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The following points highlight the top two types of monocot and dicot leafs. The types are: 1. Anatomy of Monocot Leaf 2. Anatomy of Dicot Leaf.
Monocot and Dicot Leaf: Type # 1.
Anatomy of Monocot Leaf:
Triticum-Leaf:
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T.S. shows prominent ridges and grooves and reveals the following tissues:
Epidermis:
1. Two epidermal layers are present, one each on upper and lower surfaces.
2. Uniseriate upper and lower epidermal layers are composed of more or less oval cells.
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3. Few big, motor cells or bulliform cells are present in groups here and there in the furrows of upper epidermis.
4. Stomata, each consisting of a pore, guard cells and a stomatal chamber, are present on both the epidermal layers.
5. A thick cuticle is present on the outer walls of epidermal cells.
6. Bulliform cells help folding of leaves.
Mesopbyll:
7. It is not clearly differentiated into palisade and spongy parenchyma but the cells just next to the epidermal layers are a bit longer while the cells of the central mesophyll region are oval and irregularly arranged.
8. The cells are filled with many chloroplasts.
9. Many intercellular spaces are also present in this region.
10. Sub-stomatal chambers of the stomata are also situated in this region.
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Vascular System:
11. Many vascular bundles are present. They are arranged in a parallel series.
12. The central vascular bundle is largest in size.
13. Vascular bundles are conjoint, collateral and closed.
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14. Each vascular bundle remains surrounded by a double-layered bundle sheath.
15. Outer layer of bundle sheath consists of thin-walled cells while the inner layer is made up of thick-walled cells.
16. On the upper as well as lower surfaces of large vascular bundles are present patches of sclerenchyma which are closely associated with the epidermal layers. There is no such association between the sclerenchyma and small vascular bundles.
17. Xylem occurs towards the upper surface and phloem towards to lower surface.
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18. Xylem consists of vessels and tracheids. Sometimes small amount of xylem parenchyma is also present.
19. Phloem consists of sieve tubes and companion cells.
Xerophytic Characters:
(i) Thick cuticle on epidermis.
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(ii) Presence of motor cells.
(iii) Sclerenchyma patches are present.
(iv) Stomata in furrows.
Identification:
(a) 1. Presence of upper and lower epidermal layers.
2. Mesophyll is present.
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3. Each vascular bundle is surrounded by bundle sheath…………. Leaf
(b) 1. Many vascular bundles are arranged parallaly.
2. Absence of cambium.
3. Vascular bundles are collateral and closed.
4. Stomata on both the surfaces.
Isobilateral monocot leaf.
Monocot and Dicot Leaf: Type # 2.
Anatomy of Dicot Leaf:
Mangifera indica-Leaf:
Following tissues are visible in the transverse section of the material:
Epidermis:
1. An epidermal layer is present on the upper as well as lower surfaces.
2. One-celled thick upper and lower epidermal layers consist of barrel-shaped, compactly arranged cells.
3. A thick cuticle is present on the outer walls of epidermal cells. Comparatively, thick cuticle is present on the upper epidermis.
4. Stomata are present only on the lower epidermis.
Mesophyil:
5. It is clearly differentiated into palisade and spongy parenchyma.
6. Palisade lies just inner to the upper epidermis. It is composed of elongated cells arranged in two layers.
7. The cells of palisade region are compactly arranged and filled with chloroplasts. At some places the cells are arranged loosely and leave small and big intercellular spaces.
8. Palisade cells are arranged at a plane at right angle to the upper epidermis, and the chloroplasts in them are arranged along their radial walls.
9. Parenchymatous cells are present above and below the large vascular bundles. These cells interrupt the palisade layers and are said to be the extensions of the bundle sheath.
10. Spongy parenchyma region is present just below the palisade and extends upto the lower epidermis.
11. The cells of spongy parenchyma are loosely arranged, filled with many chloroplasts and leave big intercellular spaces.
Vascular Region:
12. Many large and small vascular bundles are present.
13. Vascular bundles are conjoint, collateral and closed.
14. Each vascular bundle is surrounded by a bundle sheath.
15. Bundle sheath is parenchymatous and in case of large bundles it extends upto the epidermis with the help of thin-walled parenchymatous cells.
16. The xylem is present towards the upper epidermis and consists of vessels and xylem parenchyma. Protoxylem is present towards upper epidermis while the metaxylem is present towards the lower epidermis.
17. Phloem is situated is present towards the lower epidermis and consists of sieve tubes, companion cells and phloem parenchyma.
Identification:
(a) 1. Presence of expanded portion or blade.
2. Presence of mesophyll.
3. Bundle sheath is present…………………………………. Leaf
(b) 1. Upper and lower epidermal layers are clearly distinguishable.
2. Mesophyll is clearly differentiated into palisade and spongy parenchyma.
3. Stomata only on the lower surface.
