Anatomy of Flowering Plants
- 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.
(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
⇒ 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]
- 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.
⇒ 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.
|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
|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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