How effective is imbibition-drying- separation?
European silver fir (Abies alba Mill.) produces good seed crops every three to five years but these crops often have a high proportion of empty seeds. In many tree species, the empty and insect-infested seeds are removed during processing and cleaning of seed lots. However, this is only possible if filled and empty seeds differ in some physical characteristic that can be detected by mechanical or electrical means. Improving seed quality is difficult for European silver fir seeds and germination capacity (maximum percentage germination) varies greatly between seed lots (from five to eighty percent). This makes seedling production expensive and inefficient, particularly in container nurseries.
This study tested whether imbibition-drying-separation (IDS) would remove dead, empty and insect-infested seeds to improve the quality of seed-lots of European silver fir. The method involves soaking seeds so that they absorb (imbibe) water, then partially drying them and then separating live seeds from dead seeds. It works on the basis that live seeds retain more absorbed water than dead seeds when they are subjected to drying so that the heavier live seeds can then be mechanically separated from lighter dead and empty seeds. It has been successfully used with several species including Lodgepole pine and Scots pine.
Germination tests showed that the germination capacity of the upgraded seed produced via IDS was higher than the bulk seed lot. IDS can therefore be used to improve the germination capacity of European silver fir seed lots. The potential benefits of this include the ability to single sow seeds, which germinate earlier and more uniformly than non-upgraded seed lots, and therefore potentially make silver fir seedling production more cost efficient in container nurseries.
This research was conducted as part of Forest Research’s work developing understanding of seed and seedling biology, including the regeneration of alternative tree species.
McCartan, S. & Jinks, R. (2015) Upgrading Seed Lots of European Silver Fir (Abies alba Mill.) using Imbibition-Drying-Separation. Tree Planters Notes, Volume 58, Number 2 (2015) pp. 21-27.