15N Content Research Articles

Deep Rooting as an Indicator of Deep Soil Water and N Uptake in Potato (Solanum tuberosum L.)

AbstractBreeding for potato deep roots can increase water and nitrogen uptake by potatoes and it can be an option to maintain stable yields with decreased inputs. This study investigates the relationship between potato root characteristics, water stress resistance and deep soil nitrogen uptake, accessing variations among cultivars and nitrogen fertilization levels. Thirteen potato cultivars were grown during 2018 and 2020 at a semi-field root phenotyping platform in Denmark. Root growth was monitored via minirhizotron tubes down to 1.8 m soil depth. Drought treatment started in the mid-June and deep soil nitrogen uptake was tracked via 15N isotope application at 1.3–1.4 m soil depth during tuber formation. Water stress resilience was identified using 13C natural discrimination process in plants. Tuber samples were analyzed for 15N and 13C content. While drought affected potato yield (not always significantly), it did not affect nitrogen uptake. Root length and distribution varied among varieties, with deeper roots (down to 1.30 m) observed in August. Statistical differences (p < 0.05) in root length, yield and nitrogen uptake were found among varieties. Cultivars with longer growing season exhibited larger, deeper roots and increased nitrogen uptake from deep soil. High correlation (R = 0.8) between deep roots and 15N uptake was observed for all varieties. Deeper roots are contributing to deep soil nitrogen uptake, but 13C content in tubers is not a reliable indicator of water stress resilience. Despite this, the study suggests the potential for breeding potatoes with deep roots to achieve stable yields, considering differences in water and nitrogen uptake among varieties.

Evidence for the translocation of fixed N in the N2-fixing lichen Stereocaulon vesuvianum.

The fruticose lichen Stereocaulon vesuvianum is among the most abundant and widespread lichens in upland Britain. It typically produces cephalodia (nodules) that contain the cyanobacterium Stigonema, which can fix atmospheric nitrogen. However, over much of England, Wales, and southern Scotland S. vesuvianum no longer produces cephalodia and does not fix nitrogen, a morphological change linked to elevated atmospheric nitrogen deposition. This provided a unique opportunity to compare the 15N natural abundance signatures in N2-fixing and non-N2-fixing lichen populations, keeping in mind that fixed nitrogen has a 15N content close to that of atmospheric N2 while, in comparison, several components of atmospheric combined N (e.g. nitrate and ammonium in precipitation) tend to be 15N depleted. We found that in N2-fixing samples, there was a steep gradient in 15N relative abundance in the terminal 15 mm of thallus branches (pseudopodetia), changing from 15N depleted tissues at 10-15 mm below the tips to values close to that of atmospheric N2 at the apices while in non-N2-fixing samples thallus branches were uniformly 15N depleted. The 15N gradient in N2-fixing material could not be explained by the presence of cephalodia since these are more abundant towards branch bases. The data provide the first evidence in lichens of translocation of recently fixed N to sink regions of active growth and production of asexual reproductive propagules, bringing lichens into line with N source-sink relationships in N2-fixing plant symbioses.

Evaluating the Effects of Reduced N Application, a Nitrification Inhibitor, and Straw Incorporation on Fertilizer-N Fates in the Maize Growing Season: A Field 15N Tracer Study

Reducing fertilizer-N rate, applying a nitrification inhibitor (NI), and incorporating straw are widely recommended to improve N use efficiency of crops and decrease N losses. A field 15N tracer study was conducted to compare their effectiveness on fertilizer-N fates during the maize growing season in Northeast China. The following six treatments were used: (1) no N fertilization (control); (2) 200 kg urea-N ha−1 (100%N); (3) 200 kg urea-N ha−1 and straw (100%N + S); (4) 160 kg urea-N ha−1 (80%N); (5) 160 kg urea-N ha−1 and NI (Nitrapyrin in this study) (80%N + NI); and (6) 160 kg urea-N ha−1, NI, and straw (80%N + NI + S). The results showed that the five N fertilization treatments yielded 16–25% more grain and 39–60% more crop N uptake than the control, but the differences among the five treatments were not statistically significant. Compared with the 100%N, 20% fertilizer-N reduction (80%N) decreased the 15N concentration in topsoil and plant pools but increased the proportion of plant 15N recovery at harvesting (NUE15N, 60% vs. 50%). Compared with the 80%N, NI co-application (80%N + NI) delayed soil nitrification and increased soil 15N retention at harvesting (52% vs. 36%), thereby decreasing NUE15N significantly. Straw incorporation decreased fertilizer-N retention in soil compared with NI co-application because it promoted NUE15N significantly. In conclusion, the results demonstrate that NI and straw additions are efficient strategies for stabilizing fertilizer-N in soils and potentially minimizing N loss; however, their effects on NUE15N vary and the related mechanism must be further clarified in long-term trials.

