Physiological basis of germination responses to seasonal cues in Arabidopsis thaliana

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Timing of seed germination is highly responsive to environmental conditions. Consequently, if environments change, due to habitat alteration, global warming, or dispersal into new regions, for example, germination behavior is likely to change as a direct and immediate response. Germination responses to seasonal cues contribute to fundamental life-history variation and can strongly influence important demographic properties of populations such as generation time and reproductive success within a generation. Characterizing the genetic and physiological basis of germination responses to seasonal environments can identify mechanisms for basic life-history variation and can identify causes of variation in population growth rates and distributions in desirable and undesirable species. The proposed research is an investigation of the physiological basis of germination responses to seasonal cues in mutant and natural genotypes of A. thaliana.The project has two components. The first component characterizes the physiological basis of germination responses to seasonal cues experienced during the maternal generation and after dispersal. This component uses mutant lineages that are defective in one or more phytochromes in order to identify the phytochromes involved in germination responses to different seasonal cues, and to further characterize the phytochrome-mediated mechanisms that regulate germination. Mutant A. thaliana lines will be grown in controlled environments in growth chambers and in the field. By combining studies in controlled environments and in the field, we will investigate the physiological basis of responses to real ecological cues that influence germination in the field. The second component uses variable natural genotypes to investigate the physiological basis of natural variation in germination responses to seasonal cues. Studies using natural genotypes will complement the mutant studies by testing whether the same physiological mechanisms that influence germination in mutants also influence germination in natural genotypes.By combining classical genetics, quantitative genetics and ecological manipulations, the research will expand the context of physiological studies on this model organism. It does so by characterizing responses of mutants to actual ecological environments and by characterizing the physiological basis of germination responses of natural genotypes in addition to those of mutants. As such, it will contribute to our knowledge of natural variation in physiological mechanisms and our knowledge of specific genes associated with variation in germination in natural populations.