Cryopreservation of dormant orthodox seeds of European hornbeam (Carpinus betulus)

The sensitivity of dormant seeds of Carpiuns betulus of Polish provenances to extreme desiccation and/or the ultra-low temperature of liquid nitrogen, LN (-196 degrees C), was investigated. Germination and seedling emergence tests in this study did not reveal any critical seed water content (WC) for deeply desiccated seeds (nuts desiccated to 0.02 g g(-1) (1.6% of fresh weight)). The seeds were tolerant to freezing (24 hours) in LN within a range of WC of 0.03-0.20 g g(-1) (3.2-16.5% of fresh weight). Two years storage in LN, after desiccation to a safe WC, did not decrease germination after thawing, in comparison to two years storage at -3 degrees C. Storage of dormant seeds in LN showed that when seeds were stored after their dormancy was broken, germination after storage was lower because of the need for reducing seed WC to 0.08-0.11 g g(-1) (7.7-9.8% of fresh weight) after stratification, i.e. before storage. The results show the possibilities of long-term cryopreservation of European hornbeam seeds in forest gene banks.