Song, X., Kristie, D.N., and Reekie, E.G. 2009. Why does elevated CO­₂ affect time of flowering? An exploratory study using the photoperiodic flowering mutants of Arabidopsis thaliana. New Phytologist 181: 339-346.

The ten mutants of Arabidopsis thaliana are each defective at a different loci in the pathway of the photoperiod. It is hypothesized that elevated CO₂ levels is affected flowering time due to its interactions in the photoperiod. The plants were grown under two light conditions: short days (SD) and long days (LD). There were also two CO­₂ conditions: ambient and high. There were four total combinations between these two factors that each mutant and wild type was submitted to. The characteristic that was used to quantify growth of plants was number of leaves when the plant began flowering. In this study, it was found that high CO­₂ levels had no effect on leaf number in plants experiencing long days, but increased the number of leaves in short day plants. No mechanism has yet been found that could, with certainty, explain the difference in the growth rate of leaves between these two conditions. Due to elevated CO₂ levels, the rate of flowering time was reduced for plants that were in SD and LD conditions. This data suggests that CO­₂ levels may have an effect on the perception of light signals as well as the internal time-keeping mechanism for flowering (at least in LD plants for the latter).

http://onlinelibrary.wiley.com/store/10.1111/j.1469-8137.2008.02669.x/asset/j.1469-8137.2008.02669.x.pdf?v=1&t=i63rzbr9&s=b17d9d112c32687087101243ce1855d4b7c6a0df

Strain, B.R. and Ward, J.K. 1997. Effects of low and elevated CO₂ partial pressure on growth and reproduction of Arabidopsis thaliana from different elevations. Plant, Cell and Environment 20: 254-260.

The objective of this study is to observe the effects of atmospheric CO₂ partial pressure on Arabidopsis thaliana plants as they may have been in the past or may be in the future. Low atmospheric pressure is connected to the most recent Pleistocene era, in which they were thought to have been as low as 18 Pa. In the future, atmospheric CO₂ is predicted to increase to between 35 and 70 Pa within the next century. An important consideration of this study is how these levels effect the seed production at high or lower levels. There was found to be no significant difference in seed production among the six different genotypes, between 35 and 70 Pa. Each of the genotypes produced about the same number of seeds. When exposed to low levels of CO₂, between 20 and 35 Pa, the genotypes did have a significant difference of seed reduction. The results of this research suggest that, in the past, CO₂ was a strong selective force among plants. However, it may not be so in the future; this is only speculation based on the observation of the results of this study.

http://onlinelibrary.wiley.com/store/10.1046/j.1365-3040.1997.d01-59.x/asset/j.1365-3040.1997.d01-59.x.pdf?v=1&t=i62bvsw4&s=45e8b6dbddfd44b84bf665f4b817ba2f2c3e2210

Peng et. al. 1997. The Arabidopsis GAI gene defines a signaling pathway that negatively regulates gibberellin responses. Genes & Development 11: 3194-3205.

The objective of this paper is to determine the signaling pathway of gibberellin, which was previously described as stimulation, but is now thought of as a derepression pathway. This signal pathway was found by using the GAI protein and gai mutant protein. The gai mutant is a gain-of-function mutation that results when a 17-amino-acid segment is removed from wild type GAI. GAI is a repressor of stem elongation and the presence of gibberellin derepresses this pathway, allowing for stem growth. When the 17-amino-acid sequence was removed to create the mutant gai, the gibberellin no longer had a derepressing effect on the Arabidopsis and was shown as constitutive dwarfism in the plants. The gai, as a loss-of-function mutation, has presented itself as dominant over the GAI in the experiments done on these plants.

http://genesdev.cshlp.org/content/11/23/3194.full

Bray, Elizabeth. 2004. Genes commonly regulated by water-deficit stress in Arabidopsis thaliana. Journal of Experimental Botany 55 (407): 2331-2341.

The objective of this study was to create water-deficit stress in Arabidopsis thaliana (Columbia) by using three different methods of water deprivation. After this, the genes affected by each method were documented and compared to one another. It was found that these methods shared 27 induced genes in common as well as 3 repressed genes. The methods used to generate stress on the plants are simply labeled: Filter paper, Mannitol, and Soil water deficit. For each individual method, many genes were affected, but using a Venn diagram for comparison showed only 27 that were shared by each method. Of these, a majority of genes were in control of hydrophilic proteins, followed by the second greatest category that was unknown functions. Other gene groups that were induced include metabolism, transport, signaling, and transcription. Of all the genes that were repressed by these experimental methods, only 3 were shared by all of the methods. These 3 genes function primarily in the leaves of the Arabidopsis plants. Their effects were seen by, but are not limited to, cell wall synthesis and degradation. This paper’s intention is to show how Arabidopsis plants will react in drought conditions but it is not yet confirmed if these laboratory studies are conclusive on farm grown plants.

http://jxb.oxfordjournals.org/content/55/407/2331.full

Wilson, Ruth N., Heckman, John W., and Somerville, Chris R. 1992. Gibberellin Is Required for Flowering in Arabidopsis thaliana under Short Days. Plant Physiology 100: 403-408.

The objective in this project was to determine the role that gibberellin plays in flowering under the “short days” and continuous light conditions. The samples used for growth were the ga1-3 mutant, the gai mutant (gibberellin-insensitive), and the wild-type Landsberg (erecta) line. A short day in this study is defined by 6 hours under cool white fluorescent bulbs and 16 hours of darkness. Continuous light uses the same bulbs, but continuous lights the plants. The application of the hormone gibberellin occurred 17 days after planting; the plants were sprayed “generously” once a week. The controls were sprayed with the solution containing the solvent but not the actual gibberellin component. The results of the study showed the ga1-3 mutant never flowered in short days or continuous light unless gibberellin was added to induce flowering. The gai and WT both flowered in short days. In continuous light, the other mutants grew but ga1-3 was delayed in its initial growth. These results were concluded with the findings that gibberellin plays a role in flowering initiation in Arabidopsis thaliana.

http://www.plantphysiol.org/content/100/1/403.full.pdf+html