Table 1. Mean values of GY, gs, and stable isotope compositions (‰) of δ2H, δ18O, and δ13C.
Mean values of GY, gs, and stable isotope composition (‰) of δ2H, δ18O, and δ13C of DM and the WSF of different plant parts (flag leaves, ears, and roots) sampled at mid-grain-filling plus mature kernels (grains) and in the water from the basal part of the stem [stem water (stem W)] under SI, RF, N fertilized (HN), and nonfertilized (LN) conditions, as examined in modern cultivars (cultivars) and old landraces (landraces) We measured δ13C DM and δ13C WSF, and δ18O WSF and δ2H WSF in 108 plots (five cultivars and four landraces, four growing conditions and three replicates); whereas we measured δ18O DM and δ2H DM in 48 plots (two cultivars and two landraces, four growing conditions and three replicates) during the 2010 crop cycle. Each value represents the mean ±sd. Mean values across plant tissues with different letters (a and b) are significantly different from SI versus RF and HN versus LN, and landraces versus cultivars, according to Tukey’s Honest Significant Difference Test (P < 0.05).
| Isotope/Organ/Fraction | Cultivars | Landraces | SI | RF | HN | LN |
|---|---|---|---|---|---|---|
| Hydrogen | ||||||
| δ2Hroots DM | −67.1 ± 18.6a | −73.2 ± 20.6a | −64.3 ± 23.5a | −75.8 ± 13.3b | −72.5 ± 17.7a | −68.0 ± 21.5a |
| δ2Hstem W | −46.4 ± 7.2a | −45.3 ± 5.7a | −46.3 ± 7.6a | −45.6 ± 5.6a | −47.1 ± 7.3a | −44.8 ± 5.7a |
| δ2Hflag DM | −114.9 ± 8.7a | −115.5 ± 8.8a | −120.6 ± 6.7a | −109.6 ± 6.8b | −111.5 ± 9.6a | −119.1 ± 5.5b |
| δ2Hflag WSF | −100.9 ± 6.9a | −104.4 ± 7.4b | −104.1 ± 7.8a | −100.9 ± 6.4b | −101.8 ± 8.1a | −103.2 ± 6.4a |
| δ2Hear DM | −90.0 ± 8.6a | −95.3 ± 10.6a | −99.0 ± 7.1a | −86.4 ± 8.1b | −88.9 ± 10.0a | −96.4 ± 8.4b |
| δ2Hear WSF | −65.7 ± 7.0a | −71.4 ± 9.2b | −72.5 ± 6.7a | −64.3 ± 8.0b | −65.4 ± 9.5a | −71.2 ± 6.4b |
| δ2Hgrain | −33.6 ± 8.2a | −30.9 ± 9.4a | −36.6 ± 6.6a | −28.2 ± 8.9b | −27.4 ± 7.7a | −35.8 ± 6.9b |
| Oxygen | ||||||
| δ18Oroots DM | 28.1 ± 7.5a | 30.8 ± 8.8a | 29.6 ± 9.0a | 29.3 ± 7.6a | 32.3 ± 9.4a | 26.7 ± 5.9b |
| δ18Ostem W | −6.3 ± 1.0a | −6.1 ± 0.6a | −6.4 ± 0.9a | −6.0 ± 0.8a | −6.4 ± 0.9a | −6.0 ± 0.7a |
| δ18Oflag DM | 0.8 ± 1.7a | 31.0 ± 1.1a | 30.3 ± 1.0a | 31.4 ± 1.6b | 31.1 ± 1.6a | 30.7 ± 1.3a |
| δ18Oflag WSF | 30.7 ± 2.2a | 30.0 ± 2.3a | 28.9 ± 1.9a | 32.3 ± 0.9b | 29.6 ± 2.7a | 31.2 ± 1.3a |
| δ18Oear DM | 26.6 ± 2.4a | 26.1 ± 2.6a | 26.5 ± 2.0a | 26.2 ± 2.9a | 26.7 ± 2.2a | 26.0 ± 2.7a |
| δ18Oear WSF | 30.9 ± 1.1a | 29.9 ± 1.0a | 30.2 ± 0.9a | 30.7 ± 1.3a | 30.3 ± 1.2a | 30.7 ± 1.1a |
| δ18Ograin | 30.4 ± 0.7a | 30.6 ± 0.9b | 30.4 ± 0.7a | 30.6 ± 0.9a | 30.3 ± 0.6a | 30.7 ± 0.9a |
| Carbon | ||||||
| δ13Cflag DM | −25.9 ± 0.9a | −25.5 ± 0.9b | −26.2 ± 0.7a | −25.2 ± 0.8b | −25.3 ± 0.8a | −26.2 ± 0.8b |
| δ13Cflag WSF | −27.0 ± 1.1a | −27.2 ± 1.1a | −27.9 ± 0.9a | −26.3 ± 0.7b | −27.2 ± 1.4a | −26.9 ± 0.7a |
| δ13Cear DM | −24.5 ± 1.0a | −25.0 ± 0.9b | −25.4 ± 0.7a | −24.1 ± 0.8b | −24.5 ± 1.0a | −25.0 ± 0.9b |
| δ13Cear WSF | −23.3 ± 0.9a | −24.4 ± 1.0b | −24.5 ± 0.9a | −23.1 ± 0.8b | −23.6 ± 1.1a | −24.0 ± 1.1a |
| δ13Cgrain | −24.6 ± 0.9a | −23.9 ± 1.0b | −25.0 ± 0.6a | −23.5 ± 0.7b | −24.0 ± 1.1a | −24.6 ± 0.8b |
| gs (mmol·H2O·m−2s−1) | 184.7 ± 78.1a | 170.2 ± 59.0a | 222.8 ± 56.2a | 133.8 ± 52.8b | 163.6 ± 84.5a | 193.1 ± 49.0b |
| GY (Mg·ha−1) | 1.9 ± 0.1a | 1.5 ± 0.1b | 2.1 ± 0.1a | 1.3 ± 0.1b | 1.8 ± 0.1 a | 1.6 ± 0.1 a |