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Fast development of farming practices in China is projected to result in additional carbon emissions and thus affect farmland ecosystems' environmental performance. Based on 454 farm surveys on the North and Northeast China Plain, the carbon footprint (CF) of two farmland ecosystems (irrigated system for wheat and maize on the North China Plain and rainfed system for maize on the Northeast Plain) were assessed and emission reduction pathways explored by quantifying greenhouse gas emissions of agricultural inputs and farm practices during the entire crop growing seasons with an agricultural footprint model. The results demonstrated that the GHG emissions from wheat and maize rotation in the irrigated system were 7.63 t CO 2 eq ha−1 and 3.17 t CO 2 eq ha−1 for single season maize in the rainfed system. While energy consumption accounted for 12.5%–21.3% of the carbon footprint in both systems, the group assessment found that the largest difference in GHG emissions between the high and low emission groups came from mechanical energy consumption. Approximately 50.6% and 39.2% of the mechanical carbon footprint of wheat and maize, respectively, were caused by irrigation practices in the irrigated system. Regarding the rainfed system, where 46.6% of mechanical carbon emissions were generated by maize tillage operations. In addition, scenario analysis indicated that the mechanical carbon footprint could be reduced to 56 kg CO 2 eq t−1 for NCP-wheat and 26 kg CO 2 eq t−1 for NCP-maize, respectively, by optimizing yields and irrigation practices in irrigated systems and that the mechanical carbon footprint of NEP-maize could be reduced to 25 kg CO 2 eq t−1 by optimizing yields and tillage practices in rainfed systems. Therefore, improvement in mechanization in irrigation and tillage practices can contribute to reduce GHG emissions in China. Water-saving irrigation technology is recommended in irrigated area and conservation tillage is recommended in rainfed agricultural area to reduce carbon footprints. [Display omitted] • Carbon footprint of farming practices was studied on the North and Northeast China Plains. • Irrigation practice affects the carbon footprint of the winter wheat–summer maize system. • Tillage practice determines the carbon footprint of the rain-fed spring maize system. • Promoting drip irrigation in irrigated system and strip-tillage in rainfed system could reduce the carbon intensity. [ABSTRACT FROM AUTHOR]

It is a great challenge to increase nitrogen (N) remobilization from leaves while ensuring high grain yield of maize (Zea mays L.). One possible way is to increase photosynthetic N use efficiency (PNUE) of leaves during post‐silking. This study aimed to understand the strategies required to maintain high PNUE during post‐silking in a N‐remobilizing high‐yielding maize hybrid. In this study, the high‐yielding hybrid XY335 with high N remobilization efficiency (NRE) and the high‐yielding hybrid ZD958 with low NRE were used in a three‐year field experiment under normal N levels. The results show that specific leaf N contents were similar in lower, middle, and upper leaves of the two hybrids from silking stage to maturity. Throughout the grain filling period, net photosynthetic rate (PN), stomatal conductance (gs), intercellular CO2 concentration, and PNUE of XY335 were similar to that in ZD958 in lower leaves, but higher in middle and upper leaves. Stomatal density and maximum rate of carboxylation in upper leaves and maximum rate of electron transport in middle leaves was higher in XY335 than that in ZD958. It is concluded that maintaining the PNUE of lower leaves together with increasing the PNUE of middle and upper leaves at canopy‐level are the possible regulatory mechanisms to improve NRE without penalty in whole‐plant photosynthesis during post‐silking in modern high‐yielding cultivars. The higher PNUE is at least partly related to the higher proportion of N allocation to the carboxylation and bioenergetics systems and the higher stomatal density and greater gs. Therefore, genetic improvement in N allocation to the carboxylation and bioenergetics systems and stomatal density and gs might increase PNUE. [ABSTRACT FROM AUTHOR]

Inadequate supply of nitrogen (N) fertilizers results in lower N use efficiency (NUE) and higher N losses which cause environmental deterioration, such as nitrate pollution of groundwater and emission of nitrous greenhouse gases. One way to increase NUE is to use N-efficient cultivars, which grow better under reduced N supplies. Both elite inbred lines and landraces are the basis for hybrid breeding in maize. While inbred lines are mostly selected from high N input conditions, landraces are historically distributed in poor soils with low N availability. Therefore, some potential NUE-related traits conserved in the landraces may have been lost during modern breeding processes. In the present study, the N accumulation and utilization efficiency of 15 elite inbred lines and four landraces of maize were compared at low (LN) and high N (HN) input conditions. In general, the grain yields of the inbred lines and the landraces were similar at both N rates. However, nitrogen accumulation ability in landraces was much higher than that of the inbred lines. The high N accumulation of landraces was closely related to their higher biomass, indicating that growth potential is the main driving force for N accumulation. Nevertheless, N utilization efficiency (grain produced per unit N absorbed) of the landraces was significantly lower than that in inbred lines. Correspondingly, assimilation allocation for grain formation, as indicated by the harvest index, was much lower in landraces than in inbred lines. The higher growth potential, and hence, the ability of N accumulation in landraces may be a valuable trait in breeding programs aiming to further improve N use efficiency. [ABSTRACT FROM AUTHOR]

Selection for nitrogen (N)-efficient crops is considered to be an effective approach for minimizing the input and the loss of N fertilizers in agricultural fields. This study investigated the hypothesis that nitrate supply may induce changes in root morphology so that N uptake efficiency can be influenced. Different levels of nitrate concentration (0.04, 0.2, 2, and 4 mM) were supplied to five maize (Zea mays L.) inbred lines that had shown different N efficiencies. Possible correlations between N-uptake efficiency and several root parameters of root morphology were evaluated. The two N-efficient varieties, 478 and H21, had higher shoot and root weight and absorbed more N than the two N-inefficient lines, Wu312 and Zong31, especially under low N supply. In general, high nitrate levels (2 and 4 mM) increased the total length of lateral roots (LR), but limited the total length of primary roots (PR) (including seminal and nodal roots) as well as the average length of primary roots. As a result, the total root length (TR) increased with the increasing of nitrate levels. Total N accumulation had significant positive correlations with the root dry weight, TR, and PR at low N supply (0.04–2 mM). At high N supply (4 mM), however, only LR was to some extent correlated to N accumulation. It is concluded that, under N deficient situation, a larger root system (total root length and root surface area) that resulted mainly from the longer primary roots contributed to the efficient N accumulation. At sufficient N supply, longer lateral roots are the main factor contributed to N accumulation. [ABSTRACT FROM AUTHOR]

Exploring the genetic resource of crops is one alternative way to utilize the less available phosphorus (P) in soils, and copy with the incoming shortage of rock phosphate (Rock P). Genotypic differences in low-P tolerance exist in many crop species and result from various physiological and morphological mechanisms. In this study, low-P tolerance of two maize genotypes that had been identified to have contrasting P efficiency (grain yield) in a calcareous soil was investigated. Parameters measured were biomass accumulation, root growth and root exudation of organic acids, root acid phosphatase (APase) activity, and rhizosphere pH under P-deficient (-P) and P-sufficient (+P) conditions in solution culture. The results showed that -P treatment increased root biomass (from 6th to the 15th day), root to shoot ratio, lateral root length, and APase activity in roots and on the root surface, but reduced root exudation of organic acids and pH in rhizosphere for both genotypes. The P-efficient line 181 had a larger root system in terms of root weight and lateral root length than the P-inefficient line 197 in both P treatments, indicating root morphology of line 181 is an advantageous but non-specific trait in adaptation to low P stress. Genotype 181, when grown with -P markedly reduced the pH of the solution and rizhosphere and increased the APase activity in the roots and on the root surfaces. Surprisingly, root exudation of organic acids was reduced by -P in both genotypes. Exudation rate of organic acids in 181 was lower than that of 197 under both P treatments. It was concluded that efficient use of P in the calcareous soil by 181 is related to its large root system, greater ability to acidify the rhizosphere, and positive response of APase production and excretion to low P conditions. [Copyright &y& Elsevier]

Maize (Zea mays L.) is an important cereal crop with multiple uses in the world. Stay-green hybrids have been developed because of their higher productivity. Few studies have been conducted to evaluate the influence of nitrogen (N) levels on N uptake, remobilization, grain yield and N concentration in stay-green hybrids compared to senescent ones. Field studies were undertaken in P.R. China on an Ustochrepts soil to determine the effects of N levels and hybrids differing in leaf senescence on grain yield and N concentration, N uptake, remobilization, and residual in vegetative tissues in 1996 and 1997. The stay-green hybrid ND108 had greater yields than TK5 (intermediate senescing) and ZD120 (fast senescing) under both high (225 kg N ha-1) and low N (0 in 1997 or 45 kg N ha-1 in 1996, respectively) supply. ND108 took up more N than the two other hybrids. Grain N concentration of ND108 did not decrease by low N significantly, excepting the experiment sown in the summer of 1996, when post-silking N uptake was reduced greatly by the shortened grain filling duration. Nitrogen remobilization efficiency in vegetative tissue was higher in senescent hybrids ZD120 than ND108. Nitrogen retained in the stover at harvest was higher in ND108, which can lead to a deficit of soil N for the next crop if the stover is not returned into soil. It was suggested that, though stay-green hybrids have been developed for high N conditions, they have advantages over senescent hybrids also under N limited conditions. [ABSTRACT FROM AUTHOR]

