Higher Nitrate Reductase Activity Research Articles

Optimal phosphorus proportion increases cotton yields in low nitrogen environments by enhancing mid-upper canopy biomass and nitrogen utilization

To elucidate the physiological mechanism of optimal phosphorus (P) proportion under reduced nitrogen (N) environments on cotton yield, dry matter (DM) spatiotemporal distribution, and N utilization. A three-year experiment was conducted with reduced N (299 kg hm−2, N3), four proportions of P fertilizer (25:75 % at squaring and bloom-bolling stages (P1), 50 %:50 % (P2), 75 %:25 % (P3), 100 %:0 % (P4)), and a traditional N application (402.5 kg hm−2, N2) with P2 as control. Under the N3 treatment, the seed yield of P2 was 6.7–24.5 % higher than other P, and the yield of N3P2 was 1.6–2.6 % lower than N2P2. During the whole growth period, P2 demonstrated 12.4–46.9 % higher leaf and reproductive organs dry matter (LDM and RoDM) compared to other P, and primarily due to more mid-upper DM. Throughout the growth period, N3P2 maintained dominant LDM and exhibited RoDM 2.5 % higher at late-full bolling stage (LFB) compared to N2P2. Trends in leaf N content and reproductive organ N content were similar to DM, with N3P2 consistently maintaining higher levels. Regarding N metabolism activities, N3P2 displayed 8.5–16.1 % higher activity of nitrate reductase, 9.5–21.9 % higher activity of glutamine synthetase, and 7.5 %-15.6 % higher activity of glutamate synthase compared to other P across all growth stages, with no significant differences observed with N2P2. Moreover, N3P2 and N2P2 exhibited higher relative expression of NR, GS1, and ferredoxin-dependent glutamate synthase compared to other treatments. In Conclusion, at 25 % reduced N (N3), optimizing the proportion of P fertilizer (P2, 50 %:50 %) could lead to higher yields due to enhanced N re-utilization capabilities in the later growth stage and increased distribution of DM in leaves and reproductive organs, particularly in the middle and upper layers (especially the fruiting branches). The study findings hold significant theoretical implications for achieving sustainable and efficient production in drip-irrigated cotton fields under reduced N management.

Diverse nitrogen enrichments enhance photosynthetic resistance of Sargassum horneri to ultraviolet radiation

In recent years, golden tides caused by floating Sargassum have induced severe ecological disasters globally. Eutrophication is a significant factor contributing to the massive spread of Sargassum golden tides. Furthermore, the thalli of Sargassum that float on the ocean surface are subjected to more ultraviolet radiation (UVR). The coupled impact of eutrophication and UVR on the photosynthetic physiology of golden tide species remains unclear. In this study, the thalli of Sargassum horneri, known to cause golden tide, were cultured and acclimated to three distinct nitrogen (N) conditions (natural seawater, NSW; NH4+-N enrichment; and NO3–N enrichment) for 6 days. Subsequently, the thalli were exposed to two different radiation treatments (photosynthetically active radiation (150 W m-2), PAR, 400–700 nm; PAR (150 W m-2) + UVR (28 W m-2), 280–700 nm) for 120 min, to investigate the photosynthetic effects of UVR and N on this alga. The findings demonstrated that exposure to UVR impeded the photosynthetic capacity of S. horneri, as evidenced by a decrease in the maximum photochemical quantum yield (Fv/Fm), photosynthetic efficiency (α) and chlorophyll content. Under diverse N-enrichment conditions, the alga tended to adopt various strategies to mitigate the adverse effects of UVR. NH4+-enrichment dissipated excess UVR energy through a greater increase in non-photochemical quenching (NPQ). While NO3–enrichment protected alga by enhancing N assimilation (higher nitrate reductase activity (NRA) and soluble protein content), and maintained a stable energy captured per unit reaction center for electron transfer (ET0/RC) and a higher net photosynthetic rate. Although different N enrichments could not completely offset the damage caused by UV radiation, they secured the photoprotective ability of S. horneri in several ways.