Mineralized nitrogen uptake by plants of the use of synthetic nitrogen fertilization in agriculture

The underground transfer of nitrogen from non-food crop residues to cash crops is an important tool to ensure decent crop yields and balance N use in agroecosystems. Laboratory experiments were performed to determine nitrogen migration in spring wheat at different growth stages using labelled nitrogen. In the first stage of the experiment, Artemisia dubia was grown in climate chambers (Climacell CLC-707-TV), with air temperature cycles of 8 h at 15 °C and 16 h at 20 °C, and fertiliz using 15N isotope enriched ammonia nitrate. In the second stage of the experiment, spring wheat was sown and grown to full maturity in two soils of differing soil acidity (pH 3.93 ± 0,04 and pH 7.07 ± 0,08) and mixed with the chopped pieces (3–5 cm mean length) of Artemisia dubia above-ground biomass obtained in the first stage of the experiment. Each soil had four experimental treatments: non-enriched biomass; non-enriched biomass and fertilizer (170 N kg h−1); biomass enriched by 15N and no fertilizer, and 15N enriched biomass and fertilizer (170 N kg h−1). Spring wheat and soil were sampled every two weeks for dry matter (DM), total N and 15N content measurements during the experiment (13 weeks). The results showed that improved crop nitrogen utilization from Artemisia dubia residues were achieved when additional crop fertilizers was not used. It implies that adding additional nitrogen might increase the degradation of plant biomass, but at the same time cause environmental pollution by leaching as plants use it slightly for their growth.

Quantifying Nitrogen Uptake Rates of Maize Roots Using Stable Isotopes.

Nitrogen is an essential element for plant growth and development; however, application of nitrogen (N)-based fertilizers comes with a high environmental cost. This includes the energy required for production, volatilization from fields, and runoff or leaching to waterways triggering algal blooms. As such, a key goal in plant breeding programs is to develop varieties that maintain yield while requiring less fertilization. Central to this goal is understanding how roots take up nitrogen and finding traits that represent improvements in the net uptake. Maize, one of the most widely produced crops in the world, has seminal, crown, and brace root types, each under independent developmental control. Recent evidence suggests that these independent developmental patterns may result in different nutrient uptake characteristics. As such, understanding the uptake dynamics of each root type under different environmental conditions is an essential aspect for the selection of new maize varieties. A key method for tracking nitrogen uptake is the use of the 15N stable isotope, which is naturally less abundant than the main 14N isotope. This method involves replacing the 14N in nutrient solutions with 15N, exogenously providing it to the plant tissues (roots in this case), and then measuring the 15N content of the tissues after a fixed amount of time. Here, we provide a brief overview of nitrogen uptake and remobilization in maize, and discuss current techniques for measuring nutrient uptake, with a focus on methods using stable isotopes of nitrogen.

Do plants directly absorb nitrogen derived from deposition of wildfire smoke?

Biomass burning generates a substantial amount of smoke through high-energy combustion. This smoke is deposited into forest ecosystems either as aerosol smoke or as smoke-laden water in rainfall. The smoke contains essential elements like nitrogen (N) and other elements essential for plant growth and development. However, it is not well understood whether plant roots directly absorb the wildfire-derived N. An understanding of such a phenomenon is of significant importance in revealing the impact of forest fires on N input into forest ecosystems. Thus, this study examined the effects of different smoke concentrations on total N content in the soil and δ15N in plant and biomass production of Cunninghamia lanceolata seedlings under different cultivation methods using the 15N tracing technique. The main findings showed that smoke at a certain concentration had a promoting effect on plant growth, and the contribution of fire wildfire-derived 15N to soil total N was higher in low concentration smoke treatment than high concentration. After 180 days of cultivation, the wildfire-derived 15N content of various plant organs was higher for low than high smoke concentration treatment, and the content being higher for fine roots, where N absorption was enhanced in aeroponics-cultivated than soil-cultivated seedlings. The study demonstrated that plant roots directly absorb N from smoke and transported it to the aboveground parts for internal circulation. The effect of smoke on plant growth was concentration-dependent, with high concentration of smoke inhibiting plant growth compared to the control, while low concentration stimulated growth. The findings emphasize that smoke generated from low-intensity fires can have a positive impact on unburnt patches within the footprint of a fire through N deposition.

