Table 2.
Means (±SE), Student’s t for planned contrast, and F-values for photosynthetic rate (A), inferred maximal electron transport rate (Jmax), maximal RuBP carboxylation rate (VCmax), and maximal triose phosphate utilization capacity (TPU) in 2-year-old and 5-year-old wheatgrass (Thinopyrum intermedium) at multiple sampling dates in a 2015 study at Kellogg Biological Station (Hickory Corners, MI)
Values given for V Cmax, J max, and TPU are standardized to 25 ºC, while values for A are not. At the first three dates, second year plants were not measured.
| Date | Cohort | A (μmol m −2 s −1) | J max | V Cmax | TPU | Temperature (ºC) |
|---|---|---|---|---|---|---|
| 18 March | Wheatgrass (5-year-old) | 8.89±0.9 | 208.8±42.9 | 36.5±8.5 | 33.5±3.2 | 5.2 |
| 24 March | Wheatgrass (5-year-old) | 8.12±0.9 | 234.6±39.2 | 38.6±1.8 | 30.5±5.1 | 7.4 |
| 4 April | Wheatgrass (5-year-old) | 5.09±0.7 | 135.2±30.9 | 35.6±9.1 | 28.7±3.3 | 2.8 |
| 8 April | Wheatgrass (2-year-old) | 17.6±1.6 | 224.4±20.5 | 112.0±13.7 | 26.2±3.1 | 12.8 |
| 8 April | Wheatgrass (5-year-old) | 25.5±1.3 | 356.8±27.7 | 79.7±14.3 | 41.9±3.5 | 12.8 |
| 25 April | Wheatgrass (2-year-old) | 9.9±1.7 | 193.7±28.0 | 56.0±14.0 | 22.2±3.5 | 6.8 |
| 25 April | Wheatgrass (5-year-old | 10.2±1.9 | 199.1±30.6 | 101.3±13.5 | 30.5±1.3 | 6.8 |
| 20 May | Wheatgrass (2-year-old) | 30.8±3.4 | 198.4±30.4 | 118.4±17.1 | 20.7±2.7 | 19.9 |
| 20 May | Wheatgrass (5-year-old) | 24.4±1.6 | 235.2±30.8 | 108.6±14.6 | 19.2±2.8 | 19.9 |
| 10 July | Wheatgrass (2-year-old) | 28.3±3.3 | 142.0±18.0 | 93.0±8.1 | 14.0±1.2 | 28.6 |
| 10 July | Wheatgrass (5-year-old) | 25.2±2.8 | 174.0±16.0 | 92.3±7.3 | 14.9±1.0 | 28.6 |
| 20 November | Wheatgrass (2-year-old) | 11.4±1.6 | 197.1±13.2 | 65.6±10.3 | 27.1±2.0 | 7.5 |
| 20 November | Wheatgrass (5-year-old) | 19.4±2.4 | 253.3±22.6 | 109.9±15.3 | 37.8±2.5 | 7.5 |
| Planned contrast | ||||||
| Student’s t-value | 6.52**** | 1.80 | 5.34** | 2.59* | ||
| Source of variation | ||||||
| Stress | 170.39**** | 13.19*** | 3.39† | 28.20**** | ||
| Age | 0.11 | 6.61* | 1.14 | 9.37** | ||
| Age×stress | 15.28*** | 1.97 | 1.26 | 6.60* | ||
| Date | 18.55**** | 7.02*** | 0.68 | 23.46**** | ||
†, *, **, ‘***’ and ‘****’ indicate significance at α= 0.075, 0.05, 0.01, 0.001 and 0.0001, respectively.
Significance of the cold stress×age interaction may be assessed either by the F-value or by the planned contrast.