在大田试验条件下，以宜香优2115为试验材料，设地力（高、较高、中、低）和施氮量（0、75、150 和225 kg/hm²）两因素处理，探明不同地力条件下施氮量对杂交籼稻干物质积累、转运和产量及氮肥利用率的影响。结果表明，随着施氮量增加，穗前和成熟期干物质积累量有增加趋势；抽穗期至成熟期，随着施氮量的增加，茎叶干物质转运量和茎叶干物质转运对穗部贡献率均呈先增加后降低的趋势；随着施氮量的增加，氮肥吸收利用率、农学利用率和偏生产力，以及千粒重和结实率逐渐降低，每穗粒数和产量先增加后降低，而有效穗数逐渐升高。随着地力条件的降低，穗前、成熟期和穗后干物质积累量、茎叶干物质转运量和茎叶干物质对穗部的贡献率及穗部干物质增加量均呈逐渐下降趋势，氮肥吸收利用率和生理利用率亦有降低趋势，而偏生产力呈先增后降的趋势。水稻有效穗数和产量均随土壤地力的提高而增加，而每穗粒数表现为下降。回归分析表明，在高、较高、中、低地力条件下，水稻可获得的最高产量分别为10 829.94、10 107.20、9 757.30和9 112.37 kg/hm²，其对应的适宜施氮量分别为141.96、165.47、154.86和152.98 kg/hm²。综上所述，中等施氮量能够使杂交籼稻在不同地力条件下获得较高的干物质积累量和转运能力，及较高的氮肥利用率，实现高产稳产。

Rice (Oryza sativa L.) is a daily staple food crop for more than half of the global population and improving productivity is an important task to meet future demands of the expanding world population. The application of nitrogen (N) fertilization improved rice growth and productivity in the world, but excess use causes environmental and economic issues. One of the main goals of rice breeding is reducing N fertilization while maintaining productivity. Therefore, enhancing rice nitrogen use efficiency (NUE) is essential for the development of sustainable agriculture and has become urgently needed. Many studies have been conducted on the main steps in the use of N including uptake and transport, reduction and assimilation, and translocation and remobilization, and on transcription factors regulating N metabolism. Understanding of these complex processes provides a base for the development of novel strategies to improve NUE for rice productivity under varying N conditions.

近年来重金属污染等生态环境问题日益受到重视,而物理、化学修复方法存在的诸如成本高、二次污染等问题,使得利用植物、微生物等进行联合治理成为环境修复的重要手段。植物根系分泌物作为植物与土壤进行营养和信息交流的重要媒介,不但对植物的生长具有重要作用,其在污染及沙化土壤修复中作用的研究也得以广泛开展。本文对根系分泌物的组成、分泌机制进行了阐述,并对其在植物吸收重金属、化感作用、植物根系与根际微生物互作、改变土壤理化性质等过程中的作用及机理进行了总结。此外,本文还对利用根系分泌物和根际微生物在生态环境治理中的应用现状、面临的难题及未来的发展等进行了讨论。希望本文可为基于植物与微生物进行的环境修复技术的实际应用提供理论支撑。

Although the global nitrogen (N) cycle is largely driven by soil microbes, plant root exudates can profoundly modify soil microbial communities and influence their N transformations. A detailed understanding is now beginning to emerge regarding the control that root exudates exert over two major soil N processes - nitrification and N fixation. We discuss recent breakthroughs in this area, including the identification of root exudates as nitrification inhibitors and as signaling compounds facilitating N-acquisition symbioses. We indicate gaps in current knowledge, including questions of how root exudates affect newly discovered microbial players and N-cycle components. A better understanding of these processes is urgent given the widespread inefficiencies in agricultural N use and their links to N pollution and climate change.Copyright © 2017 Elsevier Ltd. All rights reserved.

Sucrose and monosaccharide transporters mediate long distance transport of sugar from source to sink organs and constitute key components for carbon partitioning at the whole plant level and in interactions with fungi. Even if numerous families of plant sugar transporters are defined; efflux capacities, subcellular localization and association to membrane rafts have only been recently reported. On the fungal side, the investigation of sugar transport mechanisms in mutualistic and pathogenic interactions is now emerging. Here, we review the essential role of sugar transporters for distribution of carbohydrates inside plant cells, as well as for plant-fungal interaction functioning. Altogether these data highlight the need for a better comprehension of the mechanisms underlying sugar exchanges between fungi and their host plants.Copyright © 2012 Elsevier Ltd. All rights reserved.

