flowers

Double fertilisation is characteristic of angiosperms. One male gamete fuses with the egg to form a diploid zygote, while the other fuses with the two polar nuclei to form the usually triploid primary endosperm nucleus. The second event is triple fusion. Two separate male gametes participate; the same gamete does not perform both fusions.

The funiculus, or funicle, is a stalk-like structure that attaches an ovule to the placenta inside the ovary. It may contain vascular tissue that supplies water and nutrients to the developing ovule. The style and stigma are parts of the pistil above the ovary, while integuments are protective coverings around the ovule, not its attachment stalk.

The nucellus is the tissue located inside the ovule around the embryo sac. It can provide nourishment and support to the developing female gametophyte. Integuments form the protective layers around the ovule, the micropyle is an opening in those layers, and the embryo sac is the gametophyte itself. Hence, nucellus is the surrounding nutritive tissue.

Meiosis of the megaspore mother cell produces four haploid megaspores. In the common Polygonum type, only one megaspore, generally the chalazal megaspore, remains functional. It undergoes three successive mitotic divisions to establish the typical eight-nucleate embryo sac. The other three megaspores degenerate, so the correct number is one.

Pollen–pistil interaction enables the pistil to recognise compatible and incompatible pollen. Compatible pollen is accepted, germinates on the stigma, and forms a pollen tube that can grow toward the ovule. Incompatible pollen may be rejected through biochemical responses. The interaction is therefore related to pollen acceptance and fertilisation, not fruit colour, seed drying, or petal fall.