance of copepods and turbellarians were respectively negatively correlated to the sediment organic nitrogen content, the polychaete abundance was positively correlated with sediment chlorophyll-a concentration and bottom water salinity, while there was no correlation between the nematode standing crops and any environmental factors. BIOENV analysis indicated that the combination of bottom water salinity, sediment water content and total organic nitrogen content best correlated with the meiofaunal communities. Generally, the abundance of meiofauna decreased over the past ten years. Our study revealed a tendency of the meiofauna congregating from the lower to the upper sediments in the study area over the past ten years, to some extent indicating a changing degraded benthic environment. Based on the measurements of 702 nematode individuals from two stations, we obtained an average individual dry weight of 0.281 μg/ind in the inshore station and 0.186 μg/ind in the offshore station, with an average dry weight of 0.214 μg/ind, a value very close to that obtained from two adjacent stations in autumn-winter of 2009. However, the average dry weight varied with stations, and possibly also with seasons. Thus, simple calculation of nematode biomass using the index of 0.4 μg/ind will obviously over-estimate the biomass of nematodes as well as meiofauna. 参考文献 相似文献 引证文献

Short-term and long-term effects of human trampling on above-ground vegetation, soil density, soil organic matter and soil microbial processes in suburban beech forests

Understanding the effects of disturbance by human trampling on ecosystem processes is essential for the management of recreational areas. Discussions on recreational impacts are based either on data from trampling experiments or on field survey data from sites subjected to long-term recreational use, but rarely on a combination of both. We examined whether results from a short-term trampling experiment reflect the impact of long-term trampling around frequently used fire places. We compared short- and long-term effects of human trampling on above-ground forest vegetation and soil physical, chemical and microbial characteristics. We found both similarities and differences in short- and long-term trampling effects. Both short- and long-term trampling reduced plant cover, plant height and species density, though long-term effects were more pronounced than short-term effects. In both approaches, leaf litter biomass decreased, whereas soil density increased with trampling intensity. Other soil characteristics including soil moisture, total soil organic matter content and total organic nitrogen content were not or only marginally affected by short- and long-term trampling. Furthermore, soil microbial biomass and the activity of dehydrogenase did not change in both approaches. In contrast, the activity of β-glucosidase was only reduced by short-term trampling, whereas activity of phosphomonoesterase was reduced only by long-term trampling. Soil compaction was one factor reducing microbial activities at low and medium trampling intensities in our experiment and in the highly compacted area around the fire rings. We conclude that it could be problematic to use the results of short-term trampling experiments to predict general long-term trampling effects. Our results imply also that the restoration of degraded sites might be hampered by the low nutrient turnover resulting from the reduced litter layer and changes in enzyme activities, mitigating a successful re-establishment and growth of plants.

Carbon and nitrogen partitioning in the freshwater submerged macrophyte Vallisneria gigantea in response to ultraviolet-B irradiance

The aim of this study was to determine the effect of ultraviolet-B (UV-B) exposures (0.55 and 1.1 W m−2) on the distributional variations of plant carbon and nitrogen content in both below- and aboveground parts in Vallisneria gigantea Graebner in laboratory conditions for a 3-month period. Plant biomass, total organic nitrogen, total organic carbon, lignin, water soluble carbohydrates and chlorophyll a and b were analysed and compared using repeated measures of analysis of variance (ANOVA) between UV-B-exposed and nonexposed treatments. A significant reduction (F (2, 15) = 754.5, P < 0.001) was observed in leaf chlorophyll a concentrations at UV-B exposure levels. In the high UV-B irradiation group, a significant decrease (50.3%) was observed compared with the initial aboveground biomass. The total organic nitrogen content at both high and low UV-B exposure levels declined significantly by 25.6% and 24.3%, respectively, in aboveground samples, while significant increases of 39.6% and 40%, respectively, were observed in belowground tissues, compared with non-UV-B treatment groups. The partitioning of total organic carbon in the aboveground tissues was reflected by significant increase in lignin and water soluble carbohydrates in aboveground tissues under UV-B stress. However, total organic nitrogen demonstrated greater partitioning into the belowground tissues of V. gigantea. This study highlights the defense mechanisms of V. gigantea through changes in the percentage composition of carbon and nitrogen compounds with negative effects on nutrient regeneration, which can be accelerated in a system exposed to UV-B irradiation at or above biologically effective levels.

Influence of olive oil solid waste applications on soil pH, electrical conductivity, soil nitrogen transformations, carbon content and aggregate stability

Some of the agricultural wastes have important economic potentials to be used as a plant nutrition and/or soil conditioner. Olive oil solid waste (OSW) is one of them. The aim of this study was to determine effects of OSW on soil pH, electrical conductivity (EC), improving soil nitrogen (N) status, soil aggregate stability and soil carbon contents. Different rates of OSW (control, 2%, 4% and 8%, w/w) were applied to coarse soils and incubated for 2 months. OSW applications decreased soil pH values. The mean EC value of soil measured 2 months after the incubation was greater than that of the first month. Application of OSW at the rate of 8% has significantly increased soil total organic nitrogen contents. OSW applications at the rate of 8% (w/w) significantly increased both mean SOC content (3.5%) and aggregate stability (88%) after 2 months of incubation ( p < 0.01). Therefore, OSW has great potential to improve soil structure of coarse textured soil in short term.

