Mgm. Vancreij et al., INTERSPECIFIC CROSSES IN THE GENUS TULIPA L - IDENTIFICATION OF PREFERTILIZATION BARRIERS, Sexual plant reproduction, 10(2), 1997, pp. 116-123
Pollen tube growth in the pistil and pollen tube penetration of ovules
have both been studied in crosses between cultivars from Tulipa gesne
riana L. and 12 tulip species from all eight sections of the genus Tul
ipa to identify pre-fertilization barriers. Depending on the cross, po
llen tubes grew as far as the stigma or the style or continued growing
down into the ovary. Pollen tubes penetrated none or only a few perce
nt of the ovules of some crosses, despite the presence of many pollen
tubes in the ovary. In other crosses, from which no or only a few hybr
ids have been obtained after seed maturation on the plant, pollen tube
penetration was found in up to 79% of the ovules. Apparently, various
kinds of barriers preventing fertilization or normal embryogenesis oc
cur in interspecific tulip crosses.