Nucellar

Nucellar is an adjective used in botany to refer to the nucellus, the central tissue of the ovule that surrounds the megasporangium and provides nutrients to the developing embryo sac. The nucellus is part of the sporophytic tissue of the ovule and is bordered by the integuments that form the seed coat. In many plant species the nucellus functions primarily during ovule development, but in others its cells retain embryogenic potential.

Nucellar embryony is a process in which embryos arise directly from nucellar tissue without fertilization, a form of asexual seed formation known as apomixis. In seeds produced by nucellar embryony, multiple embryos can develop within a single seed, a condition called nucellar polyembryony. Usually there is one zygotic embryo and several nucellar embryos, which are genetic clones of the mother plant.

Occurrence and applications: Nucellar embryony is best documented in Citrus species, where nucellar embryos are common and are used to propagate uniform cultivars through seed-based methods. Mango and other crops also exhibit nucellar embryony in some cultivars. The trait offers advantages for clonal propagation and consistency of traits but can complicate breeding efforts since maternal genotypes are preserved in the seeds.