In angiosperms, pollen germinates on:
Angiosperm pollination requires efficient deposition of pollen onto receptive stigma papillae producing hydrated exudates rich in lipids, proteins, and compatibility factors. On compatible stigma, pollen rapidly hydrates, germinates forming polarized tip-growing pollen tube invading transmitting tract of style toward ovule. Germination occurs strictly on stigma surface not style or ovary, providing crucial checkpoint for self-incompatibility recognition via SRK-SCR or S-RNase molecular mechanisms. Successful germination initiates progamic phase where tube navigates along chemotropic LURE gradients secreted by synergids toward micropyle ensuring efficient and targeted fertilization.
Ref: Heslop-Harrison, Annu Rev Plant Physiol: pollen germination in angiosperms occurs on stigma papillae after hydration.