Introduction leaf
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The document describes the anatomy and morphology of leaves. It defines leaves and their key parts like the lamina, petiole, stipules, and veins. It describes the different types of leaves including foliage leaves, bracts, and modified leaves. It also covers leaf arrangements, shapes, margins, bases, textures, and venation. The second half discusses microscopical leaf structures like the epidermis, cuticle, trichomes, stomata and their types. In summary, the document provides a comprehensive overview of leaf structure from the macroscopic to microscopic level.
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Introduction leaf
- 2. The Leaf (Latin: Folium) • a lateral outgrowth or an appendage on the stem. • possesses neither nodes nor internodes and buds or lateral branches arise in its axil. • Characters: • - flattened form • - thin texture • - presence of chlorophyll • - presence of veins
- 3. Leaf Morphology Leaf lamina Stipule Petiole Node Internode Axillary bud Stem Axil
- 5. Types of Leaves • 1- Cotyledons (seed-leaves): • leaves of the embryonic plant in the seed • for food storage • i.e Almonds, Mustard and Beans • 2- Prophylls (fore-leaves): • first leaves born a branch • simpler in form and structure from foliage leaves
- 6. • 3- Foliage leaves: • The ordinary green leaves which carry on the normal leaf functions. • 4- Bracts: • leaves having a flower in their axils • usually simpler and smaller than ordinary leaves • 5- Scale leaves: • present on all subterraneran stems and on some aerial ones • thin, membranous and devoid of chlorophyll
- 7. • 6- Floral leaves: • The variously coloured sepals and petals, also the stamens and carpels • no buds in their axils • 7-Modified leaves: • where the whole leaf or a part of it is modified to carry out a certain function • i.e a- tendrils for climbing as in Pea • b- special traps for catching insects in insectivorous plants as Drosera • c- become succulent serving for storage of water as Hyoscyamus muticus
- 8. Phyllotaxis • It is the disposition of the leaves on the stem. • The leaves being arranged on the stem in a definite manner characteristic for each species of plants.
- 9. Types of Phyllotaxis Alternate Opposite Whorled decussate
- 11. Leaf base Sheathed Ligulate Stipulate Exstipulate Decurrent
- 13. Compound leaf
- 14. Forms of Compound leaves Paripinnate Imparipinnate Palmate Ternate Bipinnate
- 15. General description of the lamina of a simple leaf • general outline or shape • Size • Apex • Base • Margin • Venation • Surface • texture
- 16. General outline or shape • a- when the lamina has nearly the same width: Filiform (Fennel) Acicular (Pinus) Tubular (Onion) Linear (Grasses) Oblong (Cassia)
- 17. • b- when the lamina has the widest portion near the base: Continued: General outline or shape Lanceolate (Long Buchu) Ovate (Boldo) Ensiform (Eucaluptus) Cordate (Ipomea) Sagitate (Rumex) Hastate (Convolvulus) Reniform (Asarum)
- 18. Continued: General outline or shape • c- when the lamina has the widest portion near the apex: Obcordate (Oxalis) Obovate (Dog Senna) Spathulate (Uva Ursi ) Lyrate ( Brassica)
- 19. Continued: General outline or shape • d- when the lamina is symmetric or round: Orbicular (Nymphea) Elliptical (Pear) Oval (Boldo)
- 20. Size of the leaf • the length from the base to the apex and the broadest width • it varies from tiny leaves (few millimeters) as Savin to a very considerable size as banana • In leaves used in medicine the doesn’t exceed about 30 cm long as Digitalis • Leaves vary in size on the same plant being bigger at the base and becoming smaller as getting near the apex
- 21. Apex of the leaf Acute (Hyoscyamus) Acuminate ( Stramonium) Obtuse (Oval Buchu) Recurved (Short Buchu)
- 22. Margin of the leaf Entire (Senna) Revolute (Uva-Ursi) Dentate Serrate (peppermint) Spiny
- 23. Continued: Margin of the leaf Bidentate Crenate (Digitalis) Serrate Lobed
- 24. Base of the lamina Symmetric Asymmetric Decurrent