Effects of Nitrate Assimilation in Leaves and Roots on Biomass Allocation and Drought Stress Responses in Poplar Seedlings

Knowledge of tree biomass allocation is fundamental for estimating forest acclimation and carbon stock for global changes in the future. Optimal partitioning theory (OPT) and allometric partitioning theory (APT) are two major patterns of biomass allocation, and occurrences have been tested on taxonomical, ontogenetic, geographic and environmental scales, showing conflicting results and unclear ecophysiological mechanisms. Here, we examine the biomass allocation patterns of two young poplar (Populus) clones varying greatly in drought resistance under different soil water and nitrogen availabilities and the major physiological processes involved in biomass partitioning. We found that Biyu, a drought-sensitive hybrid poplar clone, had significant relations among biomass of leaf, stem and root, showing allometric partitioning. Xiaoye, a drought-tolerant poplar clone native to semi-arid areas, on the contrary, showed tightly regulated biomass allocation following optimal partitioning theory. Biyu had higher nitrate reductase activity in the fine roots, while Xiaoye had higher nitrate reductase activity in the leaves. Biochemical analyses and measurements of fluorescence and gas exchange showed that Xiaoye maintained more stable chloroplast membranes and photosystem electron flow, showing higher water use efficiency and a higher resistance to drought. A nitrogen addition could improve leaf photosynthesis and growth both in Biyu and Xiaoye seedlings under drought conditions. We concluded that the two poplar clones showed different biomass allocation patterns and suggest that the site of nitrate assimilation may play a role in biomass partitioning under varying water and nitrogen availabilities.

Parameters of nitrogen use efficiency of Kentucky bluegrass cultivars at different N levels under deficit irrigation

AbstractIncreasing N use efficiency (NUE) is desirable in turfgrass management. Traditional definition of NUE in turfgrass is essentially the inverse of nitrogen concentration in the clippings and is often evaluated once in a growing season. In this experiment, we followed the Brenderse and Aerts' definition of NUE as the product of mean residence time (MRT) and nitrogen productivity (NP). The objective of this experiment was to identify NP changes over time in Kentucky bluegrass cultivars at different N levels under deficit irrigation. Nine Kentucky bluegrass (Poa pratensis L.) and two hybrid bluegrass cultivars from 10 phenotypic classes were tested under N rates of 10 and 40 g m−2. Deficit irrigation at 60% of the evapotranspiration was imposed. The results showed interaction effects on NP from N level, irrigation, and cultivar. Low‐N treatment resulted in higher NP values as compared to high‐N for ‘Merit’ and ‘Martha’. No NP difference existed between N or irrigation levels for ‘Blue ghost’, ‘Geronimo’, ‘Heidi’, ‘Bandera’, ‘Impact’, ‘Fielder’, ‘Jackrabbit’, and ‘Park’. ‘Rhythm’ showed lower NP values in high‐N combined with full irrigation compared to other treatments. In general, increasing N levels resulted in lower NP, but higher nitrate reductase activity (NaR) and higher net photosynthesis. No N by irrigation interaction effect was detected for effective quantum yield or NaR. In conclusion, leaf‐level NP was shown to be an effective parameter for in‐season monitoring of the above‐ground NUE of Kentucky bluegrass, which provided more dynamic information than clipping yields or a one‐time NUE calculation based on traditional definition.

Microbial induced calcium precipitation by Zobellella denitrificans sp. LX16 to simultaneously remove ammonia nitrogen, calcium, and chemical oxygen demand in reverse osmosis concentrates

In recent years, with the rapid development of industrial revolution and urbanization, the generation and treatment of a large number of salt-containing industrial wastewater has attracted wide attention. A novel salt-tolerant Zobellella denitrificans sp. LX16 with excellent nitrogen removal and biomineralization capabilities was isolated in this experiment. Kinetic experiments were conducted to determine the optimal condition. Under this condition, chemical oxygen demand (COD) can be entirely removed together with ammonia nitrogen, and the removal efficiency of calcium was 88.09%. Growth curves and nitrogen balance tests showed that strain LX16 not only had good HNAD and MICP capabilities, but also had high nitrite reductase and nitrate reductase activities during this process. Three-dimensional fluorescence results reflected that when external carbon sources were lacking or salinity was high, humic acid could effectively enhance the metabolic activity of heterotrophic nitrifying aerobic denitrifying microorganisms through extracellular electron transfer, and the substances produced in the metabolic process could promote biommineralization. Moreover, combined with SEM, SEM-EDS, XRD and FTIR analysis, it is concluded that the microbial surface can provide nucleation sites to form calcium salts, and with the increase of alkalinity to generate Ca5(PO4)3OH. The theoretical basis for the use of biological treatment in reverse osmosis wastewater have been proved by this experiment.

