Maternal temperature effects on dormancy influence germination responses to water availability in Arabidopsis thaliana

• Both genetically based dormancy and dormancy induced by low seed-maturation temperature reduce germination under conditions of low water availability.
• Pre-incubation of seeds under low water availability accelerates germination, but the rate depends on the dormancy-inducing factor.
• Secondary dormancy induced by prolonged pre-incubation at low water availability depends on primary dormancy induced by the environment.
• Genetic differences in germination at low water availability depend on dormancy induced by seed-maturation temperature.

With climate change, germination cuing to water availability is expected to be especially important for seedling survival. Here, we examined germination responses to low water potential and tested whether dormancy status mediates these responses. We considered both genetically based dormancy (genotypes with allelic variation in dormancy genes) as well as dormancy imposed by the environment (low seed-maturation temperature or short duration of dry afterripening). We examined (a) germination capacity at low water potential, (b) germination acceleration in response to pre-incubation at low water potential, and (c) secondary dormancy induction by low water potential. We found that both environmentally imposed dormancy and genetically based dormancy influenced germination responses to low water potential. Specifically, dormancy established via introgression of a strong dormancy allele and dormancy induced by low seed-maturation temperatures both reduced the ability to germinate at low water potential. Pre-incubation at low water potential accelerated germination, but the rate differed between both dormancy-inducing environments and among dormancy genotypes. Prolonged incubation at low water potential induced secondary dormancy, and this effect was greater in fresher (more dormant) seeds and in seeds that were matured at low temperature (a dormancy-inducing treatment). Although genotypes also varied in secondary dormancy induction, their level of primary dormancy did not predict their induction into secondary dormancy. Environmentally induced dormancy also influenced the expression of genetic differences in germination responses to low water potential. Thus environmentally determined dormancy influences not only germination responses to low water potential but also their evolutionary potential.