Seed coat and aging conditions affect germination and physiological changes of aging Korean pine seeds

The study was conducted to obtain information on possible seed aging during the long-term storage period of Korean pine seeds with thick impermeable seed coat. The seeds were artificially aged at 18, 24, 37 and 45 degrees C for 35 days. Germinations percentages (GP) of aged seeds were highest on 25 days at 18 degrees C, 15 days at 24 degrees C and 10 days at 37 degrees C. The seeds exposed at 45 degrees C have completely lost their germinability after 5 days of aging. From 5 days of aging, mean germination times (MGT) were lower than control seed. The electrical conductivity on 10 days at 45 degrees C reached 1.5-2.5 times its control seed, and had a positive correlation with the GP and a negative correlation with the MGT. The K+ was the most in leaching solution, and K+ and Mg2+ showed a high negative correlation between GP and MGT. The ratio of K+/Na+ had a higher correlation with seed vigor. The malondialdehyde (MDA) increased to 21 times of control seeds at 45 degrees C after 35 days of aging, and had a negative correlation with GP and MGT. The antioxidant enzymes showed different sensitivity to aging, depending on storage conditions and enzyme species. Ascorbate peroxidase showed the highest correlation with germination following glutathion reductase and Catalase. In conclusion, the seed aging had an effect initially to increase the GP and reduce the MGT. However, as aging treatment continued, the seeds eventually lost vitality due to an increase in physiological damages.