Light condition experienced by parent plants influences the response of offspring to light via both parental effects and soil legacy effects

1. Environmental conditions experienced by parent plants can influence
offspring performance through parental effects induced by DNA methylation.
The offspring can also be influenced by environmental conditions
experienced by their parents via soil legacy effects due to plant-mediated
changes in the composition of soil microbes. These two effects are likely
to act simultaneously, but empirical evidence for combined effects is
limited. 2. We conducted a two-phase experiment with five genotypes of a
clonal plant Hydrocotyle vulgaris. In the first phase, we grew parent
plants of each genotype under two light conditions (ambient vs. shade) and
two DNA demethylation treatments (treated with water vs. 5-azacytidine).
We then collected soils and clonal offspring for each genotype from each
of these four treatments and measured soil (a)biotic properties. In the
second phase, we grew the offspring from each of the four treatments in
the four different soils, under the two light conditions. 3. When grown
under ambient light condition and in soil from ambient parents, offspring
produced by ambient parents grew larger than offspring produced by shaded
parents when the parents were treated with water. This difference was
smaller when the parents were treated with 5-azacytidine, and disappeared
when the offspring were grown in soil from shaded parents. The growth
difference was also observed when the offspring were grown under shaded
condition and in soil from shaded parents. However, this difference was
greater when the parents were treated with 5-azacytidine, and disappeared
when the offspring were grown in soil from ambient parents. Moreover,
offspring growth was associated with fungal composition and total
phosphorus of the soil in which the parents had grown. 4. Our results
show, for the first time, that light condition experienced by parents can
influence offspring responses to light through both parental effects and
soil legacies. The parental effects were mediated by changes in DNA
methylation and the soil legacies were due to plant-mediated changes in a
combination of soil biotic and abiotic properties. These impacts may
eventually influence the ecological and evolutionary trajectories of
clonal plant populations.