Life on the surface: How environment, genotype, and life history affect germination and dormancy in the field

Background/Question/Methods

Germination and dormancy behavior of natural allelic variants of Arabidopsis thaliana were studied along with maternal effects (seed-maturation conditions and dispersal season) on germination phenotypes. Studying environmental and genotypic effects on phenology will be informative in predicting effects of climate change.  Life history stages in plants are integrated. They are affected by environmental cues at multiple life stages including those experienced by the maternal plant during seed development.  Allelic effects can be masked or magnified by environmental conditions due to repression or activation of different pathway elements.  This adds to the complexity of potential climate change effects, which could affect specific alleles directly.  The allelic variants were chosen for their documented and contrasting involvement in dormancy and the flowering time pathways including FLOWERING LOCUS C (FLC), Delay of Germination genes (DOG), and wildtypes Columbia, Landsberg erecta, and Cape Verdi (Col, Ler, Cvi).  Cvi alleles have high dormancy while Ler and Col do not.  We manipulated flowering time by controlling maturation and dispersal timing in the field.  Eight genotypes were grown at 25C or 14C and were dispersed in early and late winter of 2011, and early and late spring of 2012.  Germination, bolting, flowering, and maturation were recorded.

Results/Conclusions

Environmental conditions experienced by the maternal plants affected the germination timing of seeds dispersed later in the season.  Cooler maturation temperatures induced dormancy in the seeds of the wildtypes when dispersed later in the season.  Allelic effects were observed most strongly with the DOG1 alleles.  Seeds with high DOG1 expression from the introgressed CVI allele were highly dormant while the Ler wild type was not in either dispersal season.  DOG1_cvi dormancy was eliminated however after being matured in warmer temperatures in all dispersal seasons.  Allelic patterns were not as apparent in the other variants.  This suggests that maternal conditions are especially influential on germination phenology in relation to the DOG1_cvi allele.   Maternal effects can be powerful timing tools for plants, especially in climates that have predictable seasonality.  In the case of the DOG1_cvi allele seeds matured during warmer months would remain dormant until after a cool period such as winter, before germinating.  Such allelic and environmental correlations are powerful phenological controls that encourage germination at times that are most advantageous for survival.  With increasing climatic changes around the world and changing temperature patterns, these relationships could become a detriment, encouraging germination at times that are not favorable for survival.