Ecophysiology of germination and emergence of Echinochloa crus-galli L. seeds.
Mature Echinochloa crus-galli seeds exhibited a high degree of primary dormancy at the time of ripening. This dormancy was partially and gradually lost after weeks of storage. However, dormancy-breaking most often occurred after seed piercing near the embryo. The relative degree of germination showed a strong dependence on light quality conditions. Heat shock was also effective for dormancy-breaking. Burial period was found to affect photosensitivity-induction, such that a few minutes of far-red irradiation (724 nm) were sufficient to trigger germination. Seeds induced to germinate by red irradiation (660 nm) underwent dormancy re-induction under a few centimetres planting depth. However, this soil-imposed germination inhibition was partially relieved by flushing the seed-soil matrix with an oxygen-free gas (N2). Flooding depth inhibited seedling emergence. In such conditions, light availability was crucial for increasing the chances of emergence.