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Winter annual Arabidopsis thaliana plants require a prolonged period of cold, known as vernalization, to ensure prompt floral transition occurs in spring. This thesis addresses the question of whether partial saturation of cold requirements might delay flowering under future climate scenarios. Laboratory experiments set up to parameterize a predictive model revealed a surprising optimal vernalizing temperature for the Swedish accession Lov-1. Field experiments in Northern Sweden support the theory that this optimum likely reflects adaptation to autumn, rather than winter temperatures. A chilling unit model incorporating empirically derived parameters forecast an overall increase in effective vernalizing days for A. thaliana in northern Sweden. This increase is the result of an overall reduction in sub-zero temperatures that are predicted for northerly latitudes by the end of the century. Reductions in the number of effective vernalizing days were predicted for England and Spain, however these are unlikely to counteract the forcing effects of increased spring temperatures at these locations. This thesis also presents a novel method that enables single RNA molecules to be visualized for the first time in plants. This method was used to determine cell-to-cell variation and subcellular distribution of key vernalization gene transcripts before, during and after cold exposure. These results provide a unique insight into how plants perceive and integrate longterm temperature cues at the cellular level In summary, this thesis predicts the potential impact of climate change on A. thaliana vernalization across its species’ range. It also dissects transcriptional mechanisms that underlie long-term temperature integration. Modulation of these mechanisms is likely to be key for survival of some wild species and for maximizing crop yields under future climate scenarios. |
