Anatomy of Flowering Plants
Different tissues
- A tissue is made up of group of cells which are similar / dissimilar in shape that has common origin and function.
- Two types of tissue are (i) meristematic and (ii) Permanent
- Characteristics of meristematic tissues
⇒ Only 1° cell wall is present
⇒ Metabolically active with no reserve food
⇒ No inter cellular space with compact tissue. 
- On the basis of location, meristem is of three types (i) Apical (Tip of root/shoot; length of the plants and 1° growth); (ii) Inter calary meristem (increase the length of plant organs); Eg: Base of Internode [grass, bamboo]; Base of node [min]; leaves [Pins] and (iii) Lateral meristem (increase the width / girth / Thickness)
- On the basis of plane of division; meristem is of three types
⇒ Rib/Tile (Cortex / pith formation)
⇒ Plate (leaf blade)
⇒ Mass (endosperm / embryo) - Three theories to support optical meristem formation are (i) Apical cell theory (Karl Nageli). Histogen theory (Hanotein) and Tunica corpus theory (Schmidt)
- According to histogen theory
(i) Dermatogen : give rise to epidermis
(ii) Periblem : give rise to hypodermis, cortex and endodermis
(iii) Plerome, formation of stile.
In monocot
(iv) Calyptrogen : root cap. - According to tunica corpus theory
(i) Tunica - forms epidermis
(ii) Corpus - rest other than epidermis. - Permanent tissue is of three types (i) Simple (ii) Complex and (iii) Special.
- Simple tissues are made up of similar cells that have common function
- Parenchyma is very primitive and its firstly evolude
- Characteristics:
⇒ All plant parts are obtained from it.
⇒ Central vacuole to store food
⇒ Possess Inter Cellular spaces
⇒ Eg. Flesh of a fruit - Parenchyma modifications
(i) Prosenchyma (rigidity / strength)
(ii) Aerenchyma (aquatic)
(iii) Chlorenchyma [Palisade / spongy]
(iv) Mucilage - Collenchyma which originates from ground meristem is a living mechanical tissue. Which has a localized deposition of pecto cellulose or Hemicellulose to provide tensile strength, to perform photo synthesis and flexibility.
- Occurrence:
⇒ Herbaceous dicotyledonous
⇒ Absent in plants after secondary growth - Three types of collenchyma thickening are
⇒ Angular (Tomato stem)
⇒ Lamellate (Stem of sun flower)
⇒ Lacunate (stem of cucurbita) - Sclerenchyma is a dead tissue which is the main mechanical tissue that give rise to pits. Sclerenchyma is of 2 types (i) Sclereids and (ii) Fibers.
- Types of sclereids:
→ Stone cells / Brachysclereids / grit cells Eg: Coconut, mango, almond, walnut
→ Trichosclereids Eg: Floating leaves.
→ Astrosclereid Eg: Vicloria, Nelumbo, Nymphae.
→ Osteo sclereids Eg: Hakea, Osmanthus. - Sclerenchymatous fibers are the congest cell in plant body which looks tapering that are interlocked to provide mechanical strength.
- Fibers
| Xylary fibers | Bast / phloem fibers |
| → hard | → Flexible |
| → not useful | → Commercially useful |
| → eg. munj (saccharum munja) | → eg. (Cannabis sativa, crotalaria juncea) |
- Complex permanent tissues contain more than one type cell. Which work as one unit to perform heterogeneous function. These tissues are absent in gametophytes.
- Xylem and phloem are 2 important complex tissues
| Tracheids | Vessels |
| Present in Xylem of Vascular plants | Present in Xylem of flowering plants |
| Present in all vascular plants | Only present in Angiosperms ; Gymnosperms Eg: ephedra, gnetum, welwitschia) |
| Contain narrow lumen | Contain wide lumen |
| Imperforated cells | perforated cells |
| Primitive conducting element | Advanced conducting element |
| Angiosperm: In Dracaena, Yucca, Daziharia and Drimyl, vessels are absent. |
| sieve tube | companion cells |
| Rigid cell wall necessary to support pressure gradients which lacks nucleus. | Perform many genetic / metabolic functions of sieve tube cells |
| Separated from one another by sieve plates that help to ensure a steady flow of gap in phloem | Contain many mitochondria supporting active transport with in folding plasma membrane. |
- During autumn season - β(1 - 3) glucan starts depositing on the pores of sieve elements that form thick layer called as callus pad and it is dissolved is following spring.
- Companion cell has thin wall with large nucleus that is present in angiosperm.
[Exception : Austrobaileya] - Sieve tube contain P-protein, which series a seal against leakage in case of injury.
- Sieve tube and companion cell are called siter cells and they both arise from single mother cell.
- In gymnosperm, Albuminous / strasburger cells are present instead of companion cell.
- Special Tissues: Special tissue or secretory tissue is of 2 types (i) lactiferous tissue and (ii) glandular tissue
- Lactiferous tissue [highly branched thin walled cells filled with milky juice called latex]
* latex vessels (articulated vessel) (Eg: Papaver, papaya, Argsmone)
* latex cells (non articulated latex ducts) (Eg: Calotropis, Euphorbia, Nerium) - Glandular tissue may be unicellular (or) multi cellular glands
- Unicellular → Example [urtica - dioica]
- Multi cellular glands can be either External / Internal glands.
- Glandular hairs (Eg: Drosera) and Nectar glands constitute external glands.
- Digestive glands (utricularia, Drosera); mucous secreting leaves (betel leaves) oil glands (sunflower) constitute internal glands.
View this video for the topic from 0:42 to 51:42
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