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Aims This study was conducted to investigate the capability of the microbial community networks and soil variables to promote carbon and nitrogen cycles in maize fields under straw mulch. Methods We covered the surface soil of the maize field with different amounts of wheat straw (0 kg/ha, 2250 kg/ha, and 4500 kg/ha), then used High-throughput sequencing, Biology ECO-plate, traditional enzymology, TOC analyzer, and HPLC to measure soil microbial community composition and functions, characteristics of microbial carbon source metabolism, carbon and nitrogen fraction, enzyme activity, and organic acid content in maize rhizosphere and non-rhizosphere. Results Our studies indicated that short-term straw mulch significantly influenced microbial β-diversity. The function predicts results revealed that straw mulch significantly increased the relative abundances of bacteria belonging to chemoheterotrophy, aerobic chemoheterotrophy, ureolysis, and nitrogen fixation while inhibiting fermentation and nitrate reduction in maize rhizosphere soil. The Biology ECO-plate results illustrated that straw mulch weakened the metabolism capacity of microbial labile carbon resources, resulting the soil labile C and N fractions raised. Straw mulch primarily regulated the community structure of Firmicutes, Ascomycota, and Basidiomycota. Those microbial communities direct effected on readily oxidizable organic carbon, microbial biomass carbon, available nitrogen, ammonium nitrogen, nitrate nitrogen, and dissolved organic carbon, and indirect effected on these C and N fractions by directly influencing malic acid content and activity of cellulase, protease, and amylase. Conclusions Our findings imply that straw mulch accelerate soil C and N cycle in maize field by mediating microbial community structuresto boost labile C and N components.

A two-year consecutive field experiment was conducted in purple soil in southwest China, to clarify the effects of biochar (0, 10, 20 and 40 t ha−1, namely, B0, B10, B20 and B40) combined with nitrogen reduction (100%, 80% and 60% of conventional nitrogen application rate, namely, N100, N80 and N60) on soil fertility. The performance of thirty-four indices related to soil chemical, physical and biological properties was evaluated by gray correlation analysis, principal component analysis and cluster analysis to determine the most appropriate mode for soil fertilization, and to identify the main soil environmental factors affecting rapeseed yield under the biochar combined with nitrogen reduction. The results indicated that available phosphorus, geometric mean diameter of water stability, fungi number, and the utilization of sugars, amino acids, polymers and carboxylic acids by microorganisms could be used as the main soil factors affecting rapeseed yield. The highest score of soil quality was observed in N100B10 treatment, followed by N80B10 and N100B20 treatments, which were almost in line with the results of rapeseed yields. Cluster analysis classified 12 treatments into 5 main groups on the basis of the measured parameters, which was mostly consistent with the result of soil quality scores. Considering both economic and environmental benefits, 10 t ha−1 biochar combined with 144 kg ha−1 nitrogen was the best combination to restore crop productivity and soil quality, and to achieve nitrogen decreasing and benefit increasing. This study provided scientific basis for the rational fertilization and scientific management of biochar combined with nitrogen fertilizer in purple soil area of southwest China.

Background Biochar is one kind of organic matter that can be added into soil as a soil amendment to improve its quality. To study the effect of biochar addition combined with organic and inorganic fertilizers on growth and fertility and microbial community in purple soil, a completely randomized block design was designed with three levels of biochar [B0: no biochar, B1: low-rate biochar (35 t/ha) , B2: high-rate biochar (50 t/ha)]; two levels of inorganic fertilizers [F1: low-rate inorganic fertilizer (30 kg/ha N, 87.5 kg/ha P2O5 and 60 kg/ha K2O); F2: high-rate inorganic fertilizer (60 kg/ha N, 175 kg/ha P2O5 and 120 kg/ha K2O)]; and two levels of organic fertilizers [M1: no organic fertilizer; M2: with organic fertilizer (4.5 t/ha)]. Results With the application of biochar, the plant height and stem diameter of rapeseed were increased by 6.15%-9.80% and 16.37%-20.11%, respectively. The photosynthetic capacity increased by 20.25% to 35.83%, and the yield increased by 16.40% to 19.11%, respectively. It also promoted the absorption and utilization of nitrogen, phosphorus and potassium by rapeseed to varying degrees. At the same time, the combined application of biochar and organic and inorganic fertilizers could improve soil pH, nitrogen, phosphorus and potassium content and soil microbial community richness: The pH of B1F2M1 increased 0.41 compared with the control, the nitrogen, phosphorus and potassium content in the soil increased by 103.95%, 117.88% and 99.05%, respectively. Meanwhile, soil microbial community richness was also improved. Conclusions Our research showed that biochar could promote the growth and development of rapeseed, and the combined application of biochar with organic and inorganic fertilizers could improve soil fertility and increase microbial diversity. Low-rate biochar combined with organic fertilizer and low-rate inorganic fertilizer was the most suitable application mode in rapeseed production in purple soil area of Southwest China.

