Abstract
Birdsfoot trefoil ( Lotus corniculatus L.) has both low rates of N 2 fixation and low levels of root total nonstructural carbohydrate (TNC) during midsummer regrowth. These observations suggest that reduced assimilate transport to roots may limit N 2 fixation and consequently total plant growth. The objective of this study was to determine how rate of growth, as influenced by N supply, affected the distribution and accumulation of photosynthate during regrowth of trefoil. Nutrient solution supplied to well‐nodulated plants grown in sand was either 0 or 1 mM N (NH 4 NO 3 ). Two and 4 weeks after cutting and the start of N treatments, plants were harvested and analyzed. Supplemental N caused a sharp decrease in acetylene reduction rate and a two‐fold increase in shoot dry weight 4 weeks after cutting. However, neither root dry weight nor TNC were significantly affected by supplemental N. Distribution of 14 C showed reduced amounts of photosynthate accumulated in N supplemented roots at both 2 and 4 weeks after cutting. These data suggest that shoot growth of trefoil is a dominant sink for photosynthate and that photosynthate accumulation is not readily altered by N source or amount supplied. Numerous significant differences in distribution of 14 C among classes of metabolites were evident only at the 2‐week harvest. More rapid metabolism of labeled sugars into other growth intermediates in N‐supplemented plants at this stage indicates that available soil N may be very important for rapid regrowth after cutting. Four weeks after cutting, when N 2 fixation rates had increased several fold, distribution of 14 C among various metabolites was not influenced by N source indicating little effect of N source on rate of assimilate metabolism in the plant.
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Claims 12
Claim · model-written summary
Supplemental nitrogen sharply decreased acetylene reduction rate four weeks after cutting.
Verbatim
e0“Supplemental N caused a sharp decrease in acetylene reduction rate and a two‐fold increase in shoot dry weight 4 weeks after cutting.”
e1“either 0 or 1 mM N”
t0“Birdsfoot Trefoil”
Claim · model-written summary
Supplemental nitrogen doubled shoot dry weight four weeks after cutting.
Verbatim
e0“Supplemental N caused a sharp decrease in acetylene reduction rate and a two‐fold increase in shoot dry weight 4 weeks after cutting.”
e1“either 0 or 1 mM N”
t0“Birdsfoot Trefoil”
Claim · model-written summary
Supplemental nitrogen did not significantly affect root dry weight.
Not reportedDirection
Verbatim
e0“neither root dry weight nor TNC were significantly affected by supplemental N.”
e1“either 0 or 1 mM N”
t0“Birdsfoot Trefoil”
Claim · model-written summary
Supplemental nitrogen did not significantly affect root total nonstructural carbohydrate.
Not reportedDirection
Verbatim
e0“neither root dry weight nor TNC were significantly affected by supplemental N.”
e1“either 0 or 1 mM N”
t0“Birdsfoot Trefoil”
Claim · model-written summary
Nitrogen-supplemented roots accumulated less photosynthate at both two and four weeks after cutting.
Verbatim
e0“Distribution of 14 C showed reduced amounts of photosynthate accumulated in N supplemented roots at both 2 and 4 weeks after cutting.”
e1“either 0 or 1 mM N”
t0“Birdsfoot Trefoil”
Claim · model-written summary
Shoot growth was interpreted as the dominant photosynthate sink.
Verbatim
e0“shoot growth of trefoil is a dominant sink for photosynthate”
t0“Birdsfoot Trefoil”
Claim · model-written summary
Photosynthate accumulation was interpreted as resistant to changes in nitrogen source or supply.
Verbatim
e0“photosynthate accumulation is not readily altered by N source or amount supplied.”
t0“Birdsfoot Trefoil”
Claim · model-written summary
Metabolite classes differed significantly in radiolabel distribution only at the two-week harvest.
Verbatim
e0“Numerous significant differences in distribution of 14 C among classes of metabolites were evident only at the 2‐week harvest.”
t0“Birdsfoot Trefoil”
Claim · model-written summary
At two weeks, labeled sugars were metabolized more rapidly into growth intermediates in nitrogen-supplemented plants.
Verbatim
e0“More rapid metabolism of labeled sugars into other growth intermediates in N‐supplemented plants at this stage”
e1“either 0 or 1 mM N”
t0“Birdsfoot Trefoil”
Claim · model-written summary
Available soil nitrogen was interpreted as potentially important for rapid regrowth after cutting.
Verbatim
e0“available soil N may be very important for rapid regrowth after cutting.”
t0“Birdsfoot Trefoil”
Claim · model-written summary
Nitrogen fixation rates had increased severalfold by four weeks after cutting.
Verbatim
e0“Four weeks after cutting, when N 2 fixation rates had increased several fold”
t0“Birdsfoot Trefoil”
Claim · model-written summary
Nitrogen source did not influence radiolabel distribution among metabolites at four weeks.
- Taxon
- Birdsfoot Trefoilt0
- Treatment
- N sourcee0
- Outcome
- distribution of 14 C among various metabolitese0
- Comparator
- 0e1
Not reportedDirection
Verbatim
e0“distribution of 14 C among various metabolites was not influenced by N source”
e1“either 0 or 1 mM N”
t0“Birdsfoot Trefoil”