Combined Effect of Nitrogen and Phosphorus Fertilizer on the Activity of the Nitrate Reductase Enzyme in Different Wheat Cultivars

Some characteristics of nitrogen metabolism were observed in the flag leaf on the main branch of wheat (Triticum aestivum L. and Triticum durum L.) In the current study, nine varieties were chosen and planted as test crop using split plot design and replicate at three times, with nutrient dose as the main plot and varieties as the sub plot treatment cultivated at three different soil nitrogen and phosphorus levels (0, 60, and 120 kg/hac) and (0, 30, and 60 kg/hac). These nitrogen and phosphorus levels were handled using four different treatments, where T1 served as the control, T2 as the nitrogen and phosphorus dose at its optimal level, and T3 as the half-nitrogen and full-phosphate fertilizer doses. Fertilizer dosages of T4 that were half nitrogen and half phosphorus were studied. Flag leaf blades were seen to be engaged in NO-3 assimilation. The flag leaf blade had the highest nitrate reductase activity, free amino acid content, and soluble protein content among all the leaf blades. The activity of nitrate reductase was markedly increased by the addition of nitrogen to the soil. The presence of substrate-dependent enzyme activity was demonstrated inflag leaf tissue. A coincidental association between enzyme activity and the buildup of reduced nitrogen in the plant shown the rise in nitrate reductase activity in response to more nitrogen and the increase vegetative reduced nitrogen. A substantial positive connection was discovered between nitrate reductase activity (expressed as molesN/hac.each season) and grain nitrogen (kg N/hac) at maturity because the transfer of vegetative nitrogen to the grain was homogeneous across treatments. Additionally, there was a strong and positive correlation between seasonal nitrate reductase and grain yields (kg/hac.). In cultivars resistant to lodging, maintaining nitrate reductase activity during the reproductive period might boost grain protein production and avoid the decrease of grain protein percentage that is usually seen when grain yields are high.

Variations in growth, proline content, and nitrate reductase activity of Canna edulis at different water availability

Abstract. Nugraheni W, Solichatun, Etikawati N. 2019. Variations in growth, proline content, and nitrate reductase activity of Canna edulis at different water availability. Cell Biol Dev 3: 30-39. Information on the physiological characteristics of Indian shot (Canna edulis Ker Gawl.), especially regarding the effect of water availability in its cultivation, is still limited. This study aims to determine the effect of variations in water availability on growth, proline content, and nitrate reductase activity in two intraspecies variations of C. edulis. Information on the physiological characteristics of C. edulis can be used as a basis for plant breeding efforts to optimize their cultivation. The study was conducted using a completely randomized design (CRD) with one factor, particularly water availability (A1=100% FC, A2=75% FC, A3=50% FC), with 3 replications for each intraspecies variation. The treatment of variations in water availability was given by watering once a day for 3 months. The data obtained for each intraspecies variation were analyzed by analysis of variance (ANOVA). Suppose there was a significant difference between the treatments for variations in water availability. In that case, it is followed by Duncan's Multiple Range Test (DMRT) at a 5% level. In contrast, the data obtained on both intraspecies variations were analyzed by t-test to compare the response of the two intraspecies variations towards variations in water availability. The research results on each intraspecies variation of C. edulis showed that the treatment of variations in water availability affected growth, proline content, and nitrate reductase activity. In the variables of the number of leaves, leaf area, respiration rate, plant height, gross plant weight, and plant dry weight, the optimal growth is at 100% FC water availability. Proline content and nitrate reductase activity were influenced by variations in water availability, with the highest proline accumulation at 50% FC water availability, while the highest nitrate reductase activity was at 100% FC water availability. Both intraspecies variations of C. edulis plants have the same growth response, proline content, and nitrate reductase activity towards variations in water availability.