Nitrogen Application Timing and Levels Affect the Fate and Budget of Fertilizer Nitrogen in the Apple-Soil System.

This study aimed to determine the effects of the nitrogen (N) application period and level on the fate of fertilizer N and the contribution of N absorption and translocation to apple organ N. Two N application periods (labeled by the 15N tracer technique in spring and summer, represented by SP and SU, respectively) and three N levels (N0, MN, and HN) were used to determine the physiological indexes and aboveground, root, and soil 15N content of 4-year-old dwarf ('Red Fuji'/M9T337) and arborized ('Red Fuji'/Malus hupehensis Rehd.) apple trees. The results showed that HN led to shoot overgrowth, which was not conducive to the growth of the apple root system (root length, root tips, root surface area, and root volume) or the improvement of root activity. The contribution of soil N to apple organ N accounted for more than 50%, and the contribution of N application in summer to fruit N was higher than that in spring. Under HN treatment, the proportion of soil N absorbed by trees decreased, while that of fertilizer N increased; however, the highest proportion was still less than 50%, so apple trees were highly dependent on soil N. Under MN treatment, fertilizer N residue was similar to soil N consumption, and soil N fertility maintained a basic balance. Under HN treatment, fertilizer N residue was significantly higher than soil N consumption, indicating that excessive N application increased fertilizer N residue in the soil. Overall, the 15N utilization rate of arborized trees (17.33-22.38%) was higher than that of dwarf trees (12.89-16.91%). A total of 12.89-22.38% of fertilizer 15N was absorbed by trees, 30.37-35.41% of fertilizer 15N remained in the soil, and 44.65-54.46% of fertilizer 15N was lost. The 15N utilization rate and 15N residual rate of summer N application were higher than those of spring N application, and the 15N loss rate was lower than that of spring N application. High microbial biomass N (MBN) may be one of the reasons for the high N utilization rate and the low loss rate of N application in summer.

Warming Mitigates the Impacts of Degradation on Nitrogen Allocation between Soil Microbes and Plants in Alpine Meadow

In alpine meadows, plants and soil microbes typically engage in competition for nitrogen (N) under N-deficient conditions. However, the acquisition and distribution of N among soil microbes and plants under alpine meadow degradation and climate warming induced by global climate change are still uncharacterized. In this study, we isotope labeled inorganic (NH4+-15N, NO3−-15N) and organic (glycine-15N) N in both degraded and non-degraded plots by using open-top chambers (OTC) to mimic increasing air temperatures. After 6 h, the 15N contents in soil microbes and plants were measured to investigate the effects of degradation and rising air temperature on N allocations in the ecosystems studied. Results showed that alpine meadow degradation significantly reduced soil microbial N accumulation by 52% compared to those in non-degraded plots. In non-degraded plots, warming significantly lowered the organic N levels of soil microbes by 49%, whereas in degraded ones, it reduced both NH4+-15N and NO3−-15N recovery by 80% and 45% on average but increased glycine-15N recovery by 653%. Meanwhile, warming decreased the plant recovery of NH4+-15N and NO3−-15N by 75% and 45% but increased the recovery of glycine-15N by 45% in non-degraded plots. Conversely, in degraded plots, warming markedly lowered NH4+-15N recovery by 40% but increased glycine-15N recovery by 114%. Warming mitigates the effects of alpine meadow degradation on nitrogen allocation among soil microbes and plants. In unwarmed plots, degradation significantly elevated the total 15N recovery ratio of soil microbes to plants by 60%. However, in warmed plots, the impact of degradation on this ratio was reduced. The responses of the 15N recovery ratio of soil microbes and plants to rising temperatures were closely related to alpine meadow quality. In non-degraded areas, warming enhanced the recovery ratio for NH4+-15N by 165% but reduced it for glycine-15N by 66%. Conversely, in degraded plots, warming decreased the recovery ratio for NH4+-15N by 66% but increased it for glycine-15N by 232%. This indicates that warming can increase carbon limitation for soil microbes in degraded alpine meadows, and the restoration of degraded alpine meadows should prioritize restoring carbon accumulation.

