BIO BOTANY [5 Mark each]

Botanical description of Allium cepa:

1. Habit: Perennial herb with bulb.
2. Root: Fibrous adventitious root system
3. Stem: Underground bulb
4. Leaf: A cluster of radical leaves emerges from the underground bulb, cylindrical and fleshy having sheathy leaf bases with parallel venation.
5. Inflorescence: Scapigerous i.e. the inflorescence axis (peduncle) arising from the ground bearing a cluster of flowers at its apex. Pedicels are of equal length, arising from the apex of the peduncle which brings all flowers at the same level.
6. Flower: Small, white, bracteate, bracteolate, pedicellate, complete, trimerous, actinomorphic and hypogynous. Flowers are protandrous.
7. Perianth: Tepals 6, white, arranged in two whorls of three each, syntepalous showing valvate aestivation.
8. Androecium: Stamens 6, arranged in two whorls of three each, epitepalous, apostamenous / free and opposite to tepals. Anthers dithecous. basifixed, introse and dehiscing longitudinally.
9. Gynoecium: Tricarpellary and syncarpous. Ovary superior, trilocular with two ovules in each locule on axile placentation. Style simple, slender with simple stigma.
10. Fruit: A loculicidal capsule.
11. Seed: Endospermous
12. Floral Formula:
13. 

1. Habit: Large, erect and stout herb.
2. Root: Branched tap root system.
3. Stem: Stem is hollow, green and herbaceous with strong odour.
4. Leaf: Simple, alternate, petiolate, entire or deeply lobed, glabrous exstipulate showing unicostate reticulate venation.
5. Inflorescence: Solitary and axillary cyme.
6. Flower: Flowers are large, greenish white, bracteate, ebracteolate, pedicellate, complete, heterochlamydeous, pentamerous, regular, actinomorphic, bisexual and hypogynous.
7. Calyx: Sepals 5, green synsepalous showing valvate aestivation. Calyx is mostly persistant, odd sepal is posterior in position.
8. Corolla: Petals 5, greenish white, sympetalous, plicate (folded like a fan) showing twisted aestivation, funnel shaped with wide mouth and 10 lobed.
9. Androecium: Stamens 5, free from one another, epipetalous, altemipetalous and are inserted in the middle of the corolla tube. Anthers are basifixed, dithecous, with long filament, introse and longitudinally dehiscent.
10. Gynoecium: Ovary bicarpellary, syncarpous superior ovary, basically bilocular but tetralocular due to the formation of false septum. Carpels are obliquely placed and ovules on swollen axile placentation. Style simple long and filiform, stigma two lobed.
11. Fruit: Spinescent capsule opening by four special valves with persistent calyx.
12. Seed: Endospermous
13. Floral Formula

1. Habit: Twining climber
2. Root: Branched tap root system having nodules.
3. Stem: Aerial, weak stem and a twiner.
4. Leaf: Imparipinnately compound, alternate, stipulate showing reticulate venation. Leaflets are stipellate.
   Petiolate and stipels are pulvinated.
5. Inflorescence: Solitary and axillary
6. Flower: Bracteate, bracteolate, bracteoles usually large, pedicellate, heterochlamydeous, complete, bisexual, pentamerous, zygomorphic and hypogynous.
7. Calyx: Sepals 5, synsepalous, green showing valvate aestivation. Odd repel is anterior in position.
8. Corolla: Petals 5, white or blue apopetalous, irregular papilionaceous corolla showing, descendingly imbricate aestivation.
9. Androecium: Stamens 10, diadelphous (9) + 1 nine stamens fused to form a bundle and the tenth stamen is free. Anthers are dithecous, basifixed, introse and dechising by longitudinal slits.
10. Gynoecium: Monocarpellary, uni – locular, with many ovules on marginal placentation, ovary superior, style simple and incurved with feathery stigma.
11. Fruit: Legume
12. Seed: Non – endospermous, reniform.
13. Floral Formula

The significance of Molecular Taxonomy:

1. It helps to identify a very large number of species of plants and animals by the use of conserved molecular sequences.
2. Using DNA data evolutionary patterns of biodiversity are now investigated.
3. DNA taxonomy plays a vital role in phytogeography, which ultimately helps in genome mapping and biodiversity conservation.
4. DNA – based molecular markers used for designing DNA based molecular probes, have also been developed under the branch of molecular systematics.

Classical Taxonomy:

1. It is called old systematics or Alpha (α) – taxonomy or Taxonomy
2. It is pre – Darwinean
3. Species is considered as basic unit and is static
4. Classification is mainly based on morphological characters
5. This system is based on the observation of a few samples / individuals

Modern Taxonomy:

1. It is called Neosystematics or Biosystematics or Omega (Ω) taxonomy
2. It is post – Darwinean
3. Species is considered as dynamic entity and ever changing
4. Classification is based on morphological, reproductive characters and phylogenetic (evolutionary) relationship of the organism
5. This system is based on the observation of large number of samples / individuals

1. Biosystematics: Biosystematics is an “Experimental, ecological and cytotaxonomy” through which life forms are studied and their relationships are defined.
2. Aims of Biosystematics: The aims of biosystematics are as follows:

• To delimit the naturally occurring biotic community of plant species.
• To establish the evolution of a group of taxa by understanding the evolutionary and phylogenetic trends.
• To involve any type of data gathering based on modem concepts and not only on morphology and anatomy.
• To recognize the various groups as separate biosystematics categories such as ecotypes, ecospecies, cenospecies and comparium.

Bentham and Hooker system of classification

The characters of Early angiosperm according to APG Classification:

1. Seeds always with two cotyledons.
2. Presence of ethereal oils.
3. Leaves are always simple net – veined
4. Each floral whorls with many parts
5. Perianth usually spirally arranged or parts in threes
6. Stamens with broad filaments
7. Anthers tetrasporangiate
8. Pollen monosulcate
9. Nectaries are rare
10. Carpels usually free and
11. Embryo very small

The uses of Herbarium:

1. Herbarium provides resource material for systematic research and studies.
2. It is a place for orderly arrangement of voucher specimens.
3. Voucher specimen serves as a reference for comparing doubtful newly collected fresh specimens.
4. Voucher specimens play a role in studies like floristic diversity, environmental assessment, ecological mechanisms and survey of unexplored areas.
5. Herbarium provides opportunity for documenting biodiversity and studies related to the field of ecology and conservation biology.

Botanical gardens play the following important roles.

1. Gardens with aesthetic value which attract a large number of visitors. For example, the Great Banyan Tree (Ficus benghalensis) in the Indian Botanical Garden at Kolkata.
2. Gardens have a wide range of species and supply taxonomic material for botanical research.
3. Garden is used for self-instruction or demonstration purposes.
4. It can integrate information of diverse fields like Anatomy, Embryology, Phytochemistry, Cytology, Physiology and Ecology.
5. Act as a conservation centre for diversity, rare and endangered species.
6. It offers annual list of available species and a free exchange of seeds.
7. Botanical garden gives information about method of propagation, sale of plant material to the general public.

International Code of Nomenclature is based on the following six principles.

1. Botanical nomenclature is independent of zoological and bacteriological nomenclature.
2. Application of names of taxonomic group is determined by means of nomenclatural types.
3. Nomenclature of a taxonomic group is based on priority of publication.
4. Each taxonomic group with a particular circumscription, position and rank can bear only one correct name, the earliest that is in accordance with the rules except in specified cases.
5. Scientific names of taxonomic groups are treated as Latin regardless of their derivation.
6. The rules of nomenclature are retroactive unless expressly limited.