Two rice genotypes, JX17 (Oryza sativa ssp. japonica) and ZYQ8 (Oryza sativa ssp. indica), which had been the parents of the 127-line double haploid (DH) population for construction of molecular linkage map, were chosen to study their response to low phosphorus (P) stress. The results indicated that JX17 had advantages over ZYQ8 on some traits associated with phosphorus uptake efficiency, such as root dry weight, root-exuded acid phosphatase activity, root-exuded organic acids and proton. Consequently, JX17 had higher relative total dry weight and was regarded as the non-sensitive genotype to low phosphorus stress. Physiological response of the two genotypes to P deficiency was studied in monoculture and in mixed culture. The results showed that, compared with monoculture, JX17 absorbed more P and had higher biomass in mixed culture condition under P stress. ZYQ8, by contrast, suffered from P stress to a much greater extent, with lower P uptake and biomass. JX17 had a higher P uptake rate expressed as P amount per root length which is suggested to be the main reason for its insensitivity to low P stress. [ABSTRACT FROM AUTHOR]

Wheat (Triticum aestivum L.) cultivar LZ953 is one of a type of large-spike and large-grain cultivars with delayed leaf senescence and slow grain filling. Its grain filling is adversely affected by the dry hot winds that generally occur during the late stages of the crop in northern China. This study investigated the possible reasons for the slow grain filling and compared LZ953 with an early ripening cultivar, LM14, cultivated at high and low nitrogen (N) levels. The results showed greater photosynthetic rate, carbon (14C) accumulation, leaf area, and soluble sugar accumulation in stems and sheaths at grain filling in LZ953 than LM14. However, export of soluble sugar from the stem and sheaths, as well as starch accumulation in the grains, were smaller in LZ953. As a result, grain filling was slow during the first 14 days after anthesis (DAA). Nitrogen level had no significant effect on the grain-filling rate of either cultivar. Under high N, LZ953 absorbed more N after anthesis than LM14. In LZ953 soluble sugar storage in the stems and sheaths and starch accumulation were greatly reduced under high N. Nevertheless, the soluble sugar contents of the stem and leaf sheaths of LZ953 were greater than those of LM14. At 15 DAA, the 14CO2 assimilation of LZ953 was significantly greater than that of LM14, while the percentage of assimilated 14C in the grains of LM14 was greater than that of LZ953. The proportion of 14C partitioned to the grains of LZ953 was reduced by increased N application. Our results suggest that carbohydrate utilization, starch synthesis, or both limit the rate of early grain filling in LZ953. This would lead to a negative feedback on the export of soluble sugar from vegetative organs. [ABSTRACT FROM AUTHOR]

Plant phenotypic plasticity plays an important role in nitrogen (N) acquisition and use under nitrogen-limited conditions. However, this role has never been quantified as a function of N availability, leaving it unclear whether plastic responses should be considered as potential targets for selection. A combined modelling and experimentation approach was adopted to quantify the role of plasticity in N uptake and plant yield. Based on a greenhouse experiment we considered plasticity in two maize (Zea mays) traits: root-to-leaf biomass allocation ratio and emergence rate of axial roots. In a simulation experiment we individually enabled or disabled both plastic responses for maize stands grown across six N levels. Both plastic responses contributed to maintaining a higher N uptake, and plant productivity as N availability declined compared with stands in which plastic responses were disabled. We conclude that plastic responses quantified in this study may be a potential target trait in breeding programs for greater N uptake across N levels while it may only be important for the internal use of N under N-limited conditions in maize. Given the complexity of breeding for plastic responses, an a priori model analysis is useful to identify which plastic traits to target for enhanced plant performance. [ABSTRACT FROM AUTHOR]

[Display omitted] • The water-soluble AgInSe 2 @ZnS QDs was prepared by water phase reflux method. • A "turn off-on" fluorescence sensor AC NCs was developed via covalently connecting the AISe QDs and CDs. • A "turn off-on" fluorescence sensor for DA, Lys and Arg detection was exhibited an excellent sensitive and selective. Herein, a novel and unique "off-on" single-excited dual-emissive ratio fluorescence sensor for highly selective and sensitive detection of dopamine and lysine/arginine has been developed via covalently connecting the yellowish-green fluorescent carbon dots (CDs) with the orange-red fluorescent AgInSe 2 @ZnS quantum dots (AISe QDs). This ratiometric fluorescence sensor provided with two-emission peaks at 495 and 575 nm under a single-excitation wavelength of 395 nm. The fluorescence of AISe QDs (F 575) is effective quenched by dopamine and only efficientlyrecovered by lysine/arginine; meanwhile, the light of CDs (F 495) remains unchanged. The fluorescence intensity ratio (F 495 /F 575) showed a linear relationship with the concentration of DA in the range of 0–100 μM, and the detection limit as low as 0.21 nM. lysine and arginine with the detection limit of 0.36 nM and 26 μM, respectively. Furthermore, the fluorescence probe is successfully used to detect DA in human serum. Therefore, the as-synthesized probe shows excellent potential application for the determination of DA in real samples. [ABSTRACT FROM AUTHOR]

Doxorubicin hydrochloride (DOX) is an effective anthracycline anticancer drug. However, the exceeded taken up could induce several side-effects such as cardiotoxicity, alopecia. Therefore, the level of DOX needs to be closely monitored to avoid the occurrence of its side-effects. Herein, we report a novel core CuInSe 2 - shell ZnS quantum dots (CuInSe 2 @ZnS, QDs) and Ag nanoparticles (NPs) fluorescence sensor based on the surface plasmon resonance effect (SPR) of Ag NPs. The CuInSe 2 @ZnS QDs were prepared by water phase reflux method with the 3-mercaptopropionic acid (MPA) as stabilizer and ligand. The fluorescence intensity of CuInSe 2 @ZnS QDs/Ag NPs significantly reduced by DOX, which is mainly based on the electrostatic interaction between the DOX and fluorescence sensors. The inhibition of photoluminescence (ln F 0 /F) was linearly relationship to the concentration of DOX in the range of 2–100 μM with the detection limit as low as 0.05 μM. The as-prepared sensor has a high selectivity and sensitivity to DOX. Furthermore, the new sensor has been successfully applied to the determination of DOX in human serum samples with satisfactory results. Our work provides a clue for developing a novel CuInSe 2 @ZnS QDs/Ag NPs based fluorescence sensor for DOX detection. Unlabelled Image • The water-soluble CuInSe 2 @ZnS QDs was prepared by water phase reflux method. • A fluorescence sensor for DOX detection in human serum sample was developed. • The CuInSe 2 @ZnS QDs/Ag NPs system exhibited an excellent sensitive and selective for DOX. [ABSTRACT FROM AUTHOR]

Plant–microbe interactions are key to nutrient-use efficiency. Root microbes are influenced by rhizosphere soil and plant cultivars. The impact of cultivar-by-nitrogen (N) interactions on the maize-root microbiome remains unclear, yet it is crucial for understanding N use efficiency in maize. This study evaluated the effects of maize cultivars and N forms, along with their interactions, on the diversity and composition of root bacteria and fungi. Additionally, we examined correlations between soil microbes and root metabolites. The maize cultivar Zhengdan 958 (ZD958) showed a positive response to the mixture of nitrate and ammonium N, resulting in increased in biomass, grain yield, shoot N content, grain N content, and root area. In contrast, the cultivar Denghai605 (DH605) did not exhibit a similar response. The diversity and composition of root bacteria and fungi differed between ZD958 and DH605. The N form primarily affected the community structure of rhizospheric fungi in ZD958 and rhizospheric bacteria in DH605, rather than endophytic microbes. A mixed N supply increased the relative abundance of Basidiomycota, which was positively correlated with ZD958 yield. For DH605, a mixed N treatment enhanced nitrification functions involving Bacteroidetes and Proteobacteria, while it reduced the effects of ammonium N supply. The dominant rhizospheric microbes in DH605 showed a stronger response to changes in root metabolites compared to those in ZD958. A mixed N supply increased the content of palmitoleic acid in ZD958 root exudates, facilitating the recruitment of beneficial rhizospheric microbes, which promotes maize growth. In DH605, a mixed N supply decreased the concentration of sphinganine, which is significantly correlated with Acidobacteria (negatively), Proteobacteria (negatively), Bacteroidetes (positively), and TM7 (positively). Our findings suggest that different maize cultivars respond differently to N forms, causing distinct rhizospheric microbial effects, and that root metabolites send metabolic signals to regulate and recruit key bacterial and fungal communities. [ABSTRACT FROM AUTHOR]

Key message: A total of 389 and 344 QTLs were identified by GWAS and QTL mapping explaining accumulatively 32.2–65.0% and 23.7–63.4% of phenotypic variation for 14 shoot-borne root traits using more than 1300 individuals across multiple field trails. Efficient nutrient and water acquisition from soils depends on the root system architecture (RSA). However, the genetic determinants underlying RSA in maize remain largely unexplored. In this study, we conducted a comprehensive genetic analysis for 14 shoot-borne root traits using 513 inbred lines and 800 individuals from four recombinant inbred line (RIL) populations at the mature stage across multiple field trails. Our analysis revealed substantial phenotypic variation for these 14 root traits, with a total of 389 and 344 QTLs identified through genome-wide association analysis (GWAS) and linkage analysis, respectively. These QTLs collectively explained 32.2–65.0% and 23.7–63.4% of the trait variation within each population. Several a priori candidate genes involved in auxin and cytokinin signaling pathways, such as IAA26, ARF2, LBD37 and CKX3, were found to co-localize with these loci. In addition, a total of 69 transcription factors (TFs) from 27 TF families (MYB, NAC, bZIP, bHLH and WRKY) were found for shoot-borne root traits. A total of 19 genes including PIN3, LBD15, IAA32, IAA38 and ARR12 and 19 GWAS signals were overlapped with selective sweeps. Further, significant additive effects were found for root traits, and pyramiding the favorable alleles could enhance maize root development. These findings could contribute to understand the genetic basis of root development and evolution, and provided an important genetic resource for the genetic improvement of root traits in maize. [ABSTRACT FROM AUTHOR]