Vacuolar accumulation of acidic metabolites is an important aspect of tomato fruit flavour and nutritional quality. The amino acids Asp and Glu accumulate to high concentrations during ripening, while γ-aminobutyrate (GABA) shows an approximately stoichiometric decline. Given that GABA can be catabolised to form Glu and subsequently Asp, and the requirement for the fruit to maintain osmotic homeostasis during ripening, we hypothesised the existence of a tonoplast transporter that exports GABA from the vacuole in exchange for import of either Asp or Glu. We show here that the tomato vacuolar membrane possesses such a transport property: transport of Glu across isolated tonoplast vesicle membranes was trans-stimulated in counterexchange mode by GABA, Glu and Asp. We identified SlCAT9 as a candidate protein for this exchanger using quantitative proteomics of a tonoplast-enriched membrane fraction. Transient expression of a SlCAT9-YFP fusion in tobacco confirmed a tonoplast localisation. The function of the protein was examined by overexpression of SlCAT9 in transgenic tomato plants. Tonoplast vesicles isolated from transgenic plants showed higher rates of Glu and GABA transport than wild-type (WT) only when assayed in counterexchange mode with Glu, Asp, or GABA. Moreover, there were substantial increases in the content of all three cognate amino acids in ripe fruit from the transgenic plants. We conclude that SlCAT9 is a tonoplast Glu/Asp/GABA exchanger that strongly influences the accumulation of these amino acids during fruit development. © 2015 The Authors The Plant Journal published by Society for Experimental Biology and John Wiley & Sons Ltd.

Root exudates, as an important form of material input from plants to the soil, regulate the carbon input and efflux of plant rhizosphere soil and play an important role in maintaining the carbon and nutrient balance of the whole ecosystem. Root exudates are notoriously difficult to collect due to their underlying characteristics (e.g., low concentration and fast turnover rate) and the associated methodological challenges of accurately measuring root exudates in native soils. As a result, up until now, it has been difficult to accurately quantify the soil organic carbon input from root exudates to the soil in most studies. In recent years, the contribution and ecological effects of root exudates to soil organic carbon input and efflux have been paid more and more attention. However, the ecological mechanism of soil organic carbon input and efflux mediated by root exudates are rarely analyzed comprehensively. In this review, the main processes and influencing factors of soil organic carbon input and efflux mediated by root exudates are demonstrated. Soil minerals and soil microbes play key roles in the processes. The carbon allocation from plants to soil is influenced by the relationship between root exudates and root functional traits. Compared with the quantity of root exudates, the response of root exudate quality to environmental changes affects soil carbon function more. In the future, the contribution of root exudates in different plants to soil carbon turnover and their relationship with soil nutrient availability will be accurately quantified, which will be helpful to understand the mechanism of soil organic carbon sequestration.

Phosphorus (P), iron (Fe) and zinc (Zn) are essential elements for plant growth and development, but their availability in soil is often limited. Intercropping contributes to increased P, Fe and Zn uptake and thereby increases yield and improves grain nutritional quality and ultimately human health. A better understanding of how intercropping leads to increased plant P, Fe and Zn availability will help to improve P-fertilizer-use efficiency and agronomic Fe and Zn biofortification.This review synthesizes the literature on how intercropping of legumes with cereals increases acquisition of P, Fe and Zn from soil and recapitulates what is known about root-to-shoot nutrient translocation, plant-internal nutrient remobilization and allocation to grains.Direct interspecific facilitation in intercropping involves below-ground processes in which cereals increase Fe and Zn bioavailability while companion legumes benefit. This has been demonstrated and verified using isotopic nutrient tracing and molecular analysis. The same methodological approaches and field studies should be used to explore direct interspecific P facilitation. Both niche complementarity and interspecific facilitation contribute to increased P acquisition in intercropping. Niche complementarity may also contribute to increased Fe and Zn acquisition, an aspect poorly understood. Interspecific mobilization and uptake facilitation of sparingly soluble P, Fe and Zn from soil, however, are not the only determinants of the concentrations of P, Fe and Zn in grains. Grain yield and nutrient translocation from roots to shoots further influence the concentrations of these nutrients in grains.© The Author 2016. Published by Oxford University Press on behalf of the Annals of Botany Company. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

