INTRODUCTION TO PLANT BOTANY/UNDERSTANDING PLANTS BOTANY

 

INTRODUCTION TO PLANT BOTANY

Definition of Botany (what is botany)

Botany is the Science that deals with plants. It can be studied from pure and applied aspects.

Branches of Botany (studying botany)

Comparative Morphology: In classifying plants, we compare one form with another. Example stems, leaf and root.

Comparative Anatomy: Problems of plant form involve a study of plant structure. This leads to studies of structure under Cytology and Genetics.

Physiology: Observation of form and structure in which the function is considered along with the complex chemical changes involved. Physiology therefore is the study of the processes occurring in plants and of the functions of the plant parts. The functions may be vital or mechanical.

Ecology: Form of plant linked with its environment or habitat. This study may further subdivided into auto ecology, which deals with individual plants, usually emphasizing the effect of the environment on the plant, rather than vice versa; and synecology, which deals with plant communities, including both the influence of the environment on the community and the influence of the community on the environment. Another branch of ecology is Plant geography, the study of the distribution of plants and plant communities and relationships which enable a plant to grow under particular condition of soil, climate.

Genetics is another branch of botany dealing with the study of heredity in plants.

Another branch of botany is systematic botany or plant taxonomy. Plant taxonomists attempt to classify plants into a system which reflects both evolutionary relationships and presently existing similarities and differences. Other branches are, economic botany, which is the study of the economic importance of plants. Plant pathology, which is the study of plant diseases, and palaeobotany, which is the study of plant fossils.

Angiosperms or flowering plants

The word angiosperm was coined from two Greek words; angeion, vessel, and sperma, seed. This refers to the fact that the young seeds of these plants are enclosed within a special structure, the ovary, instead of being exposed directly to the air, as in gymnosperms.

Characteristics of Angiosperms

Angiosperms are vascular plants with roots, stems and leaves. The central cylinder with leaf gaps or with scattered vascular bundles. The vascular system usually consists of vessels, tracheids, and sieve tube, with distinctive companion cells. The sporophyte is either herbaceous or absent, usually with axillay branching, and leaves of various shapes, sizes, etc.

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The ovules are enclosed in an ovary, with the female gametophyte reduced to a few-nucleate embryo sac without an archegonium. The male gametophyte produces two naked sperms, one of which fuses with the egg to form the zygote, the other fuses with the two nuclei (or the product of fusion of two nuclei) of the embryo sac to form a triploid endosperm. Since the two sperms participate in nuclear unions, this is called double-fertilization, a common phenomenon in angiosperms. Various forms of asexual reproduction are also common in angiosperms.

Taxonomy of Angiosperms

Angiosperms are naturally divisible into two major groups, the monocotyledons, with one seed-leaf, and the dicotyledons, with two seed-leaves. Monocotyledons include about 25% of the total angiosperms on earth. They include plant families such as Aloeaceae, Aracaceae, Araceae, Dioscoreaceae, Dracaenaceae, Liliaceae, Marantaceae, Musaceae, Pandanaceae, Poaceae, Zingiberaceae, etc.

The monocotyledons can be distinguished from the dicotyledons by several characteristics. Among them are: they almost always have one cotyledon in the seed and the seedling, and parallel veins in the leaves which do not branch; their flowers are always of a ‘type three’ pattern, or multiple of 3, i.e. the floral parts such as petals, sepals, etc. and their stems above ground without secondary growth.

The characteristics of dicotyledons are the two cotyledons of the seed and the seedling, and a network pattern of nerves on the leaves; the flowers’ which are rarely the pattern of ‘type three’ and the woody stem, resulting from secondary growth.