The influence of macrophytes on sedimentation and nutrient retention in the lower River Spree (Germany)

Nutrient retention due to sedimentation in running waters has been little studied. The knowledge about the processes of self-purification is important for the management of rivers. The principal aim of our investigations was to quantify nutrient retention by sedimentation within and adjacent to stands of submerged macrophytes. In addition, we examined the relationship between deposition and sedimentation patterns and the flow regime. In the summer of 2001, investigations were performed in the lower River Spree with sediment traps and sediment cores and measurement of flow velocities. The spatial distribution of macrophytes was described and related to sedimentation and flow patterns. Water and sediment samples were analysed for total phosphorus and total organic nitrogen concentrations. Macrophytes significantly enhanced water residence time by factors between 2 and 18. Trapping rates were high within and downstream of macrophyte stands due to the prevailing quiescent conditions. Trapping rates were low in regions not covered by macrophytes, where flow velocities were high. Calculated deposition of organic matter due to trapping rates accounted for 15–49% of observed deposition between May and September, the vegetation period. The difference between calculated and observed deposition can partly be attributed to an incomplete erosion of the organic sediments between October and April. Between May and September, nitrogen and phosphorus were retained by deposition by as much as 2.5% and 12.2%, respectively (% of total load). Therefore, macrophytes considerably contributed to total monthly phosphorus retention (up to 25%) by increasing deposition of particulate organic matter.

Antagonistic effect of sodium chloride to differential heavy metal toxicity regarding biomass accumulation and nitrate assimilation in Sesamum indicum seedlings

Combinations of 1.0 mM Pb 2+, Cu 2+ and Cd 2+ (1:1) differentially inhibited growth, biomass accumulation and in vivo nitrate reductase activity (NRA, EC 1.6.6.1) in root and leaves of five-day-old Sesamum indicum L cv PB-1 seedlings. Addition of 2 EC and 10 EC NaCl to the nutrient media slightly inhibited root fresh weight of the seedlings (statistically not significant), whereas it increased the leaf fresh weight and dry weight of the plant parts with a variable magnitude. The presence of NaCl could abolish the negative effect of the metal combinations on the root fresh weight to a good extent, and it caused an increase in the tissue dry mass in the presence of the metals in most of the cases. However, recovery in the leaf fresh weight was observed only if NaCl was added with Cu 2++Cd 2+ in the nutrient media. In vivo NRA of root and leaf in this cultivar was increased two-three-fold with the supply of NaCl and this increase was maintained even in the presence of the metal combinations by counteracting the toxic effect of the metals on the enzyme activity. A corresponding increase in total organic nitrogen content of the roots was also recorded. In vitro NRA, in either of the tissues, on the other hand, was drastically inhibited by the addition of 10 EC NaCl to the nutrient media. Our results show that toxic effect of Cd 2+, Cu 2+ and Pb 2+ combinations on the seedling growth and nitrate assimilation especially in the roots of sesame PB-1 was not persistent in the NaCl affected growth environment. However, in vitro NRA was drastically inhibited by some modulating effect of the salt on the enzyme.

Diurnal variations of amino acids and organic acids in xylem fluid from Lagerstroemia indica: an endogenous circadian rhythm

Diurnal variations in the concentrations of major organic compounds occurred in xylem fluid extracted from Lagerstroemia indica L. The concentration of amino acids and the N/C ratio was at a maximum and that of organic acids was at a minimum between 1230 and 2030 h. Since the concentrations of total organic nitrogen, total amino acids and most individual amino acids (but not organic acids or sugars) were also proportional to xylem tension two experiments were performed to discern whether variations in chemistry were a consequence of diurnal changes in moisture stress. In the first experiment, L. indica, exposed to variable levels of moisture stress during midday, manifested an increase in organic acids and a reduction in the N/C ratio. In the second experiment, chemical profiles of xylem fluid were collected and compared for plants exposed to a natural photoperiod, constant darkness or continuous light at noon and midnight. After 1 day amino acids increased in concentration during midday for all treatments; the variation was greatest (10‐fold) for plants in constant darkness where xylem tension varied from 0.20 to 0.25 MPa. Only plants exposed to continuous light lost a diurnal rhythm after 3 days. Thus, the circadian rhythm was endogenous, terminated in continuous light and was not mediated by changes in moisture stress. Glutamine accounted for most of the diurnal variation in total amino acids, organic nitrogen and the N/C ratio in xylem fluid.

