Practice question

Following pollen tube discharge into synergid, central cell with two polar nuclei fused with second sperm nucleus undergoes triple fusion, establishing triploid primary endosperm nucleus with two maternal to one paternal genome ratio enabling genomic imprinting crucial for seed development regulating nutrient allocation. Subsequent free-nuclear divisions produce cellular endosperm packed with starch, storage proteins lipids consumed by embryo during maturation in exalbuminous seeds or retained in albuminous seeds like cereals. Diploid endosperm occurs only in basal Nymphaeales and Austrobaileyales four-celled embryo sacs; haploid storage characterizes gymnosperms, not angiosperms, highlighting triploid unique evolutionary innovation.