Contrasting germination responses to vegetative canopies experienced in pre- versus post-dispersal environments

LINDSAY D LEVERETT; GABRIELA A AUGE; AMAN BALI; KATHLEEN DONOHUE

ANNALS OF BOTANY

OXFORD UNIV PRESS

Año: 2016

0305-7364

Background: Seeds adjust their germination based on conditions experienced before and after dispersal. Post-dispersal cues are expected to be more accurate predictors of offspring environments and in turn offspring success than pre-dispersal cues. Therefore, germination responses to conditions experienced during seed maturation are expected to be superseded by responses to conditions experienced during seed imbibition. The presence of plant neighbors likely reduces the performance of germinants, leading to the predictions that the presence of a vegetative canopy will reduce germination and that a vegetative canopy experienced during imbibition will override responses to a canopyexperienced during seed maturation. We tested these predictions in Arabidopsis thaliana.Methods: Seeds were matured under a simulated canopy (green filter) or white light. Fresh (dormant) seeds were imbibed in dark, white light, or canopy at two temperatures (10°C or 22°C), and germination proportions were recorded. Germination was also recorded in after-ripened (less dormant) seeds that were induced into secondary dormancy and imbibed in the dark at each temperature, either with or without brief exposure to red and far-red light. Key results: Unexpectedly, maturation under a canopy expanded the conditions that elicited germination compared to maturation under white light, even as seeds lost and regained dormancy. In contrast, seed imbibition under a canopy impeded or had no effect on germination. Maturation under a canopy did not modify germination responses to light wavelengths. Seed maturation under a canopy also masked genetic variation in germination. Conclusions: Our results challenge the prediction that offspring will respond more strongly to their own environment than to that of their parents. The observed relaxation of germination requirements caused by maturation under a canopy could compromise adaptive germination responses to light cues experienced after dispersal. The masking of genetic variation by maturation under a canopy, moreover, could impeded evolutionary responses to natural selection on germination.