Improvement of seed germination of Fagus orientalis Lipsky

This thesis was seeking two main approaches for improvement of seed germination of oriental beech, a timber producing species in Hyrcanian forests in northern Iran. Germination behavior of beechnuts was enhanced either by decreasing the dormancy breakage period, or by increasing seed lot quality. A simple grading based on the weight of beechnuts, before exposing the dormant nuts to dormancy breaking conditions, significantly increased germination capacity of heavy class beechnuts, and reduced the period of dormancy breakage. Almost the same results were obtained by removing the endocarp. Applying alternative chilling temperatures, during dormancy breakage had positive effects on speed of dormancy release. These simple methods can be used with little equipment in forest nurseries and are suggested to be accompanied with more advanced techniques, like restricting moisture content during moist cold stratification period to gain maximum benefit. Previous reports from European beech and the results from the effect of endocarp removal suggest a possible role of other agents in dormancy in oriental beechnuts. Water soluble phenolics extracts from the seed coats, significantly suppress the germination of radish seed. The endocarp may act as a barrier against exudation of these germination inhibitors. The deep embryo dormancy presents problems when assessing the viability of oriental beech nuts. It is therefore possible to test germination performance in semi-dormant nuts to predict the nut viability in this species. A dormant seedlot was stored in sub-chilling conditions for 15 months and a series of germination tests were conducted during the dormancy breakage period of stored and fresh nuts. The results showed that mean germination times for both nut groups were almost the same, but germination capacity was statistically different only for semi-dormant nuts. Non-dormant stored and fresh nuts showed no significant differences, which indicate the complexity of dormancy release in oriental beech nuts. Abscisic acid (ABA) contents of embryonic axes of stored and fresh nuts were measured during the dormancy breakage period, and results indicated a close correlation between ABA levels and increment in germination capacity as dormancy was released. Near infrared spectroscopy (NIRS) combined with partial least squares regression (PLS) were used as rapid and non-destructive methods for discrimination of sound and deteriorated single beechnuts. NIRS-PLS is a promising method for quality improvement of nearly all agricultural products and in this study showed 100% accuracy in separation of viable and non-viable nuts