Aims: Root system architecture (RSA) is important for nutrient and water acquisition efficiency. The adaptation of root growth and RSA to soil structure under conservative strip tillage (ST) system warrants further investigation. Methods: A three-year field experimentation was conducted in Northeast China to investigate the RSA and dynamic root growth of rain-fed maize under ST system by comparison with the conventional tillage (CT). Results: Grain yield in ST and CT was not significantly different, but their yield components differed. Compared to CT, grain number per ear was reduced by 4.4%, while 1000-grain weight was increased by 6.6% in ST. Root growth in ST plants was inhibited in the vegetative stage, as indicated by the reduced total root length (by 27.7–40.1%) compared to CT. During post-silking stage, the total root length was not different between ST and CT plants but the root xylem bleeding rate in ST plants was 70.7%-449.9% greater than that in CT. The uneven horizontal distribution of soil bulk density and soil temperature made the RSA of ST plants steeper compared to CT. Moreover, the D95 of root distribution in ST plant roots was greater. Conclusions: In ST system, colder, more compacted soil in the inter-row soil likely caused the lower root growth and consequently lower shoot dry matter during the vegetative stage. However, root senescence was delayed which was beneficial for water and nitrogen acquisition during grain filling. Strategies to improve early root growth may increase maize productivity in ST systems. [ABSTRACT FROM AUTHOR]

The rhizobial inoculation effects on the peanut rhizosphere bacterial community and metabolites were studied under different N availability following the five N application rates without rhizobial inoculation (N1–N5; 0, 40, 80, 110, 170 kg N ha−1) or with rhizobial inoculation (RN1–RN5) in a 3-year field trial. The effects of rhizobia on peanut growth, the rhizobacterial community, and root metabolites differed depending on the N availability. Plant height and nodule number were significantly increased by rhizobial inoculation, especially in RN3. Rhizobacterial abundance and richness were increased by rhizobial inoculation, except in RN1 (no N added). The number of 16S rRNA gene copies was higher in RN1–RN3 than in N1–N3 in both years. The largest number of differential bacterial genera between an inoculated treatment and its corresponding uninoculated treatment was in RN1 vs. N1. The beneficial bacteria Saccharimonadales and c_JG30-KF-CM66 (Chloroflexi) were most abundant in RN3. The concentrations of organic acids (3-methylglutaric acid, adipic acid, 3-hydroxyoctanoic acid, and octenedioic acid) were significantly increased in RN3 and were positively correlated with c_JG30-KF-CM66 (Chloroflexi), soil available N, and biomass. No metabolic pathways were significantly enriched by rhizobial inoculation at the highest N application rate (RN5). These results demonstrate that rhizobia positively affect peanut growth and yield under the best N availability via their ability to reshape the soil microbiome and metabolites. [ABSTRACT FROM AUTHOR]

A two-year field experiment was conducted to elucidate the adaptive growth mechanism of maize under strip-till (ST) compared with conventional-till (CT). The biomass accumulation of ST plants was significantly lower than CT until V14 (14th leaf), but restored thereafter with one below-ear-node leaf reduced. At silking, the accumulation of nitrogen (N) was reduced by 8.3–10.7% compared to CT. During post-silking, vegetative-N remobilization was reduced by 20.4%, post-silking N uptake increased by 33.9% in ST compared to CT. Leaf senescence was delayed and more green leaf area at physiological maturity in ST. It is concluded that ST plants have the mechanism of 'Recovery Growth Adaptation' to get the similar yield as in CT plants: (1) facilitating growth rate at around V14 when the soil temperature was greatly improved to stabilize ear growth and grain number; (2) getting to silking the same time as in CT plants, so as to ensure the duration of grain filling; (3) increasing post-silking N uptake to fulfill the demand of grain development and reduce leaf N remobilization, so as to maintain leaf function and increase thousand-grain weight, which compensate for the loss of grain number per ear. [ABSTRACT FROM AUTHOR]

Key Message: The genetic architecture of RSA traits was dissected by GWAS and coexpression networks analysis in a maize association population. Root system architecture (RSA) is a crucial determinant of water and nutrient uptake efficiency in crops. However, the maize genetic architecture of RSA is still poorly understood due to the challenges in quantifying root traits and the lack of dense molecular markers. Here, an association mapping panel including 356 inbred lines were crossed with a common tester, Zheng58, and the test crosses were phenotyped for 12 RSA traits in three locations. We observed a 1.3 ~ sixfold phenotypic variation for measured RSA in the association panel. The association panel consisted of four subpopulations, non-stiff stalk (NSS) lines, stiff stalk (SS), tropical/subtropical (TST), and mixed. Zheng58 × TST has a 2.1% higher crown root number (CRN) and 8.6% less brace root number (BRN) than Zheng58 × NSS and Zheng58 × SS, respectively. Using a genome-wide association study (GWAS) with 1.25 million SNPs and correction for population structure, 191 significant SNPs were identified for root traits. Ninety (47%) of the significant SNPs showed positive allelic effects, and 101 (53%) showed negative effects. Each locus could explain 0.39% to 11.8% of phenotypic variation. By integrating GWAS results and comparing coexpression networks, 26 high-priority candidate genes were identified. Gene GRMZM2G377215, which belongs to the COBRA-like gene family, affected root growth and development. Gene GRMZM2G468657 encodes the aspartic proteinase nepenthesin-1, related to root development and N-deficient response. Collectively, our research provides progress in the genetic dissection of root system architecture. These findings present the further possibility for the genetic improvement of root traits in maize. [ABSTRACT FROM AUTHOR]

Effective in-season crop nitrogen (N) status diagnosis is important for precision crop N management, and remote sensing using an unmanned aerial vehicle (UAV) is one efficient means of conducting crop N nutrient diagnosis. Here, field experiments were conducted with six N levels and six maize hybrids to determine the nitrogen nutrition index (NNI) and yield, and to diagnose the N status of the hybrids combined with multi-spectral data. The NNI threshold values varied with hybrids and years, ranging from 0.99 to 1.17 in 2018 and 0.60 to 0.71 in 2019. A proper agronomic optimal N rate (AONR) was constructed and confirmed based on the measured NNI and yield. The NNI (R2 = 0.64–0.79) and grain yield (R2 = 0.70–0.73) were predicted well across hybrids using a random forest model with spectral, structural, and textural data (UAV). The AONRs calculated using the predicted NNI and yield were significantly correlated with the measured NNI (R2 = 0.70 and 0.71 in 2018 and 2019, respectively) and yield (R2 = 0.68 and 0.54 in 2018 and 2019, respectively). It is concluded that data fusion can improve in-season N status diagnosis for different maize hybrids compared to using only spectral data. [ABSTRACT FROM AUTHOR]

Key message: A new strategy that integrated multiple public data resources was established to construct root gene co-expression network and mine genes regulating root system architecture in maize. A root gene co-expression network, containing 13,874 genes, was constructed. A total of 53 root hub genes and 16 priority root candidate genes were identified. One priority root candidate was further functionally verified using overexpression transgenic maize lines. Root system architecture (RSA) is crucial for crops productivity and stress tolerance. In maize, few RSA genes are functionally cloned, and effective discovery of RSA genes remains a great of challenge. In this work, we established a strategy to mine maize RSA genes by integrating functionally characterized root genes, root transcriptome, weighted gene co-expression network analysis (WGCNA) and genome-wide association analysis (GWAS) of RSA traits based on public data resources. A total of 589 maize root genes were collected by searching well-characterized root genes in maize or homologous genes of other species. We performed WGCNA to construct a maize root gene co-expression network containing 13874 genes based on public available root transcriptome data, and further discovered the 53 hub genes related to root traits. In addition, by the prediction function of obtained root gene co-expression network, a total of 1082 new root candidate genes were explored. By further overlapping the obtained new root candidate gene with the root-related GWAS of RSA candidate genes, 16 priority root candidate genes were identified. Finally, a priority root candidate gene, Zm00001d023379 (encodes pyruvate kinase 2), was validated to modulate root open angle and shoot-borne roots number using its overexpression transgenic lines. Our results develop an integration analysis method for effectively exploring regulatory genes of RSA in maize and open a new avenue to mine the candidate genes underlying complex traits. [ABSTRACT FROM AUTHOR]

Plant genotypes shape root‐associated microbiota that affect plant nutrient acquisition and productivity. It is unclear how maize hybrids modify root‐associated microbiota and their functions and relationship with nitrogen use efficiency (NUE) by regulating rhizosphere soil metabolites. Here, two N‐efficient (NE) (ZD958, DMY3) and two N‐inefficient (NIE) maize hybrids (YD9953, LY99) were used to investigate this issue under low N (60 kg N ha−1, LN) and high N (180 kg N ha−1, HN) field conditions. NE hybrids had higher yield than NIE hybrids under LN but not HN. NE and NIE hybrids recruited only distinct root‐associated bacterial microbiota in LN. The bacterial network stability was stronger in NE than NIE hybrids. Compared with NIE hybrids, NE hybrids recruited more bacterial taxa that have been described as plant growth‐promoting rhizobacteria (PGPR), and less related to denitrification and N competition; this resulted in low N2O emission and high rhizosphere NO3−‐N accumulation. NE and NIE hybrids had distinct rhizosphere soil metabolite patterns, and their specific metabolites were closely related to microbiota and specific genera under LN. Our findings reveal the relationships among plant NUE, rhizosphere soil metabolites, root‐associated microbiota, and soil nutrient cycling, and this information is informative for breeding NE crops. [ABSTRACT FROM AUTHOR]

