Chapter 1 SEM II NEP PDF

1. MORPHOLOGY: 2 L 1.1: Introduction, definition, descriptive and interpretative morphology. 1.2: Importance in identification, nomenclature, classification, phylogeny and Plant breeding. _________________________________________________________ Morphology is the one of the import...

1. MORPHOLOGY: 2 L 1.1: Introduction, definition, descriptive and interpretative morphology. 1.2: Importance in identification, nomenclature, classification, phylogeny and Plant breeding. _________________________________________________________ Morphology is the one of the important branch that deals with the science of enlightening plants in the form of structures. It is the learning of physical form and external structure of the plant, useful in visual identification. Following aspects are considered while studying plant morphology 1. Comparative Morphology were the structures (root, stem, leaf, flower, fruit, seed, sori, thallus, spore etc.) of different plants belonging to the same or different species are visually (externally) observed for formulating the thoughts of similarities. 2. Plant morphology inspects both the vegetative (somatic) structures (root, rhizoids, stem, leaf) as well as the reproductive structures (Flowers, seeds, fern sori, moss capsules, alteration of generations in algae and fungi) of the plants. 3. Plant morphology studies plant structure at a micro level. At the smallest scales is the ultra structures or the general structural features of cells, frequently involving the sectioning of tissues and microscopy. 4. Plant morphology also observes the way of development, the process by which structures initiates and mature as a plant grows. Descriptive Morphology is the way of describing the plants specifically by considering the external/internal characters and functions, developmental, embryological studies etc. External characters comprise the shape, size and structure of the plant parts. Internal characters include the cellular details, information regarding pollens, ovules, embryos etc. Interpretative Morphology is the manner to show the unseen relationships between two different plants or groups on the basis of the information obtained by comparison. It helps in making actual, knowledgeable assumptions based on the evidences derived from various sources. One of the best examples of this concept Botany II K.K.W. College Page 1 is the homology proposed by Goethe (1790). He discovered homologous nature of leaf organs in plants, from cotyledons, to photosynthetic leaves, to the petals of a flower and explained that no real boundary exists between organs such as cotyledons, leaves and petals of the flowers. Importance of Morphology 1. Plant identification is one of the important goals of plant taxonomy. It is the procedure to check the similarities between a specimen plant and a known taxon. It is very much important to be aware of the terms and methods used in the identification. The morphological characters like shape, size, structure of the root, stem, leaf, flower, fruit, seed, embryo etc. are taken into account along with the anatomical characters like tissue system, stomata, epidermal system, etc. Standard methods and keys like single – access key (dichotomous key) and multi-access key are used for proper and correct identification of the plant specimen. The process of identification connects the specimen with a published name. 2. Nomenclature is scientifically naming the plants. Adoption of binomial names for naming the plants by Linnaeus in his Species Plantarum (1753) forms the base for modern botanical nomenclature. Binomial nomenclature is a formal system of naming species of living things into two words, both of which use Latin grammatical forms. The first part of the name – the generic name – identify the genus to which the plant belongs, while the second part – the specific name or specific epithet – identify the species within the genus. E.g. Cocos nucifera L. ‘Cocos’ is the genus, ‘nucifera’ is the species name and last letter ‘L.” designates the authority- “Linnaeus” the scientists who has first published the name for that particular species. Genus name start with capital letter whereas the species name starts with small letters. Both the genus and species names are typed in italics or separately underlined when written. Botanical nomenclature is overseen by the International Code of Nomenclature (ICN), which replaces the International Code of Botanical Nomenclature (ICBN). Within the limits set by that code there is another set of rules, the International Code of Nomenclature for Cultivated Plants (ICNCP) applicable to plant cultivars that have been deliberately altered/modified or selected by humans. Botany II K.K.W. College Page 2  3. Use of Morphology for classification- Nature is enriched with millions of different plant species, some of those are not even studied yet. In order to study such plants, taxonomists try to categorize them on the basis of morphological characters. The differences in characters are used to group the plants that offer a way for classification and organization. Thus, plant classification means grouping of plants into different categories and arranging them in accordance to the rules set down by ICN.For example- Grouping of Fabaceae family Kingdom: Plantae Division: Phanerogams Sub-division: Angiospermae Class: Dicotyledonae Subclass: Polypetalae Series: Thalamiflorae Order: Ranales Family: Annonaceae 4. Phylogeny (or a tree of life) is a theory that explains how organisms are related to one another through evolutionary time or it is the study of the evolutionary development of groups of organisms. It is based on the hypothesis that more closely related species will be more analogous (similar) to one another, derived from one common ancestor and they are commonly built using genetic sequences or physical characters. It is often represented in form a diagram known as a phylogenetic tree. The branches of the tree represent ancestral and/or descendant heredity. Phylogenetic trees are based on assumptions of cladistics, or phylogenetic systematics. Cladistics is a classification system that categorizes organisms based on similar characters, as determined by genetic, anatomical, and molecular analysis. Thus, plant morphology plays an important role in phylogenetic studies. 5. Plant Breeding is a way of changing the genetic blueprint of plants to increase their value and usefulness for human welfare. It is a focused Botany II K.K.W. College Page 3  utilization of plants to produce desired plant types that are superior, suitable for cultivation, give better yield and are disease resistant. Plant breeding has the following objectives – 1. Boost the crop yield 2. Improve the quality of the crop 3. Increase tolerance to environmental conditions like salinity, extreme temperature and drought 4. Develop a disease and insect pest resistant varieties  Plant morphology has a vital role in all the below mentioned plant breeding or crop improvement programmes.  Selection is one of the major techniques of plant breeding in which plants are selectively propagating with desirable characteristics and eradicating those with unpleasant characteristics.  Hybridization, is the another technique that involves the interbreeding (crossing) of closely or distantly related individuals to produce new crop varieties or lines with desirable properties.  Plant Introduction a part of plant breeding programme means the introduction of the new plant to the area where it was not grown earlier. The propagating material may be introduced from the foreign country or from one region to another within the same country.  Mutation Breeding is another important aspect of plant breeding programme. It is the process of exposing seeds to chemicals or radiations in order to produce mutants with desirable characters to be bred with other cultivars. Plants created using this technique are called as mutants or mutagenic plants or mutagenic seeds.  Plant Tissue Culture is one of the modern aspects of plant improvement programme where a cell of tissue is regenerated or grown in in vitro conditions on a culture media. It is the way of multiplying the desired plant varieties. Botany II K.K.W. College Page 4