The growth of pollen tubes in the embryo sac of plants is due to chemical signals. Chemotropism is the growth of structure in a living organism is due to the stimulation of some chemicals from the outside of the organism. The process is also known as chemotaxis.
Several molecules are secreted by the stigma or part of the female embryo sac to attract pollen tubes are Chemocyanin (Plantacyanins) in lily, Glycosylated tobacco transmitting tissue-specific proteins in tobacco, and cysteine-rich polypeptides LUREs (LURE1 and LURE2).
