Maternal effects of drought stress and inbreeding in Impatiens capensis (Balsaminaceae)

Maternal effects can have substantial impacts on plant fitness and plant populations. Stressful environmental conditions can cause a maternal plant to inadequately provision its progeny, resulting in poor seedling growth, low reproductive success, and decreased competitive ability. Maternal effects consist of environmental and genetic load components, but the interactions between these two components have rarely been considered. To determine the effects of maternal drought stress and maternal inbreeding on progeny biomass (a fitness correlate) and physiological responses to drought stress, we conducted a greenhouse experiment with genetic lines from two populations (mesic site vs. dry site) of the herbaceous annual Impatiens capensis (Balsaminaceae). Seeds were collected from cleistogamous flowers of inbred or outcrossed maternal plants that were subject to either a drought or control treatment. These seeds were grown into juvenile plants that were also subject to either a drought stress or a control treatment. Plants from the mesic site had significantly reduced biomass from maternal drought stress, while plants from the dry site maintained biomass despite adverse maternal environmental conditions. Juvenile plants of both populations had reduced biomass only as a result of maternal inbreeding. Interestingly, inbreeding depression was more apparent when maternal environmental conditions were benign.