Waterlogging tolerance, tissue nitrogen and oxygen transport in the forage legume Melilotus siculus: A comparison of nodulated and nitrate-fed plants

Dennis Konnerup, Guillermo Toro, Ole Pedersen, Timothy David Colmer

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6 Citations (Scopus)

Abstract

Background and Aims Soil waterlogging adversely impacts most plants. Melilotus siculus is a waterlogging-tolerant annual forage legume, but data were lacking for the effects of root-zone hypoxia on nodulated plants reliant on N2 fixation. The aim was to compare the waterlogging tolerance and physiology of M. siculus reliant on N2 fixation or with access to NO3 -. Methods A factorial experiment imposed treatments of water level (drained or waterlogged), rhizobia (nil or inoculated) and mineral N supply (nil or 11 mm NO3 -) for 21 d on plants in pots of vermiculite in a glasshouse. Nodulation, shoot and root growth and tissue N were determined. Porosity (gas volume per unit tissue volume) and respiration rates of root tissues and nodules, and O2 microelectrode profiling across nodules, were measured in a second experiment. Key Results Plants inoculated with the appropriate rhizobia, Ensifer (syn. Sinorhizobium) medicae, formed nodules. Nodulated plants grew as well as plants fed NO3 -, both in drained and waterlogged conditions. The growth and total N content of nodulated plants (without any NO3 - supplied) indicated N2 fixation. Respiration rates (mass basis) were highest in nodules and root tips and lowest in basal root tissues. Secondary aerenchyma (phellem) formed along basal root parts and a thin layer of this porous tissue also covered nodules, which together enhanced gas-phase diffusion of O2 to the nodules; O2 was below detection within the infected zone of the nodule interior. Conclusions Melilotus siculus reliant on N2 fixation grew well both in drained and waterlogged conditions, and had similar tissue N concentrations. In waterlogged conditions the relatively high respiration rates of nodules must rely on O2 movement via the aerenchymatous phellem in hypocotyl, roots and the outer tissue layers of nodules.

Original languageEnglish
Pages (from-to)699-709
Number of pages11
JournalAnnals of Botany
Volume121
Issue number4
DOIs
Publication statusPublished - 14 Mar 2018

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Melilotus siculus
forage legumes
flooded conditions
nitrates
oxygen
nitrogen
drained conditions
periderm
Rhizobium
Sinorhizobium medicae
Ensifer
gases
vermiculite
tissues
nodulation
root tips
hypocotyls
porosity
water table
hypoxia

Cite this

@article{35e6cae5e45c4ea78998c6ada52f4c04,
title = "Waterlogging tolerance, tissue nitrogen and oxygen transport in the forage legume Melilotus siculus: A comparison of nodulated and nitrate-fed plants",
abstract = "Background and Aims Soil waterlogging adversely impacts most plants. Melilotus siculus is a waterlogging-tolerant annual forage legume, but data were lacking for the effects of root-zone hypoxia on nodulated plants reliant on N2 fixation. The aim was to compare the waterlogging tolerance and physiology of M. siculus reliant on N2 fixation or with access to NO3 -. Methods A factorial experiment imposed treatments of water level (drained or waterlogged), rhizobia (nil or inoculated) and mineral N supply (nil or 11 mm NO3 -) for 21 d on plants in pots of vermiculite in a glasshouse. Nodulation, shoot and root growth and tissue N were determined. Porosity (gas volume per unit tissue volume) and respiration rates of root tissues and nodules, and O2 microelectrode profiling across nodules, were measured in a second experiment. Key Results Plants inoculated with the appropriate rhizobia, Ensifer (syn. Sinorhizobium) medicae, formed nodules. Nodulated plants grew as well as plants fed NO3 -, both in drained and waterlogged conditions. The growth and total N content of nodulated plants (without any NO3 - supplied) indicated N2 fixation. Respiration rates (mass basis) were highest in nodules and root tips and lowest in basal root tissues. Secondary aerenchyma (phellem) formed along basal root parts and a thin layer of this porous tissue also covered nodules, which together enhanced gas-phase diffusion of O2 to the nodules; O2 was below detection within the infected zone of the nodule interior. Conclusions Melilotus siculus reliant on N2 fixation grew well both in drained and waterlogged conditions, and had similar tissue N concentrations. In waterlogged conditions the relatively high respiration rates of nodules must rely on O2 movement via the aerenchymatous phellem in hypocotyl, roots and the outer tissue layers of nodules.",
keywords = "Aerenchyma, messina, nitrogen fixation, oxygen microelectrode profiling, pasture legume, phellem, respiration, root nodules, soil flooding, tissue porosity, wetland legume plant",
author = "Dennis Konnerup and Guillermo Toro and Ole Pedersen and Colmer, {Timothy David}",
year = "2018",
month = "3",
day = "14",
doi = "10.1093/aob/mcx202",
language = "English",
volume = "121",
pages = "699--709",
journal = "Annals of Botany",
issn = "0305-7364",
publisher = "OXFORD UNIV PRESS UNITED KINGDOM",
number = "4",