Drought is one of the major environmental stresses that negatively affect the maize (Zea mays L.) growth and production throughout the world. Foliar applications of plant growth regulators, micronutrients or osmoprotectants for stimulating drought-tolerance in plants have been intensively reported. A controlled pot experiment was conducted to study the relative efficacy of salicylic acid (SA), zinc (Zn), and glycine betaine (GB) foliar applications on morphology, chlorophyll contents, relative water content (RWC), gas-exchange attributes, activities of antioxidant enzymes, accumulations of reactive oxygen species (ROS) and osmolytes, and yield attributes of maize plants exposed to two soil water conditions (85% field capacity: well-watered, 50% field capacity: drought stress) during critical growth stages. Drought stress significantly reduced the morphological parameters, yield and its components, RWC, chlorophyll contents, and gas-exchange parameters except for intercellular CO2 concentration, compared with well water conditions. However, the foliar applications considerably enhanced all the above parameters under drought. Drought stress significantly (p

Fertilizer-induced CO2 emission is a primary driver of global warming. The experiment was used to study whether controlled-release urea (CRU) application in winter oilseed rape can play a positive role in mitigating CO2 emission and promoting C utilization by soil microorganisms. Five fertilizer types consisted of N0 (0 g N plant−1), conventional CRU application (CRU100%), monotypic CRU at the 80% of conventional rate (CRU80%), co-application of CRU with uncoated urea (CRC), and organic fertilizer (CRO). Results showed that soil CO2 fluxes were significantly affected by N fertilizer types after the start of the stem growing (P < 0.05). CO2 emissions typically peaked during the seed filling period, with the highest emission of 1.99 μmol m−2 s−1 being registered for CRU100%. CRU100% had 25.00%, 30.60%, and 4.17% greater CO2 emissions than CRU80%, CRC, and CRO practices by harvest, respectively. Compared to the conventional CRU treatment, CRU80% led to a lower root volume and root mass ratio than CRU100%, which could partly contribute to the reduced CO2 emission. Conversely, CRU80% performed better in N agronomic efficiency than that of CRU100% treatment. Also, C source utilization by soil microbiomes as well as microbial diversity indices following CRU80% along with CRO applications was substantially higher than that under the conventional CRU supply. These observations suggest that opportunity exists to maintain N balance by N fertilization practices to mitigate CO2 emission from cropland. Further, a close and positive relationship between soil total nitrogen and CO2 emission also supports this. CRO-treated soils substantially elevated the contents of total carbon and readily oxidation carbon over CK. Moreover, the enzyme activity of β-glucosidase in CRO soil was about twice as high as the CRU100%. Consequently, CRU amendments by decreasing CRU rate application and the incorporation of organic fertilizer into CRU have the potential for mitigating of CO2 emission and positive effect on the soil microbial functional diversity to improve nitrogen use efficiency of rapeseed.

Previous studies have reported that potassium plays important roles in rapeseed drought tolerance, however, the interrelationship between potassium and metabolism under drought stress remains unclear. In this study, physiological and metabolic responses were investigated in two cultivars Youyan57 (YY57) and Chuanyou36 (CY36) exposed to 7% PEG6000 simulated drought stress with two potassium levels (0.01 and 1.0 mM K2SO4, referred to LK and NK, respectively). Compared to NK, LK caused a more dramatic reduction in biomass and led to significant lower enzymatic activities of antioxidants under drought stress for both the two cultivars. Moreover, potassium concentration in plant tissues decreased by 29.1% in LK compared to NK averagely and induced metabolic disorder. Totally 51 metabolites changed significantly under LK compared to NK, in which amino acids and amines increased dramatically. Most carbohydrates and carbohydrate conjugates decreased at LK, while organic acids increased, including α-ketoglutaric acid, succinic acid, l-malic acid and oxalacetic acid, which could participate in tricarboxylic acid cycle (TCA) and synthesis of amino acids. The results suggested that potassium deficiency under drought stress induced the accumulation of amino acids for osmotic adjustment and balance of electric charge, while resistance related biosynthesis of amino acids and enhanced TCA cycle were high demands of carbon skeletons which affected plant growth. Cultivar YY57 kept much higher potassium concentration and antioxidant capacity than CY36 at LK, and showed less disturbance of metabolism, consequently resulting in higher biomass. Therefore, potassium uptake and retention was closely associated with rapeseed drought tolerance.

Background Drought has become a dangerous threat to reduce crop productivity throughout the world. Exogenous applications of regulators, micronutrients, and/or osmoprotectants for inducing drought-tolerance in field crops have been effectively adopted. A controlled pot study was performed to investigate the relative efficacy of salicylic acid (SA), zinc (Zn), and glycine betaine (GB) as foliar applications on the growth, tissues pigments content, relative water content (RWC), leaf gas-exchange, antioxidant enzymes activity, reactive oxygen species (ROS) accumulation, osmolytes contents, and the yield parameters of wheat plants subjected to two soil water conditions (85% field capacity: well-watered, 50% field capacity: water-deficient) during reproductive growth stages. Results Water deficient conditions significantly decreased the growth, yield parameters, RWC, photosynthesis pigment, and gas-exchange attributes except for intercellular CO2 concentration. However, foliar applications remarkably improved the growth and yield parameters under water deficit conditions. Under drought condition, exogenous applications of SA, Zn, and GB increased the grain yield pot− 1 by 27.99, 15.23 and 37.36%, respectively, as compared to the control treatment. Drought stress statistically increased the contents of hydrogen peroxide (H2O2), superoxide anion radical (O2•−), and malonaldehyde (MDA), and elevated the harmful oxidation to cell lipids in plants, however, they were considerably reduced by foliar applications. Foliar applications of SA, Zn, and GB decreased MDA content by 29.09, 16.64 and 26.51% under drought stress, respectively, as compared to the control treatment. Activities of all antioxidant enzymes, proline content, and soluble sugar were increased in response to foliar applications under water deficit conditions. Conclusions Overall, foliar application of GB, SA, and Zn compounds improved the drought-tolerance in wheat by decreasing the ROS accumulation, promoting enzymatic antioxidants, and increasing osmolytes accumulation. Finally, GB treatment was most effective in thoroughly assessed parameters of wheat followed by SA and Zn applications to alleviate the adverse effects of drought stress.

