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°C. Mean seed longevity was similar for seeds produced by plants that grew in warm-wet, warm-dry and cool-dry conditions (P50 of about 20 days), but extended for plants in cool-wet conditions (P50 = 41.7 days). Cool temperatures resulted in seeds with a wider distribution of lifespans (s = 20 days) than warm conditions (s = 12 days); the large s caused the extended P50 for cool-wet plants, but not cool-dry as a result of a concomitant reduction in initial seed germination (Ki). After moving to the common environment, all plants generated new vegetative material, which went on to produce seeds with similar longevity (P50 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.

Natural variation in longevity among populations of the same species, and between species and genera was investigated to inform seed-collection strategies. Seed longevity for 30 wild Australian populations was measured with a controlled ageing test. The populations were represented by eight species from three genera, namely Minuria (Asteraceae), Wahlenbergia (Campanulaceae) and Plantago (Plantaginaceae), each collected from up to eight different locations. Seed-survival curves were fitted by using the equation v = Ki + p/σ, which allowed comparison of the initial population viability (Ki), the population distribution of seed life spans (σ), and mean seed longevity (P50, calculated as Ki × σ). At a genus level, the average P50 indicated that M. integerrima (DC) Benth. is the longest-lived, Wahlenbergia is intermediate and Plantago is the shortest-lived. However, there was also variation in P50 values among populations of most species. Some species had the same σ value for all populations, e.g. all eight populations of W. communis Carolin had the same σ value, with the differences in Ki causing the variation in P50. This consistency in σ existed even though seedlots were collected from diverse locations, with mean annual rainfall ranging from 180 to 840 mm. In comparison, for the six seedlots of W. gracilis (G.Forst.) A.DC., a large difference in σ as well as Ki led to the variability in P50, with some indication of a possible correlation between annual rainfall and P50 or σ in some species. A relationship between variation in σ and the breeding system is proposed for Wahlenbergia. The data show that it can be risky to expect accurate prediction of seed longevity for a wild species on the basis of survival data from a single collection.

BackgroundKarrikins are smoke-derived compounds that provide strong chemical cues to stimulate seed germination and seedling growth. The recent discovery in Arabidopsis that the karrikin perception system may be present throughout angiosperms implies a fundamental plant function. Here, we identify the most potent karrikin, karrikinolide (KAR1), in biochars and determine its role in species unique plant responses.MethodsBiochars were prepared by three distinct commercial-scale pyrolysis technologies using systematically selected source material and their chemical properties, including karrikinolide, were quantified. Dose-response assays determined the effects of biochar on seed germination for two model species that require karrikinolide to break dormancy (Solanum orbiculatum, Brassica tourneforttii) and on seedling growth using two species that display plasticity to karrikins, biochar and phytotoxins (Lactuca sativa, Lycopersicon esculentum). Multivariate analysis examined relationships between biochar properties and the plant phenotype.Findings and ConclusionsResults showed that karrikin abundant biochars stimulated dormant seed germination and seedling growth via mechanisms analogous to post-fire chemical cues. The individual species response was associated with its sensitivity to karrikinolide and inhibitory compounds within the biochars. These findings are critical for understanding why biochar influences community composition and plant physiology uniquely for different species and reaffirms that future pyrolysis technologies promise by-products that concomitantly sequester carbon and enhance plant growth for ecological and broader plant related applications.

Summary• Seed longevity, which is essential for germplasm conservation and survival of many land plant species, can vary considerably within species and cultivars. Here, we explore the relationship between parental and offspring phenotypes to elucidate how pre-zygotic environment affects seed longevity.• Plants of the wild species Plantago cunninghamii were exposed to wet or dry soil within a warm or cool glasshouse until flowering and then moved to a common environment. Seeds subsequently produced were collected at maturity, and longevity was assessed by controlled ageing at 45°C, 60% relative humidity. Multivariate analysis was used to examine relationships between the parental and offspring phenotypes.• The pre-zygotic environment resulted in a highly plastic parental response which was passed on to offspring seeds and changed their longevity (p 50 ) by more than a factor of 2. Seed longevity is a function of the seed population's distribution of deaths in time (r) and quality (K i ); r was associated with plant size, and K i with reproductive plant traits.• The pre-zygotic growth environment modulated seed longevity via a parental effect. Reproductive performance and seed quality (K i ) were highly correlated with each other and unrelated to the maternal plant phenotype. Hence seed quality may be associated with the paternal plant response to the environment.