100 ancient genomes show repeated population turnovers in Neolithic Denmark

Major migration events in Holocene Eurasia have been characterized genetically at broad regional scales1–4. However, insights into the population dynamics in the contact zones are hampered by a lack of ancient genomic data sampled at high spatiotemporal resolution5–7. Here, to address this, we analysed shotgun-sequenced genomes from 100 skeletons spanning 7,300 years of the Mesolithic period, Neolithic period and Early Bronze Age in Denmark and integrated these with proxies for diet (13C and 15N content), mobility (87Sr/86Sr ratio) and vegetation cover (pollen). We observe that Danish Mesolithic individuals of the Maglemose, Kongemose and Ertebølle cultures form a distinct genetic cluster related to other Western European hunter-gatherers. Despite shifts in material culture they displayed genetic homogeneity from around 10,500 to 5,900 calibrated years before present, when Neolithic farmers with Anatolian-derived ancestry arrived. Although the Neolithic transition was delayed by more than a millennium relative to Central Europe, it was very abrupt and resulted in a population turnover with limited genetic contribution from local hunter-gatherers. The succeeding Neolithic population, associated with the Funnel Beaker culture, persisted for only about 1,000 years before immigrants with eastern Steppe-derived ancestry arrived. This second and equally rapid population replacement gave rise to the Single Grave culture with an ancestry profile more similar to present-day Danes. In our multiproxy dataset, these major demographic events are manifested as parallel shifts in genotype, phenotype, diet and land use.

Root microbiomes of Zygophyllaceae in the Kazakhstan desert: a weak evidence for rhizobial nitrogen fixation

The plants of the Zygophyllaceae family are often considered to be capable of symbiotic atmosphere nitrogen fixation, forming rhizobial nodules similar to those of Fabaceae and Urticaceae. In four species of Zygophyllaceae and the related Peganum harmala (hereafter called Z-plants), collected in Dzungarian deserts (Kazakhstan), we analyzed the prokaryotic component of the root microbiome and the 15N and 13C content in the leaves of these Z-plants compared with neighboring dicots belonging to other families (R-plants). Among all studied Zygophyllum fabago root samples only one was found to have the root nodule, however the microbiome of this sample was similar to that found in other Z. fabago root samples where nodulation was not observed. If compared to Z-plants, the R-plants had a significantly higher relative abundance of bacteria of genera Glycomyces, Massilia and Streptomyces, while the Z-plants had a higher relative abundance of the representatives of genera Actinomadura, Nocardia and Pseudonocardia. Unidentified representatives of the family Rhizobiaceae were present in some of R and Z plants, being most abundant in soil samples. On average, the Z- and the R-plants did not differ in their δ13С and δ15N. Overall, the results do not allow us to consider the studied Zygophyllaceae plants as species with effective atmospheric nitrogen fixation due to rhizobial symbiosis – a characteristic feature of the most legumes.

Diet of the Small Cave Bear Ursus (Spelaearctos) rossicus Borissak, 1930 (Mammalia, Carnivora, Ursidae) As Revealed by 13C and 15N Isotope Analyses in Bone Collagen.

The 13C and 15N isotope contents in bone collagen were analyzed using bones of the small cave bear Ursus (Spelaearctos) rossicus Borissak, 1930 from localities in the Middle and Southern Urals. The bones date from the last interglacial (MIS 5) and glacial (MIS 3) periods. The bones were from males and females aged 3, 4, and >4 years. Sexual, geographical, and chronological differences in 13C and 15N contents were studied. Notable gender, geographic, and chronological differences were observed between samples. In the Middle Urals, females led a more predatory lifestyle than males during the interglacial period, and the trophic niches of males and females converged due to an increase in herbivory during the transition to the glacial period. In the Southern Urals, males led a more predatory lifestyle than in the Middle Urals during the interglacial period. The extent of changes in δ13C and δ15N values in the Southern Urals during the transition was found to correspond to differences between trophic levels.

