Photoperiod throughout the maternal life cycle influences seed germination in Arabidopsis thaliana, but seed photoperiod does not

Premise of the study: Plants adjust their phenology in response to seasonal cues experienced both by their parents and by themselves, and coordinating responses to these cues is necessary for expressing adaptive phenology. We investigated how cues are integrated across time to influence an important progeny phenotype, i.e., seed germination.

Methods: We used Arabidopsis thaliana to investigate how the photoperiod experienced by maternal parents and by progeny influences seed germination. We examined when maternal photoperiod effects on germination are imposed and how long they persist in progeny.

Key results: The photoperiod experienced by maternal plants more strongly influenced germination than the photoperiod experienced during seed imbibition. In addition, the photoperiod experienced at the prereproductive stage frequently influenced germination as strongly as that experienced during reproduction. In general, seeds from plants grown under short days had higher seed germination percentages than seeds from plants grown in longer days. These maternal effects diminished with after-ripening, but reappeared in seeds induced into secondary dormancy.

Conclusions: We found no evidence that the effect of photoperiod systematically attenuates in proportion to the time that elapsed between the cue and the timing of seed germination. Moreover, more recently experienced cues did not override the effects of cues experienced previously. Instead, specific sequences of photoperiods experienced at the prereproductive and reproductive stages appear to influence germination behavior.

Methods
Repeated census of seed germination of individual agar plates. Plates were incubated under different conditions, and the number of seeds that germinated at each census was recorded.