This book summarizes the latest studies on plant reproduction and multiple aspects of signaling in reproductive development. It also presents the most advanced processes in CrRLK1L receptor and RALF peptide studies during plant development. Focusing on signaling in pollen tube integrity and sperm release regulation, it provides significant insights into the BUPS-ANX receptor complex and the corresponding ligands RALF4/19 to promote pollen tube growth with proper cell integrity. It also proposes a working model of female tissue-derived RALF34 competing with RALF4/19 from the BUPS-ANX to trigger pollen tube rupture and sperm release. Offering a detailed overview of the spatiotemporal regulation mechanism underlying the control of pollen tube integrity and sperm release, the book fills a major gap in our understanding of plant reproductive processes, and as such is a valuable resource for those working in the area of plant signaling.