Table II.

Starch levels in shoots of wild-type and NR-null mutant

TreatmentTime DaysStarch Content ± STERR (Percentage of N-Starved)
Wild TypeNR-Null Mutant
Control1010.0 ± 1.1 (27%)7.8 ± 0.8 (23%)
N-starved1336.4 ± 1.4 (100%)33.9 ± 1.8 (100%)
Nitrate13 + 7 h29.6 ± 1.8 (81%)34.8 ± 1.5 (103%)
Ammonium13 + 7 h26.9 ± 0.91 (74%)25.0 ± 1.1 (74%)
Gln13 + 7 h30.1 ± 1.7 (82%)22.6 ± 1.3 (67%)
  • Plants were cultivated for 10 d in media with nitrogen (control) then transferred into N-free medium for additional 3 d (N-starved). At day 13, plants were treated with 250 μm of the indicated nitrogen sources (nitrate, ammonium, and glutamine) for 7 h, then the starch content in leaves was determined as described in “Materials and Methods.” Starch contents were expressed as μmol of Glc equivalents per milligram of fresh weight. ses were calculated from five to seven replicate measurements. The percentage of starch content in relation to N-starved plants (day 13) is given in parentheses.