The effect of maternal photoperiod on seasonal dormancy in Arabidopsis thaliana (Brassicaceae)

The maternal photoperiod at the time of seed maturation can predict the sea sonal conditions of newly dispersed seeds. We investigated the effects of m aternal photoperiod on seasonal dormancy in Arabidopsis thaliana using a se t of F6 recombinant inbred lines derived from a cross between individuals f rom two natural populations (CaI-0 and Tac-0) differing in cold requirement s for germination. We grew 40 Cal X Tac lines in a long-day photoperiod (8 h of full spectrum light plus 8 h of low-fluence incandescent light) and a shortday photoperiod (8 h full spectrum light). We then exposed seeds from each family and maternal photoperiod to either a cold stratification treatm ent (4 degreesC, 21 d) or no cold stratification. Both maternal photoperiod and progeny stratification influenced the percentage of seeds that germina ted and the speed of germination. The short-day photoperiod caused increase d responsiveness to stratification, with higher germination percentages and speeds in stratified seeds. Stratification influenced the expression of ma ternal photoperiod effects, such that short days increased germination perc entage and speed in stratified seeds but inhibited germination in unstratif ied seeds. Families differed significantly in their plasticity to maternal photoperiod and stratification, but genetic variation for plasticity to mat ernal photoperiod was expressed only in unstratified seeds. Because the exp ression of maternal photoperiod effects and genetic variation for photoperi od effects depended on progency stratification, the evolution of these mate rnal effects will depend on the seasonal environment experienced by progeny .