Category : NEET
Internal Structure of Root, Stem and Leaf
(1) 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 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 photosynthesis 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. |
Regulate 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. |
(2) 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.
(3) 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 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. Karanz anatomy is characteristic feature of C4 plants. The mesophyll is undifferentiated and occurs in concentric layers around vascular bundles. Cells of bundles sheath posses large chloroplast.
(4) 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 closedLarger 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 |
(5) 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 |
(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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