Flower Morphology

Flowering plants have reproductive structures that attract pollinators, such as bees and hummingbirds, that aid in dispersing pollen to flowering plants. Some plants, however, are instead dependent on the wind to pollinate. A flower's structure consists of four whorls of leafy material, including the calyx, corolla, gynoecium, and androecium. In each of these whorls are one of four organs, including petals, sepals, stamens, and pistils. Petals and sepals do not play an active role in the reproductive process. Stamens and pistils, the flower's male and female reproductive organs, do aid in reproduction. In addition to these parts, a flower also has an ovary located at the base of the pistil. The ovary is composed of leafy structures called carpels. After the flower has been fertilized, the ovary encloses the ovules to produce fruit. Let's take a further look at the different reproductive parts of a flower.

Calyx

The calyx consists of green leafy material called sepals. Sepals protect the inner parts of the flower during its development and prevent it from becoming dry. A flower typically has the same number of sepals as it does petals: In fact, sepals usually alternate with the number of petals in its arrangement. But this isn't always the case. The sepals may be fused, symmetrical, or asymmetrical in the androecium, gynoecium, and corolla. In some plant families, the sepals cannot be distinguished from the petals.

Corolla

The corolla consists of the colorful parts of the flower called petals. The petals in some plant families have limited visibility. The petals of flowers may fuse to form a tube, which may involve most of the petals or only a portion. If all of the petals develop equally and fuse the same way, the flower is symmetrical. If all of the petals develop unequally and are not fused the same way, the flower has bilateral symmetry. The symmetry of a flower may be affected by the androecium and gynoecium.

Androecium

The androecium consists of the flower's male reproductive organs, called stamens. Each stamen has a filament with an anther, the part of the stamen responsible for pollen production, at the top of it. The anther contains a number of sporangia, which produce microspores. Microspores develop into pollen granules, which assist in distributing sperm to the female reproductive organs. The number of stamens differ greatly in various plant families. The stamens may originate at the base of the pistil or fused near the base of the petals. The anthers may be attached to the filament at the base of the anther, at the back of the anther, or at a point on the anther.

Gynoecium

The gynoecium consists of pistils or carpels, which lie in the center of the flower. Pollen lands at the top of the pistil, where the stigma and style are located. When the pollen granules land, the stigma and style lead them down into the ovary. The ovary contains ovules that make up the base of the pistil. The number of pistils varies in different plant families. In many plant species, carpels may be fused to create a single ovary. These same plants may also have multiple styles fused together to create a single style. If this happens, the plant has a single pistil consisting of several fused carpels.

The ovary may have one of three positions: superior, inferior, and intermediate. If the ovary is attached to one of the three whorls, then it is considered superior. If it is below the attachment of the three whorls, then it is considered inferior. If the ovary is superior and surrounded by a receptacle, then it is considered in an intermediate position. The ovary may consist of one or more locules that enclose one or more underdeveloped seeds called ovules. The ovules are attached to the placenta within the ovary. The arrangement of the placenta varies in different plant families.

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