Breeding systems and pollen tube behaviour in compatible and incompatible crosses in New Zealand species ofRanunculusL.

Abstract

Breeding systems were investigated in 13 New Zealand species of Ranunculus; all were found to be self-compatible. In self-, cross-, and interspecific pollinations there is a very clear reduction of pollen tube number to one in the style. This suggests pollen tube competition or selection of pollen tubes by the stylar tissue but no morphological reason for this could be ascertained. The repeated observation of germination of single pollen grains on the stigma suggests that there is no population effect enhancing pollen germination in these species of Ranunculus.