Soil Acidity Conditioning the Productivity and Physiology of Wheat Inoculated with Azospirillum brasilense

ABSTRACT The increase in the world population creates the need for sustainable food production and the use of synthetic fertilizers with growth-promoting bacteria. The objective of this research was to evaluate the acidity on the physiological and productive variables of wheat inoculated with Azospirillum brasilense and treated with osmoprotective additives. Combinations of A. brasilense, osmoprotectant and chemical treatment were evaluated in wheat seeds planted in contrasting acidity soil (pHs: 4.8 and 6.5). Evaluations of the physiological parameters were carried out in the foliar tissue (hydrogen peroxide content, superoxide dismutase activity, lipid peroxidation, content of chlorophyll a, b, and total and carotenoid and nitrate reductase enzyme activity) during the vegetative period and flowering. The grain yield components were evaluated after the physiological maturation. Plants grown in uncorrected soil acidity (pH: 4.8) showed higher lipid peroxidation. The other plants (pH: 6.5) have higher levels of nitrate reductase. Higher nitrate reductase activity was also observed in plants inoculated with A. brasilense. Therefore, in soil acidity 6.5, both A. brasilense isolate or combined with osmoprotective additive increased the grain yield. Nevertheless, the osmoprotectant application did not attenuate the effects of the chemical treatment of seeds and exerted a negative effect to inoculation with A. brasilense.

Antibacterial activity of biosynthesized silver nanoparticles (AgNps) against Pectobacterium carotovorum.

In a bioprospecting study of paramo soils cultivated with potato (Solanum tuberosum), 50 fungal isolates were obtained and evaluated for their nitrate reductase (NR) activity, given the role played by this enzyme in the biosynthesis of silver nanoparticles (AgNps). Five isolates strain with high NR activity belonging to Penicillium simplicissimum, Aspergillus niger, and Fusarium oxysporum species were selected, verifying the presence of the NR enzyme in their enzymatic extract. Later, these strains showed the ability to biosynthesize AgNps with distorted spherical shapes and sizes ranging from 15 to 45nm. Subsequently, an antibiosis test was carried out by the agar diffusion method using glass fiber disks against the phytopathogenic agent Pectobacterium carotovorum, finding halos of inhibition of bacterial growth up to 15.3mm using a 100ppm solution of the AgNps obtained from F. oxysporum. These results contribute to generating the basis of a new alternative for the control of this phytopathogenic agent of potato, challenging to manage by traditional methods and of relevance at the post-harvest level.

Elevated CO2 alters tissue balance of nitrogen metabolism and downregulates nitrogen assimilation and signalling gene expression in wheat seedlings receiving high nitrate supply.

Tissue and canopy-level evidence suggests that elevated carbon dioxide (EC) inhibits shoot nitrate assimilation in plants and thereby affects nitrogen (N) and protein content of the economic produce. It is speculated that species or genotypes relying more on root nitrate assimilation can adapt better under EC due to the improved/steady supply of reductants required for nitrate assimilation. A study was conducted to examine the effect of EC on N assimilation and associated gene expression in wheat seedlings. Wheat genotypes, BT-Schomburgk (BTS) with comparatively high leaf nitrate reductase (NR) activity and Gluyas Early (GE) with high root NR activity were grown in hydroponic culture for 30days with two different nitrate levels (0.05mM and 5mM) in the climate controlled growth chambers maintained at either ambient (400 ± 10μmolmol-1) or EC (700 ± 10μmolmol-1) conditions. Exposure to EC downregulated the activity of enzyme NR and glutamate synthase (GOGAT) in leaf tissues, whereas in roots, activities of both the enzymes were upregulated by exposure to EC. In addition, EC downregulated N assimilation and signalling gene expression under high N availability. Root N assimilation was less affected in comparison with shoot N assimilation; thereby, the proportion of root contribution towards total assimilation was higher. The results suggest that EC could alter and re-programme N assimilation and signalling in wheat seedlings. The genotype and tissue-specific effects of EC on N assimilation also warrants the need for identification of suitable genotypes and revision of fertiliser regime for tapping the beneficial effects of EC conditions.

Nitrate reductase is a key enzyme responsible for nitrogen-regulated auxin accumulation in Arabidopsis roots

Nitrate reductase (NR) is one of the key enzymes for plant nitrogen assimilation and root architecture remodeling. However, crosstalk between NR-mediated signaling and auxin-mediated root development in nitrogen-status responses has not been investigated in details before. In this study, root phenotype and auxin distribution in nia1/nia2 (nitrate reductase) double mutant and chl1-5 (nitrate transporter NRT1.1) mutant under different nitrogen availabilities were compared. The nia1/nia2 mutant showed very low expression levels of auxin biosynthetic/signaling genes and was insensitive to nitrogen changes. While the chl1-5 mutant showed a high NR activity with a high level of auxin in the meristematic zone and a weaker response to nitrogen changes, when compared with the wild-type plants. We firstly found that NR activity was roughly positive-correlated with the root auxin level, and there is a crosstalk between nitrate signaling and auxin signaling. The putative signaling pathways downstream of NR have been discussed.

