Seed Wings Optimize the Regulation of Temperature and Light on the Germination Time of Smith Fir Seeds

Seed wings are well-documented as morphological adaptations for seed dispersal and environmental persistence in angiosperms, but their functional significance in gymnosperms, which dominate temperate and subalpine forest ecosystems, remains poorly understood. This study examines the germination ecology of Smith fir (Abies georgei var. smithii), a species whose seeds possess membranous, translucent wings. We tested the germination responses of three seed treatments—intact, mixed (de-winged seeds mixed with the detached wings), and de-winged seeds under two light conditions (12 hours light/12 hours dark and continuous darkness) and three temperature regimes (5/1°C, 15/2°C, and 25/5°C) to assess the interactive effects of light, temperature, and seed-wing conditions on germination. Smith fir seeds showed optimal germination between 15 and 25°C, with light exposure significantly enhancing germination under cooler conditions (< 5 ℃). De-winged seeds germinated significantly better than intact seeds (P < 0.001), confirming that seed wings inhibit germination. The germination percentages of intact and mixed seed were comparably low and significantly lower than those of de-winged seeds, suggesting that the inhibitory effect is more likely attributable to chemical inhibitors associated with the wings rather than to mechanical restriction. Smith fir seeds, dispersed in October, exhibit conditional physiological dormancy, with wing-derived inhibitors delaying germination until favorable spring conditions. These findings provide insights into the adaptive strategies of gymnosperms in regulating germination timing in responses to seasonal environmental cues in temperate mountain ecosystems.