Pre-zygotic parental environment modulates seed longevity

The potential for the pre-zygotic plant growth environment to play a role in determining seed longevity was investigated for a species that inhabits arid to semi-arid Australia. Seed longevity is particularly important for wild populations in fluctuating environments because the longer a seed-lot is able to survive in the soil seed bank the more likely it is to buffer the population from unpredictable environments. Thus Wahlenbergia tumidifructa plants received wet or dry soil moisture within a warm or cool glasshouse until flowering. Seeds subsequently produced by flowers that opened on the day that plants were moved to a common environment were collected at maturity and longevity assessed by controlled ageing at 60% relative humidity and 45 degrees C. Mean seed longevity was similar for seeds produced by plants that grew in warm-wet, warm-dry and cool-dry conditions (P(50) of about 20 days), but extended for plants in cool-wet conditions (P(50) = 41.7 days). Cool temperatures resulted in seeds with a wider distribution of lifespans (sigma = 20 days) than warm conditions (sigma = 12 days); the large sigma caused the extended P(50) for cool-wet plants, but not cool-dry as a result of a concomitant reduction in initial seed germination (K(i)). After moving to the common environment, all plants generated new vegetative material, which went on to produce seeds with similar longevity (P(50) approx. 20 days) irrespective of original environment. Visible phenotypic responses of the parent to environmental conditions correlated with longevity and quality parameters of the progeny seeds, suggesting that a parental effect modified seed longevity. Our study provides novel empirical data showing that environmental conditions expected under climate change scenarios may potentially cause seed longevity to decline for a species that inhabits arid to semi-arid Australia. These negative impacts on population buffering may weaken the storage effect mechanism of species coexistence in fluctuating environments.