Leaf Anatomy Lecture 8 PDF

 Cont. Introduction of leaves I- Definition - leaf parts II- Morphology (Macroscopically) III- Anatomy (Histology) (Microscopically) III- Leaf Anatomy...

 Cont. Introduction of leaves I- Definition - leaf parts II- Morphology (Macroscopically) III- Anatomy (Histology) (Microscopically) III- Leaf Anatomy Transverse section (T.S) Diagnostic (Key) elements  Structure of lamina  The ordinary leaf consists of Three parts: Upper epidermis I- Epidermis Lower epidermis Palisade cells II- Mesophyll Spongy cells III- Stellar tissues (Vascular tissues) Midrib region T.S. diagram  Structure of lamina I-The Epidermis Single protective layer of tabular cells, without intercellular spaces except for the pores of stomata. 1. Shape of cells 6. Contents 3. Cuticle 5. Trichomes (Hairs) 2. Anticlinal walls 4. Stomata  1. Shape of cells Polygonal isodiametric Polygonal axially elongated  2. Anticlinal walls A. Straight B. Wavy C. Strongly wavy D. Beaded  3. Cuticle  A transparent impermeable layer of waxes and fats to protect the epidermal cells Smooth Striated  4. Stomata  Stomata are openings in the epidermis, bordered by two guard cells.  In Greek, stoma means “mouth,” The plural of stoma is stomata. Guard cells Osteole Closed Open  The Stomata consists of 1-Two guard cells enclosing between them an osteole. 2-Epidermal cells surrounding the stomata are called Subsidiary cells  The guard cells differ from epidermal cells in: a- Smaller b- Contain chloroplast and starch granules. Guard cells Subsidiary cells Osteole  Types of stomata  According to the characters and arrangement of subsidiary cells Paracytic stomata Diacytic stomata  Surrounded by 2 or more  Surrounded by 2 subsidiary subsidiary cells. cells.  2 of which having their  their long axes is long axes parallel to that of perpendicular to that of the the osteole. e.g: senna osteole. e.g. saponaria Anomocytic stomata Anisocytic stomata  Surrounded by varying  Surrounded by 3 no. of subsidiary cells. or more subsidiary cells.  Having no special  One of which is arrangements. distinctly smaller e.g.: digitalis than others …? …? …? …?  5. Trichomes or hairs Small projection  Papillae Long  Hairs (trichomes) Body  Trichomes consists of 2 parts: 1- Foot  embedded in the epidermis. Foot 2- Body  The free part  Types of Trichomes (Hairs) 1- Glandular hairs. 2- Non-glandular hairs   Types of Trichomes (Hairs) Glandular hairs Non-glandular hairs Head Stalk  6. Epidermal contents - The epidermis is mainly free from chloroplasts and contents. Calcium oxalate (Caox.) e.g. Coca - It may rarely contain: Yellow crystal masses (flavonoids) e.g.: diosmin in Buchu Mucilage e.g. senna  Polygonal isodiametric 1. Shape of cells Polygonal elongated Straight 2. Anticlinal walls Wavy I-The Epidermis Strongly Wavy Beaded Smooth 3. Cuticle Striated Paracytic 4. Stomata Diacytic Anisocytic Anomocytic Glandular 5. Trichomes (Hairs) Non-Glandular 6. Contents  II-The Mesophyll Palisade Spongy  The leaf may be Dorsiventral Isobilateral - Palisade on the upper side only Palisade on the upper and lower sides e.g.: stramonium e.g.: senna The palisade may be Continuous Discontinuous Palisade cells continued in - Palisade cells the midrib region interrupted in the e.g.: senna midrib region e.g.: stramonium  Numerical values Scientific term Definition 1-Vein-islet number No. of vein-islets /mm2 2-Veinlet- No. of veinlet-terminations (Veinlet endings)/mm2 termination number 3- Stomatal number Average no. of stomata/mm2 4- Stomatal index [S.I. = (S/S + E) ᵡ 100 ] (S.I) S:no. of stomata & E: no. f epidermal cells 5- Palisade ratio Average no. of palisade cells beneath each epidermal cell of leaf N.B Numerical values are important in distinguishing between closely related species. e.g.: Alex. senna & Indian senna III-vascular tissue Midrib region  Midrib region  The midrib region consists of i.Endodermis ii.Pericycle iii.Vascular tissue - It lies between cortical -Mainly used for - It is the innermost layer and vascular tissue. conduction. of cortical tissue - It is usually indistinct, - It may be: - It composed of: and sometimes distinct 1- Parenchymatous cells. 1-Phloem (containing starch) 2- Collenchymatous cells. 2- Cambium e.g. starch sheath 3- Fibers 3- Xylem  ii. Pericycle Parenchyma Collenchyma Fibers - Simple ground tissue -Tissues for support - Elongated non-living of the plant with large having thickened cells having tappering intercellular spaces cellulosic walls ends and thick walls e.g.: -Chlorenchyma (Containing chloroplasts) -Aerenchyma (contain air spaces)  iii. Vascular tissue (Vascular bundles): - Consists of phloem outside of the bundle, and xylem towards the center, with Cambium in between. Types of V.B. Collateral V.B. Bicollateral V.B. Formed of Phloem & xylem Formed of two patches of Phloem separated by the cambium. enclosing a single patch of xylem.  The xylem Function of xylem: 1- water conducting tubes. 2- Support (Lignified) Protoxylem Towards the upper side  Radial rows of vessels Metaxylem Towards the lower side, and separated by wood parenchyma. Spiral Annular Spiral  Xylem vessels thickening Reticulate Pitted