Shade Avoidance 3 Mediates Crosstalk Between Shade and Nitrogen in Arabidopsis Leaf Development

After nitrogen treatments, plant leaves become narrower and thicker, and the chlorophyll content increases. However, the molecular mechanisms behind these regulations remain unknown. Here, we found that the changes in leaf width and thickness were largely compromised in the shade avoidance 3 (sav3) mutant. The SAV3 gene encodes an amino-transferase in the auxin biosynthesis pathway. Thus, the crosstalk between shade and nitrogen in Arabidopsis leaf development was investigated. Both hypocotyl elongation and leaf expansion promoted by the shade treatment were reduced by the high-N treatment; high-N-induced leaf narrowing and thickening were reduced by the shade treatment; and all of these developmental changes were largely compromised in the sav3 mutant. Shade treatment promoted SAV3 expression, while high-N treatment repressed SAV3 expression, which then increased or decreased auxin accumulation in cotyledons/leaves, respectively. SAV3 also regulates chlorophyll accumulation and nitrogen assimilation and thus may function as a master switch responsive to multiple environmental stimuli.

Environmental Impacts, Human Health, and Energy Consumption of Nitrogen Management for Maize Production in Subtropical Region

Over-application of fertilizers could not improve crop yield and agronomic efficiency, but result in increasing nitrogen (N) surplus and adverse effects on the ecosystem sustainability. Although some previous studies have addressed one or a few environmental aspects in crop production, an integrated assessment for the effects of N fertilizer on multiple environmental impacts, and the optional steps of normalization and weighting is required. A consecutive 2-yr plot-based field experiment was conducted with five N fertilizer levels (0, 90, 180, 270, and 360 kg N ha-1) in maize production at three sites in Southwest China, to evaluate the environmental performance and sustainability through joint use of life cycle assessment (LCA) and energy consumption analysis. Results demonstrated that the optimal N rate (180 kg N ha-1) showed greater potential for maintaining high yield (achieved 86% of the yield potential) and reducing the global warming (-31%), acidification (-47%), eutrophication (-44%) compared to farmers’ practice, and energy depletion potentials, by reducing pollutants emission during the production and transportation of N fertilizer and Nr losses at farm stage. Optimal N treatment indirectly reduced the land use, life-cycle human toxicity, aquatic eco-toxicity, and terrestrial eco-toxicity potentials by improving grain yield and agronomic efficiency. In addition, the optimal N treatment reduced the energy consumption by enhancing the energy use efficiency (EUE) (+74%) and reducing non-renewable energy form (-45%) than the farmer’s practice. This study will provide comprehensive information for both scientists and farmers involved in maize production and N management in subtropical region.

Comparison of Nitrogen Treatment by Four Onsite Wastewater Systems in Nutrient-Sensitive Watersheds of the North Carolina Coastal Plain

Wastewater may be a source of nitrogen (N) to groundwater and surface waters if not effectively treated. In North Carolina, onsite wastewater systems (OWSs) are used by 50% of the population for wastewater treatment, but most OWSs are not routinely monitored. There is a lack of information regarding the N contributions from OWSs to water resources. Four sites with OWSs were instrumented with groundwater wells near their drainfield trenches to compare N concentrations in groundwater to concentrations in wastewater and to determine the N treatment efficiency of the systems. Two OWSs (Site 200 and 300) were less than 1 year old, and two (Site 100 and 400) were more than 10 years old at the start of the study. Two OWSs (Site 100 and 200) used pressure dosing, while two OWSs (Site 300 and 400) used gravity distribution. The mean N treatment efficiency of the four OWSs was 77%. The new OWSs were more efficient (92%) relative to the older OWSs (62%) at reducing N concentrations. Similar N treatment efficiencies were observed when pooling data for the pressure dosed (77%) and gravity (79%) OWSs. Each OWS influenced groundwater by causing increases in N concentrations. It is important that new OWSs are installed at a shallow depth and with sufficient separation to groundwater to promote the aerobic treatment of wastewater. Remediation strategies including the installation of permeable reactive barriers or the use of media filters may be needed in some areas to reduce N transport from existing OWS.

