Role of endogenous hormones, glumes, endosperm and temperature on germination of Leymus chinensis (Poaceae) seeds during development

Aims Leymus chinensis is an original dominant plant in the Songnen grass- land, and it has great value for restoration of severely degraded land. However, seeds are dormant, and low germination percentage is a problem for restoringL.chinensis grassland. The mechanism of seed dormancy is not been well understood. The primary aims of the pres- ent study were to investigate the dormancy mechanism ofL.chinensis seeds (caryopses) with reference to the role of embryo-covering layers, endogenous hormones and temperature. Methods Changes in concentration of the endogenous hormones GA3, indole- acetic acid (IAA), zeatin riboside (ZR) and abscisic acid (ABA) inL.chi- nensis seeds from anthesis to maturity were measured by the enzyme- linked immunosorbent assay method. Germination at different stages of maturity were tested at 16/28C, 5/28C and 5/35C for intact seeds with glumes (control), intact seeds with glumes removed (naked- whole seeds) and intact seeds with glumes and one-half of the endo- sperm removed (naked-half seeds). Important Findings Of the four endogenous hormones monitored, only the concentra- tion of ZR differed significantly between the beginning and the end of seed development (increased); the GA3/ABA ratio also did not differ. Rank of germination percentage of control at the three tem- perature regimens was 5/28C > 16/28C > 5/35C. Germination per- centage of the naked-half seeds reached 100% under the three temperature regimens. We concluded that dormancy of L.chinensis seeds is not mainly controlled by endogenous hormones. Germina- tion temperature, mechanical resistance of glumes and inhibition of endosperm are the main factors controlling dormancy and germina- tion of L.chinensis seeds.