Flowers are considered as an organ system because they are made up of two or more sets, or whorls, of leaflike structures. A typical flower is composed of four whorls, which are the sepals, petals, stamens, and apistil with one or more carpels. Much of the variation among flowers is based on variation of these basic parts.
Complete and Incomplete Flowers
A flower that has all four whorls of floral parts is said to be a complete flower (such as the hibiscus and the lily). An incomplete flower lacks any one or more of these parts (such as those of elms, willows, oaks, and plantains). With or without sepals and petals, a flower that has both stamen and pistil is called a perfect flower. Thus, all compete flowers are prefect, but not all perfect flowers are complete. In contrast, types of flowers that have only stamens or only pistils are called imperfect flowers.
Unisexual and Bisexual Flowers
Unisexual flowers are either staminate (bearing stamens only) or pistillate (bearing pistils only) and are said to be imperfect. Bisexual flowers are perfect because they have both stamens and pistil. When staminate and pistillate flowers occur on the same individual, the plant is called monoecious (examples include corn and the walnut tree). When staminate and pistillate types of flowers are borne on separate individual flowers, the plant is said to be dioecious (examples include asparagus and willow).
Superior or Inferior Ovaries
The position of the ovary also varies among different flower types. A flower has a superior ovary when the base of the ovary is located above where the sepals, petals, and stamens are attached. This point of attachment is referred to as the receptacle or hypanthium, the fused bases of the three floral parts (tulips and St. John's wort are examples). An inferior flower has an ovary below where the sepals, petals, and stamens are attached (as do daffodils and sabatia). Some flowers show an intermediate type, where the receptacle partly surrounds the ovary; the petals and stamens branch from the receptacle about halfway up the ovary (as in cherry, peach, and almond flowers).
Hypogynous, Epigynous, and Perigynous Flowers
The position of the ovary in relation to the attachment of floral parts also varies from superior to inferior ovaries. Flowers in which the sepals, petals, and stamens are attached below the ovary are called hypogynous, and the ovaries of such flowers are said to be superior (as in pelargonium and silene). Flowers in which the sepals, petals, and stamens appear to be attached to the upper part of the ovary due to the fusion of the hypanthium are called epigynous, and the ovaries of such flowers are said to be inferior (as in cornus and narcissus). Flowers types in which the hypanthium forms a cuplike or tubular structure that partly surrounds the ovary are called perigynous. In such flowers, the sepals, petals, and stamens are attached to the rim of the hypanthium, and the ovaries of such flowers are superior.
Fused and Distinct Floral Parts
The parts of a flower may be free orunited. Fusion of like parts (such as petals united to petals) is called connation. When like parts are not fused, they are said to be distinct(one petal is distinct from another petal). Fusion of unlike parts (stamens united to petals) is called adnation, and the contrasting condition is called free(stamens are free from petals). Fused structures may be united from the moment of origin onward, or they may initially be separate and grow together as one later in development.
Regular and Irregular Flowers
In many different flowers, the petals of similar shape radiate from the center of the flower and are equidistant from one another. Such types of flowers are said to have regularor radial symmetry. In these cases, even though there may be an uneven number of sepals and petals, any line drawn through the center of the flower will divide it into two similar halves. The halves are either exact duplicates or mirror images of each other. Flowers with radial symmetry are also called actinomorphic flowers(examples: stonecrop, morning glory). Flowers with irregularor bilateral symmetryhave parts arranged in such a way that only one line can divide the flower into equal halves that are more or less mirror images of each other. Flowers with bilateral symmetry are also called zygomorphic flowers(examples: mint, pea, snapdragon). A few flowers have no plane of symmetry and are referred to as asymmetrical.
Content Source: www.flowers-gardens.net/types-of-flowers.html
Flowers Business
Why Do Flowers Smell Good?
Many people enjoy the scent of fresh flowers, either in a garden or arranged in a vase. But what is it about flowers that cause them to give off such an attractive aroma? Actually, the reasons why flowers smell good tracks back to good old-fashioned plant biology. Here is the main reason why flowers smell good, and why this is so important for our environment.
Just as with all forms of life, flowers and plants have a process that allows them to reproduce. In the case of flowers, they produce seeds that allow for more flowering plants to be produced over time. However, they do not posses everything required to produce those fertile seeds. For this reason pollination is required. In short, some sort of means is required to allow the transfer of pollen to eggs that will in turn produce the fertile seeds. To a degree, this takes place with the wind moving pollen around from plant to plant. However, many forms of flowers rely upon the use of pollinators to accomplish this process.
Pollinators are simply animals and insects that will come into contact with the flowers, and then move on, taking the pollen with them. As they progress from flower to flower, the transferred pollen interacts with the eggs and produces the seeds. As the seeds are distributed, an abundance of types of flowers will result.
Part of the mechanism that is used to attract insects and animals such as bats to roses and other flowers is the fragrance. Using this powerful lure gets the pollinator in close proximity to the plant. In like manner, the flower scent in turn attracts the pollinator to other plants, making pollination possible. The fact that flowers smell good is simply nature’s way of making sure the cycle of life for the plants continues with no interruption.
Of course, humans benefit from the fact that flowers smell good. We use the fragrances to freshen our homes, and consider the gift of flowers as one way to show esteem and affection. Part of the reason that red roses are used to convey love and physical attraction is that they have a fragrance that is considered to be especially appealing. Because flowers smell good to insects, the production of flowers will continue. Because humans find that flowers smell good, they will not doubt continue to be found in home gardens and arranged in vases inside the home for many years to come.
Content Source: Wisegeek
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