Plants forage soil for water and nutrients, whose distribution is patchy and often dynamic. To improve their foraging activities, plants have evolved mechanisms to modify the physicochemical properties and microbial communities of the rhizosphere, i.e. the soil compartment under the influence of the roots. This dynamic interplay in root-soil-microbiome interactions creates emerging properties that impact plant nutrition and health. As a consequence, the rhizosphere can be considered an extended root phenotype, a manifestation of the effects of plant genes on their environment inside and/or outside of the organism. Here, we review current understanding of how plants shape the rhizosphere and the benefits it confers to plant fitness. We discuss future research challenges and how applying their solutions in crops will enable us to harvest the benefits of the extended root phenotype.© 2020 Society for Experimental Biology and John Wiley & Sons Ltd.

This article describes the composition of root exudates, how these metabolites are released to the rhizosphere and their importance in the recruitment of beneficial microbiota that alleviate plant stress. Metabolites secreted to the rhizosphere by roots are involved in several processes. By modulating the composition of the root exudates, plants can modify soil properties to adapt and ensure their survival under adverse conditions. They use several strategies such as (1) changing soil pH to solubilize nutrients into assimilable forms, (2) chelating toxic compounds, (3) attracting beneficial microbiota, or (4) releasing toxic substances for pathogens, etc. In this work, the composition of root exudates as well as the different mechanisms of root exudation have been reviewed. Existing methodologies to collect root exudates, indicating their advantages and disadvantages, are also described. Factors affecting root exudation have been exposed, including physical, chemical, and biological agents which can produce qualitative and quantitative changes in exudate composition. Finally, since root exudates play an important role in the recruitment of mycorrhizal fungi and plant growth-promoting rhizobacteria (PGPR), the mechanisms of interaction between plants and the beneficial microbiota have been highlighted.

Low-molecular-weight organic compounds in root exudates play a key role in plant-microorganism interactions by influencing the structure and function of soil microbial communities. Model exudate solutions, based on organic acids (OAs) (quinic, lactic, maleic acids) and sugars (glucose, sucrose, fructose), previously identified in the rhizosphere of Pinus radiata, were applied to soil microcosms. Root exudate compound solutions stimulated soil dehydrogenase activity and the addition of OAs increased soil pH. The structure of active bacterial communities, based on reverse-transcribed 16S rRNA gene PCR, was assessed by denaturing gradient gel electrophoresis and PhyloChip microarrays. Bacterial taxon richness was greater in all treatments than that in control soil, with a wide range of taxa (88-1043) responding positively to exudate solutions and fewer (<24) responding negatively. OAs caused significantly greater increases than sugars in the detectable richness of the soil bacterial community and larger shifts of dominant taxa. The greater response of bacteria to OAs may be due to the higher amounts of added carbon, solubilization of soil organic matter or shifts in soil pH. Our results indicate that OAs play a significant role in shaping soil bacterial communities and this may therefore have a significant impact on plant growth.© 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

Two rice cultivars (Xiushui 09 and Chunyou 84) were used to evaluate the effects of various soil oxygen (O2) conditions on soil nitrogen (N) transformation, absorption and accumulation in rice plants. The treatments were continuous flooding (CF), continuous flooding and aeration (CFA), and alternate wetting and drying (AWD). The results showed that the AWD and CFA treatments improved soil N transformation, rice growth, and N absorption and accumulation. Soil NO3- content, nitrification activity and ammonia-oxidising bacteria abundance, leaf area, nitrate reductase activity, and N absorption and accumulation in rice all increased in both cultivars. However, soil microbial biomass carbon and pH did not significantly change during the whole period of rice growth. Correlation analysis revealed a significant positive correlation between the nitrification activity and ammonia-oxidising bacteria abundance, and both of them significantly increased as the total N accumulation in rice increased. Our results indicated that improved soil O2 conditions led to changing soil N cycling and contributed to increases in N absorption and accumulation by rice in paddy fields.