Background: Auxin plays a crucial role in nitrate (NO3–)-mediated root architecture, and it is still unclear that if NO3– supply modulates auxin reallocation for regulating root formation in maize (Zea mays L.). This study was conducted to investigate the role of auxin efflux carrier ZmPIN1a in the root formation in response to NO3– supply. Results: Low NO3– (LN) promoted primary root (PR) elongation, while repressed the development of lateral root primordia (LRP) and total root length. LN modulated auxin levels and polar transport and regulated the expression of auxin-responsive and -signaling genes in roots. Moreover, LN up-regulated the expression level of ZmPIN1a, and overexpression of ZmPIN1a enhanced IAA efflux and accumulation in PR tip, while repressed IAA accumulation in LRP initiation zone, which consequently induced LN-mediated PR elongation and LR inhibition. The inhibition rate of PR length, LRP density and number of ZmPIN1a-OE plants was higher than that of wild-type plants after auxin transport inhibitor NPA treatment under NN and LN conditions, and the degree of inhibition of root growth in ZmPIN1a-OE plants was more obvious under LN condition. Conclusion: These findings suggest that ZmPIN1a was involved in modulating auxin levels and transport to alter NO3–-mediated root formation in maize. [ABSTRACT FROM AUTHOR]

Land application of livestock manure may reduce the use of mineral fertilizers and alleviate the environmental degradation associated with mineral fertilizers application. However, how to optimize utilization of livestock manure value is not well understood and documentation regarding the nitrogen (N) and phosphorus (P) fertilizer replacement values (NFRV and PFRV, respectively) needs further scrutiny. Therefore, three representative livestock manures, i.e., pig, chicken, and cattle manure, were applied at different usages to assess their N and P availability in comparison to reference mineral fertilizers over summer maize growing seasons. The results show that the average NFRVs of pig, chicken, and cattle manures were 41.7–58.4%, 27.5–44.4%, and −3.6–36.1%, respectively, when based on different references (grain yield, total dry matter yield, grain N uptake, total N uptake), at different N application levels. The NFRV increased with the elevated N application rate for cattle manure treatment. In the P trials, livestock manure had a higher PFRV at a low P application level, and the average PFRVs of pig, chicken, and cattle manures were 80.3–164.8%, 77.9–143.7%, and 94.1–168.0%, respectively, at different P application levels. We conclude that livestock manure produced the lowest NFRV and highest PFRV at a low fertilizer application rate; pig manure had the highest N availability; and cattle manure had the highest P availability. [ABSTRACT FROM AUTHOR]

Increasing maize planting density is a major agronomic practice to enhance population grain yield, however, canopy shadowing at high density limits plant growth and per-plant grain yield. Dry mass (DM) accumulation, allocation, and remobilization are crucial factors determining grain yield. However, there is limited understanding regarding these processes in response to increasing planting density. This study aimed to evaluate how planting density affects DM accumulation, allocation, and remobilization, as affected by plant architecture, nitrogen (N) rates, N fertilization frequency, and water management. A meta-analysis was conducted, involving 2363 observations from 253 peer-reviewed studies. Globally, population grain yield increased by 11.2 %, which was attributable to increases in a population pre-silking DM (PrS-DM) accumulation of 22.9 % and remobilization efficiency of 12.6 %. Temporally, under a high planting density, per plant DM production showed a decrease (8.3–16.0 %) during the pre-silking stage, but a greater reduction (24.0–25.4 %) during the post-silking stage. DM allocation to roots was greatly reduced, with a decline of 22.1–25.1 % in the root-to-shoot ratio (R/S), and a dropping rate of 5.2 % in harvest index (HI). Compact plant architecture showed a 12.2 % increase in grain yield and a reduction of 3.4 % in HI. Appropriate N rates coupled with splitting-N applications showed an increase in grain yield (up to 13.9 %) and PrS-DM (up to 27.1 %), but a decline in post-silking DM (PoS-DM) (up to 9.7 %) and HI (up to 9.0 %). Efficient water management, i.e., fertigation increased the grain yield (up to 16.9 %). Increasing planting density increases grain yield mainly by efficiently utilizing light resources during the vegetative stage to increase population PrS-DM production and its remobilization to grain. In addition, less biomass is allocated to the root so that more assimilation is used for shoot growth. Field management practices and breeding efforts should focus on facilitating early plant growth to increase population PrS-DM accumulation and developing sound root systems to increase efficiency and canopy-lodging resistance. Scheme of impacts of increasing planting density on dynamic shoot and root growth per plant (a, b) and per hectare (c, d) in maize during the whole growth period. Numbers in black indicate the ratio of indicators under high planting density (HD) to that of the farmers' practice (FP, control) respectively. Numbers in red and blue colors indicate the ratio of the dry mass under high planting density to that of the control in shoot and root respectively. Numbers with and without underlines indicate the ratio of indicators under high planting density to that of the control in per-hectare and per-plant level respectively. All the data are pooled for the analysis. HI means harvest index; R/S-R1, R/S-R3, and R/S-R6 indicate root-to-shoot ratio at silking, milk, and maturity stage, respectively. DMRE means remobilization efficiency of dry mass within vegetative tissues. DMRC means the contribution of dry mass remobilization to grain yield. [Display omitted] • Globally, an average 57.8 % increase in planting density led to an 11.2 % increase in grain yield. • The increase in yield was supported by greater pre-silking biomass production and remobilization. • Individual biomass was less affected by high density before silking than that during post-silking. • High density displayed less biomass allocation to root and kernel. • This study brings insights into high-density planting by optimizing breeding and field management. [ABSTRACT FROM AUTHOR]

Root and rhizosphere research has been conducted for many decades, but the underlying strategy of root/rhizosphere processes and management in intensive cropping systems remain largely to be determined. Improved grain production to meet the food demand of an increasing population has been highly dependent on chemical fertilizer input based on the traditionally assumed notion of ‘high input, high output’, which results in overuse of fertilizers but ignores the biological potential of roots or rhizosphere for efficient mobilization and acquisition of soil nutrients. Root exploration in soil nutrient resources and root-induced rhizosphere processes plays an important role in controlling nutrient transformation, efficient nutrient acquisition and use, and thus crop productivity. The efficiency of root/rhizosphere in terms of improved nutrient mobilization, acquisition, and use can be fully exploited by: (1) manipulating root growth (i.e. root development and size, root system architecture, and distribution); (2) regulating rhizosphere processes (i.e. rhizosphere acidification, organic anion and acid phosphatase exudation, localized application of nutrients, rhizosphere interactions, and use of efficient crop genotypes); and (3) optimizing root zone management to synchronize root growth and soil nutrient supply with demand of nutrients in cropping systems. Experiments have shown that root/rhizosphere management is an effective approach to increase both nutrient use efficiency and crop productivity for sustainable crop production. The objectives of this paper are to summarize the principles of root/rhizosphere management and provide an overview of some successful case studies on how to exploit the biological potential of root system and rhizosphere processes to improve crop productivity and nutrient use efficiency. [ABSTRACT FROM AUTHOR]

Root system architecture (RSA) is seldom considered as a selection criterion to improve yield in maize breeding, mainly because of the practical difficulties with their evaluation under field conditions. In the present study, phenotypic profiling of 187 advanced-backcross BCF maize lines (Ye478 × Wu312) was conducted at different developmental stages under field conditions at two locations (Dongbeiwang in 2007 and Shangzhuang in 2008) for five quantitative root traits. The aims were to (1) understand the genetic basis of root growth in the field; (2) investigate the contribution of root traits to grain yield (GY); and (3) detect QTLs controlling root traits at the seedling (I), silking (II) and maturation (III) stages. Axial root (AR)-related traits showed higher heritability than lateral root (LR)-related traits, which indicated stronger environmental effects on LR growth. Among the three developmental stages, root establishment at stage I showed the closest relationship with GY ( r = 0.33-0.43, P < 0.001). Thirty QTLs for RSA were detected in the BCF population and only 13.3 % of the QTLs were detected at stage III. Most important QTLs for root traits were located on chromosome 6 near the locus umc1257 (bin 6.02-6.04) at stage I, and chromosome 10 near the locus umc2003 (bin 10.04) for number of AR across all three developmental stages. The regions of chromosome 7 near the locus bnlg339 (bin 7.03) and chromosome 1 near the locus bnlg1556 (bin 1.07) harbored QTLs for both GY- and LR-related traits at stages I and II, respectively. These results help to understand the genetic basis of root development under field conditions and their contribution to grain yield. [ABSTRACT FROM AUTHOR]

Maize (Zea mays L.) has undergone profound changes in root anatomy for environmental adaptation during domestication. However, the genetic mechanism of plasticity of maize root anatomy during the domestication process remains unclear. In this study, high-resolution mapping was performed for nine root anatomical traits using a maize-teosinte population (mexicana × Mo17) across three environments. Large genetic variations were detected for different root anatomical traits. The cortex, stele, aerenchyma areas, xylem vessel number, and cortical cell number had large variations across three environments, indicating high plasticity. Sixteen quantitative trait loci (QTL) were identified, including seven QTL with QTL × environment interaction (EIQTL) for high plasticity traits and nine QTL without QTL × environment interaction (SQTL). Most of the root loci were consistent with shoot QTL depicting domestication signals. Combining transcriptome and genome-wide association studies revealed that AUXIN EFFLUX CARRIER PIN–FORMED LIKE 4 (ZmPILS4) serves as a candidate gene underlying a major QTL of xylem traits. The near-isogenic lines (NILs) with lower expression of ZmPILS4 had 18–24% more auxin concentration in the root tips and 8–15% more xylem vessels. Nucleotide diversity values analysis in the promoter region suggested that ZmPILS4 was involved in maize domestication and adaptation. These results revealed the potential genetic basis of root anatomical plasticity during domestication. [ABSTRACT FROM AUTHOR]