Response of Corn Seedlings (Zea mays L.) to Different Concentrations of Nitrogen in Absence and Presence of Silicon

Corn plants are highly demanding of nitrogen and the application of silicon has been studied because it minimizes stress from different natures, and for the better utilization of some nutrients by the plants. Thus, the response of the plant to N can be increased by its association with silicon. The present study had the objective to evaluate the dry matter production, accumulation of nitrogen and silicon in the shoots of the plants as well as the physiological variables in corn culture, as a function of nitrogen concentrations in the nutrient solution in the absence and presence of silicon. Treatments consisted of nitrogen concentrations (1.4, 3.6, 7.1, 14.3, and 28.6 mmol L-1) in the absence and presence (1.8 mmol L-1) of silicon, silicic acid being used as the silicon source, arranged according to a completely random design with four replications. Corn plants (AG 1051) were cultivated in pots (800 mL). At 10 and 20 days after application of the treatments the dark green color index was examined and 21 days after application of the treatment the nitrate reductase activity, accumulation of N and Si, accumulation of proline and dry matter were evaluated. Significant interactions were observed only for dark green color index. Adding silicon resulted in higher N and Si concentrations in the plant shoots, and higher nitrate reductase activity with resulting higher shoot dry mass production, although it did not influence proline content in corn plant leaves.

Nitrogen source utilization in co-existing canopy tree and dwarf bamboo in a northern hardwood forest in Japan

Understory dwarf bamboo mitigated soil N competition with co-existing canopy oak trees by foraging in deeper soils and increasing dependence on N forms that differ from those used by canopy trees. Nitrogen (N) competition among co-existing plant species utilizing different mycorrhiza types was explored through the investigation of N sources of oak trees and dwarf bamboo. Vertical distribution of fine roots, soil N pools, δ15N of leaves, and possible soil N sources and nitrate reductase activity (NRA) were all quantified. The fine roots of canopy trees were more concentrated in the surface soils than roots of the understory dwarf bamboo. Soil NH4+ and extractable organic N (EON) content (based on unit weight) decreased from the organic horizon (O horizon) to the deep soils, the size of the NH4+ pool per unit volume increased with soil depth, and the EON was approximately constant. Soil NO3− was not detected at any soil depth or was not significant in value, while NO3− captured by ion-exchange resin (IER) buried at a 10 cm soil depth and net nitrification were observed via laboratory incubation at all soil depths. The δ15N of the NH4+ and EON pools increased with soil depth and the δ15N of NO3− of IER was lower than that of other N forms, except for the δ15N of NH4+ in the O horizon. Furthermore, root NRA tended to be lower in canopy trees than in the understory, implying lower dependency on NO3− by canopy trees. The pattern of root distribution and mycorrhizal fungi association of the understory vegetation (as well as the high root NRA) suggested that dependence on N in deeper soils was higher in understory plants than in canopy trees. These findings indicate that understory vegetation mitigates soil N competition against co-existing canopy trees via the use of alternative N sources.

Effects of garlic addition on bacterial communities and the conversions of nitrate and nitrite in a simulated pickle fermentation system

Garlic is a spice widely used in traditional pickle making. In this study, effects of garlic addition on bacterial communities and dynamic changes of nitrate and nitrite levels in a simulated pickle fermentation system were investigated under different conditions (with/without the inoculation of Lactobacillus plantarum or Escherichia coli). The result showed that garlic addition efficiently enhanced the growth of Lactobacillus and Weissella while inhibited a lot of undesirable microorganisms during the fermentation. Kinetic analysis revealed that garlic addition and L. plantarum inoculation both significantly decreased the conversion of nitrate and eliminated nitrite peak, but led to much higher level of remaining nitrate (above 1000 mg/kg). Correlation analysis suggested that nitrite conversion was mainly related with the growth of lactic acid bacteria, while nitrate conversion depended more on other microorganisms (like E. coli). Based on these results, introducing safe microorganisms with relatively high nitrate reductase activities and balancing the conversions of nitrate and nitrite were suggested for safer pickle production.

