Germination responses to pre-dispersal light and post-dispersal cues

Should seeds respond to their parents’ environments or their own? Leverett et al. hypothesize that germination would respond more strongly to a post-dispersal vegetative canopy than a pre-dispersal canopy, because a seed’s own environment is likely a more accurate predictor of seedling fitness than its parents’ environments. They test their hypothesis in Arabidopsis thaliana.

Germination of seeds following after-ripening and hot stratification to induce secondary dormancy. Seeds were matured under white light (A, C) or a canopy (B, D) then imbibed at either 10 °C (A, B) or 22 °C (C, D). Box colours indicate whether seeds were imbibed directly into the dark, pre-treated with an FR pulse prior to imbibition in the dark or pre-treated with FR and R pulses prior to imbibition in the dark. Black horizontal lines within boxes represent median germination proportion. Box hinges indicate 75th and 25th percentiles. Whiskers span 1·5 times the interquartile range, and black points are observations that fall outside these values.

While a post-dispersal canopy sometimes reduces germination, a pre-dispersal canopy frequently increases germination, prevented induction into secondary dormancy, and reduces germination responses to post-dispersal cues. The effects of a pre-dispersal canopy are stronger in more dormant genotypes. The study explores the mechanisms and hypothetical fitness consequences that attend the masking of post-dispersal plasticity.