Topics in the Chapter- Classification
- Numerical Taxonomy
- Cytotaxonomy
- Chemataxonomy
- Algae
- Reproduction in Algae
- Bryophytes
- Reproduction in Bryophytes
- Pteridophytes
- Gymnosperms
- Angiosperms
- Life Cycle and Alternation of Generations
Points to RememberMorphology: The study of various external features, forms and relative position of different organs of the organism is known as morphology. It may be further divided into internal and external morphology.
External Morphology: It deals with external forms like shape, size, colour, structure and relative position of different organs.
Internal Morphology: Further divided into anatomy and histology.
Anatomy: It deals with the study of internal structure exposed after dissection and opening of various parts of an organ.
Histology: The study of tissues, their composition and structure.
Adaptation: Any alteration in the structure or function of an organism or any of its part that results from natural selection and by which the organism becomes better fitted to survive and multiply in its environment.
The RootтЖТ The root is underground part of the plant and develops from elongation of radicle of the embryo.
CharacteristicsтЖТ It lies inside the soild, chlorophyll is absent, absence of nodes and internodes, leaves and budgs; positive geotropic and hydrotropic and negative phototropic.
Main functions of root system(i) Absorption of water and minerals from the soil.
(ii) Provides anchorage to plant parts.
(iii) Stores reserve food material and synthesises plant growth regulators (cytokinins)
Regions of RootsRoot Cap: The root is covered at the apex by the thimble-like structure which protect the tender apical part.
Region of meristematic activityтЖТ Cells of this region have the capability to divide; cells are small, thin walled with dense protoplasm.
Region of elongation: Cell of this region are elongated and enlarged.This region is responsible for the growth of root in length.
Region of Maturation: This region has differnentiated and matured cells.
тЖТ Some epidermal cells form very fine and delicate thread like structures called root hairs.
Modifications of Root:тЖТ Roots are modified for support, storage of food, respiration.
тАв For support: Prop roots in banyan tree, stilt roots inmaize and sugarcane.
тАв For respiration : Pneumatophores in Rhizophora (Mangrove).
тАв For storage of food: Fusiform (radish), Napiform (turnip), Conical (carrot), Fasiculated fleshy roots (Asparagus).
The StemтЖТ Stem is the aerial part of the plant and develops from plumule of the embryo. It bears nodes and internodes.
Functions of stemтЖТ Exposure of leaves, conduction of water and minerals, translocation of food, exposure of flowers and fruits.
Modifications of StemтЖТ In some plants the stems are modified to perform the function of storage of food, support, protection and vegetative propagation.
тАв For food storage: Rhizome (ginger, turmeric), Tuber (potato), Bulb (onion), Corm (Colocasia, Amorphophallus/Zamin-kand)
тАв For support: Stem tendrils of wawtermelon, grapevine, cucumber, pumpkins.
тАв For protection: Axilliary buds of stem of Citrus, Bougainvillea get modified into pointed thorns. They protect the plants from animals.
тАв For vegetative propagation : Underground stems of grass (runner), strawberry (stolons), leateral branches of mint and jasmine, Eichhornia (offsets).
тАв For assimilation of food : Flattened stem of Opuntia and cylindrical stem of Euphorbia contains chlorophyll and performs photosynthesis.
The LeafтЖТ Develops from shoot apcial meristem, flattened, green structure acropetally arranged manufacture the food by photosynthesis. It has bud in axil.
тЖТ A typical leaf has leaf base, petiole and lamina (leaf blade).
тЖТ In some leguminous plants the leaf base may become swollen which is called as pulvinus.
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Venation: The arrangement of veins and veinlets in the lamina of leaf.
Types of Venation
(i) Reticulate: Veinlets form a network as in leaves of dicotyledonous plants (China rose, peepal).
(ii) Parallel: Veins are parallel to each other as in leaves of monocotyledonous
plants (grass, maize,sugarcane).
Phyllotaxy: The pattern of arrangement of leaves on the stem or branch.
Functions of Leaf
Photosynthesis, gaseous exchange, transpiration, protection of buds and conduction.
Modifications of Leaves
(i)┬аTendrils тАФ┬аFunction: Climbing тАФ Example: Sweet Pea, Pea
(ii) Spines тАФ Function:┬аProtection тАФ Example: Aloe, Opuntia, Argemone
(iii) Pitcher тАФ┬аFunction:┬аNutrition тАФ Example: Nepenthes
(iv) Hook тАФ┬аFunction:┬аSupport тАФ Example: CatтАЩs nail
(v) Fleshy Leaves тАФ┬аFunction:┬аStoraged food тАФ Example: Onion and Garlic
Inflorescene: The arrangement of flowers on the floral axis (Peduncle)
Main types of Inflorescence
(i) Recemose:
тЖТ It is indefintie inflorescene.