Impact of Residue Incorporation on Soil Carbon Storage, Soil Organic Fractions, Microbial Community Composition and Carbon Mineralization in Rice-wheat Rotation – A Review

In agroecosystems, straw return is a useful management strategy for increasing soil fertility and crop productivity. The total organic carbon (TOC), dissolved organic C (DOC), and microbial biomass C (MBC) contents all increased significantly when compared to the no straw return (N) and straw return (S) treatments, while the easily oxidizable C content remained same. The S treatment resulted in a 28–52 percent increase in soil light fraction, light fraction organic C, and particle organic C over the N treatment. When compared to the N treatment, crop straw return increased total phospholipid fatty acid (PLFA), bacterial biomass, and actinomycete biomass by 52, 75, and 56 percent, respectively. Under short-term crop straw return, MBC and TOC were the two key determinants determining microbial populations. In comparison to residue removal, residue retention (RR) enhanced SOC storage by 11.3 percent. SOC content and contribution of macro-aggregates in the 0-20 cm depth and micro-aggregates in the 20-40 cm depth rose significantly when no-tillage and straw returns were used together. When no-tillage with straw returning (NTS) was used instead of CT, SOC content, mean weight diameter (MWD), geometric mean diameter (GMD), and fractal dimensions (FD) rose by 25%, 21%, 19%, and 12%, respectively, in the 0-20 cm depth. Soil micro-aggregates were greater in the 20-40 cm depth after CTS treatment. In the 0-20 cm depth, the percentages of macro- and micro-aggregates increased by 60% and 40%, respectively, under NTS. MWD, GMD, > 5, 2-5, 1-2, and 0.25-0.5 mm aggregates all had a positive linear relationship with the SOC. Microbial biomass C (MBC) was considerably enhanced by 20.0 percent when compared to conventional tillage (CT) and no-tillage (NT), but total organic C (TOC), dissolved organic C (DOC), readily oxidizable C (EOC), and SOC of aggregates were not affected. MBC increased by 18.3% and SOC content of 2–1-mm aggregate increased by 9.4% when residue was returned. Total PLFAs grew by 9.8%, while fungal biomass increased by 40.8 percent, thanks to NT. Total PLFAs, bacterial biomass, fungal biomass, F/B, and MUFA/STFA were all increased by 31.1, 36.0, 95.9, 42.5, and 58.8 percent, respectively, while microbial stress was reduced by 45.9%. Wheat straw return had a considerable impact on the bacterial community in the soil, but not on the fungus community. It increased the relative abundance of the bacteria phylum Proteobacteria and the fungal phylum Zygomycota, while decreasing the relative richness of the bacterial phylum Acidobacteria and the fungal phylum Ascomycota. It increased the relative abundance of nitrogen-cycling bacterial taxa including Bradyrhizobium and Rhizobium, among others. This diversity includes bacteria, cyanobacteria, archaea, planctomycetes, and -proteobacteria, as well as endophytes. The system's intricacy and dynamic nature necessitate in-depth research on the three-part interactions between plants, microorganisms, and the soil-water environment.

Cotton Emergence and Yield Response to Planter Depth and Downforce Settings in Different Soil Moisture Conditions

US cotton producers are motivated to optimize planter performance to ensure timely and uniform stand establishment early in the season, especially when planting in sub-optimal field conditions. Field studies were conducted in 2017, 2018 and 2019 to evaluate the effect of seeding depth and planter downforce on crop emergence and yield in cotton planted in different soil moisture conditions. Field conditions representative of dry, normal and wet soil moisture conditions were attained by applying 0, 1.27 and 2.54 cm of irrigation within the same field. Two cotton cultivars (representing a small-seeded and a large-seeded cultivar, 9259–10,582 and 11,244–14,330 seeds kg−1, respectively), were planted at seeding depths of 1.3, 2.5 and 3.8 cm with each seeding depth paired with three different planter downforces of 0, 445 and 890 N in each block. Cotton was planted in plots that measured 3.66 m (four-rows) wide by 10.67 m long. Results indicated that crop emergence was affected by the seeding depth across most field conditions and higher crop emergence was observed in the large-seeded cultivar at 1.3 and 3.8 cm seeding depths in dry and wet field conditions, respectively. Lint yield was also higher for the large-seeded cultivar at the 3.8 cm seeding depth across all field conditions in 2017, and in dry field conditions in 2018. Planter downforce effect on crop emergence varied among the cultivars where the large-seeded cultivar exhibited higher crop emergence than the small-seeded cultivar at 445 and 890 N downforce. Planter downforce of 445 N yielded greater than the 0 and 890 N treatment in dry field conditions in 2017. The study results suggest that matching planter depth and downforce settings for prevalent soil moisture conditions at planting along with appropriate cultivar selection can help in achieving optimal emergence and yield in cotton.

