CLASS 11TH BIOLOGY CHAPTER- 5 MORPHOLOGY OF FLOWERING PLANTS FOR NEET AND CBSE EXAM
MORPHOLOGY OF FLOWERING PLANTS
Venation: The arrangement of veins and veinlets in the lamina of leaf.
5. Basal: Placenta develop at the base of ovary, e.g., Sunflower, Marigold.
Monocotyledonous seed-Endosperm bulky and stores food, covered by proteinaceous Aleurone layer. Seed has single large cotyledon-scutellum. Plumule is enclosed in Coleoptile and Radicle is enclosed in Coleorrhiza. Dicotyledonous Seed-
Hilum-is a scar on the seed coat through which seeds attached to the fruit.
Morphology: 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 Root: The root is underground part of the plant and develops from elongation of radicle of the embryo.
Characteristics: It ies 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:
1. Absorption of water and minerals from the soil.
2. Provides anchorage to plant parts.
3. Stores reserve food material and synthesises plant growth regulators (cytokinins)
VARIOUS TYPES OF ROOT:
1. Tap root
Originates from radical
Dicotyledonous plants,
e.g., gram, pea, mango, mustard.
2. Fibrous root
Originates from base of the stem
Monocotyledonous plants,
e.g., wheat, paddy, grasses.
3. Adventitious root
Originates from parts of the plant other than radicle Banyan tree (Prop roots) Maize (stilt roots) Rhizophora (Respiratory roots)
REGIONS OF ROOTS:
Root Cap: The root is covered at the apex by the thimble-like structure which protect the tender apical part.
Region of meristematic activity: 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. Some epidermal cells form very fine and delicate thread like structures called root hairs.
Modifications of Root: Roots are modified for support, storage of food, respiration.
• For support: Prop roots in banyan tree, stilt roots inmaize and sugarcane.
• For respiration : Pneumatophores in Rhizophora (Mangrove).
• For storage of food: Fusiform (radish), Napiform (turnip), Conical (carrot), Fasiculated fleshy roots (Asparagus).
The Stem: Stem is the aerial part of the plant and develops from plumule of the embryo. It bears nodes and internodes.
Functions of stem: Exposure of leaves, conduction of water and minerals, translocation of food, exposure of flowers and fruits.
MODIFICATIONS OF STEM:
In some plants the stems are modified to perform the function of storage of food, support, protection and vegetative propagation.
• For food storage: Rhizome (ginger, turmeric), Tuber (potato), Bulb (onion), Corm (Colocasia,Amorphophallus/Zamin-kand)
• For support : Stem tendrils of wawtermelon, grapevine, cucumber, pumpkins.
• For protection: Axilliary buds of ste of Citrus, Bougainvillea get modified into pointed thorns. They protect the plants from animals.
• For vegetative propagation: Underground stems of grass (runner), strawberry (stolons), leateral branches of mint and jasmine, Eichhornia (offsets).
• For assimilation of food: Flattened stem of Opuntia and cylindrical stem of Euphorbia contains chlorophyll and performs photosynthesis.
• The Leaf : Develops from shoot apcial meristem, flattened, green structure acropetally arranged manufacture the food by photosynthesis. It has bud in axil. A typical leaf has leaf base, petiole and lamina (leaf blade). In some leguminous plants the leaf base may become swollen which is called as pulvinus.
Types of Venation:
1. Reticulate : Veinlets form a network as in leaves of dicotyledonous plants (China rose, peepal).
2. 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.
Types of phyllotaxy
(Single leaf at a node)in alternate manner
e.g., China rose Mustard,
2. Opposite
(Two leaves at anode) in opposite manner
e.g., Calotropis, guava
3. Whorled
(More than two leaves in a whorl at a node)
e.g., Nerium, Alstonia
FUNCTIONS OF LEAF
photosynthesis, gaseous exchange, transpiration, protection of buds and conduction.