Phytochemical response in rice (Oryza sativa L.) genotype during the vegetative and reproductive stage under drought stress and non-stress conditions

Drought stress is a serious threat which decreases crop production. The present investigation was taken up to study the effect of drought stress at vegetative and reproductive stages on potential biochemical and enzymatic responses were investigated in two rice cultivars Rashi (tolerant) and Swarna (sensitive). Here, we observed significant changes in the biochemical and enzymatic responses between control and treatments as well as between the genotypes. Activity of catalase, peroxidase and superoxide dismutase (SOD), and glutathione reductase were also found to be different among the rice cultivars. Moreover, phenol content and activity of superoxide dismutase, catalase and glutathione reductase were increased significantly under drought stress in Rashi compared to Swarna. Nitrogen assimilatory enzymes such as nitrate and nitrite reductase (NiR) were sensitive to drought stress and both the genotype showed decreased activity at reproductive stage. Catalase activity was significantly higher at controlled reproductive (11.72%) and vegetative stage (4.14%) compared to Swarna. Rashi also showed an elevated SOD activity in controlled reproductive (180.55%) and vegetative stage (7.67%) compared to Swarna. Similarly, highest NiR activity found in Swarna (17.03%) compared to Rashi. Highest nitrate reductase activity was found in Rashi (10.87%) compared to Swarna. Rashi showed significantly higher chlorophyll content in vegetative stage and decreased in reproductive stage (26.33%). The improved performance of drought tolerant genotype (Rashi) was associated with more efficient biochemical factors under conditions of stress compare to drought sensitive genotype (Swarna).

Performance of peanut under organic and inorganic nutrition

This study was conducted to determine the response of organic manure and inorganic N source on groundnut. The study involved a 3 x 5 factorial design with three organic manure (0, 5, 10 tons ha−1) levels and five N dose levels (0, 25, 50, 75, 100 kg N ha−1) with three replications. The combination treatment of 10 tons ha−1 manure with 100 kg N ha−1 had the highest (P<0.05) plant height, chlorophyll content, pod yield, and 100-seed kernel weight among all the treatment combinations applied. Interaction between manure and N, was not significant for leaf area index, nitrate reductase activity, kernel protein and harvest index. The highest nitrate reductase activity was with 5 tons ha−1 of manure, and 75 kg N ha−1. The highest harvest index was obtained with 50 kg N ha−1.

Physiological effects of strobilurin and carboxamides on plants: an overview

Usually, fungicides are used to control and prevent diseases, however, a group of fungicides called strobilurins has brought about a new possibility of use for these products: the physiological effects. This group of fungicides modifies the plant physiology, through changes in metabolism and growth, which increases crop yield. Another group of fungicides, which also reveal physiological effects, is carboxamides. However, there are still only a few publications in scientific journals regarding the effects of the molecules of this group, since they were just introduced in the market recently. The carboxamides when applied together with or alternately to strobilurins potentiate their action. Both are systemic fungicides that operate preventively and have a little curative effect, but the preventive application of these products yields benefits, in addition to protecting the plant by increasing production through its physiological benefits. The physiological effects detected when applying strobilurins or carboxamides in healthy plants are due to the increase in net photosynthesis (true photosynthesis minus dark respiration and photorespiration), as it temporarily reduces plant respiration, which led to less carbon dioxide loss and, consequently, generates more energy for the plant. Besides, the increase in antioxidant enzymes provokes increased tolerance to stress. It also results in higher activity of nitrate reductase and a better hormonal balance, increasing the synthesis of indolyl acetic acid (IAA) and abscisic acid (ABA), as well as reduced ethylene production, delayed senescence and prolonged photosynthetic efficiency, known as "green effect". These effects, together, increase productivity and fruit quality.

Differential Uptake and Utilization of Two Forms of Nitrogen in Japonica Rice Cultivars From North-Eastern China.