- 26. Surface of the lamina Smooth (Uva-Ursi) Bunctate (Buchu) Glabrous (Coca) Pubescent Hairy
- 27. Texture of the lamina Membranous Papery Coriaceous Succulent
- 28. Structure of the leaf (Microscopical characters)
- 29. Epidermis: • mainly a protective layer • It occurs on the surface of plants and it is a complex tissue consisting of epidermal cells, trichomes (hairs) and stomata • Epidermal cells: • It consists of a single layer of cells, but in some cases it may become many layered as a result of division • many layered epidermis often acts as water storage tissue and the inner layer is often described as hypodermis • tubular or lenticular with complete absence of intercellular spaces except where the stomata occur
- 30. • appear in surface view polygonal: - approximately isodiameteric in Dicots - axially elongated in Monocots Leaf epidermis in Dicots (suface view) Leaf epidermis in Monocots (suface view)
- 31. • The anticlinal walls perpendicular to the surface: - straight as Senna, Coca - wavy as Belladonna - beaded due to unequal thickening or thickenings as Digitalis • The epidermis outer walls are: - convex - cellulosic - mostly thickened - covered with cuticle cuticle epidermis
- 32. • Cuticle varies in thickness - thin in shady plants as Digitalis - thick in sunny regions plants as Uva Ursi Thin epidermal cuticle Thick epidermal cuticle
- 33. • Cuticle may be: - smooth as Stramonium - finely ridged appearing in surface view striated as Belladonna - formed mainly of cutin which is an aggregate of modified fatty acids, partly combined with alcohols • Epidermal cells are devoid of content • in some cases may contain certain contents • as: -calcium oxalate as Savin • - calcium carbonate as Cannabis • - diosmin as Buchu • - mucilage as Senna
- 34. Trichomes or hairs • Epidermal cells are sometimes extended outwards forming projections of variable shapes and sizes • If they are short and conical papillae and the epidermis described papillosed these appear in surface view as circles in the middle of the cells
- 35. • If the trichomes are long trichomes or hairs - The part embeded in the epidermis foot - The free part body - Covered with cuticle which may be smooth as Hyoscyamous or warty as Senna - Either of covering type as non-glandular trichomes or of secretory function as glandular trichomes - Secretions may be volatile oils or oleo-resin
- 36. Trichomes or Hairs Non-glandular Hairs (covering type) Glandular Hairs (secretory function) Uni-cellular multi-cellular multi-cellularUni-cellular
- 37. Multi-cellular (formed of more than one cell) Uni-cellular (formed of more than one cell) Unbranched (Simple) Ex: Senna Branched Ex: Crucierae Unbranched (Simple) Branched Non-glandular Hairs
- 38. Uni-seriate (formed of one row) Ex: Belladonna, Digitalis Bi-seriate (formed of two rows each contain one cell (twin hair) ex: Arnica flower, or more cells ex: Calendula flower Pluri-seriate (formed of many rows shaggy hair) ex: Cumin Non-glandular Hairs multicellular unbranched (simple) hairs
- 39. Non-glandular Hairs Multi-cellular branched hairs Simple branched (with uni-seriate body ending in 2 branches) ex: Tobacco Stellate ex: Boldo Peltate (scale hair) Very short stalk surrounded by plate like structure of closely joined cells ex: Olea Balance hair (T-shaped hair) ex: Pyrethrum
- 40. c Glandular hairs I- Unicelluar (pear gland): -not of common occurrence, present in Piper. - the foot is embedded in the epidermis and the swollen head is projecting outside
- 41. II- Multicellular glandular hairs - the most common type. - consist of several cells and are classified into: Uniseriate stalk Biseriate stalk and biseriate head (Compositae hair) Pluriseriate stalk and a head with 8 radiating cells ex: Cannabis Branched stalk (Branched hair) ex: Hyoscyamus muticus
- 42. Uni-seriate stalk multi-cellular glandular hairs Uni-cellular head Multi-cellular head One-celled stalk ex: Digitalis 2-3 celled stalk ex: Belladonna, Lavender
