Jumat, 22 Mei 2009

Flower Anatomy: Different Parts of a Flower

A flower consists of four major parts, namely, calyx, corolla, androecium and gynoecium. Here is some information about the anatomy of a flower.

A flower is the reproductive structure of an angiosperm (flowering plant). Its function is to mediate the fusion of the sperm (male gamete) and ovule (female gamete) for production of seeds. The arrangement of flowers in a stalk is called inflorescence.

In flowering plants, the process of reproduction starts with pollination (transfer of pollen to stigma), followed by fertilization (fusion of sperm and ovule) and formation of seeds. Some flowers exhibit certain designs to attract the pollinating agents such as bees and butterflies, in order to facilitate fertilization. Depending upon the pollinating agent, flowers can be categorized into anemophilous (pollinated by wind, e.g. grasses), hydrophilous (pollinated by water, e.g. seagrass) and entomophilous (pollinated by insects, e.g. orchids). To understand the mechanism of reproduction in plants, let's take a look at the different parts of a flower.

Flower Anatomy: Different parts of a flower

A flower can be studied as a modified shoot in which the apical meristem does not grow continuously, showing determinate growth. In this, the stem of the flower is the pedicel (flower stalk) and the flower parts are arranged at the end of the pedicel, also called the torus or receptacle. The four major parts or whorls of a flower, starting from the base of the receptacle are calyx, corolla, androecium and gynoecium. Let's take a look at each of them, in detail.

Calyx: Calyx are the outermost whorl of sepals in a flower, which protects the flower before it opens. In general, calyx are green in color. However, in some plant species, they are modified like the color of petals. In such a case, the sepals are referred to as petaloid sepals. Flowers can be classified into two types, based on whether the sepals are free or fused. Flowers with free sepals are called polysepalous flowers; whereas, those with fused sepals are called gamosepalous flowers.

Corolla: Corolla represents the whorl of petals. Petals are usually colorful, and serve the purpose of attracting insects for pollination. Like sepals, petals can be either free or fused in a flower. Flowers with free petals are called polypetalous flowers; whereas, gamopetalous flowers have fused petals.

Androecium: Androecium or the stamen is the male reproductive organ in a flower. A stamen consists of an anther and a filament. An anther produces and contains pollens; whereas, the filament is a hair like structure that attaches the anther to the flower. The pollen contains the male gametes or the sperms.

Gynoecium: The female reproductive organ of a flower is called the gynoecium, which consists of one or more pistils. It is usually located in the center of the flower. A pistil consists of three structures viz. ovary that produces ovules, style (a stalk that connects ovary and stigma) and the stigma that receives the pollen during fertilization.

Flowers are of different types, classified depending upon the presence or absence of the major parts. A flower consisting of all the four major parts is called complete flower. If any of the major whorls is lacking, then it is referred to as an incomplete flower. In addition, a flower having both male and female organ is called a perfect flower, for e.g. roses, hibiscus; whereas, a flower with only one reproductive organ is called an imperfect flower, for e.g. flowers of pumpkin or cucumber plants.