Abstract
According to the Dijkshoorn-Ben Zioni model, NO3− uptake in the roots is stimulated by NO3− assimilation in the shoots, through downward phloem transport of malate synthesized in response to reduction of NO2− to NH3. In this paper, one hypothesis resulting from this model was tested, i.e. that the diurnal changes in NO3− uptake are due to the light dependence of NO3− reduction in the leaves. This dependence was studied in detached leaves transferred to deionized water or supplied via the transpiration stream with similar amounts of 15NO3− in light or darkness. In the dark, the reduction of previously stored NO3− or xylem-borne 15NO3− was generally about 40–50% of that measured in the light. Glucose supply to the detached leaves stimulated NO3− reduction in the dark, but not enough to increase it up to the same rate as in the light. Nitrite reduction in detached leaves was much less affected by darkness, and could be maintained at a high level by exogenous supply of substrate. Advantage was taken from this last observation to sustain NO2−reduction in attached darkened shoots at the same rate as in the light, by ensuring an appropriate delivery of NO2− from the xylem. Although this was assumed to restore the light level of the associated synthesis of malate, it led to a marked inhibition of NO3− uptake. In addition, the direct supply of malate to the shoots or to the roots failed to prevent the decrease of NO3− uptake in darkness. Thus, our conclusion is that the mechanisms evoked in the Dijkshoorn-Ben Zioni model do not play an important role in the diurnal variations of NO3− uptake in soybean plants.
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Claims 7
Claim · model-written summary
In darkness, the reduction of stored or xylem-borne NO3- is about 40–50% of the light rate.
- Taxon
- soybean
Glycine maxe6 - Treatment
- In the darke1
- Outcome
- reduction of previously stored NO3− or xylem-borne 15NO3−e1
- Direction
- reductione1
- Value
- 40–50%e1
- Comparator
- lighte1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e1“In the dark, the reduction of previously stored NO3− or xylem-borne 15NO3− was generally about 40–50% of that measured in the light”
e6“Thus, our conclusion is that the mechanisms evoked in the Dijkshoorn-Ben Zioni model do not play an important role in the diurnal variations of NO3− uptake in soybean plants”
Claim · model-written summary
Glucose supply stimulates NO3- reduction in darkness but not up to the light rate.
- Taxon
- soybeanGlycine maxe6
- Treatment
- Glucose supplye2
- Outcome
- NO3− reductione2
- Direction
- stimulatede2
- Qualifier
- not enough to increase it up to the same rate as in the lighte2
- Comparator
- same rate as in the lighte2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e2“Glucose supply to the detached leaves stimulated NO3− reduction in the dark, but not enough to increase it up to the same rate as in the light”
e6“Thus, our conclusion is that the mechanisms evoked in the Dijkshoorn-Ben Zioni model do not play an important role in the diurnal variations of NO3− uptake in soybean plants”
Claim · model-written summary
Nitrite reduction is much less affected by darkness.
- Taxon
- soybeanGlycine maxe6
- Treatment
- darknesse3
- Outcome
- Nitrite reductione3
- Direction
- much less affectede3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e3“Nitrite reduction in detached leaves was much less affected by darkness, and could be maintained at a high level by exogenous supply of substrate”
e6“Thus, our conclusion is that the mechanisms evoked in the Dijkshoorn-Ben Zioni model do not play an important role in the diurnal variations of NO3− uptake in soybean plants”
Claim · model-written summary
Exogenous supply of substrate maintains nitrite reduction at a high level in darkness.
- Taxon
- soybeanGlycine maxe6
- Treatment
- exogenous supply of substratee3
- Outcome
- Nitrite reductione3
- Direction
- maintainede3
- Qualifier
- at a high levele3
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e3“Nitrite reduction in detached leaves was much less affected by darkness, and could be maintained at a high level by exogenous supply of substrate”
e6“Thus, our conclusion is that the mechanisms evoked in the Dijkshoorn-Ben Zioni model do not play an important role in the diurnal variations of NO3− uptake in soybean plants”
Claim · model-written summary
Delivery of NO2- from the xylem to darkened shoots markedly inhibits NO3- uptake.
- Taxon
- soybeanGlycine maxe6
- Treatment
- an appropriate delivery of NO2− from the xyleme4
- Outcome
- NO3− uptakee4
- Direction
- marked inhibitione4
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e4“by ensuring an appropriate delivery of NO2− from the xylem. Although this was assumed to restore the light level of the associated synthesis of malate, it led to a marked inhibition of NO3− uptake”
e6“Thus, our conclusion is that the mechanisms evoked in the Dijkshoorn-Ben Zioni model do not play an important role in the diurnal variations of NO3− uptake in soybean plants”
Claim · model-written summary
Direct supply of malate to shoots or roots fails to prevent the decrease of NO3- uptake in darkness.
- Taxon
- soybeanGlycine maxe6
- Treatment
- direct supply of malatee5
- Outcome
- decrease of NO3− uptake in darknesse5
- Direction
- failed to prevente5
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e5“the direct supply of malate to the shoots or to the roots failed to prevent the decrease of NO3− uptake in darkness”
e6“Thus, our conclusion is that the mechanisms evoked in the Dijkshoorn-Ben Zioni model do not play an important role in the diurnal variations of NO3− uptake in soybean plants”
Claim · model-written summary
The mechanisms of the Dijkshoorn-Ben Zioni model do not play an important role in diurnal NO3- uptake variation in soybean.
- Taxon
- soybeanGlycine maxe6
- Outcome
- diurnal variations of NO3− uptakee6
- Qualifier
- the mechanisms evoked in the Dijkshoorn-Ben Zioni modele6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e6“Thus, our conclusion is that the mechanisms evoked in the Dijkshoorn-Ben Zioni model do not play an important role in the diurnal variations of NO3− uptake in soybean plants”
The same questions in other papers
malate · nutrient: content · Glycine max (soybean)Positive and negative results
1 in the opposite direction
- positive
growing medium · molecular: metabolites · Glycine max (soybean)Positive and negative results
3 papers in the same direction as this paper · 1 in the opposite direction
- negative
- positive
- positive
1 paper more in this group
See all 5 papers →light · molecular: metabolites · Glycine max (soybean)Positive and negative results
26 papers in the same direction as this paper · 20 in the opposite direction · 1 reporting no difference from an alternative
- negative
- no effect
- negative
44 papers more in this group
See all 48 papers →Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.