Biology: MORPHOLOGY OF FLOWERING PLANTS

 MORPHOLOGY OF FLOWERING PLANTS


Seed –   Plumule – stem

Radical – root

Types of roots à Taproot, Fibrous root, Adventitious root.

Regions of root  - Region of maturation

   Region of elongation

   Region of meristematic tissues.

   Root cap

Modification of roots:

·         Storage- carrot, turnip

·         Prop root- banyan tree (support)

·         Stilt root – maize, sugarcane

·         Pneumatophores- rhizophora (mangroves)

The stem:  Plumule have nodes and internodesbears with axillary /terminal buds

Modification of stems :

1.       Storage - potato, ginger, tturmeric (perennation)

2.       Tendrils – axillary buds –coils - support (watermelon)

3.       Thorns - axillary buds – citrus (protection)

4.       Flattened stem – opuntia (do photosynthesis)

5.       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

Types of leaves: 

1.       Simple leaves

2.       Compound leaves - Pinnately compound  (eg. Neem) and Palmately compound (eg. Silk cotton)

Phyllotaxy: Pattern of arrangement of leaves on the stem /branch.

        1.      Alternate- china rose

        2       Opposite- guava

        3.      Whorled- alstonia

Modification of leaves:

1.       Tendrils - pea (support)

2.       Spines  - cacti (protection, water ioss)

3.       Storage - onion/ garlic

4.       Petiole leaves – acacia

5.       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;

1.       Racemose. Main axis continues to grow laterally  (in an acropetal succession)

2.       Cymose. Main axis terminates in a flower so limited growth (basipetal order)

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 (mustard ) zygomorphic ( pea ) asymmetric ( canna )

Based on the position of ovary:

1.       Hypogynous ovary  ( mustard ) superior

2.       Perigynous ovary ( rose ) half inferior

3.       Epigynous ovary  ( guava, cucumber )  inferior

Parts of flower:

1.       Calyx. Made of sepals. Can be gamosepalous/polysepalous

2.       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 )

3.       Androecium.

·         Staminode- sterile stamen

·         Epipetalous. Attached to the petal

·         Epiphyllous- attached to the perianth

·         Polyadelphous- Free stamens

·         Monoadelphous- united as one bunch ( china rose )

·         Diadelphous – united two bundles ( pea )

·         Polyadelphous – many bundles ( citrus )

4.       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)

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)

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:

·         Scientific language

·         Floral diagram and floral formula (check text book)

Floral formula by symbols:

Br            -  Bracteate                                                        
                                                                                          _
K             -  Calyx                                                                 G  -  Inferior ovary

C             -  Corolla

P             -  Perianth                                                             

A             - Androecium                                                   

G             - Gynoecium

G              Superior Ovary