Abstract
An acetylene reduction (AR) assay was used to measure nitrogenase activity of soil cores as an estimate of the rate of nitrogen (N2-) fixation in nodulated Medicago truncatula cv Jemalong in the field on several occasions during the growing season. The effects of date of sowing and of varying the density of sowing from 0 to 1 000 kg ha-1 seed were investigated. Results showed an increase in AR activity with increasing medic sowing densities during the vegetative period of plant growth, whereas towards maturity AR activity was slightly higher at low than at medium or high densities. Soil core AR activity was better correlated with the weight of shoot dry matter (DM) present at the time of harvest during the vegetative period of plant growth than after flowering. At all sowing densities and irrespective of sowing date, AR activity increased from sowing to full flowering and thereafter decreased rapidly. The post-flowering decline in AR activity was sharper at the high than at the lower densities and coincided with a marked decrease in plant population in the medium and high-sowing density treatments. The relations between AR activity, shoot dry weight and plant number per unit area in the pre-flowering and post-flowering periods were examined via linear regression analysis.
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Claims 7
Claim · model-written summary
Acetylene reduction activity increased with sowing density during vegetative growth.
Verbatim
e0“Results showed an increase in AR activity with increasing medic sowing densities during the vegetative period of plant growth”
t0“Medicago truncatula”
Claim · model-written summary
Near maturity, acetylene reduction activity was slightly higher at low sowing density.
Verbatim
e0“towards maturity AR activity was slightly higher at low than at medium or high densities”
t0“Medicago truncatula”
Claim · model-written summary
Acetylene reduction activity correlated better with shoot dry matter in vegetative growth than after flowering.
- Taxon
- Medicago truncatula
Medicago truncatulat0 - Organ / stage
- shoote0
- Outcome
- Soil core AR activitye0
- Direction
- better correlatede0
- Comparator
- after floweringe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Soil core AR activity was better correlated with the weight of shoot dry matter (DM) present at the time of harvest during the vegetative period of plant growth than after flowering”
t0“Medicago truncatula”
Claim · model-written summary
Acetylene reduction activity rose from sowing to full flowering.
- Taxon
- Medicago truncatulaMedicago truncatulat0
- Organ / stage
- full floweringe0
- Outcome
- AR activitye0
- Direction
- increasede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“AR activity increased from sowing to full flowering”
t0“Medicago truncatula”
Claim · model-written summary
Acetylene reduction activity declined rapidly after full flowering.
- Taxon
- Medicago truncatulaMedicago truncatulat0
- Organ / stage
- full floweringe0
- Outcome
- AR activitye0
- Direction
- decreased rapidlye0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“AR activity increased from sowing to full flowering and thereafter decreased rapidly”
t0“Medicago truncatula”
Claim · model-written summary
The decline after flowering was sharper at high than lower sowing densities.
- Taxon
- Medicago truncatulaMedicago truncatulat0
- Treatment
- highe0
- Outcome
- AR activitye0
- Direction
- sharpere0
- Comparator
- lower densitiese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The post-flowering decline in AR activity was sharper at the high than at the lower densities”
t0“Medicago truncatula”
Claim · model-written summary
Plant population decreased markedly in medium and high sowing density treatments.
- Taxon
- Medicago truncatulaMedicago truncatulat0
- Treatment
- medium and high-sowing density treatmentse0
- Outcome
- plant populatione0
- Direction
- decreasee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“a marked decrease in plant population in the medium and high-sowing density treatments”
t0“Medicago truncatula”