11th Class Biology Anatomy Of Dicot And Monocot Internal structure of root, stem and leaf

Internal structure of root, stem and leaf

Category : 11th Class

Functions of different organs and tissues of a plant tissue system

 

Roots

Stems

Leaves

(i) Functions

(i) Absorb water and minerals.

(ii) Anchor plant.

(iii) Store materials.

(i) Transport water and nutrients.

(ii) Support leaves.

(iii) Help to store materials.

Carry on photosynthesis.

 

 

(ii) Tissues

 

 

 

(a) Epidermis

Root hairs absorb water and minerals.

Protect inner tissues.

Stomata carry on gas exchange.

(b) Cortex

Store products of photosynth-esis and water.

Carry on photosynthesis if green.

 

(c) Endodermis

Regulates passage of minerals into vascular cylinder.

Regulates passage of minerals also into vascular tissue, if present.

Regulates passage of minerals into vascular tissue if present.

(d) Vascular

Transport water and nutrients.

Transport water and nutrients.

Transport water and nutrients.

(e) Pith

Store products of photosynthesis and water.

Store products of photosynthesis.

 

(f) Mesophyll

(i) Spongy layer

(ii) Palisade layer

 

 

Carry on gaseous exchange and photosynthesis.

 

Difference between internal structure of root and stem

Description

Root

Stem

(i) Epidermis or Epiblema

Epiblema or piliferous layer without cuticle.

Epidermis usually with cuticle.

(ii) Hairs

Unicellular.

Multicellular.

(iii) Chlorenchyma in cortex

Absent.

Usually present in young stems but absent in old stem.

(iv) Endodermis

Very distinct.

Poorly developed or absent.

(v) Vascular bundle

Radial.

Conjoint collateral or bicollateral or concentric.

(vi) Xylem

Exarch.

Endarch.

 

Origin of Lateral roots : Lateral roots arise endogenously i.e., form the cells inside the endodermis. They arise from pericycle cells.

 

Difference between dicot and monocot leaf

Character

Dicot leaf

Monocot leaf

(i) Type of leaf

Dorsiventral (bifacial).

Isobilateral.

(ii) Stomata

Usually more on lower epidermis.

Equal on lower and upper epidermis (amphistomatic).

(iii) Mesophyll

Made up of two types of tissues

(a) Palisade parenchyma.

(b) Spongy parenchyma with large intercellular spaces.

Only spongy parenchyma is present which has very small intercellular spaces.

(iv) Bundle sheath

Made up of parenchyma. Just above and below the vascular bundle some parenchymatous cells or collenchymatous cells are present (upto epidermis).

Made up of parenchyma but just above and below the vascular bundles are found sclerenchymatous cells (upto epidermis).

(v) Bulliform or motor cells

Absent.

Present on upper epidermis.

 

Kranz type anatomy occurs in both monocot and dicot leaves of some tropical and arid areas. Kranz anatomy is characteristic feature of \[{{C}_{4}}\] plants. The mesophyll is undifferentiated and occurs in concentric layers around vascular bundles. Cells of bundle sheath possess large chloroplast.

  

 

 

Difference between dicot and monocot stem

Characters

Monocotyledonous Stem

Dicotyledonous Stem

(i) Epidermis

Present, cells comparatively smaller and without hair.

Present, cells larger and with hair.

(ii) Hypodermis

Sclerenchymatous (non-green)

Collenchymatous (green).

(iii) Cortex

Absent, but ground tissue is present from hypodermis to the centre of stem.

Made up of several layers of parenchymatous tissue.

(iv) Endodermis

Absent

One layered, starchy sheath which is usually not well differentiated.

(v) Pericycle

Absent

Made up of 1 or more layers of parenchymatous and sclerenchymatous cells.

(vi) Medullary rays

Absent

Found in between vascular bundles.

(vii) Pith (Medulla)

Absent

Abundant, made up of parenchymatous cells situated in the centre of stem.

(viii) Vascular bundles

Scattered

Conjoint, Collateral and closed.

Larger towards centre.

Oval

Bundle sheath present.

Phloem parenchyma absent.

Xylem vessels either Y or V shaped.

Vascular bundles in a ring

Conjoint, collateral and open.

All of same size.

Usually wedge?shaped.

Bundle sheath absent.

Phloem parenchyma present.

Xylem vessels more radial.

 

 

Difference between dicot and monocot root

Character

Dicot Root

Monocot Root

(i) Pericycle

Gives rise to secondary roots and lateral meristem

Gives rise to lateral roots only

(ii) Vascular bundles

Diarch to hexarch

Hexarch to polyarch (It is more than 6 in number)

(iii) Cambium

Develops at the time of secondary growth

Absent

(iv) Pith

Absent or poorly developed

Abundant  and fully developed

(v) Secondary growth

Takes place

Does not take place

 

Narrow cortex. Endodermis is less thickened and casparian strips are more prominent.

Cortex wide. Casparian strips are visible only in young root. Later on endodermal cells become highly thickened.

 

 



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