Nitrogen allocation in PM2.5 smoke-exposed plants: implications for ecosystem nitrogen cycling and stress response

BackgroundWith the increase in forest fire emissions, an increasing amount of nitrogen is released from combustibles and taken up by plant leaves in the form of PM2.5 smoke deposition. Concurrently, the stress from PM2.5 also disrupts the physiological processes of plants. This study aims to reveal the migration paths of N in combustibles in smoke and plants during forest fires and the stress response of plant leaves to smoke particle deposition. This study conducted a simulated smoke deposition treatment on Schima superba and Cunninghamia lanceolata, analyzing the changes in plant 15N content and stress-related products.ResultsThe main findings include the following: (1) Nitrogen in combustibles can be transported to plant leaves via PM2.5 smoke during combustion and can be allocated and assimilated in various parts of the plant after being absorbed by the leaves. (2) The stress response of Schima superba to PM2.5 is less pronounced than that of Cunninghamia lanceolata. (3) Under PM2.5 stress, the correlation between nitrogen accumulation in the leaves of Schima superba and Cunninghamia lanceolata and their respective stress responses differs.ConclusionsIn forest fires involving different tree species, there are variations in the migration pathways of nitrogen and the stress effects of PM2.5 on leaves, with a significant correlation observed between leaf nitrogen accumulation and stress response.Graphical

Early and long-distance uptake by Eucalyptus grandis of N, K and Ca tracers injected down to a depth of 7 m

Eucalyptus plantations are commonly fertilized at planting to sustain high biomass production over successive rotations in nutrient-poor soils. However, the dynamics of nutrient uptake by tree roots in the early stages of stand development, depending on the lateral distance from the trees and the depth in the soil, are poorly documented. We assessed the potential uptake of N, K and Ca, from 6 to 18 months after planting, by Eucalyptus grandis trees depending on: i) the lateral distance from the tracer injection point and ii) the depth in the soil. At 6 months after planting, we injected 15NO3–, Rb+, Sr2+ and Cs+ tracers at depths of 1, 3, 5, and 7 m, respectively. Recently expanded leaves were then sampled monthly on 16 target E. grandis trees located at lateral distances ranging from 0.75 to 11.1 m from the injection points, and on 4 more distant E. grandis control trees; 15N contents (atom %) and concentrations of Rb, Cs and Sr in the leaves were determined at each sampling date, and compared to those of control trees to detect the dates of tracer uptake for each individual. A LOESS model was applied to account for the temporal trend and inter-tree variability among the control trees. Tracer uptake by a target tree was detected if the measurements exceeded the upper limit of the prediction interval (α = 0.005) generated by the model. Only the 6 target trees located within 2.0 m from the injection point took up the 15NO3– tracer. However, Rb+, Sr2+ and Cs+ tracers were taken up to lateral distances of approx. 11 m from the injection point. Tracer uptake occurred as early as 9, 7, 8 and 9 months after planting for 15NO3–, Rb+, Sr2+ and Cs+, respectively. Four trees located within 2.8 m from the injection point took up the 3 cation tracers, injected between the depths of 3 m and 7 m. All but one of the target trees took up at least one cation tracer. The potential of Eucalyptus trees to take up nutrients early, at long distance and at depth, can be promoted by silvicultural practices enhancing rapid root development after planting, as subsoiling in commercial plantations and large planting holes in smallholder plantations. Our results also suggest that fertilization could be applied only once at planting in Eucalyptus stands established on deep tropical soils, with low risks of nutrient losses by deep drainage.

Application fruit tree hole storage brick fertilizer is beneficial to increase the nitrogen utilization of grape under subsurface drip irrigation.

It is very important to promote plant growth and decrease the nitrogen leaching in soil, to improve nitrogen (N) utilization efficiency. In this experiment, we designed a new fertilization strategy, fruit tree hole storage brick (FTHSB) application under subsurface drip irrigation, to characterise the effects of FTHSB addition on N absorption and utilization in grapes. Three treatments were set in this study, including subsurface drip irrigation (CK) control, fruit tree hole storage brick A (T1) treatment, and fruit tree hole storage brick B (T2) treatment. Results showed that the pore number and size of FTHSB A were significantly higher than FTHSB B. Compared with CK, T1 and T2 treatments significantly increased the biomass of different organs of grape, N utilization and 15N content in the roots, stems and leaves, along with more prominent promotion at T1 treatment. When the soil depth was 15-30 cm, the FTHSB application significantly increased the soil 15N content. But when the soil depth was 30-45 cm, it reduced the soil 15N content greatly. T1 and T2 treatments obviously increased the activities of nitrite reductase (NR) and glutamine synthetase (GS) in grape leaves, also the urease activity(UR) in 30 cm of soil. Our findings suggest that FTHSB promoted plant N utilization by reducing N loss in soil and increasing the enzyme activity related to nitrogen metabolism. In addition, this study showed that FTHSB A application was more effective than FTHSB B in improving nitrogen utilization in grapes.

