ROOT EXUDATES FROM CANOLA EXHIBIT BIOLOGICAL NITRIFICATION INHIBITION AND ARE EFFECTIVE IN INHIBITING AMMONIA OXIDATION IN SOIL

This study investigated the ability of several plant species commonly occurring as weeds in Australian cropping systems to produce root exudates that inhibit nitrification via biological nitrification inhibition (BNI). Seedlings of wild radish (Raphanus raphanistrum), great brome grass (Bromus diandrus), wild oats (Avena fatua), annual ryegrass (Lolium rigidum) and Brachiaria humidicola (BNI-positive control) were grown in hydroponics, and the impact of their root exudates on NO3– production by Nitrosomonas europaea was measured in a pure-culture assay. A pot study (soil-based assay) was then conducted to confirm the ability of the weeds to inhibit nitrification in whole soils. All of the tested weeds slowed NO3– production by N. europaea in the pure-culture assay and significantly inhibited potential nitrification rates in soil-based assays. Root exudates produced by wild radish were the most inhibitory, slowing NO3– production by the pure culture of N. europaea by 53 ± 6.1% and completely inhibiting nitrification in the soil-based assay. The other weed species all had BNI capacities comparable to that of B. humidicola and significantly higher than that previously reported for wheat cv. Janz. This study demonstrates that several commonly occurring weed species have BNI capacity. By altering the N cycle, and retaining NH4+ in the soils in which they grow, these weeds may gain a competitive advantage over species (including crops) that prefer NO3–. Increasing our understanding of how weeds compete with crops for N may open avenues for novel weed-management strategies.

Download Full-text

Biological nitrification inhibition by root exudates of native species,Hibiscus splendensandSolanum echinatum

PeerJ ◽

10.7717/peerj.4960 ◽

2018 ◽

Vol 6 ◽

pp. e4960 ◽

Cited By ~ 1

Author(s):

Chelsea K. Janke ◽

Laura A. Wendling ◽

Ryosuke Fujinuma

Keyword(s):

Plant Species ◽

Root Exudates ◽

Native Species ◽

N Uptake ◽

Nitrification Inhibition ◽

Native Plant ◽

Native Plant Species ◽

Potential Nitrification ◽

Australian Native Plant ◽

Biological Nitrification

Australian native species grow competitively in nutrient limited environments, particularly in nitrogen (N) limited soils; however, the mechanism that enables this is poorly understood. Biological nitrification inhibition (BNI), which is the release of root exudates into the plant rhizosphere to inhibit the nitrification process, is a hypothesized adaptive mechanism for maximizing N uptake. To date, few studies have investigated the temporal pattern and components of root exudates by Australian native plant species for BNI. This study examined root exudates from two Australian native species,Hibiscus splendensandSolanum echinatum,and contrasted with exudates ofSorghum bicolor, a plant widely demonstrated to exhibit BNI capacity. Root exudates were collected from plants at two, four, and six weeks after transplanting to solution culture. Root exudates contained three types of organic acids (OAs), oxalic, citric and succinic acids, regardless of the species. However, the two Australian natives species released larger amount of OAs in earlier development stages thanS. bicolor. The total quantity of these OAs released per unit root dry mass was also seven-ten times greater for Australian native plant species compared toS. bicolor. The root exudates significantly inhibited nitrification activity over six weeks’ growth in a potential nitrification assay, withS. echinatum(ca. 81% inhibition) >S. bicolor(ca. 80% inhibition) >H. splendens(ca. 78% inhibition). The narrow range of BNI capacity in the study plants limited the determination of a relationship between OAs and BNI; however, a lack of correlation between individual OAs and inhibition of nitrification suggests OAs may not directly contribute to BNI. These results indicate that Australian native species generate a strongly N conserving environment within the rhizosphere up to six weeks after germination, establishing a competitive advantage in severely N limited environments.

Download Full-text

Biological nitrification inhibition by rice root exudates in two different soils of Uruguay

Acta Agriculturae Scandinavica Section B - Soil & Plant Science ◽

10.1080/09064710.2021.1948602 ◽

2021 ◽

pp. 1-11

Author(s):

Gabriela Illarze ◽

Jacobo Arango ◽

Jonathan Nuñez ◽

Pilar Irisarri

Keyword(s):

Root Exudates ◽

Rice Root ◽

Nitrification Inhibition ◽

Biological Nitrification ◽

Different Soils

Download Full-text

Root exudation of contrasting drought-stressed pearl millet genotypes conveys varying biological nitrification inhibition (BNI) activity

Biology and Fertility of Soils ◽

10.1007/s00374-021-01578-w ◽

2021 ◽

Author(s):

Arindam Ghatak ◽

Florian Schindler ◽

Gert Bachmann ◽

Doris Engelmeier ◽

Prasad Bajaj ◽

...

