Background: Plants exhibit phenotypic plasticity and respond to differences in environmental conditions by acclimation. We have systematically compared leaves of Arabidopsis thaliana plants grown in the field and under controlled low, normal and high light conditions in the laboratory to determine their most prominent phenotypic differences. Results: Compared to plants grown under field conditions, the "indoor plants" had larger leaves, modified leaf shapes and longer petioles. Their pigment composition also significantly differed; indoor plants had reduced levels of xanthophyll pigments. In addition, Lhcb1 and Lhcb2 levels were up to three times higher in the indoor plants, but differences in the PSI antenna were much smaller, with only the low-abundance Lhca5 protein showing altered levels. Both isoforms of early-light-induced protein (ELIP) were absent in the indoor plants, and they had less non-photochemical quenching (NPQ). The field-grown plants had a high capacity to perform state transitions. Plants lacking ELIPs did not have reduced growth or seed set rates, but their mortality rates were sometimes higher. NPQ levels between natural accessions grown under different conditions were not correlated. Conclusion: Our results indicate that comparative analysis of field-grown plants with those grown under artificial conditions is important for a full understanding of plant plasticity and adaptation.

Chloroplasts develop from undifferentiated proplastids present in meristematic tissue. Chloroplast biogenesis is thus closely connected to leaf development, which restricts our ability to study the process of chloroplast biogenesis per se. As a consequence we know relatively little about the regulatory mechanisms behind the establishment of the photosynthetic reactions and how the activities of the two genomes involved are coordinated during chloroplast development. We developed a single-cell-based experimental system from Arabidopsis with high temporal resolution allowing for investigations of the transition from proplastids to functional chloroplasts. Using this unique cell line we could show that establishment of photosynthesis is dependent on a regulatory mechanism involving two distinct phases. The first phase is triggered by rapid light-induced changes in gene expression and the metabolome. The second phase is dependent on the activation of the chloroplast and generates massive changes in nuclear gene expression required for the transition to photosynthetically functional chloroplasts.. The second phase is also associated with a spatial transition of the chloroplasts from clusters around the nucleus to the final position at the cell cortex. Thus, establishment of photosynthesis is a two-phase process with a clear checkpoint associated with the second regulatory phase allowing coordination of the activities of the nuclear and plastid genomes.