Phosphorus (P)-deficiency in rice (Oryza sativa L.) may cause yields reductions. This research was conducted to map quantitative trait loci (QTL) for tolerance to low-P stress in a double-haploid (DH) line, and to verify these loci in another SSD9 population, which is the ninth generation of single-seed-distribution population derived from the same parents. Two populations were cultured solution at different period. By using the linkage map, QTLs for traits associated with tolerance to low-P stress were located. Results indicated that for DH population, one restricted fragment length polymorphism (RFLP) marker located on chromosome 6 was closely associated with relative root dry weight, relative shoot dry weight, and relative total dry weight. Two QTLs affected relative P uptake content. One micro-effect QTL was found to be associated with relative P utilization efficiency. For relative amounts of root exuded acid phosphatase, relative P allocation between shoot and root, relative plant P concentration, and relative shoot P concentration, one micro-effect QTL was detected for each one. Quantitative trait loci for 3 traits were detected for both DH and SSD9 populations, but the loci for each located trait were inconsistent between two populations; the reason for inconsistency in QTLs was analyzed. The main reason could be the difference in solution environment. [ABSTRACT FROM AUTHOR]

Molybdenum (Mo) deficiency caused killing of winter wheat seedlings during winter season in southern China has become a problem limiting wheat yield. The effects of low temperature (-5°C–0°C) on Mo deficiency of winter wheat seedlings (Triticum aestivum L. var. “Lumai22”) were investigated in a pot experiment with an acid soil. After induction by low temperature, symptoms of Mo deficiency appeared quickly in whole plants of no Mo (-Mo) treatment, especially in lower leaves. Molybdenum deficiency increased the rate of K+ leakage at 9 h and 24 h after cold treatment in lower and upper leaves respectively. Nitrate reductase activity decreased with - Mo treatment under low temperature conditions, free amino acid content decreased corresponding to it. Total soluble sugar and sucrose contents in functional and primary leaves were raised in - Mo treatment as a whole. After low temperature treatment, total soluble sugar and sucrose content in functional leaves of Mo deficient plants dropped, while those in primary leaves increased, indicating sugar transported from old leaves to primary leaves where sugar is not enough. Mo deficiency had less influence on superoxide dismutase, and catalase activity, however peroxidase activity raised by - Mo treatment under low temperature. It is concluded that Mo deficiency has a close relationship with low temperature induction. [ABSTRACT FROM AUTHOR]

The effects of 13 plant growth–promoting rhizobacteria (PGPR) from the maize rhizosphere and a model PGPR strain Azospirillum brasilense Az39 on maize growth were monitored in a 3-year field inoculation experiment (from 2018 to 2020) with low-nitrogen (N) (N input reduced by 50%) and low-phosphorus (P) (no P supply) soils in Northeast China. The effects of four efficient PGPR that stably promoted maize plant growth and affected on the composition and function of the rhizobacterial community were further investigated in 2019 and 2020. On average, Sinorhizobium sp. A15, Bacillus sp. A28, Sphingomonas sp. A55, and Enterobacter sp. P24 stably increased grain yield by 8.1–17.8% and 11.0–20.1% in low-N and low-P soil, respectively. Inoculation of these four strains increased the abundance and species richness of rhizobacteria, enriched special beneficial bacteria such as Chloroflexia_KD4-96 and Bacilli, and decreased bacterial functions related to soil-N loss. We conclude that some PGPR can N- and P-use efficiency and maize yield through reshaping the rhizobacterial community. [ABSTRACT FROM AUTHOR]

In this work, bovine serum albumin stabilized copper nanoclusters (BSA-CuNCs) with highly red fluorescent were fast prepared by increasing the temperature in aqueous medium and used as a fluorescent probe for the sensitive detection of H 2 O 2 in water and rat serum. Unexpectedly, the prepared BSA-CuNCs showed dual emission peaks at 450 and 620 nm, respectively, and had excellent stability such as outstanding photobleaching resistance and salt tolerance. Under optimized conditions, H 2 O 2 can reduce the fluorescence signal at 620 nm (F 620) and enhance the fluorescence signal at 450 nm (F 450), meanwhile, the color of the probe changed from red to blue, resulting in ratiometric and visualization detection of H 2 O 2 with high accuracy. F 450 /F 620 was linearly proportional to H 2 O 2 concentration in the ranges from 0 to 100 μM, with limit of detection 0.082 μM. In the rat serum spiked experiment, it showed a reasonable recovery rate. More importantly, cytotoxicity tests showed that BSA-CuNCs had little cytotoxicity. Therefore, the prepared BSA-CuNCs fluorescent probe has potential practical application prospects. [Display omitted] • A method for the rapid preparation of biocompatible BSA-CuNCs was proposed. • BSA-CuNCs with double emission optical behavior were successfully synthesized. • A ratio fluorescent probe for the detection of H 2 O 2 was proposed. • The two emission peaks of BSA-CuNCs showed opposite responses to H 2 O 2. [ABSTRACT FROM AUTHOR]

Obtaining high grain yield and nitrogen use efficiency (NUE) is imperative in maize (Zea mays L.) production. Optimization of planting density is recognized as a key strategy to promote grain yield. However, its impacts on NUE have not been well investigated. This study aimed to elucidate the impact of plant density on NUE and its physiological components. A meta-analysis was conducted, including 237 peer-reviewed studies and 2226 observations. Globally, increased planting density boosts grain yield and affects NUE-related indicators. NUE shifts are attributed to increased fertilizer-N recovery efficiency (RE fer N, by ,14.5 %), enhanced N remobilization efficiency (NR em E, by 8.4 %), and promoted physiological N utilization efficiency (NU t E, by 2.3 %). High planting density reduces root to shoot ratio (R/S), root biomass (RB), root length (RL), and nodal root number (NR), showing decreases ranging from 5.1 % to 43.2 %. A 13.3 % increase in specific root length (SRL) is found. High planting density prompts changes in N allocation. At silking stage, there is a 20.6 % reduction in stalk N accumulation and a 16.0 % decline in leaf N accumulation per plant. At per hectare level, increased planting density results in a 12.8 % increase in pre-silking N accumulation (PrS-N) but a 7.1 % decrease in post-silking N accumulation (PoS-N). Optimizing N rate with a split-N application increases grain yield, RE fer N, NR em E, NU t E, NHI, and grain N concentration, with gains ranging from 6.5 % to 29.2 %. Implementing fertigation enhances grain yield and RE fer N by 13.1 % and 27.8 %. Adopting new cultivars increases NU t E by 2.7 %. In a high-yielding system with increasing planting density, efficient root N uptake, despite constraints on root size, contributes to greater population PrS-N accumulation and fertilizer-N recovery efficiency. Increased population PrS-N accumulation and its remobilization into grains contribute to elevated NU t E, and finally NUE. The findings highlight the importance of developing a robust root system for enhanced N uptake and coordinated N partitioning to improve NUE. The results provide valuable insights for advancing field management practices and breeding efforts. [Display omitted] • Globally, increased planting density boosts maize yield and greatly affects NUE-related indicators. • High planting density promotes pre-silking population N accumulation and their remobilization into the grains. • NUE improvement under high planting density is explained by efficient root N uptake, although root size is greatly restricted. • Coordinated genotypic improvement, optimizing N and water management to enhance maize yield and NUE with dense planting. [ABSTRACT FROM AUTHOR]

To test the hypothesis that stay-green genotypes help to increase stalk lodging resistance under high planting density by reducing dry matter remobilization from stalk, a two-year field study with three planting densities (60,000, 75,000, and 90,000 plants per ha) and six hybrids was conducted. When planting density changed from 75,000 to 90,000, stalk dry matter remobilization efficiency increased by 4.1–191%. Stem dry weight per length, rind penetration strength, average crushing strength for the first to fifth internode, and average bending strength for the third to fifth internode decreased by 25.4–47.2%, 5.1–24.6%, 1.4–29.9%, and 14.0–36.0%, respectively. Stalk lodging rate increased by 17–275%. Stalk dry matter remobilization efficiency was negatively correlated to either stem dry weight per length (r = 0.23, p < 0.05), rind penetration strength (r = 0.75, p < 0.01), crushing strength (r = 0.61, p < 0.01), or bending strength (r = 0.32, p < 0.01). Cultivars with higher stay-green degree (SR999, LY99, and NH101) had lower stalk lodging rate compared to the senescent cultivars XY335 and LY918. It is concluded that stay-green genotypes with low dry matter remobilization help to strengthen stem and reduce stalk lodging risk. [ABSTRACT FROM AUTHOR]

To test the hypothesis that plants could remobilize more nutrients from vegetative organs to fulfill the requirement of grain formation under high planting density, eight maize cultivars with different leaf senescence characters were chosen to study the relationship between stay-green character, nutrient (N, P, K) accumulation, post-silking nutrient remobilization and grain yield under three planting densities (60,000, 75,000, and 90,000 plants per ha) in 2 years. We found that increased plant density aggravated leaf senescence, reduced concentration of N, P and K in all organs, reduced post-silking N, P, K accumulation per ha, increased nutrient remobilized efficiency. Stay-green degree was positively correlated to yield reduction at high planting density (R2 = 0.35, P < 0.01), and negatively correlated to grain yield across planting densities and experimental years. Grain yield reduction at high planting density was negatively correlated to N (R2 = 0.29, P < 0.01), P (R2 = 0.51, P < 0.01), K (R2 = 0.17, P < 0.05) remobilization efficiency. Thus, we conclude that efficient nutrient remobilization is important for achieving higher yield at high planting density. Stay-green too much may not be a favorable trait for high-yield breeding at high planting density. [ABSTRACT FROM AUTHOR]

