Freezing response in Scots pine seeds as assessed by DSC and germination test
2003
Pamuk, G.S. | Bergsten, U. | Lingois, P.
Responses of Scots pine (Pinus sylvestris L.) seeds to freezing temperatures after incubation for 5 days at 15 degrees C were examined for dry (7%), 15%, 20%, 25%, and 30% moisture content seeds using differential scanning calorimetry (DSC) to identify critical moisture content at freezing. In a complementary experiment, seeds of the different initial moisture contents were incubated for 2 or 5 days, and subsequently exposed to -5 degrees C or -20 degrees C during 2 days or 5 days, and tested for germination (21 days, 20 degrees C). In the DSC experiments, seeds with higher moisture content (20%, 25%, and 30%) had significantly wider endothermic peaks (-30.51 J/g, -40.36 J/g, and -47.02 J/g) than seeds with lower moisture contents (15% and dry seeds; -6.94 J/g and -0.65 J/g). Germination capacity ranged from 97% (control) to 58% (30% moisture content, 5 days of incubation, 5 days of freezing at -20 degrees C). Germination capacity after freezing was significantly higher (81%-83%) for seeds with moisture contents from dry to 20%, compared to seeds with moisture contents between 25%-30% (68%-72%). Seeds exposed to -20 degrees C for 2 and 5 days had significantly lower germination capacity (72%) than seeds exposed to -5 degrees C (80%-83%). In conclusion, freeze damage increased with the combination of high seed moisture and decreasing below 0 degrees C temperatures, and increased freezing duration. The critical moisture content of Scots pine seeds is between 15%-20% according to DSC and germination tests. To enable autumn seeding, artificial seed coating should restrict water uptake under this critical moisture content during winter and allow for water uptake and germination in spring.
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