The α-Gliadins in Bread Wheat: Effect of Nitrogen Treatment on the Expression of the Major Celiac Disease Immunogenic Complex in Two RNAi Low-Gliadin Lines

Celiac Disease (CD) is an autoimmune disorder that affects approximately 1% of the worldwide population. The α-gliadins of wheat contain the 33-mer peptide, the most active peptide in CD both in adults and pediatric patients. In this study, we have characterized the variants and expression profile of an α-gliadins amplicon, harboring the 33-mer peptide, in two low-gliadin RNAi wheat lines, under two different Nitrogen (N) treatments. We estimated that the amplicon expands 45 different α-gliadin variants with high variability due to length, randomly distributed SNPs, and the presence of encoded CD epitopes. Expression of this amplicon is reduced in both RNAi lines in comparison to the wild type. High N treatment significantly increases transcripts of the amplicon in the wild type, but not in the transgenic lines. Classification of α-gliadin variants, considering the number of epitopes, revealed that amplicon variants containing the full complement of 33-mer peptide were affected by N treatment, increasing their expression when N was increased. Line D793 provided higher and more stable silencing through different N fertilization regimes, expressing fewer CD epitopes than D783. Results of this study are important for better understanding of RNAi α-gliadin silencing in response to N treatments, and for undertaking new strategies by RNAi or CRISPR/Cas toward obtaining new varieties suitable for people suffering gluten intolerances.

Variation for Composition and Quality in a Collection of the Resilient Mediterranean ‘de penjar’ Long Shelf-Life Tomato Under High and Low N Fertilization Levels

The ‘de penjar’ tomato (Solanum lycopersicum L.) is a group of local varieties from the Spanish Mediterranean region carrying the alc mutation, which provides long shelf-life. Their evolution under low-input management practices has led to the selection of resilient genotypes to adverse conditions. Here we present the first evaluation on nutritional fruit composition of a collection of 44 varieties of ‘de penjar’ tomato under two N fertilization levels, provided by doses of manure equivalent to 162 kg N ha–1 in the high N treatment and 49 kg N ha–1 in the low N treatment. Twenty-seven fruit composition and quality traits, as well as plant yield and SPAD value, were evaluated. A large variation was observed, with lycopene being the composition trait with the highest relative range of variation (over 4-fold) under both N treatments, and significant differences among varieties were detected for all traits. While yield and most quality traits were not affected by the reduction in N fertilization, fruits from the low N treatment had, on average, higher values for hue (5.9%) and lower for fructose (−11.5%), glucose (−15.8%), and total sweetness index (−12.9%). In addition, lycopene and β-carotene presented a strongly significant genotype × N input interaction. Local varieties had higher values than commercial varieties for traits related to the ratio of sweetness to acidity and for vitamin C, which reinforces the appreciation for their organoleptic and nutritional quality. Highest-yielding varieties under both conditions displayed wide variation in the composition and quality profiles, which may allow the selection of specific ideotypes with high quality under low N conditions. These results revealed the potential of ‘de penjar’ varieties as a genetic resource in breeding for low N inputs and improving the organoleptic and nutritional tomato fruit quality.

Responses of Soil C-, N-, and P-Hydrolyzing Enzyme Activities to N and P Addition in an Evergreen Broad-Leaved Forest in Southwest China

Background and Aims Human activities-mediated input of nitrogen (N) and phosphorus (P) to ecosystem may significantly affect soil hydrolyzing enzyme activities (Hy-EAs). However, the mechanisms underlying the responses of soil Hy-EAs to change in N and P availability remains unclear. Methods Here, a two-year field N and P addition experiment was conducted in a subtropical evergreen broad-leaved forest to elucidate the effects of N addition, P addition, and NP co-additions on soil Hy-EAs and biochemistry properties. Results The invertase, cellulase, and acid phosphatase activities were increased in N treatment but reduced in P treatment. The urease activity was reduced in N treatment but did not alter in P treatment. NP treatment significantly increased the invertase and cellulase activities. Furthermore, the cellulase activity was positively correlated with soil organic carbon concentration. The acid phosphatase activity was negatively correlated with microbial biomass carbon (MBC), total P, and available P concentrations. Whereas the urease activity was not strongly dependent on total N concentrations, but positively correlated with soil pH and MBC. These Hy-EAs were significantly correlated with C-to-P and N-to-P ratios, while no significantly correlation with C-to-N ratio. Conclusions Overall, our results indicated that N and P addition significantly affected the soil C-, N-, and P-hydrolyzing enzyme activities. With ongoing imbalanced N and P input in our studied subtropical evergreen broad-leaved forest, N addition may exacerbate the limitation of soil C and P availability, while the exogenous P addition may improve the soil C and P availability.