Summary: Conservation tillage in conjunction with straw mulching is a sustainable agricultural approach. However, straw mulching reduces the soil temperature, inhibits early maize growth and reduces grain yield in cold regions. To address this problem, we investigated the effects of inoculation of plant growth‐promoting rhizobacteria (PGPR) on maize growth and rhizosphere microbial communities under conservation tillage in Northeast China. The PGPR strains Sinorhizobium sp. A15, Bacillus sp. A28, Sphingomonas sp. A55 and Enterobacter sp. P24 were isolated from the maize rhizosphere in the same area and inoculated separately. Inoculation of these strains significantly enhanced maize growth, and the strains A15, A28 and A55 significantly increased grain yield by as much as 22%–29%. Real‐time quantitative PCR and high‐throughput sequencing showed that separate inoculation with the four strains increased the abundance and species richness of bacteria in the maize rhizosphere. Notably, the relative abundance of Acidobacteria_Subgroup_6, Chloroflexi_KD4‐96, and Verrucomicrobiae at the class level and Mucilaginibacter at the genus level were positively correlated with maize biomass and yield. Inoculation with PGPR shows potential for improvement of maize production under conservation tillage in cold regions by regulating the rhizosphere bacterial community structure and by direct stimulation of plant growth. [ABSTRACT FROM AUTHOR]

In plants, nitrogen remobilization from source to sink organs is an important process regulated by complex transcriptional regulatory networks. However, the relationship between nitrogen remobilization and leaf senescence and the molecular regulatory network that controls them are unknown in maize. Here, using 15N labeling and a transcriptome approach, a dynamic analysis of the nitrogen remobilization process was conducted in two elite maize inbred lines (PH4CV and PH6WC) with contrasting leaf senescence. PH4CV showed higher nitrogen remobilization efficiency (NRE) than PH6WC, mainly in the middle and lower leaves from 15 d to 35 d after silking. The co-expression network analysis revealed that ethylene and cytokinin metabolism-related genes triggered the onset of nitrogen remobilization, while abscisic acid and jasmonic acid biosynthesis-related genes controlled the progression of nitrogen remobilization. By integrating genetic analysis, functional annotation, and gene expression, two candidate genes underlying a major quantitative trait locus of NRE were identified, namely an early senescence acting gene (ZmASR6) and an ATP-dependent Clp protease gene (GRMZM2G172230). Hormone-coupled transcription factors and downstream target genes reveal a gene regulatory network for the nitrogen remobilization process after silking in maize. These results uncovered a sophisticated regulatory mechanism for nitrogen remobilization, and further provided characterization of valuable genes for genetic improvement of nitrogen use efficiency in maize. [ABSTRACT FROM AUTHOR]

Plants can develop root systems with distinct anatomical features and morphological plasticity to forage nutrients distributed heterogeneously in soils. Lateral root proliferation is a typical nutrient-foraging response to a local supply of nitrate, which has been investigated across many plant species. However, the underlying mechanism in maize roots remains largely unknown. Here, we report on identification of a maize truncated MIKC-type MADS-box transcription factor (ZmTMM1) lacking K- and C-domains, expressed preferentially in the lateral root branching zone and induced by the localized supply of nitrate. ZmTMM1 belongs to the AGL17-like MADS-box transcription factor family that contains orthologs of ANR1, a key regulator for root nitrate foraging in Arabidopsis. Ectopic overexpression of ZmTMM1 recovers the defective growth of lateral roots in the Arabidopsis anr1 agl21 double mutant. The local activation of glucocorticoid receptor fusion proteins for ZmTMM1 and an artificially truncated form of AtANR1 without the K- and C-domains stimulates the lateral root growth of the Arabidopsis anr1 agl21 mutant, providing evidence that ZmTMM1 encodes a functional MADS-box that modulates lateral root development. However, no phenotype was observed in ZmTMM1-RNAi transgenic maize lines, suggesting a possible genetic redundancy of ZmTMM1 with other AGL17-like genes in maize. A comparative genome analysis further suggests that a nitrate-inducible transcriptional regulation is probably conserved in both truncated and non-truncated forms of ZmTMM1-like MADS-box transcription factors found in grass species. [ABSTRACT FROM AUTHOR]

Aims: To investigate genotypic differences in the plasticity of root system architecture in response to increasing planting density and understand how this plastic response affects grain yield. Methods: A two-year field study was conducted with eight maize hybrids and three planting densities (60,000, 75,000, and 90,000 plants per ha). High-throughput imaging system and an automatic analysis method with Root Estimator for Shovelomics Traits (REST) software were adopted to study root architecture. The coefficient of variation (CV) was determined to reflect the plastic response of the root traits at different planting densities. Results: Root size and root architecture varied with increasing plant density and among the genotypes. With increasing planting density, root biomass and root length per plant decreased. The average root opening angle in inter-row and intra-row directions (RA), average root maximal width in inter-row direction and intra-row directions (RMW), ratio of root opening angle between intra-row and inter-row directions (RatioRA), and ratio of root maximal width between intra-row and inter-row directions (RatioRMW) were also reduced. These results suggest that plants growing under high planting density have narrower root extension width, steeper root angle, and greater root distribution in inter-row direction. The CV of all the root traits between the neighboring plants increased with increasing plant density. Although significant genotype × planting density interactions occurred with most of the root traits, there was a quadratic correlation between grain yield and most of the root traits, especially at high planting density (R2 = 0.17 ~ 0.48). There was a negative linear relationship between grain yield and the CV of root biomass, root length, RA, RMW, RatioRA, and RatioRMW (R2 = 0.21 ~ 0.37). Among the eight hybrids, JQ202 had medium root size, more inter-row root distribution, and the smallest CV in root traits across three planting densities, and the highest grain yield. LY99, SR999 and DY39 had largest CV for root traits and the smallest grain yield. Conclusions: Genotypes with less variation in root size, medium root size, medium broad root system and more inter-row root distribution help to reduce root-to-root competition and tend to have higher yield at high planting density. [ABSTRACT FROM AUTHOR]

The use of mixed nitrate and ammonium as a nitrogen source can improve plant growth. Here, we used metabolomics and transcriptomics to study the underlying mechanisms. Maize plants were grown hydroponically in the presence of three forms of nitrogen (nitrate alone, 75%/25% nitrate/ammonium, and ammonium alone). Plants grown with mixed nitrogen had a higher photosynthetic rate than those supplied only with nitrate, and had the highest leaf area and shoot and root biomass among the three nitrogen treatments. In shoot and root, the concentration of nitrogenous compounds (ammonium, glutamine, and asparagine) and carbohydrates (sucrose, glucose, and fructose) in plants with a mixed nitrogen supply was higher than that with nitrate supply, but lower than that with ammonium supply. The activity of the related enzymes (glutamate synthase, asparagine synthase, phosphoenolpyruvate carboxylase, invertase, and ADP-glucose pyrophosphorylase) changed accordingly. Specifically, the mixed nitrogen source enhanced auxin synthesis via the shikimic acid pathway, as indicated by the higher levels of phosphoenolpyruvate and tryptophan compared with the other two treatments. The expression of corresponding genes involving auxin synthesis and response was up-regulated. Supply of only ammonium resulted in high levels of glutamine and asparagine, starch, and trehalose hexaphosphate. We conclude that, in addition to increased photosynthesis, mixed nitrogen supply enhances leaf growth via increasing auxin synthesis to build a large sink for carbon and nitrogen utilization, which, in turn, facilitates further carbon assimilation and nitrogen uptake. [ABSTRACT FROM AUTHOR]

The use of mixed nitrate and ammonium as a nitrogen source can improve plant growth. Here, we used metabolomics and transcriptomics to study the underlying mechanisms. Maize plants were grown hydroponically in the presence of three forms of nitrogen (nitrate alone, 75%/25% nitrate/ammonium, and ammonium alone). Plants grown with mixed nitrogen had a higher photosynthetic rate than those supplied only with nitrate, and had the highest leaf area and shoot and root biomass among the three nitrogen treatments. In shoot and root, the concentration of nitrogenous compounds (ammonium, glutamine, and asparagine) and carbohydrates (sucrose, glucose, and fructose) in plants with a mixed nitrogen supply was higher than that with nitrate supply, but lower than that with ammonium supply. The activity of the related enzymes (glutamate synthase, asparagine synthase, phosphoenolpyruvate carboxylase, invertase, and ADP-glucose pyrophosphorylase) changed accordingly. Specifically, the mixed nitrogen source enhanced auxin synthesis via the shikimic acid pathway, as indicated by the higher levels of phosphoenolpyruvate and tryptophan compared with the other two treatments. The expression of corresponding genes involving auxin synthesis and response was up-regulated. Supply of only ammonium resulted in high levels of glutamine and asparagine, starch, and trehalose hexaphosphate. We conclude that, in addition to increased photosynthesis, mixed nitrogen supply enhances leaf growth via increasing auxin synthesis to build a large sink for carbon and nitrogen utilization, which, in turn, facilitates further carbon assimilation and nitrogen uptake. [ABSTRACT FROM AUTHOR]

