Table 2.
Photosynthesis-related parameters in needles of maritime pine plants derived from somatic embryos matured at different temperatures (18, 23, or 28 °C), before (t0) and after (t10) a heat stress treatment (for 10 days at 45 °C for 3 h/day), as well as after a recovery period of further 10 days (tR). Six samples were employed for determining net photosynthetic CO2 assimilation rates (AN; µmol CO2 m−2 s−1), stomatal conductance (gs; mol H2O m−2 s−1), and substomatal CO2 concentration (Ci; µmol CO2 mol−1).
| Parameter | Plants | t0 | t10 | tR |
|---|---|---|---|---|
| AN x | M18 | 7.4 ± 2.4 b | 7.0 ± 4.5 (−5.2%) a | 9.0 ± 2.7 (22.4%) a |
| M23 | 10.9 ± 3.8 a | 8.7 ± 2.9 (−20.5%) a | 10.6 ± 2.0 (−3.2%) a | |
| M28 | 9.9 ± 2.0 a | 9.1 ± 0.7 (−8.4%) a | 9.5 ± 1.0 (−4.0%) a | |
| gs y | M18 | 0.24 ± 0.06 a | 0.17 ± 0.06 (−29.2%) a | 0.17 ± 0.12 (−29.2%) a |
| M23 | 0.24 ± 0.11 a | 0.16 ± 0.07 (−33.3%) a | 0.17 ± 0.09 (−29.2%) a | |
| M28 | 0.25 ± 0.12 a | 0.19 ± 0.09 (−24.0%) ab | 0.13 ± 0.01 (−48.0%) b | |
| M18 | 313 ± 31 a | 294 ± 54 (−6.1%) ab | 264 ± 39 (−15.4%) b | |
| (Ci) z | M23 | 282 ± 12 a | 270 ± 36 (−4.3%) a | 255 ± 35 (−9.6%) a |
| M28 | 292 ± 21 a | 271 ± 52 (−7.2%) ab | 235 ± 39 (−19.4%) b |
x, mean separation within each sampling time according to Tukey-b test. y, mean separation within each group of plants according to Kruskal-Wallis ANOVA test with Bonferroni correction for multiple comparisons. z, mean separation within each group of plants according to the Tukey-b test.