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Location of ovules inside a Helleborus foetidus flower. In seed plants, the ovule is the structure that gives rise to and contains the female reproductive cells. It consists of three parts: the integument, forming its outer layer, the nucellus (or remnant of the megasporangium), and the female gametophyte (formed from a haploid megaspore) in its center.
A pistil typically consists of an expanded basal portion called an ovary, an elongated section called a style and an apical structure called a stigma that receives pollen. The ovary (from Latin ovum , meaning egg) is the enlarged basal portion which contains placentas , ridges of tissue bearing one or more ovules (integumented megasporangia ).
In seed plants, a structure called the ovule contains the female gametophyte. The gametophyte produces an egg cell. After fertilization, the ovule develops into a seed containing the embryo. [14] In flowering plants, the female gametophyte (sometimes referred to as the embryo sac) has been reduced to just eight cells inside the ovule.
The ovules are attached to parts of the interior ovary walls called the placentae. Placental areas occur in various positions, corresponding to various parts of the carpels that make up the ovary. See Ovule#Location within the plant. An obturator is present in the ovary of some plants, near the micropyle of each ovule.
Diagram of an ovule in gymnosperms and angiosperms Photomicrograph of an ovule of a monocotyledon. In angiosperms the gynoecium, also called pistil, consists of one or more carpels or carpel leaves that form a cavity, the ovary, inside which the ovules or seminal primordia are protected from both desiccation and attack by phytophagous insects.
The ovules inside a flower's ovary (which later become the seeds inside a fruit) are attached via funiculi, the plant part equivalent to an umbilical cord. The part of the ovary where the funiculus attaches is referred to as the placenta. In botany, the term placentation most commonly refers to the arrangement of ovules inside an ovary.
After the pollen tube grows through the carpel's style, the sex cell nuclei from the pollen grain migrate into the ovule to fertilize the egg cell and endosperm nuclei within the female gametophyte in a process termed double fertilization. The resulting zygote develops into an embryo, while the triploid endosperm (one sperm cell plus two female ...
The ovary changes structure and function beginning at puberty. [2] Since the ovaries are able to regulate hormones, they also play an important role in pregnancy and fertility. When egg cells (oocytes) are released from the fallopian tube, a variety of feedback mechanisms stimulate the endocrine system, which cause hormone levels to change. [10]