3.1.1 ⎪ Photosynthesis and related features
For both IT and SW, the highest levels of photosynthetic capacity (Fig. 1a), leaf dry mass (Fig. 1b), and chlorophyll a + b (Fig. 1c) per leaf area were seen in plants grown under high light and cool temperature (HLC). Whereas photosynthetic capacity and leaf dry mass per area were higher in plants of both ecotypes grown under high light and warm temperature (HLW) compared to low light and warm temperature (LLW), chlorophyll a + b levels were similar. Chlorophylla /b ratios were higher in both ecotypes in high compared to low growth light irrespective of growth temperature (Fig. 1d). Significant ecotype-specific differences were also observed, with higher photosynthetic capacity per area in SW compared to IT under HLC and HLW (Fig. 1a), higher leaf dry mass per area in SW compared to IT under HLC (Fig. 1b), higher chlorophyll a + b in SW compared to IT under all conditions tested (Fig. 1c) and higher chlorophylla /b ratios in IT compared to SW under HLW and a similar, albeit not significant, trend under HLC (Fig. 1d).
Excitation pressure in the chloroplast was ascertained as photosystem II (QA) reduction state after short experimental exposure to a range of light intensities in leaves of plants grown in HLC and LLW. QA reduction state was similar in the two LLW-grown ecotypes grown across a range of light intensities (Fig. 2a), with both ecotypes exhibiting a relatively steep increase to high QA reduction states with increasing light intensities. In contrast, plants of both ecotypes grown under HLC compared to LLW exhibited considerably lower QA reduction states (Fig. 2a,b). Furthermore, the light response of QA reduction state differed between IT and SW plants grown under HLC, with a significantly lower QA reduction state (more oxidized QA) in SW compared to IT under experimental exposure to higher light intensities (Fig. 2b).