}

TY - JOUR

T1 - Waterlogging tolerance, tissue nitrogen and oxygen transport in the forage legume Melilotus siculus

T2 - A comparison of nodulated and nitrate-fed plants

AU - Konnerup, Dennis

AU - Toro, Guillermo

AU - Pedersen, Ole

AU - Colmer, Timothy David

PY - 2018/3/14

Y1 - 2018/3/14

N2 - Background and Aims Soil waterlogging adversely impacts most plants. Melilotus siculus is a waterlogging-tolerant annual forage legume, but data were lacking for the effects of root-zone hypoxia on nodulated plants reliant on N2 fixation. The aim was to compare the waterlogging tolerance and physiology of M. siculus reliant on N2 fixation or with access to NO3 -. Methods A factorial experiment imposed treatments of water level (drained or waterlogged), rhizobia (nil or inoculated) and mineral N supply (nil or 11 mm NO3 -) for 21 d on plants in pots of vermiculite in a glasshouse. Nodulation, shoot and root growth and tissue N were determined. Porosity (gas volume per unit tissue volume) and respiration rates of root tissues and nodules, and O2 microelectrode profiling across nodules, were measured in a second experiment. Key Results Plants inoculated with the appropriate rhizobia, Ensifer (syn. Sinorhizobium) medicae, formed nodules. Nodulated plants grew as well as plants fed NO3 -, both in drained and waterlogged conditions. The growth and total N content of nodulated plants (without any NO3 - supplied) indicated N2 fixation. Respiration rates (mass basis) were highest in nodules and root tips and lowest in basal root tissues. Secondary aerenchyma (phellem) formed along basal root parts and a thin layer of this porous tissue also covered nodules, which together enhanced gas-phase diffusion of O2 to the nodules; O2 was below detection within the infected zone of the nodule interior. Conclusions Melilotus siculus reliant on N2 fixation grew well both in drained and waterlogged conditions, and had similar tissue N concentrations. In waterlogged conditions the relatively high respiration rates of nodules must rely on O2 movement via the aerenchymatous phellem in hypocotyl, roots and the outer tissue layers of nodules.

AB - Background and Aims Soil waterlogging adversely impacts most plants. Melilotus siculus is a waterlogging-tolerant annual forage legume, but data were lacking for the effects of root-zone hypoxia on nodulated plants reliant on N2 fixation. The aim was to compare the waterlogging tolerance and physiology of M. siculus reliant on N2 fixation or with access to NO3 -. Methods A factorial experiment imposed treatments of water level (drained or waterlogged), rhizobia (nil or inoculated) and mineral N supply (nil or 11 mm NO3 -) for 21 d on plants in pots of vermiculite in a glasshouse. Nodulation, shoot and root growth and tissue N were determined. Porosity (gas volume per unit tissue volume) and respiration rates of root tissues and nodules, and O2 microelectrode profiling across nodules, were measured in a second experiment. Key Results Plants inoculated with the appropriate rhizobia, Ensifer (syn. Sinorhizobium) medicae, formed nodules. Nodulated plants grew as well as plants fed NO3 -, both in drained and waterlogged conditions. The growth and total N content of nodulated plants (without any NO3 - supplied) indicated N2 fixation. Respiration rates (mass basis) were highest in nodules and root tips and lowest in basal root tissues. Secondary aerenchyma (phellem) formed along basal root parts and a thin layer of this porous tissue also covered nodules, which together enhanced gas-phase diffusion of O2 to the nodules; O2 was below detection within the infected zone of the nodule interior. Conclusions Melilotus siculus reliant on N2 fixation grew well both in drained and waterlogged conditions, and had similar tissue N concentrations. In waterlogged conditions the relatively high respiration rates of nodules must rely on O2 movement via the aerenchymatous phellem in hypocotyl, roots and the outer tissue layers of nodules.

KW - Aerenchyma

KW - messina

KW - nitrogen fixation

KW - oxygen microelectrode profiling

KW - pasture legume

KW - phellem

KW - respiration

KW - root nodules

KW - soil flooding

KW - tissue porosity

KW - wetland legume plant

UR - http://www.scopus.com/inward/record.url?scp=85044308745&partnerID=8YFLogxK

U2 - 10.1093/aob/mcx202

DO - 10.1093/aob/mcx202

M3 - Article

VL - 121

SP - 699

EP - 709

JO - Annals of Botany

JF - Annals of Botany

SN - 0305-7364

IS - 4

ER -