MODIFICATIONS OF LEAVES :
Inflorescene: The arrangement of flowers on the floral axis (Peduncle)
MAIN TYPES OF INFLORESCENCE
(i) Recemose
1. It is indefintie inflorescene.
2. Main axis continues to grow and flowers borne in acropetal succession.
e.g.: Radish, Mustard, Amaranthus
(ii) Cymose
1. It is defintie inflorescence.
2. Main axis terminates in flowers and the flowers borne in basipetal succession.
e.g.: Cotton, Jasmine, Calotropis
Special Inflorescence type-Ficus, Salvia, Euphorbia,Sunflower
Flower-Modified shoot meant for reproduction
ON THE BASIS OF SYMMETRY FLOWER CAN BE:
1. Actinomorphic (Radial symmetry)
Flower can be divided into two equal halves in any radial plane passing through centre.
eg: Mustard, Datura, Chilli
2. Zygomorphic (Bilateral symmetry)
Flower can be divided into two similar halves only in one plane.
eg: Pea, bean, Gulmohar, cassia
3.Asymmetric (Irregular)
Flower cannot be divided in two similar halves by any vertical plane passing through centre.
eg: Canna
ON THE BASIS OF FLORAL APPENDAGES FLOWER CAN BE:
1.Trimerous (multiples of 3)
2.Tetramerous (multiples of 4)
3.Pentamerous (multiples of 5)
On the basis of position of Calyx, corolla and androecium in respect of ovary, flower can be
OF POSITION OF CALYX, COROLLA AND ANDROECIUM
1. Hypogynous (Superior Ovary)
e.g Mustard, China rose, Brinjal
2. Perigynous (Half inferior ovary)
e.g, Plum, Rose, Peach
3. Epigynous (inferior ovary)
e.g, Guava, Cucumber ray florets (sun flower)
Thalamus/Receptacle: Swollen end of flower stalk (pedicel) which bears four whorls of flower viz., Calyx (K), Corolla (C), Androecium (A) and Gynoecium (G).
Flower can be Bisexual and Unisexual
• Bisexual if have both Androecium and Gynoecium.
• Unisexual have only Androecium/Stamen or Gynoecium Carpel.
Bract: Reduced leaf base found at the base of pedicel. Flowers with bracts are called bracteale and without bracts are called ebracteate.
Perianth: If calyx and corolla are not distinguishable, they are called perianth.
Example: Lily
Aestivation: The mode of arrangement of sepals or petals infloral bud.
TYPES OF AESTIVATION :
1. Valvate: Sepals or petals just touch one another at the margin, without overlapping. e.g.. Calotropis.
2. Twisted: Sepals or petals overlap the next sepal or petal e.g., China rose, Cotton, lady's finger.
3. Imbricate: The margins of sepals or petals overlap one another but not in any defintite direction, e.g., Cassia, Gulmohar.
4. Vexillary: The largest petal overlaps the two lateral petals which in turn overlap two smallest anterior petals, e.g., Bean, Pea.
Placentation: The arrangement of ovules within the ovary.
TYPES OF PLACENTATION :
1. Marginal: Placenta forms a ridge along the ventral suture of ovary, e.g. Pea.
2. Axile: Margins of carpels fuse to form central axis, e.g., China rose, Tomato, Lemon.
3. Perietal: Ovules develop on inner wall of ovary, e.g., Mustard, Argemone.
4. Free central: Ovules borne on central axis, lacking septa, e.g.. Dianthus, Primrose.
Placenta: Parenchymatous flattened cushion inside ovary where ovules are borne.
The fruit: After fertilisation, the mature ovary develops into fruit. The parthenocarpic fruits are formed from ovary without fertilisation (seedless fruit Banana).
Micropyle-small pore, above hilum.
Cotyledons-two; freshly, full of preserve food materials.
Embryonal axis-Radicle and plumule.
Endospermous seed-endosperm present in mature seed. eg. castor.
Non-endospermous seed-endosperm not present in mature seeds, eg. bean.
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