Effects of collection time and after-ripening on chemical constituents and germinability of scotch thistle (Onopordum acanthium) cypselas

Earlier studies have shown that seed germinability decreases with the physiological age of plants during seed development, but the effects of plant physiological age on the chemical constituents of fresh and after-ripened seeds and the relationship between chemicals and germination of such seeds have not been investigated fully. We studied this phenomenon in Scotch thistle (Onopordum acanthium L.) cypselas. Mature cypselas were collected twice (early and late) from the same mother plants, which were grown under the temperature regime of 25/10 °C (14 h light, 10 h dark) in a walk-in growth chamber in 2000 and 2001. Cypselas were used fresh and after 4 months of dry storage at room temperature (~25 °C, ~37% relative humidity). Germination percentage, coefficient of germination rate, moisture content, wax load, lignin content, and phenolic compounds were determined for cypselas from all treatments. Germination percentages were higher for early-matured than for late-matured cypselas, and higher for after-ripened cypselas than for fresh ones. Late-matured fresh cypselas had greater moisture content than the early-matured fresh cypselas. After-ripening decreased cypsela moisture content and wax load. Plant physiological age and after-ripening did not affect lignin content. Overall, after-ripened cypselas had more phenolic compounds than fresh cypselas. Plant physiological age and after-ripening affect the chemical constituents of O. acanthium cypselas and their germination patterns.