Abstract
The effects of NO − 3 and NH + 4 nutrition on the rates of dark incorporation of inorganic carbon by roots of hydroponically grown Zea mays L. cv. 712 and on the metabolic products of this incorporation, were determined in plants supplied with NaH 14 CO 3 in the nutrient solution. The shoots and roots of the plants supplied with NaH 14 CO 3 in the root medium for 30 min were extracted with 80%; (v/v) ethanol and fractionated into soluble and insoluble fractions. The soluble fraction was further separated into the neutral, organic acid, amino acid and non‐polar fractions. The amino acid fraction was then analyzed to determine quantities and the 14 C content of its individual components. The rates of dark incorporation of inorganic carbon calculated from H 14 CO − 3 fixation and attributable to the activity of phosphoenolpyuvate carboxylase (EC 4.1.1.31), were 5‐fold higher in ammonium‐fed plants than in nitrate‐fed plants after a 30‐min pulse of 14 C. This activity forms a small, but significant component of the carbon budget of the root. The proportion of 14 C located in the shoots was also significantly higher in ammonium‐fed plants than in nitrate‐fed plants, indicating more rapid translocation of the products of dark fixation to the shoots in plants receiving NH + /sp 4 nutrition. Ammonium‐fed plants favoured incorporation of 14 C into amino acids, while nitrate‐fed plants allocated relatively more 14 C into organic acids. The amino acid composition was also dependent on the type of nitrogen supplied, and asparagine was found to accumulate in ammonium‐fed plants. The 14 C labelling of the amino acids was consistent with the diversion of 14 C‐oxaloacetate derived from carboxlyation of phosphoenolpyruvate into the formation of both asparatate and glutamate. The results support the conclusion that inorganic carbon fixation in the roots of maize plants provides an important anaplerotic source of carbon for NH + 4 assimilation.
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Claims 7
Claim · model-written summary
Ammonium-fed roots incorporated inorganic carbon at five times the rate of nitrate-fed roots.
- Treatment
- ammonium‐fed plantse0
- Gene
- phosphoenolpyuvate carboxylasee0
- Outcome
- rates of dark incorporation of inorganic carbone0
- Direction
- highere0
- Value
- 5‐folde0
- Comparator
- nitrate‐fed plantse0
Zea maysOrganisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize roots”
e0“rates of dark incorporation of inorganic carbon calculated from H 14 CO − 3 fixation and attributable to the activity of phosphoenolpyuvate carboxylase (EC 4.1.1.31), were 5‐fold higher in ammonium‐fed plants than in nitrate‐fed plants”
Claim · model-written summary
A higher proportion of labeled carbon reached shoots in ammonium-fed plants.
- Treatment
- ammonium‐fed plantse0
- Outcome
- proportion of 14 C located in the shootse0
- Direction
- highere0
- Comparator
- nitrate‐fed plantse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize roots”
e0“The proportion of 14 C located in the shoots was also significantly higher in ammonium‐fed plants than in nitrate‐fed plants”
Claim · model-written summary
Ammonium-fed plants allocated more labeled carbon into amino acids.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize roots”
e0“Ammonium‐fed plants favoured incorporation of 14 C into amino acids”
Claim · model-written summary
Nitrate-fed plants allocated relatively more labeled carbon into organic acids.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize roots”
e0“nitrate‐fed plants allocated relatively more 14 C into organic acids”
Claim · model-written summary
Asparagine accumulated in ammonium-fed plants.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize roots”
e0“asparagine was found to accumulate in ammonium‐fed plants”
Claim · model-written summary
Labeling was consistent with carbon from oxaloacetate entering aspartate and glutamate formation.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize roots”
e0“The 14 C labelling of the amino acids was consistent with the diversion of 14 C‐oxaloacetate derived from carboxlyation of phosphoenolpyruvate into the formation of both asparatate and glutamate”
Claim · model-written summary
Root inorganic carbon fixation provides an anaplerotic carbon source for ammonium assimilation.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“maize roots”
e0“inorganic carbon fixation in the roots of maize plants provides an important anaplerotic source of carbon for NH + 4 assimilation”
The same questions in other papers
nitrogen · molecular: metabolites · Zea mays (maize)Positive and negative results
94 papers in the same direction as this paper · 43 in the opposite direction · 4 reporting no difference from an alternative
- no effect
- no effect
- negative
138 papers more in this group
See all 142 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.