Format: ORAL

Daniel Ballesteros1,2; Rida Ajmal2, Antonia Martin2, Marina López-Pozo3; Davide Gerna2; Christina Walters4; Hugh W. Pritchard5

1University of Valencia, Burjassot, Spain. 2Royal Botanic Gardens, Kew, Wakehurst Place, UK. 3University of the Basque Country (UPV/EHU), Vizcaya, Spain 4USDA-Agriculture Research Service, Fort Collins, USA. 5Chinese Academy of Sciences, Kunming, China

Orthodox seeds, when dry, solidify their cell’s aqueous cytoplasm forming a glass (i.e., an amorphous non-crystalline solid) where most biochemical reactions are inhibited. However, ageing is not completely stopped at this quiescent state and slowly progress mainly via oxidative reactions. Seed ageing kinetics is species dependant, but the causes for these differences are not well known. However, it has been well characterized that the seeds of some particular species age faster than the average. For example, “green seeds” ? i.e., those containing chlorophyll at maturity, generally in fully developed chloroplasts ? age fast at any storage temperature, like those from Salicaceae species. In addition, diverse “fatty (oily) seeds” age abnormally fast when stored to high subzero temperatures, as those standard in seeds bank (e.g., -20°C). The causes for the faster ageing rates in these two particular seed types have been related to specific reactions modulated by their “dry architecture” (Ballesteros et al., 2020). In other words, the particular physical-chemical properties of the cell cytoplasm of “green” or “fatty” seeds when dry and stored to low temperatures strongly influences their ageing kinetics. This influence is focused in two aspects: (1) the source of Reactive Oxygen Species (ROS), the target of oxidative reactions, and the antioxidant potential, and (2) the differential physical changes occurring in the glassy aqueous phase of the cytoplasm and the lipid oil droplets distributed therein. In this talk we will review the state of art of ageing kinetics in dry seeds with green and fatty architectures. Moreover, we will show recent advances on our understanding of this topic using both multicellular seeds but also fern spores as a unicellular model. Ballesteros D, Pritchard HW, Walters C. (2020). Dry architecture: towards the understanding of the variation of longevity in desiccation-tolerant germplasm. Seed Science Research 30(2): 142-155.