part_of part of part of primary endosperm cell c&#233lula primaria del endosperma (Spanish, exact) plant_anatomy Cell produced by the fusion of sperm cell nucleus and two polar nuclei of the central cell (or diploid secondary endosperm nucleus, in cases where two polar nuclei fuse together before double fertilization). The first cell of the endosperm, often triploid. 一次胚乳細胞 (Japanese, exact) PO:0000038 endosperm embryo sac cell