Natural variation in germination responses of Arabidopsis to seasonal cues and their associated physiological mechanisms.
OBJECTIVE
Despite the intense interest in phenological adaptation to environmental change, the fundamental character of natural variation in germination is almost entirely unknown. Specifically, it is not known whether different genotypes within a species are germination specialists to particular conditions, nor is it known what physiological mechanisms of germination regulation vary in natural populations and how they are associated with responses to particular environmental factors.


METHODS
We used a set of recombinant inbred genotypes of Arabidopsis thaliana, in which linkage disequilibrium has been disrupted over seven generations, to test for genetic variation and covariation in germination responses to distinct environmental factors. We then examined physiological mechanisms associated with those responses, including seed-coat permeability and sensitivity to the phytohormones gibberellic acid (GA) and abscisic acid (ABA).


RESULTS
Genetic variation for germination was environment-dependent, but no evidence for specialization of germination to different conditions was found. Hormonal sensitivities also exhibited significant genetic variation, but seed-coat properties did not. GA sensitivity was associated with germination responses to multiple environmental factors, but seed-coat permeability and ABA sensitivity were associated with specific germination responses, suggesting that an evolutionary change in GA sensitivity could affect germination in multiple environments, but that of ABA sensitivity may affect germination under more restricted conditions.


CONCLUSIONS
The physiological mechanisms of germination responses to specific environmental factors therefore can influence the ability to adapt to diverse seasonal environments encountered during colonization of new habitats or with future predicted climate change.
Indian Institute of Science Education and Research, Pune 411021, India.
Deepak
D
Barua
Colleen
C
Butler
Tracy E
TE
Tisdale
Kathleen
K
Donohue
D000040:Abscisic Acid / Q000378:metabolism; D000222:Adaptation, Physiological; D017360:Arabidopsis / Q000235:genetics / Q000254:growth & development / Q000378:metabolism / Q000502:physiology*; D004739:England; D004777:Environment; D014644:Genetic Variation; D018525:Germination / Q000502:physiology; D005875:Gibberellins / Q000378:metabolism; D007178:Inbreeding; D057445:Plant Dormancy / Q000502:physiology; D010937:Plant Growth Regulators / Q000378:metabolism; D012621:Seasons; D012639:Seeds / Q000502:physiology; D014861:Washington
D005875:Gibberellins; D010937:Plant Growth Regulators; D000040:Abscisic Acid; C007842:gibberellic acid