note on root development, bud activity, and survival of Douglas-fir, and survival of western hemlock and noble-fir seedlings, following exposure to ethylene during cold storage

Three cold storage experiments were conducted with bare-root Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) seedlings from coastal Oregon and eastern Washington Cascade sources. The objectives were to determine the effects of ambient, below-ambient (KMnO4 pellets), and 0.5 and 5 ppm ethylene during short-term storage on subsequent root development (expt. 1) and bud activity (expt. 2), and to relate these results to survival in the field after prolonged cold storage (expt. 3). Root numbers and lengths were measured 28 days following a 7-day storage period after lifting seedlings on September 27 and December 1. In the coastal source, root numbers and lengths in the 5 ppm ethylene treatment were, respectively, 46 and 49% greater in September, and 22 and 13% greater in December, than the controls. No comparable treatment effects were found for the Cascade source. Neither the KMnO4 nor the 0.5 ppm ethylene treatments affected root development in either seed source. For terminal buds in the controls, the number of days to 50% bud break was increased 2-8 days by a 30-day cold storage period compared with a 7-day period. For the coastal source, no increase in the time to 50% bud break was observed in the 5 ppm ethylene treatment. Seedling survival was evaluated in the field for the same treatments following 4 months cold storage for the Douglas-fir sources, coastal western hemlock (Tsuga heterophylla (Raf.) Sarg.), and noble fir (Abies procera Rehd.). Survival for the 5 ppm ethylene treatment compared with the control was increased by 55% in the coastal Douglas-fir source and by 13% in western hemlock. These results suggest that stimulated root development and bud activity may be partially responsible for the observed survival increase following cold storage at elevated ethylene levels.