Pollen tube and plant reproduction

The pollen tube was a fundamental step forward in the evolution of terrestrial plants; in fact, it allowed plants to liberate themselves from water demand during reproduction. The importance of this simple organism (the plant gametophyte) is also due to its peculiar cytological structure, characterized by tip growth and a cell wall that is not canonically structured but perfectly adapted to the growth mechanism. Being both a critical factor in sexual reproduction and an excellent cell model has made the pollen tube attractive to many researchers around the world. The growth of pollen tubes is a complex mechanism that summarizes the basic machineries of cellular expansion: polysaccharides and enzymes are transported by secretory vesicles to a specific location, a set of molecules and proteins translate external signals that influence the cytoskeleton of pollen tubes and thus its growth direction.