Dry after-ripening does not stimulate the germination of shallowly dormant sitka spruce (Picea sitchensis [Bong.] Carr.) seeds.

Untreated seeds of Sitka spruce were 'shallowly' dormant and did not germinate at 10 degrees C. A comparison of dormancy breakage pretreatments was carried out on dry versus moist seeds. Seeds were incubated at either 7% moisture content (fresh weight basis [mc]) or 30% mc, combined with 3 degrees, 20 degrees and 30 degrees C for 3, 6, 12, and 24 weeks. Dry seeds (7% me) remained viable for 24 weeks at 3 degrees and 20 degrees C, but were killed by 24 weeks at 30 degrees C. Imbibed seeds (30% me) only remained viable for 24 weeks at the lowest temperature (3 degrees C) and were all dead after 24 weeks at both 20 degrees and 30 degrees C. Only seeds incubated under moist conditions (30% mcf were subsequently stimulated to germinate. Shorter durations (3-12 weeks) at 30% me combined with 20 degrees or 30 degrees C led to a small proportion of seeds germinating. 12 and 24 weeks incubation at 3 degrees C and 30% moisture content (equivalent to typical prechill conditions) led to virtually 100% germination. None of the seeds incubated at 7% moisture content were ever induced to germinate. Clearly, seeds of shallowly dormant Sitka spruce did not dry after-ripen within 24 weeks at any of the temperatures tested.