Abstract
Supplying wheat plants with mixtures of NO 3 ‐ and NH 4 + increases growth and tiller production, but the physiological basis is unclear. Our objectives were to evaluate the roles for cytokinins and N use (e.g., accumulation, distribution, and utilization of absorbed N to produce tillers) in eliciting this response. Two species of spring wheat ( Triticum aestivum L. cv. Len and Triticum durum Desf. cv. Inbar) were grown hydroponically in the greenhouse with N supplied as all NO 3 ‐ , all NH 4 + , or an equal mixture of each form. In one experiment, the synthetic cytokinin N 6 ‐benzylaminopurine (100 µ M ) was applied repeatedly (a total of five times) to the shoots during tiller initiation and development, while in another, xylem exudate was collected from cut stumps during the early stages of tiller development. Plants not sprayed with cytokinins produced more tillers and accumulated more N when grown with mixed N than with either N form alone. Cytokinin sprays did not affect tillering of mixed N plants but increased tillers in all‐NO 3 ‐ grown or all‐NH 4 + ‐grown plants to levels close to that obtained with mixed N. For unsprayed plants, the presence of NH 4 + increased the shoot/root ratio, the proportion of N in the shoot, and the efficiency with which absorbed N was used to produce tillers, compared with plants grown with all NO 3 ‐ . Exogenous cytokinin appeared to mimic the effects of mixed N (and in some cases NH 4 + ) in altering the distribution and use of N by the plant. In addition, plants grown with mixed N or all NH 4 + exhibited higher concentrations and mass transfer of cytokinins in the xylem than those supplied with all NO 3 ‐ . These data are consistent with the interpretation that mixed N enhancement of tillering in wheat is due to increased synthesis of cytokinins, induced in part by use of NH 4 + ‐N.
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Claims 8
Claim · model-written summary
Wheat plants not sprayed with cytokinins produced more tillers when grown with mixed N than with either N form alone.
- Taxon
- Wheat
Triticum aestivumt0 - Treatment
- mixed Ne0
- Outcome
- tillerse0
- Direction
- moree0
- Qualifier
- Plants not sprayed with cytokininse0
- Comparator
- either N form alonee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Wheat”
e0“Plants not sprayed with cytokinins produced more tillers and accumulated more N when grown with mixed N than with either N form alone”
Claim · model-written summary
Wheat plants not sprayed with cytokinins accumulated more N when grown with mixed N than with either N form alone.
- Taxon
- WheatTriticum aestivumt0
- Treatment
- mixed Ne0
- Outcome
- accumulated more Ne0
- Direction
- moree0
- Qualifier
- Plants not sprayed with cytokininse0
- Comparator
- either N form alonee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Wheat”
e0“Plants not sprayed with cytokinins produced more tillers and accumulated more N when grown with mixed N than with either N form alone”
Claim · model-written summary
Cytokinin sprays did not affect tillering of wheat plants grown with mixed N.
- Taxon
- WheatTriticum aestivumt0
- Treatment
- Cytokinin sprayse0
- Outcome
- tillering of mixed N plantse0
- Direction
- did not affecte0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Wheat”
e0“Cytokinin sprays did not affect tillering of mixed N plants”
Claim · model-written summary
Cytokinin sprays increased tillers in wheat plants grown with all nitrate or all ammonium to levels close to those obtained with mixed N.
- Taxon
- WheatTriticum aestivumt0
- Treatment
- Cytokinin sprayse0
- Outcome
- tillerse0
- Direction
- increasede0
- Qualifier
- to levels close to that obtained with mixed Ne0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Wheat”
e0“Cytokinin sprays did not affect tillering of mixed N plants but increased tillers in all‐NO 3 ‐ grown or all‐NH 4 + ‐grown plants to levels close to that obtained with mixed N”
Claim · model-written summary
In unsprayed wheat, the presence of NH4+ increased the shoot/root ratio, the proportion of N in the shoot and the efficiency of using absorbed N to produce tillers compared with plants grown with all NO3-.
- Taxon
- WheatTriticum aestivumt0
- Treatment
- the presence of NH 4 +e0
- Outcome
- shoot/root ratio, the proportion of N in the shoot, and the efficiency with which absorbed N was used to produce tillerse0
- Direction
- increasede0
- Comparator
- plants grown with all NO 3 ‐e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Wheat”
e0“For unsprayed plants, the presence of NH 4 + increased the shoot/root ratio, the proportion of N in the shoot, and the efficiency with which absorbed N was used to produce tillers, compared with plants grown with all NO 3 ‐”
Claim · model-written summary
Exogenous cytokinin appeared to mimic the effects of mixed N in altering the distribution and use of N by wheat.
- Taxon
- WheatTriticum aestivumt0
- Treatment
- Exogenous cytokinine0
- Outcome
- distribution and use of Ne0
- Direction
- alteringe0
- Comparator
- mixed Ne0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Wheat”
e0“Exogenous cytokinin appeared to mimic the effects of mixed N (and in some cases NH 4 + ) in altering the distribution and use of N by the plant”
Claim · model-written summary
Wheat plants grown with mixed N or all NH4+ had higher xylem concentrations and mass transfer of cytokinins than plants supplied with all NO3-.
- Taxon
- WheatTriticum aestivumt0
- Organ / stage
- xyleme0
- Treatment
- mixed N or all NH 4 +e0
- Outcome
- concentrations and mass transfer of cytokininse0
- Direction
- highere0
- Comparator
- those supplied with all NO 3 ‐e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
t0“Wheat”
e0“plants grown with mixed N or all NH 4 + exhibited higher concentrations and mass transfer of cytokinins in the xylem than those supplied with all NO 3 ‐”
Claim · model-written summary
The authors interpret the mixed-N enhancement of tillering in wheat as due to increased cytokinin synthesis, induced in part by use of NH4+-N.
- Taxon
- wheatTriticum aestivume0
- Treatment
- mixed Ne0
- Compound
- cytokininse0
- Outcome
- enhancement of tilleringe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“mixed N enhancement of tillering in wheat is due to increased synthesis of cytokinins, induced in part by use of NH 4 +”
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