Effect of nitrogen fertiliser on the rate of lipid peroxidation of different maize hybrids in a long-term multifactorial experiment

The presented research aimed to confirm that the differences in the lipid peroxidation of three maize (Zea mays L.) hybrids with different genotypes and maturity are due to different nitrogen levels, which was observed based on the amount of malondialdehyde (MDA) measured in the leaves at the main phenological stages of plants. The experiments were performed in a multi-factorial long term fertilisation field trial. In the study, phosphorus and potassium were constantly provided at the optimal level for the plants. The phosphorus and potassium fertilisation were applied in autumn. However, N levels varied from 0 to 300 kg ha−1. Sampling was done at different growth stages 5 times during the growing season (4 leaves, 6 leaves, 8 leaves, 14 leaves, silking). The 300 kg ha−1 N (dose 3) resulted in a significant increase in lipid peroxidation (MDA level), but not a statistically significant difference between the control (dose 1) and the 120 kg ha−1 (dose 2) N doses. The H1 hybrid had the lowest level of lipid peroxidation at the first sampling date. High volume nitrogen fertilisation (dose 3: 300 kg ha−1) increased lipid peroxidation in the hybrids. Averaging the values obtained for the same hybrid at the different sampling times, the medium (dose 2) 120 kg ha−1 N treatment had no significant effect on the lipid peroxidation of the hybrids compared to the values of the control plants. Based on the lipid peroxidation response of the hybrids to N treatment, the exact N dose inflection point can be determined to make the fertiliser utilisation of plants more efficient. Based on our results, we found that inadequate, low (120 kg ha−1) or high (300 kg ha−1) nitrogen fertilisation could affect the MDA levels of plants, thereby affecting the functioning of the lipid peroxidation mechanism.

Effects of elevated ozone and nitrogen addition on leaf nitrogen metabolism in poplar

Aims Ozone (O3) pollution and nitrogen (N) deposition/fertilization often simultaneously affect plant growth. However, research of their interactive effects on leaf N metabolism is still scarce. We investigated their interactive effects, aiming to better understand plant N metabolism processes and biogeochemical cycles under high O3 pollution and N deposition/fertilization. Methods Poplar saplings were exposed to two O3 levels (NF, non-filtered ambient air; NF60, NF + 60 ppb O3) and four N treatments (N0, no N added; N50, N0 + 50 kg N ha -1 yr -1; N100, N0 + 100 kg N ha -1 yr -1; N200, N0 + 200 kg N ha -1 yr -1) in open-top chambers for 95 days. The indicators related to leaf N metabolism were analyzed, including the activities of N-metabolizing enzymes and the contents of total N, NO3 --N, NH4 +-N, total amino acid (TAA) and total soluble protein (TSP) in the leaves. Important Findings NF60 stimulated the activities of nitrate reductase (NR) by 47.2% at August relative to NF, and stimulated glutamine synthetase (GS) by 57.3% when averaged across all N treatments and sampling times. In contrast, O3 did not significantly affect TSP and even reduced TAA content in August. Relative to N0, N200 significantly increased light-saturated rate of CO2 assimilation (Asat) by 24%, and increased total N content by 70.3% and 43.3% in August and September, respectively, while it reduced photosynthetic N-use efficiency by 26.1% in August. These results suggest that the increase in Asat and total N content are uncoupled, and that the surplus N is not used to optimize the capacity for carbon assimilation under high N treatment. Simultaneously, high N treatment significantly promoted leaf N metabolism by increasing NO3 --N contents, NH4 +-N contents, TAA contents and the activities of NR and GS. There was no significant interaction between O3 and N for all variables.