Non-invasive phenotyping for water and nitrogen uptake by deep roots explored using machine learning

Background and aimsRoot distribution over the soil profile is important for crop resource uptake. Using machine learning (ML), this study investigated whether measured square root of planar root length density (Sqrt_pRLD) at different soil depths were related to uptake of isotope tracer (15N) and drought stress indicator (13C) in wheat, to reveal root function.MethodsIn the RadiMax semi-field root-screening facility 95 winter wheat genotypes were phenotyped for root growth in 2018 and 120 genotypes in 2019. Using the minirhizotron technique, root images were acquired across a depth range from 80 to 250 cm in May, June, and July and RL was extracted using a convolutional neural network. We developed ML models to explore whether the Sqrt_pRLD estimates at different soil depths were predictive of the uptake of deep soil nitrogen - using deep placement of 15N tracer as well as natural abundance of 13C isotope. We analyzed the correlations to tracer levels to both a parametrized root depth estimation and an ML approach. We further analyzed the genotypic effects on root function using mediation analysis.ResultsBoth parametrized and ML models demonstrated clear correlations between Sqrt_pRLD distribution and resource uptake. Further, both models demonstrated that deep roots at approx. 150 to 170 cm depth were most important for explaining the plant content of 15N and 13C isotopes. The correlations were higher in 2018.ConclusionsThe results demonstrated that, parametrized models and ML-based analysis provided complementary insight into the importance of deep rooting for water and nitrogen uptake.

Relative uptake of organic and inorganic nitrogen by common weed species

AbstractThe extent to which weed species vary in their ability to acquire and use different forms of nitrogen (N) (inorganic and organic) has not been investigated but could have important implications for weed survival and weed–crop competition in agroecosystems. We conducted a controlled environment experiment using stable isotopes to determine the uptake and partitioning of organic and inorganic N (amino acids, ammonium, and nitrate) by seven common weed and non-weed species. All species took up inorganic and organic N, including as intact amino acids. Concentrations of 15N derived from both ammonium and amino acids in shoot tissues were higher in large crabgrass [Digitaria sanguinalis (L.) Scop.] and barnyardgrass [Echinochloa crus-galli (L.) P. Beauv] than in common lambsquarters (Chenopodium album L.), redroot pigweed (Amaranthus retroflexus L.), and sorghum-sudangrass [Sorghum bicolor (L.) Moench × Sorghum bicolor (L.) ssp. drummondii (Nees ex Steud.) de Wet & Harlan]. In contrast, the concentration of 15N derived from nitrate was higher in wild mustard (Sinapis arvensis L.) shoots than in wild oat (Avena fatua L.) shoots. Root concentration of 15N derived from ammonium was lower in sorghum-sudangrass compared with other species, except for A. retroflexus and A. fatua, while root concentration of 15N derived from nitrate was lower in A. retroflexus compared with other species, except for C. album and S. arvensis. Discriminant analysis classified species based on their uptake and partitioning of all three labeled N forms. These results suggest that common agricultural weeds can access and use organic N and differentially take up inorganic N forms. Additional research is needed to determine whether species-specific differences in organic and inorganic N uptake influence the intensity of competition for soil N.

Uptake of Fertilizer Nitrogen and Soil Nitrogen by Sorghum Sudangrass (Sorghum bicolor × Sorghum sudanense) in a Greenhouse Experiment with 15N-Labelled Ammonium Nitrate

