Multiple paths to similar germination behavior in Arabidopsis thaliana.

Germination timing influences plant fitness, and its sensitivity to temperature may cause it to change as climate shifts. These changes are likely to be complex because temperatures that occur during seed maturation and temperatures that occur post-dispersal interact to define germination timing. We used the model organism Arabidopsis thaliana to determine how flowering time (which defines seed-maturation temperature) and post-dispersal temperature influence germination and the expression of genetic variation for germination. Germination responses to temperature (germination envelopes) changed as seeds aged, or after-ripened, and these germination trajectories depended on seed-maturation temperature and genotype. Different combinations of genotype, seed-maturation temperature, and after-ripening produced similar germination envelopes. Likewise, different genotypes and seed-maturation temperatures combined to produce similar germination trajectories. Differences between genotypes were most likely to be observed at high and low germination temperatures. The germination behavior of some genotypes responds weakly to maternal temperature but others are highly plastic. We hypothesize that weak dormancy induction could synchronize germination of seeds dispersed at different times. By contrast, we hypothesize that strongly responsive genotypes may spread offspring germination over several possible germination windows. Considering germination responses to temperature is important for predicting phenology expression and evolution in future climates.