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The physiological role of lipid droplets (LDs) in plants is largely unknown. To gain insight into the function of LDs, we have characterized the Arabidopsis homologs of SEIPIN proteins, which are crucial for LD biogenesis in yeast and animals. LDs are the main source of carbon storage, but are also involved in stress responses, development and signaling. SEIPIN1 is expressed in embryo; SEIPIN2 and SEIPIN3 in embryo and pollen. Single, double and triple SEIPIN knockout mutants have been obtained. The double seipin2 seipin3 and triple mutants accumulate enlarged LDs in seeds and pollen, hindering their mobilization during germination. Electron microscopy analysis reveals the presence of nuclear LDs in triple mutant embryos, supporting that SEIPINs are essential for maintaining the correct polarity of LD budding. In pollen, the perturbations in LD biogenesis and turnover reduced germination in vitro with a lower fertilization efficiency in vivo. In seeds there was an increase in seed dormancy levels. Our findings reveal the importance of SEIPIN-dependent LD biogenesis in pollen transmission and in adjusting the timing of seed germination, traits of great importance in agriculture.