synergids

Synergids are two specialized cells within the embryo sac of the female gametophyte in flowering plants. They flank the egg cell at the micropyle end of the ovule and are connected to neighboring cells, forming a functional unit that participates in fertilization. The synergids typically have a prominent cytoplasm and a distinctive filiform apparatus at their micropylar end, a structure formed by wall ingrowths that increases surface area for secretion and reception of signals.

Functionally, synergids play a central role in pollen tube guidance and fertilization. They produce signals that attract the pollen tube to the ovule and facilitate its entry. Upon arrival, the synergids assist in the controlled rupture of the pollen tube and the release of the two sperm cells into the embryo sac. One sperm fertilizes the egg cell to form the zygote, while the other fertilizes the central cell to initiate endosperm development. After fertilization, synergids are typically degraded or absorbed, although the exact timing and pattern can vary among species.

Developmentally, synergids arise from the same megagametophyte that gives rise to the egg cell and central cell during megagametogenesis. In most species there are two synergids, and their functional lifespan is relatively short, ending as part of the fertilization process. Their proper function is essential for successful double fertilization and subsequent seed development.

Etymology: the name synergid derives from Greek roots meaning “working together,” reflecting their cooperative role with the egg cell in plant reproduction.