NtARF6 overexpression represses nicotine biosynthesis in tobacco. Transcriptome analysis suggests that NtARF6 acts as a regulatory hub that connect different phytohormone signaling pathways to antagonize the jasmonic acid-induced nicotine biosynthesis. Plant specialized metabolic pathways are regulated by a plethora of molecular regulators that form complex networks. In Nicotiana tabacum, nicotine biosynthesis is regulated by transcriptional activators, such as NtMYC2 and the NIC2-locus ERFs. However, the underlying molecular mechanism of the regulatory feedback is largely unknown. Previous research has shown that NbARF1, a nicotine synthesis repressor, reduces nicotine accumulation in N. benthamiana. In this study, we demonstrated that overexpression of NtARF6, an ortholog of NbARF1, was able to reduce pyridine alkaloid accumulation in tobacco. We found that NtARF6 could not directly repress the transcriptional activities of the key nicotine pathway structural gene promoters. Transcriptomic analysis suggested that this NtARF6-induced deactivation of alkaloid biosynthesis might be achieved by the antagonistic effect between jasmonic acid (JA) and other plant hormone signaling pathways, such as ethylene (ETH), salicylic acid (SA), abscisic acid (ABA). The repression of JA biosynthesis is accompanied by the induction of ETH, ABA, and SA signaling and pathogenic infection defensive responses, resulting in counteracting JA-induced metabolic reprogramming and decreasing the expression of nicotine biosynthetic genes in vivo. This study provides transcriptomic evidence for the regulatory mechanism of the NtARF6-mediated repression of alkaloid biosynthesis and indicates that this ARF transcription factor might act as a regulatory hub to connect different hormone signaling pathways in tobacco.

Cadmium (Cd) contamination in agricultural soils is a prevalent environmental issue and poses potential threats to food security. Foliar ascorbic acid might prove a potent tool to alleviate toxicity of Cd toxicity in maize. An experiment was conducted with objectives to study exogenous ascorbic acid-modulated improvements in physiochemical attributes of maize under Cd toxicity. The experiment was conducted under completely randomized design. Treatments were comprised of varying concentrations of foliar ascorbic acid viz. 0.0, 0.1, 0.3, and 0.5 mM of AsA. Toxicity of Cd decreased the maize growth, increased lipid peroxidation, disturbed protein metabolism, and reduced the antioxidant defense capabilities compared with the control. However, foliar AsA significantly improved maize growth and development, photosynthetic capabilities, and protein concentrations in Cd-stressed maize plants. Meanwhile, the malondialdehyde contents and hydrogen peroxide accumulation levels in Cd-stressed maize plants decreased remarkably with increasing AsA concentrations. Furthermore, the combined treatments conspicuously boosted activities of superoxide dismutase, peroxidase, catalase, and glutathione reductase under the Cd stress alone. In addition, the application of AsA reduced the Cd uptake by 10.3-12.3% in grains. Conclusively, foliar ascorbic acid alleviated the negative effects of Cd stress in maize and improved photosynthetic processes, osmolytes, and antioxidant defense systems.

Maize is a sensitive crop to drought and heat stresses, particularly at the reproductive stages of development. The present study investigated the individual and interactive effects of drought (50% field capacity) and heat (38 °C/30 °C) stresses on morpho-physiological growth, yield, nutrient uptake and oxidative metabolism in two maize hybrids i.e., ‘Xida 889’ and ‘Xida 319’. The stress treatments were applied at tasseling stage for 15 days. Drought, heat and drought + heat stress caused oxidative stress by the over-production of ROS (O2−, H2O2, OH−) and enhanced malondialdehyde contents, which led to reduced photosynthetic components, nutrients uptake and yield attributes. The concurrent occurrence of drought and heat was more severe for maize growth than the single stress. However, both stresses induced the metabolites accumulation and enzymatic and non-enzymatic antioxidants to prevent the oxidative damage. The performance of Xida 899 was more prominent than the Xida 319. The greater tolerance of Xida 889 to heat and drought stresses was attributed to strong antioxidant defense system, higher osmolyte accumulation, and maintenance of photosynthetic pigments and nutrient balance compared with Xida 319.

The farming practices of ridge-furrow with film mulching (RFFM) have been extensively reported as a valuable technique for improving crop productivity and enhancing water-use efficiency. However, research on the high-yield mechanism of RFFM measures under drought stress from the perspective of microbial diversity has been scared. Field experiments were conducted to analyze the effects of conventional flat planting (FP), no film mulching (NR), white polyethylene film mulching (WR), black polyethylene film mulching (BR), and biodegradable film mulching (BDR) with 40 and 80 cm furrow width levels on soil temperature, soil water storage (SWS), microbial carbon utilization, and yield of winter oilseed rape. The RFFM significantly increased the SWS as well as rapeseed yield and yield components. However, these treatments did not cause obvious differences in soil temperature. A relative high value of average color change rate (AWCD) was observed during the incubation time of 24–216 h, and it reached the peak value at 240 h. The AWCD in the furrow with 80 cm width was greater than that of 40 cm. The RFFM also could improve the utilization intensities of soil microorganism on the carbon sources of carbohydrates, amino acids, and miscellaneous in rapeseed rhizosphere. This result was consistent with that of the principal component analysis. The Shannon–Wiener diversity index, Simpson’s diversity index, and Shannon–Wiener evenness in BDR40, BR40, and BR80 were significantly higher than other treatments, respectively. In addition, correlation analysis results suggested that the indicator of affecting the diversity of carbon source was mainly due to the water storage capacity. The methods of film mulching have a remarkable effect on microbial diversity. The yield of BR and BDR were significantly higher than other treatments. Compared with FP, RFFM increased rapeseed yield by 9.61–86.10%. In the year of less rainfall, production has decreased in comparison with the first season, while BDR80 guarantees continuous high yield and substantially promoted carbon utilization and soil microbial diversity. Soil microbial diversity is positively correlated with soil water content, which is beneficial to increase production. Wider furrow (80 cm) is recommended a sustainable high-yield method due to convenient labor in the region in Southwest China.