Highlights • Drip fertigation improved soil water status and post-silking NPK uptake. • Drip fertigation increased maize yield, water and nutrient use efficiency. • No significant difference in yield and PFP between SDF, SSDF and SDFP. • SDF and SSDF are recommended in maize production in sandy soil. Abstract Maize growth in Northeast China is suffering from climate change (seasonal drought, cold springs) and low nutrient use efficiency caused by one-time fertilization. Drip fertigation is widely used in vegetable and fruit plant production, yet an efficient, practicable and cost-effective drip fertigation system is lacking for maize production. A two-year field experiment was conducted to evaluate the potential of different drip fertigation methods for increasing maize yield, and water and nutrient use efficiency in sandy and clay soil. Five irrigation methods were applied in each soil: conventional (rain-fed, CK), drip irrigation (DI), surface drip fertigation (SDF), fertigation plus plastic film mulching (SDFP), and subsurface fertigation (SSDF). Compared with rain-fed method (CK), water optimization by DI increased grain yield by (28% in sandy soil and 12% in clay soil), partial fertilizer productivity (PFP) and nitrogen (N), phosphorus (P) and potassium (K) uptake, without effect on water productivity (WP) in both soils. The optimization of both water and nutrient management by SDF increased grain yield by (41% in sandy soil and 17% in clay soil), PFP and NPK uptake, at greater extent than DI. Furthermore, SDF also increased the water productivity in both soils. Compared with DI, SDF increased post-silking N in both soil, and K accumulation in sandy soil. There was no significant difference in yield and PFP between SDF, SSDF and SDFP methods in both soils. In sandy soil, the net profit of DI, SDF, SSDF and SDFP was 13%, 28%, 31% and 10% higher than that of CK, respectively. In clay soil, However, No obvious advantage in net income was found in either DI or fertigation treatments. SDF and SSDF are recommended to increase maize yield, water and nutrient use efficiency, as well as economic benefit synchronously in sandy soil. [ABSTRACT FROM AUTHOR]

Highlights • Water-N interaction significantly affect maize seedling growth and root development. • Drought and N deficiency stress limit root growth but generate deeper distribution. • low basal N optimizes early root growth, morphology and distribution in soil layers. • low basal N improves plant resistance, water and N use efficiencies under drought. • High basal N stimulates growth, water and N capture but aggravates drought effect. Abstract Frequent spring droughts and nitrogen (N) fertilizer overuse limit rain-fed maize production in Northeast China. However, the interactions between water-stress and N rates on maize seedling growth and root development remain elusive. In this study, a pot experiment was conducted with maize grown under three N rates (N omission, low and high N rates, i.e., N0, LN and HN) and severe water-stress (SS), moderate water-stress (MS) and well-watered (WW) conditions for 2-week from 4-leaf stage. Dry biomass (DM), leaf rolling performance, water use efficiency (WUE), N fertilizer use efficiency (NUE), root morphology and distribution were evaluated. It was showed that soil water levels and N rates had significant individual and interactive effects on most measured parameters. The dual stress of drought and N deficiency severely limited maize growth and N uptake. Nitrogen fertilization improved maize growth, N uptake and WUE under water-stress. However, compared with HN treatment, LN treatment had less water consumption, higher leaf relative water content and less leaf rolling symptom both under the MS and SS conditions. The reason is that LN enhanced root growth and elongation with more fine roots, especially in deep soil. Notably, maize plants in MS-LN treatment had an optimal root distribution characterized by higher root length density (0.30 cm cm−3), larger and deeper penetration scale throughout the soil layers, and thus showed fewer drought responses and obtained the highest WUE (4.1 g L−1) and NUE (17.2%) among all the water-stress treatments. In contrast, HN limited root growth and extension in deep soil and in turn increased water and N depletion, resulting in more serve leaf rolling and lower WUE and NUE. Therefore, reducing basal N rate is recommended to optimize root growth, morphology and distribution at the seedling stage in rain-fed maize production, to enhance drought resistance and improve WUE and NUE. [ABSTRACT FROM AUTHOR]

Strip-till (ST) is a conservation tillage wherein the "inter-row" is not tilled and remains covered with protective residues, while the "row zone" is strip tilled. In comparison to conventional ridge tillage (CT), maize yield under ST is maintained due to its growth recovery at grain filling stage (GFS), though its growth lag at early growth stage in cold regions. To explore microbial mechanisms underlying the growth recovery, compared with CT, we investigated relationships among rhizosphere ammonia-oxidizing archaea and bacteria (AOA and AOB), rhizosphere soil characteristics, and maize growth under ST through a two-year field experiment in a Mollisol of Northeast China. Compared with CT, ST led to rhizosphere NO 3 --N accumulation at 0–5 cm location, which positively correlated with maize N accumulation and growth at GFS. ST significantly affected rhizosphere AOA and AOB communities at 0–5 and 20–30 cm locations, and decreased AOA abundance, norank_p_ Thaumarchaeota relative abundance and bio-markers, but increased AOB abundance, richness, Nitrosospira relative abundance and bio-markers at 0–5 cm location. ST obviously increased the number of OTU hubs belonging to AOB Nitrosospira in networks and their complexity at 0–5 cm location. AOB community play a more important function role than AOA at 0–5 cm location. Rhizosphere NO 3 --N accumulation, maize N accumulation and growth recovery were closely related with AOB (especially Nitrosospira), but not AOA. It is concluded that, in contrast to CT, ST mainly stimulate rhizosphere AOB activity at 0–5 cm location (especially Nitrosospira) during grain filling stage, which contributes to more rhizosphere NO 3 --N accumulation and maize N absorption and faster growth. Our findings provide a theoretical basis for efficient crop-soil management to increase maize productivity under conservation tillage system. • Maize growth recovery in strip-till relied on its N absorption at filling stage. • Strip-till increased topsoil rhizosphere NO 3 --N related to maize N accumulation. • Strip-till enhanced topsoil rhizosphere AOB copies, richness, Nitrosospira abundance. • Strip-till enhanced topsoil network complexity, hubs of Nitrosospira , AOB centrality. • Topsoil rhizosphere NO 3 --N accumulation, maize growth recovery in relation to AOB. [ABSTRACT FROM AUTHOR]

Aims: This paper aims to investigate the adaptation of maize root system architecture (RSA) in response to increasing planting densities.Methods: A three-year field study was conducted with three planting densities (40,000, 70,000, and 90,000 plants per ha, which are abbreviated as D40000, D70000 and D90000, respectively). The dynamic change of root morphological traits and the 3-dimensional RSA were quantified.Results: The grain yield per ha increased with increasing plant density from D40000 to D70000, and then decreased at D90000. Compared to D70000, high planting density of D90000 did not changed the total root biomass per ha but increased shoot biomass per ha by 4 to 8% in two of the three experimental years. Grain yield per plant and plant NPK concentration decreased with increasing planting density. Total accumulation of P and K per ha also decreased at D90000 compared to D70000. Root to shoot ratio was reduced at high planting density beginning 50 days after emergence. Compared to the control (D70000), total root length (TRL) per plant was reduced by 18 to 30% at D90000 and increased by 43 to 56% at D40000, root biomass per plant was reduced by 23 to 34% at D90000 and increased by 66 to 75% at D40000. High plant density reduced the number of nodal roots, lateral root density (LRD) and the average lateral root (LR) length, but with less effect on the length of axial roots. The RSA is characteristic of “intra-row contraction and inter-row extension”. Vertically, root growth in top soil layer (0- to 36- cm) was enhanced under supra-optimal plant density, but had a negligible effect in deep soil layers (36- to 60- cm).Conclusions: To adapt to the limited photosynthesis capacity in the roots under high planting density, maize plants tend to reduce nodal root number and inhibit lateral root growth. They maintain nodal root length to explore a larger soil space, and adjust root growth in the intra-row and inter-row direction to avoid root-to-root competition. [ABSTRACT FROM AUTHOR]

Remobilization of leaf nitrogen (N) contributes greatly to grain N in maize, but leads to low photosynthetic rate (P n ). P n is determined by various N components involving in light harvest and CO 2 reduction. However, it is less clear which N component is the major contributor for the reduction of photosynthesis in modern stay-green maize hybrids. In this study, we analyzed the relationship between remobilization of different N components and P n during grain filling stage under low N (no N application) and high N (180 kg N ha −1 ) in a field experiment. The remobilization efficiency of photosynthetic enzymes (PEPc, PPDK and Rubisco) in the leaf was much higher than that of thylakoid N and other N components. Low N supply increased the remobilization efficiency of all the leaf N components. During grain filling stage, the amount of all the N components decreased together with P n . The ratio of P n to the N in the PEPc, PPDK and Rubisco kept increase in the whole grain filling stage, while the ratio of P n to chlorophyll and thylakoid-N decreased. Correlation analysis indicated that P n was more related to the content of photosynthetic enzymes than to chlorophyll and thylakoid N. It is concluded that photosynthetic enzymes serve as an N storage reservoir at early grain filling stage and their degradation is critical in the reduction of P n during later grain filling stage. Future breeding targets may be focused on enhancing the efficiency of photosynthetic enzymes during late grain filling stage. [ABSTRACT FROM AUTHOR]

One strategy for plants to adapt to low nitrogen is to reduce shoot growth and allocate more nitrogen and carbon for root growth. The mechanism underlying the response of leaf growth to low-nitrogen remains unknown. In this study, we investigated cell division and elongation in maize leaf growth in response to low-nitrogen by using an integrated approach. Kinematic analysis revealed that low-nitrogen inhibited leaf elongation mainly by shortening length of division zone, reducing cell flux and elemental growth rate. Hormone analysis revealed that changes of gibberellins caused by low-nitrogen correlate with the observed changes in division zone size and elemental growth rate in response to low-nitrogen, suggesting role of gibberellin in low-nitrogen induced inhibition of leaf elongation. RNA-Seq identified that GA20ox4 (GRMZM2G060940), a key enzyme for synthesis of gibberellins, was down-regulated in both division and elongation zone of leaf under low-nitrogen supply. Furthermore, exogenous GA 3 application on low-nitrogen plants restored leaf growth. However, application of gibberellin biosynthesis inhibitor reduced leaf growth. It is concluded that low-nitrogen reduces cell flux and elemental growth rate in maize leaf via reducing gibberellin synthesis. As a result, leaf elongation rate was slower and leaf area was smaller, freeing nitrogen for export to roots. [ABSTRACT FROM AUTHOR]

