Suppressive Effects of Low Seed-Soaking Temperatures on Germination of Long-Term-Stored Rice Seeds

We investigated the effects of soaking temperature and duration on the germinability of seeds of rice (Oryza sativa L., cv. Koganemochi, Gohyakumangoku, and Koshihikari) that had been stored for a long period. The germinability of the seeds soaked at 5 degrees C for 5 d was markedly lower than that of seeds soaked at 12 degrees C for 5 d. The germinability of the seeds soaked at 5 degrees C for 24 hr was not increased by subsequent soaking at 12 degrees C for 4 d. On the other hand, the germinability of the seeds soaked either at 12 degrees C for 24 hr or at 30 degrees C for 80 min was similar to that of seeds soaked at 12 degrees C for 5 d, even when followed by treatment at 5 degrees C. Thus, the soaking temperature during the first 24 hr was most important for the germination of rice seeds that had been stored for a long period. Western blotting analysis revealed characteristic expression patterns of alpha-amylase isoforms in cultivars correlating with the germinability after soaking at a low-temperature.