Potassium (K) reduces the deleterious effects of drought stress on plants. However, this mitigation has been studied mainly in the aboveground plant pathways, while the effect of K on root-soil interactions in the underground part is still underexplored. Here, we conducted the experiments to investigate how K enhances plant resistance and tolerance to drought by controlling rhizosphere processes. Three culture methods (sand, water, and soil) evaluated two rapeseed cultivars’ root morphology, root exudates, soil nutrients, and microbial community structure under different K supply levels and water conditions to construct a defensive network of the underground part. We found that K supply increased the root length and density and the organic acids secretion. The organic acids were significantly associated with the available potassium decomposition, in order of formic acid > malonic acid > lactic acid > oxalic acid > citric acid. However, the mitigation had the hormesis effect, as the appropriate range of K facilitated the morphological characteristic and physiological function of the root system with increases of supply levels, while the excessive input of K could hinder the plant growth. The positive effect of K-fertilizer on soil pH, available phosphorus and available potassium content, and microbial diversity index was more significant under the water stress. The rhizosphere nutrients and pH further promoted the microbial community development by the structural equation modeling, while the non-rhizosphere nutrients had an indirect negative effect on microbes. In short, K application could alleviate drought stress on the growth and development of plants by regulating the morphology and secretion of roots and soil ecosystems.

Maize belongs to a tropical environment and is extremely sensitive to drought and chilling stress, particularly at early developmental stages. The present study investigated the individual and combined effects of drought (15% PEG-Solution) and chilling stress (15/12 °C) on morpho-physiological growth, osmolyte accumulation, production of reactive oxygen species (ROS), and activities/levels of enzymatic and non-enzymatic antioxidants in two maize hybrids (i.e., “XD889” and “XD319”) and two inbred cultivars (i.e., “Yu13” and “Yu37”). Results revealed that individual and combined exposure of drought and chilling stresses hampered the morpho-physiological growth and oxidative status of maize cultivars, nevertheless, the interactive damage caused by drought + chilling was found to be more severe for all the studied traits. Between two individual stress factors, chilling-induced reductions in seedling length and biomass of maize cultivars were more compared with drought stress alone. Greater decrease in root length and biomass under chilling stress ultimately decreased the volume and surface area of the root system, and restricted the shoot growth. All the stress treatments, particularly chilling and drought + chilling, triggered the oxidative stress by higher accumulation of superoxide anion, hydrogen peroxide, hydroxyl ion, and malondialdehyde contents compared with the control. Variations in response of maize cultivars were also apparent against different stress treatments, and XD889 performed comparatively better than the rest of the cultivars. The better growth and greater stress tolerance of this cultivar was attributed to the vigorous root system architecture, as indicated by higher root biomass, root surface area, and root volume under drought and chilling stresses. Moreover, efficient antioxidant defense system in terms of higher total antioxidant capability, superoxide dismutase, peroxidase, catalase, and glutathione reductase activities also contributed in greater stress tolerance of XD889 over other cultivars.

Optimum water&ndash, fertilizer management in rainfed agriculture is an important factor in improving crop productivity and the ecological environment under fluctuating climate conditions, especially in Southwest China, where seasonal drought and waterlogging occur frequently. In order to investigate the effects of different cultivation technologies on growth and the water and fertilizer use efficiency of rapeseed (Brassica napus L.), a two-year field study was conducted in rainy (2016&ndash, 2017) and drought (2017&ndash, 2018) seasons which included three cultivation patterns: (1) conventional flat planting (FP), (2) straw mulching (SM), (3) ridge-furrow rainfall harvesting system (RF), and three fertilization patterns: (1) conventional fertilization (CF), (2) reduced slow-release fertilizer (SR), and (3) no fertilizer as a control treatment. The results indicated that the yield and its composition values were lower in the rainy year than in the seasonal dry year. The single water-saving technology had no significant effect on yield increase when seasonal drought occurred. The two technologies (SM + SR and RF + SR) improved the height, leaf SPAD value and dry matter of the rapeseed and adjusted the root&ndash, shoot ratio under two different climate conditions. In the rainy season, these technologies reduced the loss of nutrients, while in the seasonal drought year, it increased the soil moisture. The SM + SR and RF + SR increased the yield of rapeseed by 7.71% and 29.93% and enhanced oil content by 4.64% and 7.91%, respectively, compared with the local cultivation pattern. Meanwhile, these treatments decreased the total water consumption during whole growth stages and promoted water use efficiency by 14.84% and 28.71%, respectively. The combination of SM + SR and RF + SR also increased the accumulation of N, P, and K and significantly promoted the utilization efficiency of fertilizer. In the future, the adverse effects of environmental factors could be relieved, and the goal of cost savings and increasing efficiency could be achieved by adopting the optimal cultivation technologies in rapeseed production of Southwest China.