тЖТ Main axis continues to grow and┬аflowers borne in acropetal succession.
e.g. : Radish, Mustard, Amaranthus
(ii) Cymose:
тЖТ It is defintie inflorescence.
тЖТ Main axis terminates in flowers and the┬аflowers borne in basipetal succession.
e.g. : Cotton, Jasmine, Calotropis
тАв Special Inflorescence typeтАФFicus, Salvia, Euphorbia,Sunflower
тАв FlowerтАФModified shoot meant for reproduction
On the basis of symmetry flower can be
(i)┬аActinomorphic (Radial symmetry)
тЖТ┬аFlower can be divided┬аinto two equal halves┬аin any radial plane┬аpassing through centre.┬аeg : Mustard, Datura,┬аChilli┬а
(ii)┬аZygomorphic┬а(Bilateral symmetry)
тЖТ┬аFlower can be divided into┬аtwo similar halves only in┬аone plane.┬аeg : Pea, bean, Gulmohar,┬аcassia
(iii)┬аAsymmetric┬а(Irregular)
тЖТ┬аFlower cannot be divided┬аin two similar halves by┬аany vertical plane passing┬аthrough centre.┬аeg : Canna
On the basis of floral appendages flower can be:
(i)┬аTrimerous┬а(multiples of 3)
(ii) Tetramerous (multiples of 4)
(iii) Pentamerous (multiples of 5)
On the basis of position of Calyx, corolla and androecium in respect of ovary, flower can be:
(i) Hypogynous (Superior Ovary): eg. Mustard, China rose, Brinjal
(ii) Perigynous (Half inferior ovary): eg. Plum, Rose, Peach
(iii) Epigynous (inferior ovary): eg. Guava, Cucumber, ray florets (sun flower)
тАв Thalamus/Receptacle: Swollen end of flower stalk (pedicel) which bears four whorls of flower viz., Calyx (K), Corolla (C), Androecium (A) and Gynoecium (G).
тАв Bract: Reduced leaf base found at the base of pedicel. Flowers with bracts are called bracteale and without bracts are called ebracteate.
тАв Perianth: If calyx and corolla are not distinguishable, they are called perianth.
Example : Lily
Aestivation
тЖТ The mode of arrangement of sepals or petals infloral bud.
Types of aestivation
(i) Valvate: Sepals or petals just touch one another at the margin, withut overlapping. e.g., Calotropis
(ii) Twisted: Sepals or petals overlap the next sepal or petal e.g., China rose, Cotton, ladyтАЩs finger.
(iii) Imbricate: The margins of sepals or petals overlap one another but not in any defintite direction, e.g., Cassia, Gulmohar.
(iv) Vexillary:The largest petal overlaps the two lateral petals which in turn overlap two smallest anterior petals, e.g., Bean, Pea.
Placentation
тЖТ The arrangement of ovules within the ovary.
Types of Placentation
(i) Marginal: Placenta forms a ridge along the ventral suture of ovary, e.g., Pea.
(ii) Axile: Margins of carpels fuse to form central axis, e.g., China rose, Tomato, Lemon
(iii) Perietal: Ovules develop on inner wall of ovary, e.g., Mustard, Argemone
(iv) Free central: Ovules borne on central axis, lacking septa, e.g., Dianthus, Primrose
(v) Basal: Placenta develop at the base of ovary, e.g., Sunflower, Marigold
тАв Placenta : Parenchymatous flattened cushion inside ovary where ovules are borne.
тАв The fruit : After fertilisation, the mature ovary develops into fruit. The parthenocarpic fruits are formed from ovary without fertilisation (seedless fruit-Banana)
Monocotyledonous seed
тЖТ Endosperm bulky and stores food, covered by proteinaceous Aleurone layer.┬а
тЖТ Seed has single large cotyledonтАУscutellum.
тЖТ Plumule is enclosed in Coleoptile and Radicle is enclosed in Coleorrhiza.
Dicotyledonous Seed
тАв Hilum: Is a scar on the seed coat through which seeds attached to the fruit.
тАв Micropyle: Small pore, above hilum
тАв Cotyledons: two; freshly, full of preserve food materials
тАв Embryonal axis: Radicle and plumule.
тАв Endospermous seed: endosperm present in mature seed. eg. castor
тАв Non-endospermous seed: endosperm not present in mature seeds, eg. bean,
NCERT Solutions of Class 12 Morphology in Flowering Plants 
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