8A Elgersma, R Sniezko-Euphytica. Cytology of seed development related to floret position in perennial ryegrass( Lolium perenne L. )[J]. Euphytica, 1988,39 (3) :59-68.
9Anslow R C. Seed formation in perennial ryegrass. Ⅱ Maturation of seed (J]. Grass and forage science , 1964,19(3) : 349-357.