B4: Plant Histology

• size (relative)
• shape
• structure (including color)
• organization

Types of Tissues

Based on A) POSITION, B) COMPOSITION

Made up of 3 cell types:

• parenchyma - uniform primary cell wall METABOLISM
• collenchyma - unevenly thick (patterns of cell - cell wall - cell - cell wall) PLASTIC GROWTH
• sclerenchyma - secondary cell wall (red, has thicker outlines) MECHANICAL SUPPORT, FLEXIBILITY

A. POSITION
Meristems - founder cells in the mature plant (this is where they come from)

• apical - found at tips (shoot/root apical meristem)
• lateral - circumferential growth (ex. flat cells)

dermal, ground, vascular tissue systems

Epidermis:

• uniseriate - single layer of cells
• multiseriate - multiple layer of cells (e.g. Ficus elastica)

Composed of: guard cells, accessory cells, pavement cells (surrounding accessory cells). Specimen examined: Tradescantia, abaxial side.



Trichomes - epidermal outgrowths

B. COMPOSITION
a) SIMPLE (1 cell type)
1) Parenchyma
i) chlorenchyma - chloroplast
ii) aerenchyma - airspaces
iii) storage parenchyma - contain plastids, food

3) sclerenchyma
i) sclereids - short and round, compact
ii) fibers - cells elongated and tapering

b) COMPLEX (more than 1 cell type)
1) xylem
i) water conducting elements
- tracheids - thin, long, tapering ends
- vessels - wide diamater, open ends

2)  phloem
i) sieve tubes - sugar; companion cells - metabolism & maintenance
   parenchyma cells, no nuclei

------

Shoot apical meristem of Coleus

------
Pyrus  - (pear) pulp, squash mt w/ alcohol phloroglucinol

sclereid - stained violet
parenchyma - bubble like structures

Gossypium - (cotton) wet mount

------

TRICHOMES - epidermal outgrowths (all under LPO)

1. Stellate (Urena lobata)
   
2. Scale (Eleagnus philippinensis)
   
3. Branching (Vervascum thapscus) LPO
   
4. Bristle (mucuna pruriens)
   
5. Glandular (munligia calabure)
   
6. T-shaped (Chrysophyllum)
   
7. Simple hairs (Theobroma cacao)
   
8. Stinging (Laportea meyeniana)
   

------

TRACHEARY ELEMENTS - vessels in macerated stems of different plants

Patterns of secondary wall thickening:

*Tracheids:
annular - fine ring along walls of xylem
helical - spiral

pitted - walls have deposits, pits (empty spaces on walls)

*Tracheids/Vessels:

scalariform - look like ladders

reticulate/netted - "gulo gulo"

1. Pinus HPO - pitted, tracheid
   
2. Tilia HPO - scalariform, vessel
   
3. Helianthus HPO - reticulate, vessel
   
4. Cucurbita HPO - helical (can't tell if vessel or tracheid)
   
5. Zea HPO - annular
   

----

Assignments: