Table 1.
Parameters for the controlled in situ heat treatments using the heat tolerance testing system (HTTS)
| Species | Date | Tstart [°C] | WR [K·h−1] | Texp [°C] | Tc [°C] | LT5 [°C] | T [°C] | PPFD |
|---|---|---|---|---|---|---|---|---|
| Rhododendron ferrugineum | 9 August 2012 | 30 | 6.5 | 43 | 44 | 46 | 11 | 261 |
| Rh. ferrugineum | 9 August 2012 | 30 | 7.5 | 45 | 44 | 46 | 11 | 261 |
| Senecio incanus | (10) 11 July 2013 | 30 | 7 | 44 | 45 | 47 | (17) 19 | (732) 1047 |
| S. incanus | (10) 11 July 2013 | 30 | 8 | 46 | 45 | 47 | (17) 19 | (732) 1047 |
| Ranunculus. glacialis | (10) 11 August 2013 | 25 | 8 | 41 | 43 | 44 | (5) 8 | (1351) 1501 |
| Ra. glacialis | (10) 11 August 2013 | 25 | 9 | 43 | 43 | 44 | (5) 8 | (1351) 1501 |
Leaves were treated at each exposure temperature (Texp) in the light mode and in the dark mode. Tstart, starting temperature of the heat treatment, WR, warming rate, Texp, exposure temperature, Tc, critical temperature that causes an increase in basic fluorescence, LT5, temperature at which first visible heat injury to the leaf blade (5% of total leaf area) occurs. T and PPFD: mean values of leaf temperature and photosynthetic photon flux density [μmol photons·m−2 s−1] determined for untreated control plants outside the HTTS. Values outside brackets refer to the heat treatment applied to determine the effects on photosynthetic gas exchange, values in brackets (date, T, PPFD) refer to the determination of the effects on free radical scavenging and xanthophyll cycle activities.