Partitioning of the nitrogen stock in the vicinity of a Fijian seagrass bed dominated by Syringodium isoetifolium (Ascherson) Dandy

Partitioning of the nitrogen stock in a Fijian seagrass bed dominated by Syringodium isoetifolium (Ascherson) Dandy and in an adjacent area bare of macrophytic vegetation was assessed to evaluate the effect of the presence of seagrass on coral sediment. Concentrations of major nutrients, such as nitrogen and phosphate, were as low in the water column at the seagrass bed and the bare area as they were in the open ocean. Concentrations of ammonium and dissolved organic nitrogen, however, were higher in the water within the seagrass canopy than they were in other waters. In sediments at the seagrass bed and the bare area, interstitial nitrogen, such as nitrate and dissolved organic nitrogen, was a minor component of the total nitrogen (0.3-0.05%). On the other hand, concentrations of total organic nitrogen in seagrass-bed sediment (about 70% of which was in the form of amorphous organic nitrogen and the rest of which came from living and dead seagrass) were more than three times higher than those in bare-area sediment. Concentrations of organic carbon from amorphous organic materials in seagrass-bed sediment showed no large change with depth, resulting in an apparent decrease in the carbodnitrogen atom ratio from 60 to 10. These results suggest some mechanisms to minimize the loss of nitrogen stock from the sediment of tropical seagrass beds.

Relationship between Leaf Structure and Gas Exchange in Wheat Leaves at Different Insertion Levels

Araus, J. L., Alegre, L., Tapia, L. and Calafell, R. 1986. Relationship between leaf structure and gas exchange in wheat leaves at different insertion levels.—J. exp. Bot. 37: 1323-1333. Net photosynthesis rate (Pn), stomatal conductance to C02 and residual conductance to C02 were measured in the last six leaves (the sixth or flag leaf and the preceding five leaves) of Triticum aestivum L. cv. Kolibri plants grown in Mediterranean conditions. Recently fully expanded leaves of well-watered plants were always used. Measurements were made at saturating photosynthetic photon flux density, and at ambient C02 and 02 levels. The specific leaf area, total organic nitrogen content, some anatomical characteristics, and other parameters, were measured on the same leaves used for gas exchange experiments. A progressive xeromorphic adaptation in the leaf structure was observed with increasing leaf insertion levels. Furthermore, mesophyll cell volume per unit leaf area (VmtJA) decreased by 52-6% from the first leaf to the flag leaf. Mesophyll cell area per unit leaf area also decreased, but only by 24-5%. However, nitrogen content per unit mesophyll cell volume increased by 50-6% from the first leaf to the flag leaf. This increase could be associated to an observed higher number of chloroplast cross-sections per mm2 of mesophyll cell cross-sectional area in the flag leaf: values of 23 000 in the first leaf and 48 000 in the flag leaf were obtained. Pn per unit leaf area remained fairly constant at the different insertion levels: values of 33-83 + 0-93 mg dm 2 h1 and 32-32 + 1-61 mg dm2 h1 were obtained for the first leaf and the flag leaf, respectively. Residual conductance, however, decreased by 18-2% from the first leaf to the flag leaf. Stomatal conductance increased by 41-7%. The steadiness in Pn per unit leaf area across the leaf insertion levels could be mainly accounted for by an opposing effect between a decrease in VmcJA and a more closely packed arrangement of photosynthetic apparatus. Adaptative significance of structural changes with increasing leaf insertion levels and the steadiness in Pn per unit leaf area was studied. Key words—Photosynthesis, structure, wheat. Correspondence to: Department of Plant Physiology, Faculty of Biology, University of Barcelona, 08028 Barcelona, Spain.

Determination of total organic nitrogen and organometallic nickel in oil, sediments and marine products.

As a fingerprint of oil pollution in the sea environment, n-paraffins, olefins, polynuclear aromatic hydrocarbons, sulfur containing oil compounds, and heavy metals in crude oil are often selected and evaluated for the oil contamination of marine products and sediments. Nitrogen containing oil compounds, however, are not documented for these analyses due to their trace existence in oil and the lack of more sensitive detection methods excepting high pressure liquid chromatography (HPLC) and gas liquid chromatography (GC) equipped with a nitrogen selective detector. These nitrogen compounds consist of several categories of compounds, i.e., basic and weak basic aromatic compounds such as quinoline, isoquinoline, carbazole, and porphirins. Drushell reported a high sensitive method for determination of nitrogen containing oil compounds by a digital nitrogen analyzer using a chemiluminescence detection method. In this paper, the authors determined total organic nitrogen contents in heavy oil, marine products and sediments by a digital nitrogen analyzer. As another parameter in heavy oil, Ikebe and Tanaka reported nickel and vanadium contents in marine products by flame and flameless atomic absorption spectrometry (AAS). These metals often exist in the forms of organometals such as petroporphirins. Therefore, organic Ni in oil and marine samples are also measured with respectmore » to porphirins by flameless AAS. And the relation between nitrogen contents and organometallic nickel are evaluated.« less