The Function of Flowers

Everyone loves flowers. Their beauty and fragrance have earned them an important part in our lives. Without flowers we could not survive: they play a vital role in plant reproduction and we depend on flowers to ensure that we can continue to gather the majority of our food needs (bread, rice, vegetables and fruit) and many other useful materials.

Flowers are the key to a plant’s survival. The beauty that we admire and enjoy is only a small part of an often elaborate exercise that ensures pollination and seed production and one that safeguards future generations of plants. The myriads of brilliant yellow flowers of Alyssum sax/tile attract pollinating insects to ensure the production of a mass of seeds and the continuation of the species.

Not all plants produce flowers, and not all flowers are attractive to our eyes. Those with blooms which we consider showy attract pollinators which share our perception of an appealing colour, form or fragrance. Pollinators include bees, flies, other insects, birds, even slugs and snails (the latter pollinate Aspidistras — Cast Iron Plants — whose flowers are produced at soil level).

Pollen is also distributed by the wind. Some flowers give off what we consider to be very unpleasant smells to attract pollinators: flowers of plants in the Stapelia family for instance smell of rotting flesh to attract blowflies, giving them the name Carrion Plants. Sometimes plants produce dull and insignificant flowers but these are surrounded by brightly coloured, showy bracts.

The structure of flowersThe Function of Flowers

Flowers are made up of several highly specialized parts and during evolution these parts have developed in a way best suited to their environment or to the creatures available to pollinate them. Some make large, heavily-scented, trumpet-shaped flowers to entice long-tongued humming birds; some have nodding bell-shaped blooms whose shape protects the important stamens and stigmas within them from frequent rain; others have simple saucer-shaped blooms which only need an insect to crawl over them to fertilize them.

Flowers may be made up of both male parts and female parts and these could be called the simplest flowers. They form the great majority and could be termed ‘self-fertile’.

Male flowers only may be borne on one plant and female flowers only on another. When plants carry only male orfemale flowers they are called dioecious (many Palms, Holly and Laurel are examples). For seeds, berries or fruits to be produced on these plants it is necessary for a male plant to be adjacent to within an insect’s flying distance of a female plant to ensure cross fertilization.

Plants with separate male and female flowers on the same plant are called monoecious. (Begonias, Hazel Nut and Walnut are examples).

Most flowers are made up of sepal, petals, stamen (the male part) and pistil (the female part). Male parts comprise a filament (the long piece) and an anther (the tip). Female parts include the style (the long central shaft), the stigma (the tip) and the ovary (at the bottom of the style).

Sepals are often green, but they can come in other colours. They have a protective role, being the outermost part of the flower. Their primary function is to give protection to the flower before it opens. They may have a collar of leaves under them (called bracts) but they are not really part of the flowers. Anemones display these frilly bracts. The sepal may drop off when the bloom opens or they may remain attached to the flowerhead. Petals are the showy part and form the greater portion of the flowerhead, attracting pollinating insects.

Stamens are part of the male organ, are usually prominent and are capped with anthers, which carry the pollen. The number of stamens carried by a flower is often an aid to identifying what family a particular plant is in. The Swedish botanist Linnaeus introduced the system of counting the stamens in the classification of plants. This system still continues.

The stigma is a female part, and is often sticky so that it can collect pollen. It is usually situated in the centre of the flower. Pollination is the act of pollen reaching the stigma, resulting in seed germination in the ovary and the continuation of the species.

In the composition of a particular flower any of the main parts of a flower may be absent or the number of each of the parts may vary, but the parts of a plant of a single species are normally constant. This is what makes a species different from other species, and provides so many attractive flowers.

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