Principals of Flowering Plants Taxonomy BOT 222 Dr. Najat Abdulwahab Bukhari Lecture 3

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Plant taxonomy use many characters : Morphology Anatomy Photochemistry Cytology Palynology

Plant Morphology is the general term for the study of the morphology (physical form and external structure) of plants: Vegetative characteristics: (leaves and stems). Floral characteristics: ( Flower and inflorescence )

Flower is valuable in plant classification and taxonomy, It is considered one of the most important part of the plant in the plant classification process for the following reasons: The flower is less affected by different environmental and climate conditions. Contain many basic and obvious differences that distinguish the various plants . Therefore, plants are arranged into several Orders, families , Genus and species . For example: aquatic plants may be similar in outward appearance and internal structure, but differ in the composition of flowers and plants as well as xerosis and salt-loving plants.

The flower is a unique thing in the life of plants angiosperms ,as it is the axis that holds reproduction in organs in the flowering plants, and it’s the key part of sexual reproduction

flower is regarded as a modified stem with shortened internodes and bearing, at its nodes, structures that may be highly modified leaves. Flowers may be attached to the plant in a few ways. If the flower has no stem but forms in the axil of a leaf, it is called sessile. When one flower is produced, the stem holding the flower is called a peduncle.

If the peduncle ends with groups of flowers, each stem that holds a flower is called a pedicel. The flowering stem forms a terminal end which is called the torus or receptacle. The parts of a flower are arranged in whorls on the torus. The four main parts or whorls (starting from the base of the flower or lowest node and working upwards) are as follows:

Calyx: the outer whorl of sepals; typically these are green, but are petal-like in some species. Corolla: the whorl of petals, which are usually thin, soft and colored to attract animals that help the process of pollination. The coloration may extend into the ultraviolet, which is visible to the compound eyes of insects, but not to the eyes of birds.

Androecium : one or two whorls of stamens, each a filament topped by an anther where pollen is produced. Pollen contains the male gametes. Gynoecium: one or more pistils. The female reproductive organ is the carpel: this contains an ovary with ovules (which contain female gametes). The sticky tip of the pistil, the stigma, is the receptor of pollen. The supportive stalk, the style becomes the pathway for pollen tubes to grow from pollen grains adhering to the stigma, to the ovules, carrying the reproductive material.

a bract is a modified leaf or leaf like part just below and protecting an inflorescence Bracts are often (but not always) different from foliage leaves, for example being smaller, larger, or of a different color or texture. Bracts are found in the front of the flower ( the part of flower facing the bracts is called “Anterior Side”) and the other side “Posterior Side”.

bracteole or bractlet : a small bract that arises on a pedicel instead of subtending it. Bractlets can be 2 in dicotyledons, and one in monocots one which may be green or squamous They can differ from each other on where are inserted.

Receptacle is the thickened part of a stem from which the flower organs grow. It is often a shape of bulging disc or a rectangular or circular or in the platoon as the cruciferae family. When the receptacle elongate between the Corolla and calyx and its called Anthophore, and between the corolla and the stamen it is called Andero gynophore. Or elongate between Anderoecium and gynoecium it is called Gynophore. Receptacle contain glands to attract insects so the process of pollination and fertilization, nectar is a sugar syrup .

The receptacle (grey) in relation to the ovary (red) in three types of flowers: hypogynous (I), perigynous (II), and epigynous (III)

Why is the flower the most important parts of the plant in the classification process: The least part of the plant affected by different environmental and climate conditions. Contain many basic and obvious differences that distinguish the various plants (For example, aquatic plants may be similar in outward appearance and internal structure, but differ in the composition of its flowers to belong to different plant families).

The flower is a unique thing in the life of floral plants angiosperms and It is also the axis that holds the reproduction organs in the flowering plants. The center of plant reproduction as it is composed to ensure that sexual reproduction and fertilizing eggs .

Calyx

Calyx: Is composed of a number of sepals may be rarely 2-3 or 4 in one specie the cruciferae family or 5 in most of the families. The calyx is the outermost whorl of a flower. Function: protection of the flower internal organs. Sepals are often green but sometimes it takes the petals colure ( Petaloid sepalous). The number of sepals often equal to the number of petals.

Sepals are often green but sometimes it takes the petals colure ( Petaloid sepalous). The number of sepals often equal to the number of petals. Sepals often form one ring, but it may sometimes be in two rings. sepals may be loose, as in roses and or it could be fused, as in peas. There may be additional external pericalyceal called “Epipetalous" as in the cotton flower or Malvavceae family.

Calyx could stay on the receptacle and does not fall after the pollination and fertilization, in this case it is called “presistant”, as in the eggplant. Calyx could fall early when the flower opens, in this case it is called “Cadocous” as in the Poppy.

When the petals and sepals of a flower look similar they are called tepals. They both form Perianth. Sepals help in the process of spreading seed and fruit. In some cases specially in the tropical flowers the calyx is in the form of portfolio wrapped around a floral bud, and filled with water.

Calyx shapes: Tubular

Petaloid

Pitcher-like

Labaitae

Bell-form