Abstract
Nitrate uptake and in vivo , nitrate reductase activity (NRA) in roots of Phaseolus vulgaris , L. cv. Witte Krombek were measured in nitrogen‐depleted plants of varying sugar status, Variation in sugar status was achieved at the start of nitrate nutrition by excision, ringing, darkness or administration of sugars to the root medium. The shape of the apparent induction pattern of nitrate uptake was not influenced by the sugar status of the absorbing tissue. When measured after 6 h of nitrate nutrition (0.1 mol m −3 ), steady state nitrate uptake and root NRA were in the order intact>dark>ringed>excised. Exogenous sucrose restored NRA in excised roots to the level of intact plants. The nitrate uptake rate of excised roots, however, was not fully restored by sucrose (0.03–300 mol m −3 ). When plants were decapitated after an 18 h NO 3 − pretreatment, the net uptake rate declined gradually to become negative after three hours. This decline was slowed down by exogenous fructose, whilst glucose rapidly (sometimes within 5 min) stimulated NG − 3 uptake. Presumably due to a difference in NO 3 − due to a difference in NO 3 − uptake, the NRA of excised roots was also higher in the presence of glucose than in the presence of fructose after 6 h of nitrate nutrition. The sugar‐stimulation of, oxygen consumption as well as the release of 14 CO 2 from freshly absorbed (U‐ 14 C) sugar was the same for glucose and fructose. Therefore, we propose a glucose‐specific effect on NO 3 − uptake that is due to the presence of glucose rather than to its utilization in root respiration. A differential glucose‐fructose effect on nitrate reductase activity independent of the effect on NO 3 − uptake was not indicated. A constant level of NRA occurred in roots of NO 3 − induced plants. Removal of nutrient nitrate from these plants caused an exponential NRA decay with an approximate half‐life of 12 h in intact plants and 5.5 h in excised roots. The latter value was also found in roots that were excised in the presence of nitrate, indicating that the sugar status primarily determines the apparent rate of nitrate reductase decay in excised roots.
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Claims 18
Claim · model-written summary
Sugar status did not influence the apparent induction pattern of nitrate uptake.
Verbatim
e0“The shape of the apparent induction pattern of nitrate uptake was not influenced by the sugar status of the absorbing tissue”
t0“dwarf bean”
Claim · model-written summary
After 6 hours, steady-state nitrate uptake ranked intact above dark, ringed and excised plants.
Verbatim
e0“steady state nitrate uptake and root NRA were in the order intact>dark>ringed>excised”
t0“dwarf bean”
Claim · model-written summary
After 6 hours, root nitrate reductase activity ranked intact above dark, ringed and excised plants.
Verbatim
e0“steady state nitrate uptake and root NRA were in the order intact>dark>ringed>excised”
t0“dwarf bean”
Claim · model-written summary
Exogenous sucrose restored nitrate reductase activity in excised roots to intact plant levels.
Verbatim
e0“Exogenous sucrose restored NRA in excised roots to the level of intact plants”
t0“dwarf bean”
Claim · model-written summary
Sucrose did not fully restore nitrate uptake in excised roots.
- Taxon
- dwarf beant0
- Treatment
- sucrose (0.03–300 mol m −3 )e0
- Outcome
- nitrate uptake rate of excised rootse0
- Direction
- not fully restorede0
Not reportedComparator
Verbatim
e0“The nitrate uptake rate of excised roots, however, was not fully restored by sucrose (0.03–300 mol m −3 )”
t0“dwarf bean”
Claim · model-written summary
Decapitation after nitrate pretreatment caused net uptake to decline and become negative after three hours.
- Taxon
- dwarf beant0
- Treatment
- decapitated after an 18 h NO 3 − pretreatmente0
- Outcome
- net uptake ratee0
- Direction
- declinede0
- Value
- three hourse0
Not reportedComparator
Verbatim
e0“When plants were decapitated after an 18 h NO 3 − pretreatment, the net uptake rate declined gradually to become negative after three hours”
t0“dwarf bean”
Claim · model-written summary
Exogenous fructose slowed the decline in net nitrate uptake after decapitation.
