MORPHOLOGY OF FLOWERING PLANTS

POINTS TO REMEMBER :

• Morphology: The study of various external features of the organism is known as morphology.
• 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.

Various types of root :

• Tap root:
  • Originated from the radicle.
  • Persistent in dicot plant. E.g. gram, pea , mango
• Fibrous root
  • Originates from the base of the stem.
  • Large number of roots replaces the primary root.
  • This type of root found in monocot plant. E.g. wheat, paddy, grass.
• Adventitious root
  • Roots developed from any part of the plant other than radicle.
  • Found in grass, Monstera and the banyan tree.

Function of root :

• Absorption of water and mineral from soil
• Anchorage of the plant body
• Storing reserve food material.
• Synthesis of plant growth regulators.

Regions of root :

• Root Cap : The root is covered at the apex by the thimble-like structure which protects the tender apical part.
• Region of meristematic activity :
  • Cells of this region have the capability to divide.
  • The cells of this region are very small, thin-walled and with dense protoplasm.
• Region of elongation :
  • Cells of this region are elongated and enlarged.
• Region of Maturation :
  • This region has differentiated into matured cells.
  • Some of the epidermal cells of this region form thread-like root hairs, which absorbs water and minerals from the soil.

Modifications of Root :

• Roots are modified for support, storage of food, respiration.
• For  support  :  Prop  roots  in  banyan  tree,  stilt  roots  in  maize  and sugarcane.
• For respiration: pneumatophores in Rhizophora (Mangrove).
• For storage of food:  Fusiform (radish), Napiform (turnip), Conical (carrot).

The Stem :

• Stem is the aerial part of the plant and develops from plumule of the embryo.
• It bears nodes and internodes.
• Bears bud, may be axillary or terminal
• Main function is to spreading branches bearing leaves, flower and fruits.

Modifications of Stem :

• For food storage: Rhizome (ginger), Tuber (potato), Bulb (onion), Corm and Colocasia).
• For support: Stem tendrils of watermelon, grapevine, and cucumber.
• For protection: Axillary buds of stem of citrus, Bougainvillea get modified into pointed thorns. They protect the plants from animals.
• For vegetative propagation: Underground stems of grass, strawberry, lateral branches of mint and jasmine.
• For assimilation of food: Flattened stem of opuntia contains chlorophyll and performs photosynthesis.

The Leaf :

• Developed from shoot apical meristem, flattened, green structure.
• Manufacture the food by photosynthesis. It has bud in axil.
• A typical leaf has leaf base, petiole and lamina.
• Leaf attached to the stem by leaf base.
• May bear two small leaves like structure called stipules.
• Leaf base may swollen to form pulvinus.
• The structure that holds the leaf called petiole.
• The green expanded part of the leaf is called lamina or leaf blade.

Venation :

• The arrangement of veins and the veinlets in the lamina of leaf is termed as venation.
• Veinlets form a network – reticulate venation. (dicot leaf)
• Vein runs parallel to each other – parallel venation. (monocot leaf)

 

CBSE Biology (Chapter Wise) Class XI ( By Mr. Hare Krushna Giri ) 
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