Changes in Reserve Materials Deposited in Cotyledons of Pedunculate Oak (Quercus robur L.) Seeds during 18 Months of Storage

Pedunculate oak (Quercus robur L.) produces desiccation-sensitive seeds, the long-term storage of which is limited. We investigated the effectiveness of using a slightly lowered storage temperature (−5 °C) in combination with slight dehydration of acorns (38% MC) for improving seed viability during 18 months of storage. To this end, we performed a factorial experiment using storage temperatures of −5 °C and −3 °C combined with 38% and 40% seed MC and subsampled the acorns at 4-month intervals over 18 months. The modified regime of −5 °C combined with 38% MC resulted in increased germination and emergence rates but only when seeds were stored for 12 months. It also restricted seed biomass loss. Starch depletion was recorded on consecutive sampling dates, showing little dependence on storage conditions. At −5 °C at both MC, it was accompanied by an accumulation of soluble carbohydrates. Fat reserves also decreased under all storage conditions, but the slowest decrease was at −5 °C and 38% MC. We conclude that storing acorns in a slightly dehydrated state (38% MC) at −5 °C produced a transient improvement in seed viability and that the observed increase in soluble carbohydrates may indicate initiation of prosurvival mechanisms, such as osmo- and cryoprotection.