ROLES OF DIFFERENT SEED COMPONENTS IN CONTROLLING TOMATO SEED-GERMINATION AT LOW-TEMPERATURE

The role of different seed components in controlling the germination of tomato (Lycopersicon esculentum) seeds under low temperature conditions was studied in cold-resistant plant line PI341988 and cold-sensitive commercial cultivar UC82B, as well as in eight progeny lines of these two parents. At 12 degrees C, PI341988 and UC82B seeds had a mean time of germination (MTG) of 8.7 days and 19.7 days, respectively. Removal of seed testa by NaOCl treatment shortened the time required for germination by 3 days in both plant lines, but did not reduce the significant differences in germination rate between them. Removal of the seed coat and the endosperm layer in front of the embryo's radicle tip eliminated the differences in germination rate under low temperature conditions between the ten tested lines. All lines exhibited similar radicle elongation rates, both at 25 degrees C and at 12 degrees C. These results indicate that the main barrier to germination of tomato seed at low temperatures is imposed by the endosperm layer. At 12 degrees C, plant line PI341988 exhibited a higher respiration rate than UC82B, indicating its higher metabolic activity under low temperature conditions.