Biological nitrification inhibition by root exudates of native species, Hibiscus splendens and Solanum echinatum

Chelsea K. Janke, Laura A. Wendling, Ryosuke Fujinuma

Research output: Contribution to journalArticleScientificpeer-review

Abstract

Australian native species grow competitively in nutrient limited environments, par- ticularly 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 splendens and Solanum echinatum, and contrasted with exudates of Sorghum 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 than S. 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 to S. bicolor. The root exudates significantly inhibited nitrification activity over six weeks' growth in a potential nitrification assay, with S. 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.

Original languageEnglish
Article numbere4960
Pages (from-to)e4960
JournalPeerJ
Volume6
Issue number6
DOIs
Publication statusPublished - 1 Jan 2018
MoE publication typeA1 Journal article-refereed

Fingerprint

Solanum echinatum
Hibiscus
Nitrification
Solanum
root exudates
Exudates and Transudates
nitrification
indigenous species
Organic acids
organic acids and salts
Sorghum
Sorghum bicolor
Acids
Rhizosphere
rhizosphere
Plant Exudates
Succinates
Oxalates
oxalic acid

Keywords

  • Biological nitrification inhibition
  • Ecology
  • Native species
  • Nitrogen
  • Nutrient cycling
  • Root exudates

Cite this

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title = "Biological nitrification inhibition by root exudates of native species, Hibiscus splendens and Solanum echinatum",
abstract = "Australian native species grow competitively in nutrient limited environments, par- ticularly 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 splendens and Solanum echinatum, and contrasted with exudates of Sorghum 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 than S. 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 to S. bicolor. The root exudates significantly inhibited nitrification activity over six weeks' growth in a potential nitrification assay, with S. 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.",
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Biological nitrification inhibition by root exudates of native species, Hibiscus splendens and Solanum echinatum. / Janke, Chelsea K.; Wendling, Laura A.; Fujinuma, Ryosuke.

In: PeerJ, Vol. 6, No. 6, e4960, 01.01.2018, p. e4960.

Research output: Contribution to journalArticleScientificpeer-review

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AB - Australian native species grow competitively in nutrient limited environments, par- ticularly 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 splendens and Solanum echinatum, and contrasted with exudates of Sorghum 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 than S. 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 to S. bicolor. The root exudates significantly inhibited nitrification activity over six weeks' growth in a potential nitrification assay, with S. 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.

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