Sentence:  In plants, the ability to recognize self from nonself plays an important role in <WSD>fertilization</WSD>, because self-<WSD>fertilization</WSD> will result in less diverse offspring than <WSD>fertilization</WSD> with pollen from another individual. 
Meaning of the word marked with <WSD> tags:  The act of fecundating or impregnating animal or vegetable gametes; especially, the process by which in flowers the pollen renders the ovule fertile, or an analogous process in flowerless plants