Table II.
Vegetative shoot biomass at harvest and total leaf nitrogen (N) content of gas exchange leaves for studies that included a nutrient limitation treatment
If no treatment is designated (–), then all plants in that study received sufficient levels of that resource. Values are lsmeans ± 1 se. F values and associated degrees of freedom (Fdf num, df denom) are presented for each model effect (PROC MIXED ANOVA, block as random). F values in bold indicate statistical significance (*, P < 0.05; **, P < 0.01; ***, P < 0.001).
| Study and Species | Nutrient Treatment | Water Treatment | Model Effects | Shoot | N for Gas Exchange Leaf |
|---|---|---|---|---|---|
| g | mg g−1 | ||||
| Fall 2003-1 | |||||
| H. annuus | Sufficient | – | 7.3 ± 3.3 | 5.54 ± 0.39 | |
| Limited | – | 1.8 ± 3.3 | 4.17 ± 0.41 | ||
| Nutrient effect | 29.571,14*** | 26.571,6** | |||
| H. anomalus | Sufficient | – | 14.5 ± 3.0 | 4.30 ± 0.22 | |
| Limited | – | 5.1 ± 3.0 | 4.13 ± 0.22 | ||
| Nutrient effect | 10.461,14** | 1.241,6 | |||
| H. deserticola | Sufficient | – | 15.4 ± 3.3 | Not assessed | |
| Limited | – | 3.3 ± 3.9 | Not assessed | ||
| Nutrient effect | 5.61,8* | Not assessed | |||
| H. petiolaris | Sufficient | – | 10.4 ± 2.9 | 5.85 ± 0.36 | |
| Limited | – | 4.7 ± 2.9 | 4.89 ± 0.32 | ||
| Nutrient effect | 7.011,12* | 4.101,5 | |||
| Fall 2003-2 | |||||
| H. annuus dom. | Sufficient | Sufficient | 8.0 ± 0.4 | Not assessed | |
| Limited | Sufficient | 4.2 ± 0.4 | Not assessed | ||
| Sufficient | Limited | 2.8 ± 0.4 | Not assessed | ||
| Limited | Limited | 1.7 ± 0.4 | Not assessed | ||
| Water effect | 78.331,42*** | ||||
| Nutrient effect | 30.691,42*** | ||||
| Water×nutrient | 9.831,42** | ||||
| Fall 2004-1 | |||||
| H. annuus | Sufficient | – | 4.5 − 1.0, +1.2 | 2.86 ± 0.23 | |
| Limited | – | 1.6 − 0.3, +0.4 | 2.82 ± 0.223 | ||
| H. anomalus | Sufficient | – | 7.3 − 1.6, +2.1 | 3.70 ± 0.24 | |
| Limited | – | 1.0 − 0.3, +0.3 | 3.44 ± 0.26 | ||
| H. deserticola | Sufficient | – | 7.8 − 1.7, +2.2 | 3.53 ± 0.24 | |
| Limited | – | 2.9 − 0.6, +0.8 | 3.19 ± 0.23 | ||
| H. petiolaris | Sufficient | – | 7.9 − 1.7, +2.1 | 4.17 ± 0.23 | |
| Limited | – | 1.2 − 0.3, +0.4 | 3.44 ± 0.26 | ||
| Nitrate effect | 70.561,56*** | 6.781,56* | |||
| Species effect | 2.453,56 | 10.163,56*** | |||
| Nitrate×species | 2.383,56 | 1.213,56 | |||
| Spring 2005 | |||||
| H. annuus | Sufficient | – | 81.7 − 5.5, +5.9 | Not assessed | |
| Limited | – | 7.8 − 0.5, +0.6 | Not assessed | ||
| Nitrate effect | 561.231,33*** | Not assessed | |||
| Summer 2005 | |||||
| H. annuus | Sufficient | Sufficient | 114.0 − 10.5, +11.6 | 3.83 ± 0.10 | |
| Sufficient | Limited | 71.6 − 6.3, +6.8 | Not assessed | ||
| Limited | Sufficient | 6.2 − 0.6, +0.6 | 2.17 ± 0.10 | ||
| Limited | Limited | 4.6 − 0.4, +0.4 | Not assessed | ||
| Water effect | 38.41,29*** | – | |||
| Nitrate effect | 2,065.791,29*** | 130.651,32*** | |||
| Water×nitrate | 1.621,29 | – | |||
| Fall 2005-1 | |||||
| H. annuus | Sufficient; 15.5 week age | – | 87.2 − 16.6, +20.5 | 2.75 ± 0.18 | |
| Sufficient; 10 week age | – | 10.2 − 2.0, +2.5 | 3.87 ± 0.18 | ||
| Sufficient; 5.5 week age | – | 0.6 ± 0.1 | 5.17 ± 0.18 | ||
| Limited; 15.5 week age | – | 7.6 − 1.4, +1.8 | 1.82 ± 0.18 | ||
| Limited; 10 week age | – | 1.3 − 0.2, +0.3 | 2.81 ± 0.18 | ||
| Limited; 5.5 week age | – | 0.3 ± 0.1 | 4.27 ± 0.18 | ||
| Nitrate effect | 180.161,46*** | 42.811,46*** | |||
| Plant age effect | 351.872,46*** | 91.462,46*** | |||
| Nitrate×plant age | 18.492,46*** | 0.112,46 |