A greenhouse experiment with sorghum sudangrass (Sorghum bicolor × Sorghum sudanense) and maize (Zea mays) was conducted to assess information on differences in their nitrogen and fertilizer utilization when used as energy crops. The aim was to contribute to the scarce data on sorghum sudangrass as an energy crop with regards to nitrogen derived from fertilizer (NdfF) in the plant’s biomass and fertilizer nitrogen utilization (FNU). Sorghum sudangrass and maize were each grown in eight bags of 45 L volume and harvested at maturity after 154 days. Each crop treatment was further divided in a control treatment (four bags each) that did not receive N fertilization and a fertilization treatment (four bags each) that received 1.76 g N, applying a 15N-labelled liquid ammonium nitrate fertilizer. Fertilization took place at the start of the experiment. After harvest, the whole plant was divided in the fractions “aboveground biomass” (ABM) and “stubble + rootstock” (S + R). Weight, N content and 15N content were recorded for each fraction. In addition, N content and 15N content were assessed in the soil before sowing and after harvest. The experiment showed that FNU of sorghum sudangrass (65%) was significantly higher than that of maize (49%). Both crops accumulated more soil N than fertilizer N. The share of fertilizer N on total N uptake was also higher with sorghum sudangrass (NdfF = 38%) compared to maize (NdfF = 34%). The observations made with our control plant (maize), showed that the results are plausible and comparable to other 15N studies on maize regarding yields, NdfF, and FNU, leading to the assumption that results on sorghum sudangrass are plausible as well. We therefore conclude that the results of our study can be used for the preliminary parametrization of sorghum sudangrass in soil organic matter (SOM) balance at field level.

Light induced shoot-sourced transcription factor HY5 regulates the nitrate uptake of cotton by shoot-to-root signal transport

Elongated hypocotyls 5 (HY5) is a transcription factor that can be induced by illumination and promotes nitrate uptake in Arabidopsis. However, whether GhHY5 regulates nitrate uptake in cotton is unknown. In this study, the cotton seedlings growing in light and dark conditions were treated with 15N-labeled nutrient solution to study whether the GhHY5 regulates nitrate uptake in cotton. The results showed that the 15N content and GhNRT1.1 expression in the light condition were higher than that in the dark condition, indicating that light induced the expression of GhNRT1.1 and subsequently promoted N uptake. Additionally, the expression of GhHY5 in the leaf and root of cotton was induced by light and the expression pattern of GhHY5 in the root was similar to that of GhNRT1.1. Furthermore, when the GhHY5 expression in the root was reduced, the 15N content and GhNRT1.1 expression were both decreased, indicating that the GhNRT1.1 expression was regulated by GhHY5. The root expression of GhHY5 was decreased in the grafted seedlings which the GhHY5 in the shoot was silenced by VIGS or the seedlings which the hypocotyl was girdled, but the expression of GhHY5 on one side root of the grafted cotton seedling was not changed if the GhHY5 was silenced on the other side root. Thus, we proposed that the light induced shoot-derived GhHY5 gene or GhHY5 protein may be transported from the xylem to the root, regulating the expression of GhHY5 and GhNRT1.1, and thus regulating N uptake at the root of cotton.

THE FIRST DATA ON THE NUTRITION OF THE URAL CAVE BEAR (MAMMALIA, CARNIVORA, URSIDAE, <i>URSUS</i> (<i>SPELAEARCTOS</i>) KANIVETZ VERESTCHAGIN, 1973) BASED ON THE RESULTS OF THE ANALYSIS OF ISOTOPES <sup>13</sup>C and <sup>15</sup>N

The first data on the content of isotopes 13C and 15N in the collagen of 16 bones of the Ural cave bear (Ursus (Spelaearctos) kanivetz Verestchagin, 1973) were obtained from the Tayn (Secrets) cave (55°25' N, 57°46' E). The bones date from the middle of MIS 3. The bones of males and females aged about 2 years, about 3 years and older than 4 years were studied. There are no noticeable differences in isotope signatures between individuals of different ages and different sexes. Since the second year of life, cave bears have been eating plant food on their own. The values of δ13C and δ15N of the Ural cave bear are close to the values for U. (S.) spelaeus ingressus.

Spatial dependency and independency of nitrogen in lowbush blueberry commercial fields

Rhizomes of wild lowbush blueberry ( Vaccinium angustifolium Aiton) extend horizontally, creating spatial dependency when fertilization trials are performed. Knowing this spatial dependency would help researchers to better design field studies. Here, we used labelled nitrogen (N) fertilizer (15N-(NH4)2SO4) to measure N translocation among blueberry stems for one old (56 year) and one younger (15 year) commercial field. Leaf 15N concentrations at the tip-dieback stage were used to monitor N acquisition. No difference between sites suggests no field age effect on N translocation. Spatial dependency and independency were reached for distances of ≤0.75 and ≥1.75 m from the fertilizer application point, respectively.