Germination in recalcitrant seeds of Holm Oak (Quercus ilex L.): effect of storage conditions

Storage of recalcitrant seeds of wild species is one of thorniest problems not yet resolved in forestry science. In particular, the acorns show a rapid deterioration and a sudden decrease in germination within the first year of storage. The aim of this work was to study phenomena related to the loss of germination of a Mediterranean recalcitrant forest species, the holm oak (Quercus ilex L.), possibly suggesting some treatments able to improve the storage of the oaks. Two different provenances were taken in order to check if the geographical area can affect the conservation of the seed lots. Three different treatments were applied to determine the best conservation method suited to increase seed storage: 1) standard conditions in plastic can with lid at +3°C with 60% RH, 2) stratification in sand and 3) airtight storage in thin polyethylene bags. During the crop year 2008-2009, every two months samples from each storage treatment were tested for moisture content and germination, two of the main characteristics of seed quality. Furthermore, leakage conductivity of acorns was measured as marker of seed membrane integrity. Preliminary data regarding some physiological markers involved in the decrease of the seed quality are presented, as possible explanation of the phenomenon; in particular the role played by oxidative stress during the storage process is discussed.