Mechanism of the glumes in inhibiting seed germination of Leymus chinensis (Trin.) Tzvel. (Poaceae)

Germination of Leymus chinensis is significantly inhibited by glumes but the mechanisms are still unclear. This work aimed to investigate the effects of glumes on seed dormancy from the aspects of water permeability, bioassay of inhibitors, endogenous hormones, and microstructure. Results showed that lemmas rather than paleas played a critical role. Water absorption curves of intact and naked seeds were similar and seeds increased in weight by 68.1 and 44.4%, respectively after 24 h. Inhibitors in glumes significantly decreased germination of Chinese cabbage and the endogenous hormones of GA(3), Zeatin, IAA, and ABA were all significantly higher in the glumes than in the naked seeds. However, these inhibitors did not significantly affect L. chinensis seed germination. The outside of the glumes was compact-structured and had a cuticle layer, and many enclosed lids in the surface. Seed germination of and extent of glume erosion increased with increase in H2SO4 concentration. Most of the lids opened with 40% H2SO4 treatment. On the inside of the glumes, there were many structures similar to needles which might make the glumes and caryopsis bind tightly by increasing mechanical resistance. It could be concluded that the main mechanisms of L. chinensis glumes was the mechanical resistance of glumes rather than water permeability, inhibitors and endogenous hormones in glumes.