Germination Characteristics of Photoblastic Weedy Rice (Oryza sativa L.) Seed

The effects of different light qualities on the germination characteristics of a newly-discovered black-hulled weedy rice line that shows photoblastism was evaluated. In addition, the effects of rice hull and dark imbibition duration on germination was also studied. The germination percentage under white light was greater than 98% and less than 6% in darkness, indicating that the black-hulled weedy rice sees as positively photoblastic. While red light (R) stimulated germination, the germination was lower than in the white light treatment and the germination percentage of the seeds exposed to far-red light (FR) was similar to those maintained in darkness. The exposure to R for 30 sec. increased germination and this effect was saturated at an exposure of 15 min. The R effect was reversed by subsequent exposure to FR. Phytochrome control of the photoblastic weedy rice seed germination was confirmed by R/FR reversibility. The removal of the hull restored seed germination completely even in dark condition. Non-dormant weedy rice seeds imbibed in the dark enter a deep secondary dormancy, the depth of which was positively related to the duration of imbibition period. These results show that the black-hulled weedy rice seeds exhibit phytochrome-meditated photoblasticity, hull-imposed dormancy and secondary dormancy.