Modern maize cultivars have high nitrogen responsiveness of grain yield. However, the underlying physiological mechanism is unclear. In the present study, from 17 cultivars released from 1950 s to 2010 s in China, three maize cultivars released in 1950 s (BMY), 1970 s (ZD2), and 1990 s (ZD958) were selected according to their growth responses to nitrogen supply. Nitrogen responsiveness of shoot biomass was highest in the new cultivar ZD958, and the lowest in the old cultivar BMY, with the medium cultivar ZD2 in between. Shoot biomass was closely related to leaf elongation rate. Leaf elongation was further analyzed using kinematic analysis method. Cell division rate and cell production rate were greater and more responsive to nitrogen supply in ZD958 than in the other cultivars. In agreement, there were more cells in the elongation zone of ZD958 and they were more responsive to increasing supply, resulting a longer leaf elongation zone. The interaction effect between cultivar and nitrogen supply on leaf elongation was in consistence with the change in gibberellin (GA 1 and GA 3) concentration in leaf growth zone. Accordingly, the genes encoding gibberellin biosynthesis or signal transduction was more up-regulated in ZD958, which was positively correlated to the up-regulation of genes related to cell cycle and DNA replication. On the contrary, the genes related to the inactivation of gibberellin was more down-regulated in ZD958. Exogenous application of bioactive gibberellin or its biosynthesis inhibitor eliminated the interaction effect between cultivar and nitrogen supply on leaf elongation rate. In conclusion, modern maize breeding may have increased nitrogen responsiveness in maize by enhancing the gibberellins-dependent leaf elongation response to high nitrogen supply. • Nitrogen responsiveness is partly explained by leaf elongation rate. • Nitrogen responsiveness of leaf elongation is driven by gain in cell division. • Nitrogen-dependent gibberellin biosynthesis and signal transduction promote cell division in leaf growth zone. [ABSTRACT FROM AUTHOR]

In order to understand the regulation of source-sink relationship on leaf senescence in maize, we investigated the effect of pollination prevention on leaf senescence, post-silking dry matter and nitrogen accumulation and remobilization in different vegetative organs in one landrace and ten representative maize hybrids released between 1973 and 2000 in China. When pollination was prevented by covering silk with paper bags at silking stage, leaf senescence of Nongda 60, Yedan 13, Shendan 7 and Zhengdan 958 was delayed as shown by the remaining green leaf area per plant at maturity. However, pollination-prevention did not have obvious effect on the leaf senescence of Baimaya, Danyu 6, Yedan 2 and Xianyu 335. By contrast, pollination-prevention accelerated the leaf senescence of maize hybrids Zhongdan 2, Danyu13 and Yedan 4. It was found that leaf senescence of the late-released (since 1985) Chinese hybrids tended to be delayed by pollination-prevention, except XY335. From silking to physiological maturity, nitrogen content increased in the stem (plus the sheath, cob, husk, and tassel) and root of the non-pollinated plants. However, there was still a net reduction in leaf nitrogen content. We also found that pollination-prevention reduced leaf nitrogen remobilization efficiency, with genotypic difference and variation between the two years of testing. The results suggested that the response of leaf senescence to pollination-prevention is at least partially due to the change of leaf nitrogen remobilization efficiency. Leaf senescence tended to be delayed if leaf nitrogen remobilization efficiency is highly reduced by pollination-prevention. [ABSTRACT FROM AUTHOR]

To understand how root growth responds to temperature, we used kinematic analysis to quantify division and expansion parameters in the root of Arabidopsis thaliana. Plants were grown at temperatures from 15 to 30 °C, given continuously from germination. Over these temperatures, root length varies more than threefold in the wild type but by only twofold in a double mutant for phytochrome-interacting factor 4 and 5. For kinematics, the spatial profile of velocity was obtained with new software, Stripflow. We find that 30 °C truncates the elongation zone and curtails cell production, responses that probably reflect the elicitation of a common pathway for handling severe stresses. Curiously, rates of cell division at all temperatures are closely correlated with rates of radial expansion. Between 15 to 25 °C, root growth rate, maximal elemental elongation rate, and final cell length scale positively with temperature whereas the length of the meristem scales negatively. Non-linear temperature scaling characterizes meristem cell number, time to transit through either meristem or elongation zone, and average cell division rate. Surprisingly, the length of the elongation zone and the total rate of cell production are temperature invariant, constancies that have implications for our understanding of how the underlying cellular processes are integrated. [ABSTRACT FROM AUTHOR]

Genotypic difference in nitrogen responsiveness of maize grain yield has gained considerable attention, however, the underlying physiological mechanism is less understood. Leaf area and plant type are important factors determining biomass production, and both of them are regulated by nitrogen supply. The current research aims to assess whether high nitrogen responsiveness is related to leaf growth and plant type. A 2-year field experiment was conducted with three maize cultivars (BMY, ZD2 and ZD958) differing in nitrogen responsiveness under a wide range of nitrogen supply (0, 60, 120, 180 and 240 kg N ha-1). The links between grain yield, leaf area dynamics, leaf angle and orientation value, and radiation use efficiency were investigated. Nitrogen responsiveness, defined as yield increment per unit of increased nitrogen supply, was 8.3–29.1% higher in ZD958 compared with the other cultivars. The maximum grain yield of ZD958 was 21.4–74.6% higher than that of the other cultivars. With increasing nitrogen supply, the increments in maximum leaf area and linear growth rate of leaf area were greater in ZD958, which was positively correlated with grain yield. The interaction effect between cultivar and nitrogen supply was significant on leaf length, but not on leaf width. Across the combinations between cultivar and nitrogen supply, the variation in grain yield was explained by leaf length rather than leaf width. High nitrogen supply increased leaf angle and reduced leaf orientation value, so as to make the leaf more horizontally distributed. However, this change was less significant in ZD958, indicating that the plant type was more compact under high nitrogen supply in maize cultivars with high nitrogen responsiveness. Radiation use efficiency, defined as the slope of the linear relationship between above-ground biomass produced and cumulated intercepted photosynthetic active radiation (PAR) was 5.2–13.2% higher in ZD958 than that of BMY. In conclusion, with increasing nitrogen supply, the cultivars with fast leaf growth and compact plant type have higher conversion efficiency of intercepted PAR into the above-ground biomass and get higher grain yield. • Nitrogen increased leaf area to a larger extent in the maize cultivar with high N responsiveness. • A compact plant type contributed to high N responsiveness under high N supply. • Grain yield increased via gains in radiation use efficiency under high N supply. [ABSTRACT FROM AUTHOR]

The introduction of new hybrids and integrated crop-soil management has been causing maize grain yield to increase. However, less attention has been paid on the nutrient concentration of the grain; this aspect is of great importance to supplying calories and nutrients in the diets of both humans and animals worldwide. Increasing the retranslocation of nutrients from vegetative organs to grain can effectively increase the nutrient concentration of grain and general nutrient use efficiency. The present study involved monitoring the dynamic change of macro- and micronutrients in different organs of maize during the grain filling stage. In addition, the mobility of different elements and their contribution to grain nutrient content were evaluated in a 2-year experiment under low (LN, no N supplied) and high N (HN, 180 kg N ha −1 ) supply. Under HN supply, the net remobilization efficiency ( RE ) of the vegetative organs as a whole (calculated as nutrient remobilization amount divided by nutrient content at silking) of N, P, K, Mn, and Zn were 44%, 60%, 13%, 15%, and 25%, respectively. The other nutrients (Mg, Ca, Fe, Cu, and B) showed a net accumulation in the vegetative organs as a whole during the grain filling stage. Among the different organs, N, P, and Zn were remobilized more from the leaves ( RE of 44%, 51% and 43%, respectively) and the stalks (including leaf sheaths and tassels) ( RE of 48%, 71% and 43%, respectively). K was mainly remobilized from the leaves with RE of 51%. Mg, Ca, Fe, Mn, and Cu were mostly remobilized from the stalks with the RE of 23%, 9%, 10%, 42%, and 28%, respectively. However, most of the remobilized Mg, Ca, Fe, Mn, Cu, and Zn were translocated to the husk and cob, which seemingly served as the buffer sink for these nutrients. The RE s of all the nutrients except for P, K, and Zn were vulnerable to variations in conditions annually and were reduced when the grain yield and harvest index were lower in 2014 compared with 2013. Under LN stress, the RE was reduced in P and Zn in 2013, increased in Cu and unchanged in other nutrients. The concentration of these nutrients in the grain was either unchanged (P, K, Ca, Zn, and B) or decreased (N, Mg, Fe, Mn, and Cu). It is concluded that grain N, P, K, Mn, and Zn, but not Mg, Ca, Fe, Cu, and B concentration, can be improved by increasing their remobilization from vegetative organs. However, enhancing the senescence of maize plant via LN stress seems unable to increase grain mineral nutrient concentration. Genetic improvement aiming to increase nutrient remobilization should take into account the organ-specific remobilization pattern of the target nutrient. [ABSTRACT FROM AUTHOR]