Abstract
The aim of this study was to determine the relationship between shoot nitrate concentration, mediated by nitrate supply to roots, and root exudation from Hordeum vulgare. Plants were grown for 14 d in C-free sand microcosms, supplied with nutrient solution containing 2 mM nitrate. After this period, three treatments were applied for a further 14 d: (A) continued supply with 2 mM nitrate (zero boost), (B) supply with 10 mM nitrate (low boost), and (C) supply with 20 mM nitrate (high boost). At the end of the treatment period, a bacterial biosensor (Pseudomonas fluorescens 10586 pUCD607, marked with the lux CDABE genes for bioluminescence) was applied to the microcosms to report on C-substrate availability, as a consequence of root exudation. The nitrate boost treatments significantly affected shoot nitrate concentrations, in the order C>B>A. In treatments receiving a nitrate boost (B, C), increased shoot nitrate concentration was correlated with increased plant biomass, reduced root length, reduced number of root tips, and increased mean root diameter, relative to the no boost treatment (A). Imaging of biosensor bioluminescence (proportional to metabolic activity in response to availability of root exudates) indicated that root exudation increased with decreasing shoot nitrate concentration. Biosensor reporting of root C-flow indicated that exudation was greater from root tip regions than from the whole root, but that specific exudation rates for all sites were unaffected by treatments. Total root exudation across treatments was found to be closely correlated with total root length, indicating that increased root exudation, per unit root biomass, with decreasing nitrate supply was associated with altered root morphology, as a consequence of systemic plant responses to internal N-status.
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Claims 10
Claim · model-written summary
Nitrate boosts significantly increased shoot nitrate concentration in C>B>A order.
- Taxon
- Hordeum vulgare
.jpg?width=60)
Hordeum vulgaret0 - Treatment
- nitrate boost treatmentse0
- Outcome
- shoot nitrate concentrationse0
- Direction
- higherinferrede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
.jpg?width=500)
Verbatim
e0“The nitrate boost treatments significantly affected shoot nitrate concentrations, in the order C>B>A”
t0“Hordeum vulgare”
Claim · model-written summary
Higher shoot nitrate concentration correlated with increased plant biomass.
- Taxon
- Hordeum vulgareHordeum vulgaret0
- Compound
- nitratee0
- Outcome
- plant biomasse0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increased shoot nitrate concentration was correlated with increased plant biomass”
t0“Hordeum vulgare”
Claim · model-written summary
Higher shoot nitrate concentration correlated with reduced root length.
- Taxon
- Hordeum vulgareHordeum vulgaret0
- Compound
- nitratee0
- Outcome
- root lengthe0
- Direction
- reducede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increased shoot nitrate concentration was correlated with increased plant biomass, reduced root length”
t0“Hordeum vulgare”
Claim · model-written summary
Higher shoot nitrate concentration correlated with fewer root tips.
- Taxon
- Hordeum vulgareHordeum vulgaret0
- Compound
- nitratee0
- Outcome
- number of root tipse0
- Direction
- reducede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increased shoot nitrate concentration was correlated with increased plant biomass, reduced root length, reduced number of root tips”
t0“Hordeum vulgare”
Claim · model-written summary
Higher shoot nitrate concentration correlated with increased mean root diameter.
- Taxon
- Hordeum vulgareHordeum vulgaret0
- Compound
- nitratee0
- Outcome
- mean root diametere0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increased shoot nitrate concentration was correlated with increased plant biomass, reduced root length, reduced number of root tips, and increased mean root diameter”
t0“Hordeum vulgare”
Claim · model-written summary
Root exudation increased as shoot nitrate concentration decreased.
- Taxon
- Hordeum vulgareHordeum vulgaret0
- Compound
- nitratee0
- Outcome
- root exudatione0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“root exudation increased with decreasing shoot nitrate concentration”
t0“Hordeum vulgare”
Claim · model-written summary
Root tip regions exuded more carbon than the whole root.
- Taxon
- Hordeum vulgareHordeum vulgaret0
- Organ / stage
- root tip regionse0
- Outcome
- exudatione0
- Direction
- greatere0
- Comparator
- the whole roote0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“exudation was greater from root tip regions than from the whole root”
t0“Hordeum vulgare”
Claim · model-written summary
Specific exudation rates were unaffected by treatments.
- Taxon
- Hordeum vulgareHordeum vulgaret0
- Treatment
- treatmentse0
- Outcome
- specific exudation ratese0
- Direction
- unaffectede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“specific exudation rates for all sites were unaffected by treatments”
t0“Hordeum vulgare”
Claim · model-written summary
Total root exudation correlated closely with total root length.
- Taxon
- Hordeum vulgareHordeum vulgaret0
- Organ / stage
- root lengthe0
- Outcome
- Total root exudatione0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Total root exudation across treatments was found to be closely correlated with total root length”
t0“Hordeum vulgare”
Claim · model-written summary
Greater exudation per root biomass at lower nitrate supply was associated with altered root morphology.
- Taxon
- Hordeum vulgareHordeum vulgaret0
- Treatment
- decreasing nitrate supplye0
- Outcome
- root exudation, per unit root biomasse0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increased root exudation, per unit root biomass, with decreasing nitrate supply was associated with altered root morphology”
t0“Hordeum vulgare”