Diagrammatic illustration of PD withdrawal. (A) PD is produced constantly by nucellar tip cells and reaches its maximum volume at pollination. (B)Ginkgo biloba pollen grains entered the PD, and the nucellar tip cells terminated secretion. (C) Pollen grains entered the pollen chamber along with PD withdrawal. I, integument; Mc, micropyle canal; Mi, micropyle; Nu, nucellus; P, pollen grains; Pc, pollen chamber; PD, pollination drop.
Jin et al. BMC Plant Biology 2012 12:59 doi:10.1186/1471-2229-12-59