Figure 2.

Sperm cell movement into and within the pollen tube of maize. (A) The position of the twin sperm cells was determined at different time points after germination in vitro. Time points of 40 (n = 29), 55 (n = 45) and 85 min (n = 31) are given. Position of sperm cells in percentage is indicated inside the the pollen grain (black bars), while leaving the grain (white bars), in the middle of the pollen tube (dark grey bars) and at the tip of the tube (light grey bar). (B) Time series showing stretched sperm cells (leading and trailing sperm cell SC_VN and SC_UA, respectively) leaving the pollen grain (left). Movement is shown within a period of 130 seconds (s) as indicated. Please note that movement is very fast after pollen grain exit (top left image) and slows down in the middle of the tube (lower right image). Sperm cells are labelled with α-tubulin-YFP. The tubular knot connecting twin sperm cells is visible in some images (asterisks). Scale bar: 20 µm.