Advancements in reproductive assurance and delayed selfing .
繁殖保障和延迟自交的研究进展。
Homozygous races do not segregate on selfing .
自体受精不能分离纯合的生理小种。
However , the growth rate of pollen tubes is faster in the crossing combination than selfing .
花粉管生长速度则以杂交组合快於自交组合。
They produce no offspring of their own , one consequence of which is that populations of plants and animals capable of self-fertilisation , or " selfing " , grow at twice the rate of populations that depend on sexual reproduction .