Rapid assessments of cold hardiness and quality deterioration during storage of bare root conifer transplants.

Chlorophyll fluorescence and trace gas analysis techniques were evaluated with the aim of providing nursery and establishment managers a rapid prediction of dormancy status and seedling quality deterioration during storage. Dark-adapted maximal fluorescence (Fv/Fm) assessments of excised shoots following freezing treatments accurately predicted cold tolerance as determined using the temperature at which 50% of seedlings are damaged (LT50). The Fv/ Fm of excised shoots was correlated with visual assessments of needle damage and survival following extended storage of seedlings at different temperatures. We suggest that these Fv/ Fm-based methods provide a more rapid and robust indicator of seedling quality during period of extended storage when compared to other physiological measures, such as root electrolyte leakage (REL) and the build-up of volatile compounds such as ethanol and ammonia. This modified fluorescence-based estimate of LT50 (F.LT50) can be conducted within 3 days, compared to 14 days using the conventional visual assessment LT50. The F.LT50 fluorescence based technique is now been routinely used to assess hot lift and cold storage suitability of Sitka spruce seedlings in Coillte nurseries.