1. Plant Tissues

2. Plant Histology Parenchyma Collenchyma Sclerenchyma Xylem Tissue
Phloem Tissue

3. Parenchyma Plant cells with thin cell wall and living protoplasm
Roughly isodiametric with intercellular spaces
Found in cortex and pith of stems and root, mesophyll of leaves and packing tissues in xylem and phloem

4. Function of Parenchyma
Act as packing tissues between more specialized tissues
Turgidity of these cells can provide support in herbaceous plant
Store food
Intercellular air spaces allow gaseous exchange
Metabolically active
Their cell walls are important pathway for the water and mineral salts through the plant

5. Collenchyma
Characterized by the deposition of extra cellulose at the corners of the cells so have thickening cell wall of their corners
They are living cells
Found in regions beneath the epidermis of stem (hypodermis) and near the vascular tissues, eg, midrib of leaves

6. Sclerenchyma
Plant cells with uniformly thickened cell wall which is usually lignified
They are dead cells
Support the cells
There are two types: fibres and Sclerids

7. Fibre Long narrow cell shape with tapering ends, wall with few piths
Found in cortex, pericycle, vascular tissues, surrounding vascular bundles

8. Sclereids
Shorter, vary much in shape, may be spherical, polyhedral, elongated or branched with numerous pits
Found in almost everywhere in plant body, especially in cortex, phloem of stems and roots, in fruit wall and seed coat
Act as main cell type for mechanical support

9. Xylem Tissue
Tracheary elements (tracheids, vessels) which are dead and empty cells for conducting water and support

10. Tracheids
Narrow elongated cell with finely tapering ends, without protoplasm at maturity, with heavily lignified and pitted secondary cell wall
Passage of water from cell to cell is facilitated through pit-pairs which allow lateral transport of water
Act as the only water conducting elements in gymnosperms and primitive vascular plant; small amount in angiosperms

11. Vessel I
Long, pipe-like cell shape, with complete or incomplete perforation at the end wall
Without protoplasm at maturity
Join each other at perforated end walls to form longitudinal conducting tubes
Shorter, greater in diameter than tracheids

12. Vessel II
Water moves from cell to cell through perforations and pit pairs
Cell wall lignified and strengthened to prevent collapse
More specialized for water conducting than tracheids
Only present in angiosperms

13. Diagram of Phloem

14. Phloem Tissue
Sieve elements (sieve cells, sieve tube elements) for conduction of food materials
Sieve elements are elongated cells, cell wall with sieve areas
Sieve elements is absence of nucleus, tonoplast, decrease in number of ER and ribosomes, with thin layer cytoplasm to facilitate the translocation of food

15. Sieve Cell With sieve areas evenly distributed
Present in gymnosperms and lower vascular plant

16. Sieve Tube Element Located on the end walls called sieve plates
Connected by sieve plates with each other to form sieve tube
Present in angiosperms
With companion cell to help translocation of food