- 43. 1- celled stalk & 2-celled head ex: Digitalis 1-or more celled stalk & many celled ovoid head ex: Hyoscyamous Uni-seriate stalk multi-cellular glandular hairs Uni-cellular head Multi-cellular head very short: 1- celled stalk & a head of 8 radiating cells ex: F: Labiatae Labiacious hair
- 44. • These are openings in the epidermis of stem and leaves. They occur in both surfaces or only on lower surface. • It’s a type of epidermal structure of a great diagnostic value • Consists of: - a central pore - two similar cells; the guard cells, kidney shaped in Dicots while they are dum-bell shaped in Monocots cStomata
- 45. • Stomatal number: • The average number of stomata per square mm. • It is of little value in distinguishing between closely allied species • Stomatal index: Stomatal index = S x 100 E + S • It is the percentage of number of stomata (S) in a certain area to the sum of total number of epidermal cells (E) and stomata together in same unit area. • Stomatal index is constant for a given species
- 46. Types of Stomata • 1-Moss type - The guard cells, during development, fuse with each other by lysis of the separating walls, thus the osteole becomes surrounded by a single cell Types of stomata according to characters of guard cells:
- 47. • 2- Gymnospermous: - The guard cells are oval or elliptical and inclined to the epidermis at an angle of approximately 45°. • 3- Graminaceous: - Stomata are usually rectangular in outline and the guard cells are dumbell-shaped, thin walled ends and narrow flat middle parts with outer and inner walls thickened. - It is frequently with 2 subsudary cells lying parallel to the long axis of the osteole
- 48. • 4- Dicotyledonous: - Stomata are elliptical or circular in shape as seen in surface view and surrounded by epidermal cells which vary in characters and arrangement. Types of stomata according to the characters and arrangement of surrounding cells (subsidary cells): 1- Ranunculaceous (Anomocytic) stomata: -Equal celled type - The stoma is surrounded by three to five subsidary cells are of varying number and almost of equal size -ex: Digitalis leaves
- 49. • 2- Rubiaceous (Paracytic) stomata: - Paracytic stomata - Parallel celled type - The stoma is surrounded by two or three subsidary cells , two of which having their long axis parallel to the axis of the osteole - ex: Senna leaf, Coca leaf
- 50. • 3- Caryophyllaceous stomata: - Diacytic stomata - Cross-celled type - The stoma is surrounded by two or three subsidary cells showing their long axis perpendicular to the axis of the osteole - ex: Mentha leaf
- 51. • 4- Cruciferous stomata: - Anisocytic stomata - Unequal celled type - The stoma is surrounded by usually three or more subsidary cells one of which is distinctly smaller than the others - ex: Solanaceous leaves
- 52. Mesophyll
- 53. • Palisade layer: • formed of one or more layers of cylindrical cells perpendicular to the epidermis with narrow intercellular spaces which is usually corrupted with the cortical tissues in the mid- rib region. • The upper palisade may form a continuous layer as Senna or dis-continuous as Hyoscyamus.
- 54. • Spongy tissue: • formed of chlorenchyma with large irregular cells with intercellular spaces. • Hypodemis: • The mesophyl is sometimes separated from the epidrmis by one or more layers of cells devoid of chlorenchyma called hypodermis • This is a protective tissue or water, it may be parechymatous, collenchymatous or sclerenchymatous
- 55. • Cortical tissue: • It is present in the mid-rib region • Can be formed of parenchyma as in Belladonna, or collenchyma as Uva Ursi. • Endodermis: • It is the inner-most layer of cortical tissue which is usually indistinguishable in medicinal plants.
- 56. • Pericycle: • present between the phloem and cortical tissue • mostly parenchyma but sometimes formed of collenchyma as Digitalis • Vascular system:
- 57. Bulliform cells Bundle sheath cells with chloroplasts Parenchyma with chloroplasts Phloem Xylem Lower epidermis Upper epidermis Sclerified fibers Collenchyma
Editor's Notes
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