We summarize nitrate transporters and discuss their potential in breeding for improved nitrogen use efficiency and yield.© The Author 2017. Published by Oxford University Press on behalf of the Society for Experimental Biology. All rights reserved. For permissions, please email: journals.permissions@oup.com.

In Arabidopsis thaliana, root high-affinity nitrate (NO3–) uptake depends mainly on NRT2.1, 2.4, and 2.5, which are repressed by high NO3– supply at the transcript level. For NRT2.1, this regulation is due to the action of (i) feedback down-regulation by N metabolites and (ii) repression by NO3– itself mediated by the transceptor NRT1.1(NPF6.3). However, for NRT2.4 and NRT2.5, the signalling pathway(s) remain unknown as do the molecular elements involved. Here we show that unlike NRT2.1, NRT2.4 and NRT2.5 are not induced in an NO3– reductase mutant but are up-regulated following replacement of NO3– by ammonium (NH4+) as the N source. Moreover, increasing the NO3– concentration in a mixed nutrient solution with constant NH4+ concentration results in a gradual repression of NRT2.4 and NRT2.5, which is suppressed in an nrt1.1 mutant. This indicates that NRT2.4 and NRT2.5 are subjected to repression by NRT1.1-mediated NO3– sensing, and not to feedback repression by reduced N metabolites. We further show that key regulators of NRT2 transporters, such as HHO1, HRS1, PP2C, LBD39, BT1, and BT2, are also regulated by NRT1.1-mediated NO3– sensing, and that several of them are involved in NO3– repression of NRT2.1, NRT2.4, and NRT2.5. Finally, we provide evidence that it is the phosphorylated form of NRT1.1 at the T101 residue, which is most active in triggering the NRT1.1-mediated NO3– regulation of all these genes. Altogether, these data led us to propose a regulatory model for high-affinity NO3– uptake in Arabidopsis, highlighting several NO3– transduction cascades downstream of the phosphorylated form of the NRT1.1 transceptor.

<p><List> <ListItem><ItemContent><p>&#8226;Ÿ Long-chain fatty acids and amino acids application could form foliar disease resistant-soil microbial community </p></ItemContent></ListItem> <ListItem><ItemContent><p>&#8226;Ÿ Population of <i>Pseudomonas</i> was enriched by long-chain fatty acids and amino acids application</p></ItemContent></ListItem> <ListItem><ItemContent><p>&#8226;Ÿ The enriched <i>Pseudomonas</i> could help plant resistant foliar pathogens.</p></ItemContent></ListItem></List></p> <p><fig><graphic-alternatives><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="2662-2289-3-1-42/sel-00057-jy-tu1.jpg"/><graphic xmlns:xlink="http://www.w3.org/1999/xlink" xlink:href="2662-2289-3-1-42/SEL-00057-JY-tu1.tif"/></graphic-alternatives></fig></p> <p>Plants are capable of releasing specific root exudates to recruit beneficial rhizosphere microbes upon foliar pathogen invasion attack, including long-chain fatty acids, amino acids, short-chain organic acids and sugars. Although long-chain fatty acids and amino acids application have been linked to soil legacy effects that improve future plant performance in the presence of the pathogen, the precise mechanisms involved are to a large extent still unknown. Here, we conditioned soils with long-chain fatty acids and amino acids application (L+ A) or short-chain organic acids and sugars (S+ S) to examine the direct role of such exudates on soil microbiome structure and function. The L+ A treatment recruited higher abundances of Proteobacteria which were further identified as members of the genera <i>Sphingomonas</i>, <i>Pseudomonas</i>, <i>Roseiflexus,</i> and <i>Flavitalea</i>. We then isolated the enriched bacterial strains from these groups, identifying ten <i>Pseudomonas</i> strains that were able to help host plant to resist foliar pathogen infection. Further investigation showed that the L+ A treatment resulted in growth promotion of these <i>Pseudomonas</i> strains. Collectively, our data suggest that long-chain fatty acids and amino acids stimulated by foliar pathogen infection can recruit specific <i>Pseudomonas</i> populations that can help protect the host plant or future plant generations.</p>

