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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