Two levels of morphophysiological dormancy in Korean pine (Pinus koraiensis) seeds.

Warm-cold stratification (20°C then 5°C) produced greater embryo growth and germination in Korean pine (Pinus koraiensis) seeds from Heilongjiang, Jilin, and Liaoning than cold stratification alone.

• Why it matters: Provenance-specific differences in morphophysiological dormancy type and stratification responses are unclear, limiting the ability to tailor dormancy-breaking protocols for different seed sources.
• What they did: Embryo length, embryo-to-seed ratio, and germination percentage were tracked during cold stratification (5°C) and warm-cold stratification (8 weeks at 20°C then 12 weeks at 5°C); in Liaoning, ABA, GA 3, and ACC were quantified and tested with exogenous GA 3 and excised-embryo assays.
• The result: ABA and GA 3 dynamics differed by treatment and tissue (embryo vs endosperm), and GA 3 increased embryo growth and accelerated germination but could not replace stratification; excised embryos stayed germinable under ABA yet became more GA 3 sensitive.

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