Which of the following phenomena is observed in Citrus?

In Citrus and Mango, some of the nucellar cells surrounding the embryo sac start dividing, protrude into the embryo sac, and develop into embryos. This leads to the presence of multiple embryos within a single seed, a condition known as polyembryony.

Since these embryos develop directly from the diploid sporophytic cells of the nucellus or integument (maternal tissue) without fertilization, this specific phenomenon is termed adventive polyembryony.

Answer: Adventive polyembryony.