A poster with flowers or clusters of flowers produced by twelve species of flowering plants from different families. The biological function of a flow
A poster with flowers or clusters of flowers produced by twelve species of flowering plants from different families. The biological function of a flower is to bloom’s taxonomy poster pdf reproduction, usually by providing a mechanism for the union of sperm with eggs.
The essential parts of a flower can be considered in two parts: the vegetative part, consisting of petals and associated structures in the perianth, and the reproductive or sexual parts. A stereotypical flower consists of four kinds of structures attached to the tip of a short stalk. Ovules are megasporangia and they in turn produce megaspores by meiosis which develop into female gametophytes. These give rise to egg cells. A pistil may consist of a single carpel or a number of carpels fused together.
The sticky tip of the pistil, the stigma, is the receptor of pollen. Although the arrangement described above is considered “typical”, plant species show a wide variation in floral structure. These modifications have significance in the evolution of flowering plants and are used extensively by botanists to establish relationships among plant species. The four main parts of a flower are generally defined by their positions on the receptacle and not by their function. Flowers show great variation and plant scientists describe this variation in a systematic way to identify and distinguish species. Specific terminology is used to describe flowers and their parts.
Connate petals may have distinctive regions: the cylindrical base is the tube, the expanding region is the throat and the flaring outer region is the limb. Flowers with connate petals or sepals may have various shaped corolla or calyx, including campanulate, funnelform, tubular, urceolate, salverform or rotate. Referring to “fusion,” as it is commonly done, appears questionable because at least some of the processes involved may be non-fusion processes. For example, the addition of intercalary growth at or below the base of the primordia of floral appendages such as sepals, petals, stamens and carpels may lead to a common base that is not the result of fusion. Left: A normal zygomorphic Streptocarpus flower.
Both of these flowers appeared on the Streptocarpus hybrid ‘Anderson’s Crows’ Wings’. Many flowers have a symmetry. Some inflorescences are composed of many small flowers arranged in a formation that resembles a single flower. Floral formulae have been developed in the early 19th century and their use has declined since. The format of floral formulae differs in different parts of the world, yet they convey the same information. The use of schematic diagrams can replace long descriptions or complicated drawings as a tool for understanding both floral structure and evolution.
Such diagrams may show important features of flowers, including the relative positions of the various organs, including the presence of fusion and symmetry, as well as structural details. The transition to flowering is one of the major phase changes that a plant makes during its life cycle. CONSTANS, FLOWERING LOCUS C and FLOWERING LOCUS T. The first step of the transition is the transformation of the vegetative stem primordia into floral primordia. This occurs as biochemical changes take place to change cellular differentiation of leaf, bud and stem tissues into tissue that will grow into the reproductive organs.
Growth of the central part of the stem tip stops or flattens out and the sides develop protuberances in a whorled or spiral fashion around the outside of the stem end. Once this process begins, in most plants, it cannot be reversed and the stems develop flowers, even if the initial start of the flower formation event was dependent of some environmental cue. Once the process begins, even if that cue is removed the stem will continue to develop a flower. The molecular control of floral organ identity determination appears to be fairly well understood in some species. These gene functions are called A, B and C-gene functions. In the first floral whorl only A-genes are expressed, leading to the formation of sepals. In the second whorl both A- and B-genes are expressed, leading to the formation of petals.