Reduction of soil fertility and production efficiency resulting from excessive application of chemical fertilizers is universal in rapeseed-growing fields. The main objective of our study was to assess the effects of biochar combined with nitrogen fertilizer reduction on soil aggregate stability and rapeseed yield and to identify the relationship between yield and soil aggregate stability. A two-factor field experiment (2017&ndash, 2019) was conducted with biochar (0 (C0), 10 (C10), 20 (C20) and 40 t&middot, ha&minus, 1 (C40)) and nitrogen fertilizer (180 (N100), 144 (N80) and 108 kg N&middot, 1 (N60)). Experimental results indicated that under N100 and N80 treatments, C10 significantly increased the macro-aggregates (R0.25), mean weight diameter (MWD) and geometric mean diameter (GMD) of soil water stable aggregate by 14.28%&ndash, 15.85%, 14.88%&ndash, 17.08% and 36.26%&ndash, 42.22%, respectively, compared with C0. Besides, the overall difference of the soil water-stable aggregate content in 2&ndash, 5 mm size range among nitrogen treatments was significant under the application of C10, which increased by 17.04%&ndash, 33.04% compared with C0. Total organic carbon (TOC) in R0.25 of soil mechanical-stable aggregates was basically all increased after biochar application, especially in 0.25&ndash, 1 mm and 1&ndash, 2 mm aggregates, and had an increasing trend with biochar increase. C10 significantly increased rapeseed yield by 22.08%&ndash, 45.65% in 2019, compared with C0. However, the reduction of nitrogen fertilizer reduced the two-year average rapeseed yield, which decreased by 11.67%&ndash, 31.67% compared with N100. The highest yield of rapeseed was obtained by N100C10 in two consecutive years, which had no statistical difference with N80C10. However, the two-year yields of N80C10 were all higher than those of N100C0 with increase rate of 16.11%, and which would reduce 35.43% nitrogen fertilizer in the case of small yield difference, compared with the highest yield (2.67 t&middot, 1) calculated by multi-dimensional nonlinear regression models. The regression analysis indicated R0.25, MWD and GMD had the strong positive associations with rapeseed yield, whereas percentage of aggregate destruction (PAD0.25) had a significant negative correlation with rapeseed yield. This study suggests that the application of biochar into upland purple soil could improve soil structure, increase the content of TOC in macro-aggregates under nitrogen fertilizer reduction as well as replace part of nitrogen fertilizer to achieve relatively high rapeseed yield.

Fertilizer-induced CO

The present study was conducted to determine the effect of exogenous application of brassinolide (BR) on Leymus chinensis grown under shade, i.e., control (100% natural light), mild shade (70% natural light), and moderate shade (50% natural light). Shade substantially enhanced the plant growth, synthesis of photosynthetic pigments, photosynthetic efficiency, and chlorophyll (Chl) fluorescence attributes of L. chinensis as compared with control. The order of increase was mild shade > moderate shade > natural light except Chl content, where the order of increase was moderate shade > mild shade > natural light. Likewise, application of BR resulted in further exacerbation of plant height, plant fresh and dry mass, but less in case of Chl and carotenoids contents, gas-exchange characteristics, and Chl fluorescence attributes. The results conclude that shade significantly enhanced plant growth through alterations in physiological attributes of L. chinensis, while, application of BR may not further improve the plant growth under shade.

Maize belongs to tropical environment and is extremely sensitive to drought and chilling stress, particularly at early developmental stages. The present study investigated the individual and combine effects of drought (15% PEG-Solution) and chilling stress (15°C/12°C) on the morpho-physiological growth, osmolyte accumulation, production and regulations of reactive oxygen species (ROS) and the activities of antioxidants in two maize hybrids i.e., ‘XD889’ and ‘XD319’ and two inbred cultivars i.e., ‘Yu13’ and ‘Yu37’. Individual and combined drought and chilling stresses stimulated the production of O2□, H2O2, OH□ and enhanced malondialdehyde (MDA) contents which led to reduced photosynthetic pigments and morphological growth. Drought, chilling and drought + chilling stress conditions induced the compatible osmolytes, ROS detoxifying proteins and antioxidants to counterbalanced the oxidative damage. It was found that the concurrent occurrence of drought + chilling stress was more lethal for maize seedling growth than the drought and chilling individual stresses. However, the performance of hybrid maize cultivars (XD889 and XD319) was better than the inbred maize cultivars (Yu13 and Yu37). For improving tolerance to individual and concurrent drought and chilling stress in maize, future research focus should be on developing genetically engineer plants that have the ability to generate specific response against sub-optimal temperature and water deficit conditions.

The increasing penetration of inverter-based distributed generations (DGs) significantly affects the fault characteristics of distribution networks. Fault analysis is a keystone for suitable protection scheme design. This paper presents the modelling methodology for distribution networks with inverter-based DGs and performs fault simulation based on the model. Firstly, a single inverter-based DG model based on the cascaded control structure is developed. Secondly, a simulation model of distribution network with two inverter-based DGs is established. Then, different fault simulations are performed based on the Real Time Digital Simulator (RTDS). Theoretical analyses are conducted to justify the simulation results, including the equivalent circuit of distribution networks with inverter-based DGs and the solution method for loop currents.

Agricultural production systems are immensely exposed to different environmental stresses in which heavy metal stress receives serious concerns. This study was conducted to explore the deleterious effects of different chromium (Cr) stress levels, i.e., 0, 30, 60, 90, 120, and 150 μmol L−1, on two maize genotypes, Wandan 13 and Runnong 35. Both genotypes were evaluated by measuring their growth and yield characteristics, Cr accumulation in different plant tissues, alterations in osmolyte accumulation, generation of reactive oxygen species (ROS), and anti-oxidative enzyme activity to scavenge ROS. The results showed that Cr stress decreased the leaf area, cob formation, 100-grain weight, shoot fresh biomass, and yield formation, while Cr accumulation in different maize tissues was found in the order of roots > leaves > stem > seeds in both genotypes. The increased Cr toxicity resulted in higher free proline, soluble sugars and total phenolic contents, and lower soluble protein contents. However, enhanced lipid peroxidation was noticed in the forms of malondialdehyde, hydrogen peroxide (H2O2) and thiobarbituric acid reactive substance accumulation, and electrolyte leakage. The hyperactivity of superoxide dismutase, peroxidase, catalase, ascorbate peroxidase, especially glutathione peroxidase and glutathione reductase indicated that these anti-oxidative enzymes had a central role in protecting maize from Cr toxicity, especially for Wandan 13. Moreover, higher uptake and less translocation of Cr contents into the grains of Wandan 13 implied its importance as a potential candidate against soil Cr pollution.

