Figure 1.

Schematics of fertilization in vivo and in vitro. (A) Schematic depiction of the pollen tube path through the ovary. Dashed box shows growth between the rows of ovules after emergence in the ovary chamber. pg-pollen grain, pt-pollen tube, si-stigma, st-style, oc-ovary chamber, ov-ovules. (B) Schematic depiction of an ovule and a pollen tube approaching the micropyle. In vivo, pollen tubes extend along the funiculus, a cylindrical structure that connects the ovule to the placenta, and enter the ovule through the micropyle, an opening in the integuments that line the embryo sac. pt--pollen tube, f--funiculus, mp--micropyle, s--synergid cell, e--egg cell, c--central cell, a--antipodal cell. (C) Schematic depiction of semi-in vitro experiments with a cut style and dissected ovules. The pollen tube grows through the cut style (dashed portion), emerges and grows on the surface of the agar medium where it locates and fertilizes an ovule. For simplicity, only one pollen tube is depicted here. Abbreviations are the same as in A.