Defensin-like ZmES4 mediates pollen tube burst in maize via opening of the potassium channel KZM1.

In contrast to animals and lower plant species, sperm cells of flowering plants are non-motile and are transported to the female gametes via the pollen tube, i.e. the male gametophyte.

Establishment of the male germline and sperm cell movement during pollen germination and tube growth in maize.

Two sperm cells are required to achieve double fertilization in flowering plants (angiosperms). In contrast to animals and lower plants such as mosses and ferns, sperm cells of flowering plants (angiosperms) are immobile and are transported to the female gametes (egg and central cell) via the pollen tube. The two sperm cells arise from the generative pollen cell either within the pollen grain or after germination inside the pollen tube.

Sporophytic control of pollen tube growth and guidance in maize.

Pollen tube germination, growth, and guidance (progamic phase) culminating in sperm discharge is a multi-stage process including complex interactions between the male gametophyte as well as sporophytic tissues and the female gametophyte (embryo sac), respectively. Inter- and intra-specific crossing barriers in maize and Tripsacum have been studied and a precise description of progamic pollen tube development in maize is reported here. It was found that pollen germination and initial tube growth are rather unspecific, but an early, first crossing barrier was detected before arrival at the transmitting tract.