Not reportedComparator
Verbatim
e0“This decline was slowed down by exogenous fructose”
t0“dwarf bean”
Claim · model-written summary
Glucose rapidly stimulated nitrate uptake, sometimes within five minutes.
Not reportedComparator
Verbatim
e0“glucose rapidly (sometimes within 5 min) stimulated NG − 3 uptake”
t0“dwarf bean”
Claim · model-written summary
Excised-root nitrate reductase activity was higher with glucose than fructose after six hours.
Verbatim
e0“the NRA of excised roots was also higher in the presence of glucose than in the presence of fructose after 6 h of nitrate nutrition”
t0“dwarf bean”
Claim · model-written summary
Glucose and fructose stimulated oxygen consumption equally.
Verbatim
e0“The sugar‐stimulation of, oxygen consumption as well as the release of 14 CO 2 from freshly absorbed (U‐ 14 C) sugar was the same for glucose and fructose”
t0“dwarf bean”
Claim · model-written summary
Glucose and fructose stimulated labeled carbon dioxide release equally.
Verbatim
e0“The sugar‐stimulation of, oxygen consumption as well as the release of 14 CO 2 from freshly absorbed (U‐ 14 C) sugar was the same for glucose and fructose”
t0“dwarf bean”
Claim · model-written summary
The authors propose a glucose-specific effect on nitrate uptake due to glucose presence rather than respiration.
Verbatim
e0“we propose a glucose‐specific effect on NO 3 − uptake that is due to the presence of glucose rather than to its utilization in root respiration”
t0“dwarf bean”
Claim · model-written summary
There was no indicated differential glucose–fructose effect on nitrate reductase independent of nitrate uptake.
Verbatim
e0“A differential glucose‐fructose effect on nitrate reductase activity independent of the effect on NO 3 − uptake was not indicated”
t0“dwarf bean”
Claim · model-written summary
Nitrate-induced roots maintained constant nitrate reductase activity.
Verbatim
e0“A constant level of NRA occurred in roots of NO 3 − induced plants”
t0“dwarf bean”
Claim · model-written summary
Removing nitrate caused exponential nitrate reductase decay with a roughly 12-hour half-life in intact plants.
- Taxon
- dwarf beant0
- Treatment
- Removal of nutrient nitratee0
- Outcome
- NRA decaye0
- Direction
- decaye0
- Value
- 12 he0
Not reportedComparator
Verbatim
e0“Removal of nutrient nitrate from these plants caused an exponential NRA decay with an approximate half‐life of 12 h in intact plants”
t0“dwarf bean”
Claim · model-written summary
Removing nitrate caused exponential nitrate reductase decay with a 5.5-hour half-life in excised roots.
Verbatim
e0“Removal of nutrient nitrate from these plants caused an exponential NRA decay with an approximate half‐life of 12 h in intact plants and 5.5 h in excised roots”
t0“dwarf bean”
Claim · model-written summary
Roots excised with nitrate present also had a 5.5-hour nitrate reductase decay half-life.
Verbatim
e0“The latter value was also found in roots that were excised in the presence of nitrate”
t0“dwarf bean”
Claim · model-written summary
The authors infer that sugar status primarily sets the apparent nitrate reductase decay rate in excised roots.
Verbatim
e0“the sugar status primarily determines the apparent rate of nitrate reductase decay in excised roots”
t0“dwarf bean”
The same questions in other papers
glucose · nutrient: content · Phaseolus vulgaris (common bean)Results agree
1 paper in the same direction as this paper
- positive
nitrogen · physiology: enzyme activity · Phaseolus vulgaris (common bean)Positive and negative results
3 papers in the same direction as this paper · 3 in the opposite direction
- positive
- positive
- positive
3 papers more in this group
See all 7 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.