CONSTANT CROSS-TALK. “During its journey, the angiosperm pollen tube communicates with its environment, allowing the maternal reproductive tissues to recognize and support compatible pollen in order to avoid fertilization failure. The acceptance of compatible pollen and the subsequent steps leading to successful fertilization comprise complex and cooperative processes between the pollen and the receptive pistil.”
http://www.sciencedirect.com/science/article/pii/S1674205214608996