Allelopathic interactions among phytoplankton species are regarded as one of the important factors contributing to phytoplankton species competition and succession. The role and extent of allelopathic effects of blooming freshwater cyanobacteria on other phytoplankton species in eutrophied waters, however, are still unknown. We examined the allelopathic effect of Microcystis aeruginosa on two common green algae ( Scenedesmus quadricauda , Chlorella pyrenoidosa ) and a diatom ( Cyclotella meneghiniana ) by adding exudates from different growth phases and in co-culture tests. Exudates of M. aeruginosa from the exponential growth phase and the stationary phase significantly inhibited the growth of S. quadricauda , C. pyrenoidosa and C. meneghiniana , whereas those from the decline phase increased their growth. The presence of M. aeruginosa extremely inhibited the growth of all tested species in co-cultures within 24 h. Our results indicate that under the tested environmental conditions (25 °C, light 80 μmol quanta m −2 s −1 , manual shaking twice a day), allelopathic effects of M. aeruginosa on other phytoplankton species can significantly contribute to their competitive success.

Soil disturbance by tillage practices promotes soil respiration which is a main source of carbon dioxide emission into the atmosphere. The present study was conducted to investigate the effect of different tillage practices on soil respiration and the carbon source/sink characteristics of maize farmland ecosystems in the wheat&ndash, maize&ndash, soybean cropping system. Six tillage treatments, namely, traditional tillage (T), ridge tillage (R), traditional tillage + straw mulching (TS), ridge tillage + straw mulching (RS), traditional tillage + straw mulching + decomposing inoculants (TSD), and ridge tillage + straw mulching + decomposing inoculants (RSD), were used to measure the soil respiration and its hydrothermal factors. The results showed that the intensity of soil respiration increased initially and decreased afterwards throughout the growth period of maize ranging from 1.011 to 5.575 &mu, mol (m2&middot, s)&minus, 1. The soil respiration rate under different treatments varied remarkably presenting a trend of RSD &gt, TSD &gt, TS &gt, RS &gt, T &gt, R. Ridge tillage reduced the soil respiration rate of maize farmland while straw mulching improved it. Meanwhile, ridge tillage and straw mulching increased the soil temperature sensitivity index of soil respiration, but the addition of decomposing inoculants reduced this trend. The soil moisture response threshold under ridge tillage was lower, while the straw mulching was found to increase it, compared with the control. Moreover, there was a positive correlation between trapped soil fauna and soil respiration. Compared with the control, ridge tillage and straw mulching were beneficial to the carbon sink of the farmland ecosystem as shown by the maize field for the entire growing season.

Carbon (C) losses induced by soil amendments have been shown to trigger soil conservation concerns. However, the mechanisms of fertilizer-induced CO2 emissions are still unclear. Here, we investigated the impact of soil nitrogen (N) amendments at an upland site on soil C stocks, CO2 emission, microbial functional diversity, and soil enzymatic activities during the stem elongation and harvest stages of rapeseed in 2016–2018. Five treatments were designed including non-N fertilizer (N0), conventional urea (U), monotypic CRU fertilization (CRU), co-application of U with CRU (CRC), and CRU plus organic fertilizer (CRO). The key finding is that the significant increases in CO2 emissions from CRO soils were ephemeral compared with the N0 treatment. Root biomass and root: shoot ratio partly explained the significant effect of N addition to CO2 production. Further, improved amylase activities and increasing consumptions of carboxylic acids, polymers and miscellaneous by soil microbes were mainly responsible for enhanced soil CO2 emissions in both growing seasons (P

Drought stress is one of the major environmental factors responsible for reduction in crop productivity. In the present study, responses of two maize cultivars (Rung Nong 35 and Dong Dan 80) were examined to explicate the growth, yield, leaf gas exchange, leaf water contents, osmolyte accumulation, membrane lipid peroxidation, and antioxidant activity under progressive drought stress. Maize cultivars were subjected to varying field capacities (FC) viz., well-watered (80 % FC) and drought-stressed (35 % FC) at 45 days after sowing. The effects of drought stress were analyzed at 5, 10, 15, 20, ad 25 days after drought stress (DAS) imposition. Under prolonged drought stress, Rung Nong 35 exhibited higher reduction in growth and yield as compared to Dong Dan 80. Maize cultivar Dong Dan 80 showed higher leaf relative water content (RWC), free proline, and total carbohydrate accumulation than Run Nong 35. Malondialdehyde (MDA) and superoxide anion were increased with prolongation of drought stress, with higher rates in cultivar Run Nong 35 than cultivar Dong Dan 80. Higher production of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) and glutathione reductase (GR) resulted in improved growth and yield in Dong Dan 80. Overall, the cultivar Dong Dan 80 was better able to resist the detrimental effects of progressive drought stress as indicated by better growth and yield due to higher antioxidant enzymes, reduced lipid peroxidation, better accumulation of osmolytes, and maintenance of tissue water contents.

