Table 5. The effect of a late spring frost on 15N uptake by leaf protein during nutrition of wheat from a mixture of different forms of nitrogen. N-protein content is from the dry weight of two plants.
 Assay and variant  Within 1 day  Within 3 days    Within 9 days
 N protein content (mg)  Weight % (excess ^15^N)  ^15^N protein content (mg)  N protein content (mg)  Weight % (excess ^15^N)  ^15^N protein content (mg)  N protein content (mg)  Weight % (excess ^15^N)  ^15^N protein content (mg)
 Control  4.19 ± 0.36  0.33  14.5 ± 0.70  3.65 ± 0.20  0.95  36.5 ± 2.41  6.08 ± 0.46  2.14  137.0 ± 5.02
 I; frost  3.77 ± 0.05  0.42  16.6 ± 0.73  4.11 ± 0.22  0.67  29.0 ± 1.53  6.17 ±0.15  2.29  148.8 ± 7.41
 
 Control  4.46 ± 0.07  0.02  0.90 ± 0.06  4.23 ± 0.33  0.24  11.3 ± 0.83  7.41 ±0.12  0.89  73.8 ± 8.01
 II; frost  4.01 ± 0.22  0.05  2.20 ± 0.17  4.19 ± 0.18  0.32  15.0 ± 1.03  6.88 ± 0.18  1.50  115.6 ± 8.15
 
 Control  4.19 ± 0.09  1.12  50.2 ± 4.31  4.23 ± 0.11  4.32  195.5 ± 8.13  7.62 ± 0.16  6.78  552.9 ± 27.00
 II; frost  4.45 ± 0.41  1.09  51.9 ± 3.81  4.22 ± 0.15  4.99  225.3 ± 9.41  7.46 ± 0.04  10.37  827.9 ± 41.30