Keyword(s):

Drought Stress ◽

Pearl Millet ◽

Root Exudates ◽

Root Exudation ◽

Potential Effect ◽

Nitrification Inhibition ◽

Primary And Secondary Metabolites ◽

Soil Microbial ◽

Biological Nitrification ◽

Stress Dependent

AbstractRoots secrete a vast array of low molecular weight compounds into the soil broadly referred to as root exudates. It is a key mechanism by which plants and soil microbes interact in the rhizosphere. The effect of drought stress on the exudation process and composition is rarely studied, especially in cereal crops. This study focuses on comparative metabolic profiling of the exudates from sensitive and tolerant genotypes of pearl millet after a period of drought stress. We employed a combined platform of gas and liquid chromatography coupled to mass spectrometry to cover both primary and secondary metabolites. The results obtained demonstrate that both genotype and drought stress have a significant impact on the concentration and composition of root exudates. The complexity and function of these differential root exudates are discussed. To reveal the potential effect of root exudates on the soil microbial community after a period of drought stress, we also tested for biological nitrification inhibition (BNI) activity. The analysis revealed a genotype-dependent enhancement of BNI activity after a defined period of drought stress. In parallel, we observed a genotype-specific relation of elongated root growth and root exudation under drought stress. These data suggest that the drought stress-dependent change in root exudation can manipulate the microbial soil communities to adapt and survive under harsh conditions.

Download Full-text

Revisiting plant biological nitrification inhibition efficiency using multiple archaeal and bacterial ammonia-oxidising cultures

Biology and Fertility of Soils ◽

10.1007/s00374-020-01533-1 ◽

2021 ◽

Author(s):

Jasmeet Kaur-Bhambra ◽

Daniel L. R. Wardak ◽

James I. Prosser ◽

Cécile Gubry-Rangin

Keyword(s):

Ammonia Oxidation ◽

Nitrous Oxide Emissions ◽

Natural Soil ◽

Nitrification Inhibitors ◽

Nitrification Inhibition ◽

Major Process ◽

Pure Cultures ◽

Biological Nitrification ◽

New Compounds ◽

Ammonia Oxidising Archaea

AbstractNitrification is a major process within the nitrogen (N) cycle leading to global losses of N, including fertiliser N, from natural and agricultural systems and producing significant nitrous oxide emissions. One strategy for the mitigation of these losses involves nitrification inhibition by plant-derived biological nitrification inhibitors (BNIs). Cultivation-based studies of BNIs, including screening for new compounds, have predominantly investigated inhibition of a single ammonia-oxidising bacterium (AOB), Nitrosomonas europaea, even though ammonia oxidation in soil is usually dominated by ammonia-oxidising archaea (AOA), especially in acidic soils, and AOB Nitrosospira sp., rather than Nitrosomonas, in fertilised soils. This study aimed to assess the sensitivity of ammonia oxidation by a range of AOA and AOB pure cultures to BNIs produced by plant roots (methyl 3-(4-hydroxyphenyl) propionate, sakuranetin and 1,9-decanediol) and shoots (linoleic acid, linolenic acid and methyl linoleate). AOA were generally more sensitive to BNIs than AOB, and sensitivity was greater to BNIs produced by shoots than those produced by roots. Sensitivity also varied within AOA and AOB cultures and between different BNIs. In general, N. europaea was not a good indicator of BNI inhibition, and findings therefore highlight the limitations of use of a single bioassay strain and suggest the use of a broader range of strains that are more representative of natural soil communities.

Download Full-text

Biological nitrification inhibition by rice root exudates and its relationship with nitrogen-use efficiency

New Phytologist ◽

10.1111/nph.14057 ◽

2016 ◽

Vol 212 (3) ◽

pp. 646-656 ◽

Cited By ~ 49

Author(s):

Li Sun ◽

Yufang Lu ◽

Fangwei Yu ◽

Herbert J. Kronzucker ◽

Weiming Shi

Keyword(s):

Root Exudates ◽

Nitrogen Use Efficiency ◽

Rice Root ◽

Nitrification Inhibition ◽

Nitrogen Use ◽

Use Efficiency ◽

Biological Nitrification

Download Full-text

Biological nitrification inhibition in the rhizosphere: determining interactions and impact on microbially mediated processes and potential applications

FEMS Microbiology Reviews ◽

10.1093/femsre/fuaa037 ◽

2020 ◽

Vol 44 (6) ◽

pp. 874-908

Author(s):

Pierfrancesco Nardi ◽

Hendrikus J Laanbroek ◽

Graeme W Nicol ◽

Giancarlo Renella ◽

Massimiliano Cardinale ◽

...

