Morphology of Flowering Plants

K C MEENA

PGT BIOLOGY

KV VIKASPURI II SHIFT

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THE ROOT

• Seed – Plumule – stem
• Radical – root
• Types of roots
• Taproot, Fibrous root, Adventitious root.
• Regions of root –
• Region of maturation
• Region of elongation
• Region of meristematic tissues.
• Root cap

Different types of roots : (a) Tap (b) Fibrous (c) Adventitious

MODIFICATIONS OF ROOT

• Roots in some plants change their shape and structure and become modified to perform functions other than absorption and conduction of water and minerals
• Storage- carrot, turnip
• Prop root- banyan tree (support)
• Stilt root – maize, sugarcane
• Pneumatophores- rhizophora (mangroves

Modification of root for support: Banyan tree

Modification of root for : (a) storage (b) respiration: pneumatophore in Rhizophora

THE STEM

• It develops from the plumule of the embryo of a germinating seed. The stem bears nodes and internodes.
• The region of the stem where leaves are born are called nodes while internodes are the portions between two nodes
• The main function of the stem is spreading out branches bearing leaves, flowers and fruits.
• It conducts water, minerals and photosynthates.
• Some stems perform the function of storage of food, support, protection and of vegetative propagation.

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MODIFICATIONS OF STEM

• Underground stems of Sucker,rhizome,corn,tuberand bulb,(potato, ginger, turmeric, zaminkand, Colocasia are modified to store food in them)
• Sucker-Chrysanthemum,Mint,Banana,Pineaple
• Rhizome- ginger, turmeric
• Corn-

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Modifications of stem for : (a) storage (b) support (c) protection (d) spread and vegetative propagation

• Storage - potato, ginger, tturmeric (perennation)
• Tendrils – axillary buds –coils - support (watermelon)
• Thorns - axillary buds – citrus (protection)
• Flattened stem – opuntia (do photosynthesis)
• Vegetative propagation (grass, jasmine, banana)

The leaf

• Short apical meristem gives rise to leaves arranged in acropetal order
• Do photosynthesis
• Three main parts are leaf base, petiole and lamina (leaf blade)
• Have stipules
• Leguminous petioles have pulvinus. (midrib)
• Venation - arrangement of veins and veinlets on a leaf.
• Types of venation
• Parallel- monocot leaves
• Reticulate – dicot leaves

Structure of a leaf : (a) Parts of a leaf (b) Reticulate venation (c) Parallel venation

Types of leaves:

• Simple leaves
• Compound leaves –
• Pinnately compound (eg. Neem) and
• Palmately compound (eg. Silk,cotton)

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• Phyllotaxy: Pattern of arrangement of leaves on the stem /branch.
• Alternate- china rose
• Opposite- guava
• Whorled- alstonia

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Different types of phyllotaxy : (a) Alternate (b) Opposite (c) Whorled

Compound leaves : (a) pinnately compound leaf (b) palmately compound leaf

Modification of leaves

• Tendrils - pea (support)
• Spines - cacti (protection, water loss)
• Storage - onion/ garlic
• Petiole leaves – acacia
• Pitcher leaves – insectivorous plant (venus fly trap)

The inflorescence

• Arrangement of flowers on the floral axis
• Types of inflorescence: Depending on whether the apex gets converted in to a flower/continues to grow
• there are two major types;
• Racemose. Main axis continues to grow laterally (in an acropetal succession)
• Cymose. Main axis terminates in a flower so limited growth (basipetal order)

Racemose inflorescence

Cymose inflorescence

The flower

• Four whorls. Sepal, petal, gynoecium, and androecium
• Thalamus/receptacle
• Trimerous/tetramerous/pentamerous/polymerous
• Bracteates/ebracteate/bract. (Protective sheet around the flower)
• Bisexual/unisexual
• Actinomorphic(radial symmetry) (mustard ) zygomorphicbilateral symmetry) ( pea ) asymmetric ( canna )

Based on the position of ovary

• Hypogynous ovary ( mustard ) superior
• Perigynous ovary ( rose ) half inferior
• Epigynous ovary ( guava, cucumber ) inferior

Position of floral parts on thalamus : (a) Hypogynous (b) and (c) Perigynous (d) Epigynous

Parts of flower

• Calyx. Made of sepals. Can be gamosepalous/polysepalous
• Corolla. Made of oetals. Gamopetalous/ polypetalous
• Aestivation: Arrangement of sepals/ petals in floral bud
• Main types are valvate (petunia alba , calotropis)
• twisted(china rose ), imbricate( gulmohur) vexillary (pea, bean )
• Androecium.
• Staminode- sterile stamen
• Epipetalous. Attached to the petal
• Epiphyllous- attached to the perianthPolyadelphous- Free stamens
• Monoadelphous- united as one bunch ( china rose )
• Diadelphous – united two bundles ( pea )
• Polyadelphous – many bundles ( citrus

Types of aestivation in corolla : (a) Valvate (b) Twisted (c) Imbricate (d) Vexillary

Parts of a flower

• Gynoecium- one/ more carpels
• Ovules attached on the wall of ovary called placenta.
• Apocarpous - Free carpels ( lotus, rose )
• Syncarpous - Carpels are fused (mustard, tomato )
• After fertilization ovules devopls into seed.
• Ovary develops into fruit
• Placentation:
• Arrangement of ovules within the ovary.
• Different types are marginal (pea), axile (china rose, lemon, tomato),
• Parietal (mustard), freecentral (primrose) and basal (sunflower)

Types of placentation : (a) Marginal (b) Axile (c) Parietal (d) Free central (e) Basal

The fruit

• Parthenocarpic fruit: Formation of fruits without fertilization of ovary. Ex. Seedless grapes,
• seedless orange.
• Two parts of a fruit are pericarp and seeds.
• Pericarp has epicarp, mesocarp and endocarp
• Both mango and coconut are known as drupe fruits (fruits formed from single ovary /carpel)
• Perianth: Fused petals and sepals

The seed:

• Fertilized ovules.
• Made up of seed coat and an embryo
• Embryo with radical and plumule with one cotyledon or two cotyledon
• Structure of a dicot seed:
• Seed coat, Testa and tegmen
• Hilum - small pore (place where it is attached to fruit)
• Micropyle. (water enters)
• Endosperm, cotyledons, embryonal axis (plumule and radicle)
• Mature seeds in dicot do not have endosperm called non-endospermic seeds. ( stored food is utilized by embryo)

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Structure of monocotyledonous seed:

• Mostely endosperm except orchids
• Endosperm is bulky and store food
• Aleurone layer (produce enzymes to hydrolise proteins for embryo )
• Cotyledon is scutellum
• Protective coats- coleoptiles (piumule ), coleorhizae ( radical)

Semi – technical description of a typical flowering plant

• Floral formula by symbols:
• Br - Bracteate _
• K - Calyx G - Inferior ovary
• C - Corolla
• P - Perianth
• A - Androecium
• G - Gynoecium
• G -Superior Ovary
• G - Inferior ovary

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