Seed dormancy and dormancy-breaking methods in Leymus chinensis (Trin.) Tzvel. (Poaceae)

Leymus chinensis (Trin.) Tzvel. is a perennial grass with high productivity and forage value; however, poor stand establishment, often due to seed dormancy, limits its widespread use for forage production. To investigate the mechanism of seed dormancy and to develop effective methods of improving germination, the contribution of each part of the caryopsis to dormancy was investigated, and a number of single or combined dormancy-breaking pre-treatments were conducted using three seed lots. The palea, lemma, pericarp/testa, and endosperm all contributed to seed dormancy. The contribution of each part to dormancy was 234%, lemma; 62%, palea; 284%, pericarp/testa; and 420%, endosperm. Hull (palea and lemma) removal, pericarp/testa piercing, and soaking in distilled water or 30% sodium hydroxide (NaOH) significantly decreased the percentage of dormant seeds (i.e. increased germination). Treating hull-removed and pericarp/testa-pierced seeds with gibberellic acid (GA(3)) also significantly decreased the percentage of dormant seeds. Compared with each of the single pre-treatments, the combined pre-treatment of pre-soaking in water for 1d, then 30% NaOH for 60min and treating with 300m GA(3) resulted in the highest germination (89%); and seed viability was 91%.