Japonica rice is widely planted in north-eastern China because of its superior food quality and stable grain yields. Nitrogen (N) is an essential element for rice growth, and development and its availability directly impacts on rice yields. The knowledge of N uptake and its utilization characteristics in japonica are thus important areas of research. Three japonica rice cultivars, SN265, SN1401, and SN9816, which are planted across large areas of north-eastern China, were used here to evaluate the uptake and utilization along the life cycle of both ammonium and nitrate in hydroponically grown plants. The plants were grown in one of three different solutions with varying : ratios: 1:0, 0:1, and 1:1 (The total N content was 40 mg L−1 for each treatment). At the tillering stage, when only was provided, lower rates of N uptake and enzyme activities of three rice plants resulted in reduced tiller numbers. During the reproductive stage, the and uptake rates in SN1401 were consistently maintained at high levels, whereas the rates in SN265 and SN9816 were significantly lower, across all three treatments. At the booting stage, when only was provided, SN1401 plants had significantly higher expression levels of OsNRT2.1 and OsNRT2.2, higher activity of nitrate reductase in the roots, and higher activity levels of glutamine synthetase and glutamate synthase in the leaves, compared with the SN265 and SN9816 plants. The higher enzyme activity was beneficial to the secondary assimilation of N, which ultimately promoted panicle development in SN1401. Consequently, the grain yield per plant of SN1401 was the highest with solutions of both and . These results indicate that selecting a rice cultivar with higher utilization of is beneficial for increasing the number of grains per panicle, grain yield, and N use efficiency.

Nitrogen-utilization efficiency during early deficiency after a luxury consumption is improved by sustaining nitrate reductase activity and photosynthesis in cotton plants

Understanding mechanisms underlying N use efficiency (NUE) after luxury consumption and nitrate deprivation is crucial to crop productivity. The aim was to elucidate the importance of photosynthesis, assimilatory nitrate reduction and N-reserve remobilization to NUE in cotton. Plants were exposed to three conditions in nutrient solution: (a) previous exposure to high nitrate supply (10 mM) for long-term (8 days); (b) nitrate deprivation (NO3− withdrawal) for 8 days followed by (c) an early N-deficiency for 4 days. Plants supplied with nitrate excess were able to display increment in shoot NUE related to dry matter gain, whereas photosynthetic N use efficiency did not change, evidencing that excess N per se was not able to improve CO2 assimilation. Nitrate reductase (NR) activity was crucial to remobilize stored nitrate through deprivation phase and free amino acids, total proteins, and chlorophylls were also essential to N-remobilization. High NUE was important to kept high root growth rates throughout deprivation and early deficiency phases. Despite the great decrease in chlorophyll content, PSII and PSI activities were kept stable until the onset of early N-deficiency, when cotton plants displayed high shoot NUE. These responses are closely associated with high NR activity and sustaining of photosynthesis, which contribute to N-homeostasis in different nutritional regimes.

The diversity and physiological activities of weeds in land cultivated with various corn cultivars and fertilized with various nitrogen doses

Abstract. Rahayu M, Yudono P, Indradewa D, Hanudin E. 2019. The diversity and physiological activities of weeds in land cultivated with various corn cultivars and fertilized with various nitrogen doses. Biodiversitas 20: 622-628. Both weeds and corn have nutrient needs. Nitrogen is one of the essential elements required by weeds and corn. Each corn cultivar and weed also has different ability to absorb nitrogen. This study aimed to determine the effect of corn cultivar and nitrogen dose on the diversity and physiological activities of weeds. The research was conducted in Banguntapan, Bantul, Yogyakarta from December 2016 to May 2017. The study used a completely randomized block design with 2 factors with three replications. The first factor was corn cultivar, consisting of four cultivars (Bisi 18, NK 33, DK 95 and Sukmaraga) and the second factor was the nitrogen dose, consisting of three levels (25 kg N ha-1, 150 kg N ha-1 and 275 kg N ha-1). The data were analyzed using 5% variance analysis and continued with Duncan test at 5% level. The results showed that the most commonly found weeds were broadleaves, but the most dominant weed was a grass, namely Dactyloctenium aegyptium, except Sukmaraga with nitrogen doses of 25 kg ha-1 and 150 kg ha-1 in 4 weeks after planting (WAP). In 8 WAP, weeds that grew in land planted with all combinations of cultivars and nitrogen doses were Cyperus rotundus, Dactyloctenium aegyptium, Digitaria ciliaris, Eleusine indica, Eragrostis tenella, Amaranthus spinosus, and Richardia scabra. There were no significant differences on the nitrate reductase activity, chlorophyll content, leaf area index, and dry weight among cultivars. The treatment of 25 kg N ha-1 resulted in the lowest leaf area index and total chlorophyll content, but the highest nitrate reductase activity.