Table 4.
Means (±SE) and F-values for the ratio of variable to maximal fluorescence in the light (Fv '/Fm '), PSII efficiency (ΦPSII), intrinsic water-use efficiency (IWUE), and imputed triose phosphate utilization (TPU; estimated as the carbon-saturated photosynthetic rate at 2000 μmol mol−1) in 3-year-old and 6-year-old intermediate wheatgrass (Thinopyrum intermedium) at three dates (differing in leaf temperature) in a spring 2016 study at Kellogg Biological Station (Hickory Corners, MI)
| Date | Cohort | F v '/F m ' | ΦPSII | IWUE (mmol mol−1) | TPU (imputed; μmol m−2 s−1) | Temperature (ºC) |
|---|---|---|---|---|---|---|
| 14 March | Wheatgrass (6-year-old) | 0.368±0.021 | 0.050±0.007 | 42±9 | 14.7±1.9 | 1.2 |
| 14 March | Wheatgrass (3-year-old) | 0.376±0.019 | 0.024±0.001* | 12±4 | 11.0±1.3 | 1.2 |
| 3 April | Wheatgrass (6-year-old) | 0.399±0.023 | 0.096±0.010 | 109±29 | – | 5.1 |
| 3 April | Wheatgrass (3-year-old) | 0.474±0.033 | 0.078±0.008 | 88±22 | – | 5.1 |
| 17 March | Wheatgrass (6-year-old) | 0.452±0.011 | 0.138±0.016 | 170±21 | – | 9.7 |
| 17 March | Wheatgrass (3-year-old) | 0.455±0.054 | 0.139±0.006 | 110±43 | – | 9.7 |
| Source of variation | ||||||
| Temperature | 6.65** | 63.30**** | 23.3**** | – | ||
| Age | 0.65 | 12.10** | 8.27** | 2.53 | ||
| Age×temperature | 0.56 | 10.91*** | 0.40 | – | ||
*, **, ***, and **** indicate significance at α=0.075, 0.05, 0.01, and 0.001, respectively.