Increasing soil contamination by cadmium (Cd) has emerged one of the gravest threats to environmental sustainability and global food security. Maize, a major staple food, is supposed as the conspicuous source for intake of Cd by human beings. The present study investigated the morpho-physiological growth and yield responses of two contrasting maize cultivars (Run Nong 35 and Wan Dan 13) to different Cd toxicity levels (0, 75, 150, 225, 300, and 然). A considerable reduction in the growth and yield performance of both maize cultivars were noticed upon exposure to Cd stress and such a reduction governed by Cd was concentration dependent. Therefore, an increase in Cd concentration resulted in a proportional decrease in all growth (plant height, number of leaves per plant, leaf area, and ear length) and yield attributes (number of kernels per row, number of kernels per cob, and 100-kernel weight). Osmolytes accumulation (soluble proteins, soluble sugar, and proline contents) also varied in the response to different Cd toxicity levels and maximum values for these attributes were recorded at 然 Cd in both cultivars. Furthermore, pronounced reduction in gas exchange attributes (photosynthesis, stomatal conductance, transpiration rate, and water use efficiency), relative water contents and chlorophyll contents were observed in Cd-stressed plants. Cultivar variations were also apparent and Wan Dan 13 outperformed the Run Nong 35 for all studied attributes. Wan Dan 13 appeared a promising maize cultivar manifesting Cd tolerance that was related to higher osmolytes accumulation and better photosynthetic activity.

A novel method based on plasma etching was proposed for monolithically integrating planar nanochannels and microelectrodes on a poly (methyl methacrylate) (PMMA) plate, and complete PMMA nanofluidic electrochemical chips with integrated microelectrodes were constructed by bonding with another PMMA plate containing microchannels. The fabrication sequences of nanochannels and microelectrodes were optimized. The oxygen plasma etching rate of PMMA nanochannels was studied, and the average rate was 15 nm/min under optimal conditions. An UV-ozone assisted thermal bonding method was developed to realize a low-temperature chip bonding, and the variations in width and depth of nanochannels before and after bonding were 2% and 5%, respectively. As a demonstration, a nanoparticle crystal (NPC)-based nanofluidic biosensor with integrated Ag microelectrodes was designed and fabricated. Sub-microchannel arrays with a depth of 400 nm and a width of 30 μm on the biosensor functioned as filters, and trapped 540 nm silica nanoparticles modified with streptavidin inside the connected microchannel to assemble the NPC. The interspaces in the NPC formed a three-dimensional nanochannel network with an equivalent diameter of 81 nm. By measuring the conductance across the NPC, a high quality nanofluidic sensing of biotin was achieved. The limit of detection was 1 aM, and the detection range was from 1 aM to 0.1 nM.

Plants face a combination of different abiotic stresses under field conditions which are lethal to plant growth and production. Simultaneous occurrence of chilling and drought stresses in plants due to the drastic and rapid global climate changes, can alter the morphological, physiological and molecular responses. Both these stresses adversely affect the plant growth and yields due to physical damages, physiological and biochemical disruptions, and molecular changes. In general, the co-occurrence of chilling and drought combination is even worse for crop production rather than an individual stress condition. Plants attain various common and different physiological and molecular protective approaches for tolerance under chilling and drought stresses. Nevertheless, plant responses to a combination of chilling and drought stresses are unique from those to individual stress. In the present review, we summarized the recent evidence on plant responses to chilling and drought stresses on shared as well as unique basis and tried to find a common thread potentially underlying these responses. We addressed the possible cross talk between plant responses to these stresses and discussed the potential management strategies for regulating the mechanisms of plant tolerance to drought and/or chilling stresses. To date, various novel approaches have been tested in minimizing the negative effects of combine stresses. Despite of the main improvements there is still a big room for improvement in combination of drought and chilling tolerance. Thus, future researches particularly using biotechnological and molecular approaches should be carried out to develop genetically engineered plants with enhanced tolerance against these stress factors.

Ramie (Boehmeria nivea L.) is an important crop that serves as fine fiber material, high protein feedstuff, and valuable herbal medicine in China. However, increasing salinity in soil limits the productivity. We investigated in a greenhouse experiment responses to salinity in two ramie cultivars, Chuanzhu-12 (salt-tolerant cultivar, ST) and Xiangzhu-2 (salt-sensitive cultivar, SS), to elucidate the salt tolerance mechanism of this species. Salinity stress substantially reduced both chlorophyll and carotenoid contents. In addition, net photosynthesis, transpiration rate, stomatal conductance, intercellular CO2 concentration, and the ratio of intercellular CO2 to ambient CO2 were affected, less in ST. Nevertheless, salinity stress markedly improved water use efficiency and intrinsic water use efficiency in both species. Moreover, relative water contents, soluble proteins, and catalase activity were substantially impaired, while proline accumulation and superoxide dismutase activity were enhanced substantially, more in ST. Furthermore, noteworthy increase in peroxidase activity and decrease in malondialdehyde content was recorded in ST, whereas, in SS, these attributes changed conversely. Overall, the cultivar ST exhibited salt tolerance due to its higher photosynthetic capacity, chlorophyll content, antioxidative enzyme activity, and nonenzymatic antioxidants, as well as reduced lipid peroxidation and maintenance of the tissue water content. This revealed the salt tolerance mechanism of ramie plants for adaptation to salt affected soil.

Drivers of soil respiration (R s ) in farmland ecosystem have already been widely studied. However, the relationship between R s and soil fauna (F s ), hydrothermic factor in the triple intercropping system remains poorly known. An LI-6400 XT portable photosynthesis measurement system equipped with a soil respiratory chamber was adopted in the experimental field. Straw mulching treatment increased soil respiration rate but ridge tillage treatment did not have a consistent effect. A regression analysis of the relationship revealed that exponential equation fitted well the relationship between R s and soil temperature at 10 cm soil depth. However, the relationship between R s and soil moisture was best confirmed by a parabolic function. The common dominant groups of F s in wheat, corn, and soybean farmland were Collembola and Acarina, while Diptera emerged in the two rear crops farmlands. Compared to the control, ridge tillage reduced the number of F s , but straw mulching increased it and improved the index of soil fauna diversity. In conclusion, the higher was the amount of animals being active above soil surface, the stronger was the soil respiration.