Keyword(s):

Ammonia Oxidation ◽

Natural Phenomenon ◽

Nitrification Inhibitors ◽

Nitrification Inhibition ◽

Microbial Conversion ◽

N Losses ◽

N2o Production ◽

N Transformations ◽

Potential Applications ◽

Biological Nitrification

ABSTRACT Nitrification is the microbial conversion of reduced forms of nitrogen (N) to nitrate (NO3−), and in fertilized soils it can lead to substantial N losses via NO3− leaching or nitrous oxide (N2O) production. To limit such problems, synthetic nitrification inhibitors have been applied but their performance differs between soils. In recent years, there has been an increasing interest in the occurrence of biological nitrification inhibition (BNI), a natural phenomenon according to which certain plants can inhibit nitrification through the release of active compounds in root exudates. Here, we synthesize the current state of research but also unravel knowledge gaps in the field. The nitrification process is discussed considering recent discoveries in genomics, biochemistry and ecology of nitrifiers. Secondly, we focus on the ‘where’ and ‘how’ of BNI. The N transformations and their interconnections as they occur in, and are affected by, the rhizosphere, are also discussed. The NH4+ and NO3− retention pathways alternative to BNI are reviewed as well. We also provide hypotheses on how plant compounds with putative BNI ability can reach their targets inside the cell and inhibit ammonia oxidation. Finally, we discuss a set of techniques that can be successfully applied to solve unresearched questions in BNI studies.

Download Full-text

Biological nitrification inhibition by sorghum root exudates impacts ammonia-oxidizing bacteria but not ammonia-oxidizing archaea

Biology and Fertility of Soils ◽

10.1007/s00374-020-01538-w ◽

2021 ◽

Author(s):

Yaying Li ◽

Yang Zhang ◽

Stephen James Chapman ◽

Huaiying Yao

Keyword(s):

Root Exudates ◽

Ammonia Oxidizing Bacteria ◽

Nitrification Inhibition ◽

Ammonia Oxidizing Archaea ◽

Biological Nitrification

Download Full-text

Biological nitrification inhibition in maize—isolation and identification of hydrophobic inhibitors from root exudates

Biology and Fertility of Soils ◽

10.1007/s00374-021-01577-x ◽

2021 ◽

Author(s):

Junnosuke Otaka ◽

Guntur Venkata Subbarao ◽

Hiroshi Ono ◽

Tadashi Yoshihashi

Keyword(s):

Root Exudation ◽

Root Systems ◽

Root Surface ◽

Maize Root ◽

Nitrification Inhibition ◽

Isolation And Identification ◽

N Losses ◽

Chemical Structures ◽

Maize Roots ◽

Biological Nitrification

AbstractTo control agronomic N losses and reduce environmental pollution, biological nitrification inhibition (BNI) is a promising strategy. BNI is an ecological phenomenon by which certain plants release bioactive compounds that can suppress nitrifying soil microbes. Herein, we report on two hydrophobic BNI compounds released from maize root exudation (1 and 2), together with two BNI compounds inside maize roots (3 and 4). On the basis of a bioassay-guided fractionation method using a recombinant nitrifying bacterium Nitrosomonas europaea, 2,7-dimethoxy-1,4-naphthoquinone (1, ED50 = 2 μM) was identified for the first time from dichloromethane (DCM) wash concentrate of maize root surface and named “zeanone.” The benzoxazinoid 2-hydroxy-4,7-dimethoxy-2H-1,4-benzoxazin-3(4H)-one (HDMBOA, 2, ED50 = 13 μM) was isolated from DCM extract of maize roots, and two analogs of compound 2, 2-hydroxy-7-methoxy-2H-1,4-benzoxazin-3(4H)-one (HMBOA, 3, ED50 = 91 μM) and HDMBOA-β-glucoside (4, ED50 = 94 μM), were isolated from methanol extract of maize roots. Their chemical structures (1–4) were determined by extensive spectroscopic methods. The contributions of these four isolated BNI compounds (1–4) to the hydrophobic BNI activity in maize roots were 19%, 20%, 2%, and 4%, respectively. A possible biosynthetic pathway for zeanone (1) is proposed. These results provide insights into the strength of hydrophobic BNI activity released from maize root systems, the chemical identities of the isolated BNIs, and their relative contribution to the BNI activity from maize root systems.

Download Full-text