Germination dynamics of Nothofagus glauca seeds: provenance-specific responses to temperature variation

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Background: The influence of temperature on seed germination is crucial, and climate change effects on plant distribution are significant. To grasp climate change’s impact on terrestrial ecosystems, understanding plant adaptation to temperature shifts is vital. Nothofagus glauca, a vulnerable species endemic to Chile’s Mediterranean region, is the most representative species of South American Mediterranean forests. Methods: Seeds of N. glauca were collected from two Andean provenances during mast years (2017, 2022) and processed according to the standards of the International Seed Testing Association (ISTA). Germination experiments were conducted under controlled laboratory conditions in the absence of light, testing four temperature levels (18°C, 22°C, 26°C, and 30°C) and two provenances (El Colorado, located further north, and San Fabian, located further south). Seeds were pretreated with gibberellic acid to break physiological dormancy, and germination parameters were assessed over a 40-day period. Results: Temperature had a significant impact on germination process, although the effect varied by provenance. The optimal germination capacity temperature was 22°C for the northern origin and 26°C for the southern origin. In both provenances, germination capacity remained relatively high at temperatures of 18°C and 30°C, suggesting that these temperatures did not approach the minimum or base and maximum or ceiling temperature thresholds. Furthermore, no clear trend was observed in the germination start day for either provenance. Significant differences were observed in average germination speed and germination vigour between the two provenances. Considering all variables, the optimal temperature differs between them (22°C for El Colorado and 26°C for San Fabian). Conclusions: Temperature’s pivotal role in germination and diverse provenance responses highlight potential impacts on genetic distribution and conservation. Understanding provenance-specific adaptation to changing climates is essential for comprehending climate change’s effects on terrestrial ecosystems. Tailoring conservation approaches to distinct provenances, like N. glauca, is crucial. This approach can effectively tackle climate change challenges and protect vulnerable species.

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