Golden-rain tree seed has an impermeable testa which can be overcome by acid scarification and requires cold stratification to overcome embryo dormancy. The following seed treatments were performed: 1) control treatment of acid scarification followed by 84 days of cold stratification; 2) either acid scarification (A), cold stratification for 21, 42, 63, or 84 days (B) or electromagnetic field exposure (C) alone; 3) electromagnetic field treatment applied either before or after an A or B treatment; 4) all possible combinations of A, B, and C. Each treatment was replicated five times with 20 seeds per test.
Exposure duration: continuous for 4.3 s
seeds were treated in four groups: i) control = treatment of acid scarification followed by 84 days of cold stratification ii) either acid scarification (A) or cold stratification (C) or electromagnetic treatment (M) iii) M applied either before or after A or C treatment iv) all possible combinations of A, C and M
Germination of more than 10% occurred only when scarification was followed by cold stratification as expected. Seed germination following scarification was directly proportional to time in cold stratification. Magnetic field treatment applied after both acid scarification and cold stratification did not significantly improve germination as compared to the control (AB). When the electromagnetic field was applied between scarification and 21, 42, 63, or 84 days of cold stratification, germination increased although the effect was significant only at the last two periods. After 84 days of cold stratification, germination was 97% with the electromagnetic treatment as compared to 56% obtained with the control (AB). Seed exposure to the electromagnetic field prior to the conventional AB sequence inhibited germination.
The author concludes that an electromagnetic field treatment of 100 Gauss will partially substitute for cold stratification and significantly increase seed germination of golden-rain tree. These findings suggest that seed exposure to an electromagnetic field increases germination through an unknown effect on the cold-requiring reaction.