Ramie (Boehmeria nivea L.) is one of the oldest and most important fiber crops in China due to the comfortable textile of its fine fiber. Increased ramie fiber demand brings ramie cultivation to salt-affected regions. The aim of this research was to determine morphological, physiological and biochemical responses of ramie by subjecting plants to varying concentrations of NaCl (0, 2, 4, 6 and 8 g NaCl/kg dry soil) at vigorous growth stage for 10 and 20 days. Results indicated that salinity stress substantially inhibited the growth of hybrid ramie plants and led to remarkable decline in fiber yield. However, when grown at 2 g NaCl/kg growth and fiber yield were similar to non-saline control. In addition, chlorophyll fluorescence and gas exchange parameters were correlated with growth and yield response. Salt treatments promoted a subsequent decrease in maximum quantum efficiency of PSII photochemistry (Fv/Fm), quantum efficiency of open PSII reaction centers (Fv'/Fm') and quantum yield of PSII (φPSII) while non-photochemical quenching (NPQ) changed conversely. Photochemical quenching (qP) and electron transport rate of PSII (ETR) increased at 2 and 4 g NaCl/kg then decreased at 6 and 8 g NaCl/kg. Substantial decline in the PSII activity at high salinity was associated with the loss of chlorophyll contents. Moreover, marked decrease in net photosynthetic rate (A), transpiration rate (E), stomatal conductance (gs) was also recorded. Nonetheless, intercellular CO2 (Ci) decreased at low salt stress, subsequently increased at high salt stress while water use efficiency (WUE) and instantaneous water use efficiency (WUEi) altered in opposite direction. Substantial decrease of photosynthesis at high salinity was due to non-stomatal factors. Furthermore, salinity stress led to decrease of proteins and accumulation of proline and malondialdehyde (MDA), as well as enhanced activities of superoxide dismutase (SOD, EC 1.15.1.1) and peroxidase (POD, EC 1.11.1.6), whereas, catalase (CAT, EC 1.11.1.7) enhanced at low salinity, decreased at high salinity. Nonetheless, these changes were closely related with the severity and duration of the salinity stress and their interaction. The results suggested a certain tolerance to salinity stress for hybrid ramie. This meets the essential condition for utilization in salinity-prone environments.

Increasing soil contamination by heavy metals is a major threat to environmental safety and global food security. The present study examined the influence of Cd and As stresses on morpho-physiological growth and yield of two contrasting maize cultivars (Run Nong 35 and Dong Dan 80). The Cd (100 μM) and As (200 μM) were applied individually as well as in combination (Cd + As) at 30 DAS. A control without Cd or As stress was also maintained for comparison. Application of Cd and As alone or in combination substantially reduced the growth (plant height, number of leaves per plant, leaf area, stem diameter, and shoot fresh and dry weight) and yield (number of ears per plant, number of kernels per ear, and 100-kernel weight) contributing traits in both maize cultivars particularly in Run Nong 35. Furthermore, pronounced reductions in gas exchange attributes (photosynthesis, stomatal conductance, transpiration rate, and intercellular CO2) and chlorophyll contents were observed in metal-stressed plants. The combined application of Cd and As was more detrimental for maize, and this treatment recorded the maximum reductions in morpho-physiological growth and yield of both cultivars. Cultivar variations were also apparent, and Dong Dan 80 performed better than Run Nong 35 for all the studied attributes. The higher tolerance of Dong Dan 80 was associated with better leaf gas exchange and maintenance of chlorophyll contents in this cultivar under Cd and As stress.

Phytotoxic effects of a single heavy metal on different crops are widely reported; however, consequences of combined metal toxicity on maize are rarely investigated. In this study, a pot experiment was conducted to assess the phytotoxic effects both Al and Cr on morphophysiological and biochemical traits, photosynthetic gas exchange capacities, metal uptake, and translocation in different plant parts. Plants were exposed to Al3+ (100 μM), Cr6+ (100 μM), and Al3+ + Cr6+ (100 + 100 μM), and data were collected at pre- and post-silking stages while uncontaminated pots were served as control (Ck). Results depicted that both Al and Cr impaired maize growth and yield response and inhibited photosynthesis and gas exchange attributes i.e., transpiration, stomatal conductance, inter-cellular CO2, as well as water use efficiency (WUE) and intrinsic water use efficiency (WUEi). Moreover, Al and Cr toxicities caused lipid peroxidation and membrane damage while activated antioxidative defense system in terms of superoxide dismutase (SOD), peroxidaes (POD), and catalase (CAT) and mediated reduced glutathione contents (GSH). Increased proline and reduced protein contents were also observed with a combined metal toxicity. Interestingly, Cr proved to be more toxic than Al whereas affects were more apparent where both Al and Cr were applied simultaneously. Plant exposure to both Al and Cr increased metal contents in different plant parts, while maximum metal contents were recorded in roots followed by stem, leaves, corn ear, and grains. Overall severity in phytotoxic effects was observed as Al+Cr > Cr > Al > Ck. Additionally, values of combined application of both Al + Cr were higher than those of the linear sum of Al and Cr alone, suggesting that synergistic effects of Al + Cr were more toxic than their individual effects. Hence, combined metal toxicity proved more damaging for maize than individual metal stress.

Active distribution networks (ADN) connect many distributed generators (DG), and compared with traditional distribution network, running state and fault characteristics of ADN change greatly, especially the ADN with connection of inverter-based DG (IBDG). To analyze and test the protection applicability in ADN, a model of ADN with IBDG is established based on RTDS in this paper, including primary system of distribution network, photovoltaic (PV) generation and control strategy for grid-connected inverter. Based on this model, both the characteristics of normal and fault condition are simulated and analyzed, and then compared with traditional distribution network. Meanwhile, based on the ADN model platform, a close-loop test for the protection device we developed is introduced briefly.