The current world of climate change, global warming and a constantly changing environment have made life very stressful for living entities, which has driven the evolution of biochemical processes to cope with stressed environmental and ecological conditions. As climate change conditions continue to develop, we anticipate more frequent occurrences of abiotic stresses such as drought, high temperature and salinity. Living plants, which are sessile beings, are more exposed to environmental extremes. However, plants are equipped with biosynthetic machinery operating to supply thousands of bio-compounds required for maintaining internal homeostasis. In addition to chemical coordination within a plant, these compounds have the potential to assist plants in tolerating, resisting and escaping biotic and abiotic stresses generated by the external environment. Among certain biosynthates, flavonoids are an important example of these stress mitigators. Flavonoids are secondary metabolites and biostimulants; they play a key role in plant growth by inducing resistance against certain biotic and abiotic stresses. In addition, the function of flavonoids as signal compounds to communicate with rhizosphere microbes is indispensable. In this review, the significance of flavonoids as biostimulants, stress mitigators, mediators of allelopathy and signaling compounds is discussed. The chemical nature and biosynthetic pathway of flavonoid production are also highlighted.

为了探讨局部根系水分胁迫下不同形态氮素对水稻幼苗氮素吸收、生理特性和根系生长的影响，以水稻品种金优402为材料，设置非胁迫、局部根系胁迫、全根胁迫3种水分条件和全硝、铵硝比为50/50、全铵3个氮素形态，采用PEG模拟水分胁迫的室内分根营养液培养方法，研究其氮素吸收和累积、光合速率、蒸腾速率、气孔导度及根长、根表面积、根体积的变化规律。结果表明，在局部根系水分胁迫下，两侧根系同时供应NH₄⁺-N和NO₃^--N最有利于水稻氮素的吸收和累积，两侧根系均单一供应NO₃^--N的水稻氮素吸收和累积量最少；与未受胁迫处理的水稻相比，局部根系胁迫下两侧根系同时供应NH₄⁺-N和NO₃^--N的水稻光合速率受影响较小，而气孔导度和蒸腾速率则明显下降。不同氮形态处理间，两侧根系同时供应NH₄⁺-N和NO₃^--N的水稻光合速率和气孔导度均为最大，单一供应NO₃^--N的最小。在所有处理中，局部根系水分胁迫下两侧根系同时供应NH₄⁺-N和NO₃^--N的水稻WUE最高。在局部根系水分胁迫下，两侧同时供应NH₄⁺-N和NO₃^--N的水稻根长、根表面积、根体积绝大多数大于其他2种氮素形态，且受胁迫一侧和不受胁迫一侧根系相差较小。除左右根室均单一供应NO₃^--N的水稻外，局部根系胁迫处理的根长、根表面积、根体积均大于非胁迫处理。研究结果表明，局部根系水分胁迫和氮素形态耦合可以提高水稻幼苗的水、氮素吸收。

Ammonium is a preferential nitrogen form for rice (Oryza sativa) grown in paddy field, but the molecular mechanisms for ammonium uptake have not been well understood. We functionally characterized three members belonging to ammonium transporter 1 (AMT1) and investigated their contributions to ammonium uptake. Spatial expression analysis showed that the up-regulated expression of OsAMT1;1 and OsAMT1;2 and down-regulated expression of OsAMT1;3 by ammonium were higher in the root mature region than in the root tips. All OsAMT1 members were polarly localized at the distal side of exodermis in the mature region of crown roots and lateral roots. Upon exposure to ammonium, localization of OsAMT1;1 and OsAMT1;2 was also observed in the endoplasmic reticulum, but their abundance in the plasma membrane was not changed. Single knockout of either gene did not affect ammonium uptake, but knockout of all three genes resulted in 95% reduction of ammonium uptake. However, the nitrogen uptake did not differ between the wild-type rice and triple mutants at high ammonium and nitrate supply. Our results indicate that three OsAMT1 members are cooperatively required for uptake of low ammonium in rice roots and that they undergo a distinct regulatory mechanism in response to ammonium.This article is protected by copyright. All rights reserved.