Seed lot, nursery, and bud dormancy effects on root electrolyte leakage of Douglas-fir (Pseudotsuga menziesii) seedlings

The effects of seed lot, nursery culture, and seedling bud dormancy status on root electrolyte leakage (REL) of Douglas-fir (Pseudotsuga menziesii (Mirb.) France) seedlings were assessed to determine if these factors should be considered when interpreting REL for seedling quality. The relationships of REL to survival, net photosynthesis (P-n), stomatal conductance (g(wv)), mid-day shoot water potential (Psi(mid)), root growth capacity (RGC), and relative height growth were determined for each factor. Nursery culture had no effect on the relationship between REL and all other measured attributes. Seed lot affected the relationship between REL and P-n, Psi(mid), and survival. However, critical REL (i.e., lowest value associated with detectable root damage) and PS80 REL (i.e., level associated with an 80% probability for survival) were similar between seed lots. Bud dormancy status affected the relationship between REL and survival, RGC, and relative height growth. Control levels of REL, critical REL, and PS80 REL decreased as the number of days required for 50% terminal bud break declined. Thus, terminal bud dormancy status must be known before REL can be used to assess seedling quality. If the bud dormancy status of Douglas-fir populations is known, then critical and PS80 REL levels may be useful as indices of root damage.