Plant Tissue: 

Plant Tissue: 

  • Plant tissue it divided into 2 categories, those two categories are then further divided.


First Group of Plant Tissue:

Simple tissue group 1:

Ground Tissue:  

  • Parenchyma (also Chlorenchyma and Aerenchyma)
  • Collenchyma
  • Sclerenchyma -/ Both: Sclereids and Fibers

 

Simple tissue group 2: 

Dermal tissue: 

  • Epidermis
  • Root hairs, other trichomes and stomata


Second Group of Plant Tissue:

Vascular Tissues Group 1: 

Xylem: 

  • Wood vessels segments
  • Tracheids
  • Xylem parenchyma
  • Xylem fibers


Vascular Tissues Group 2:

Phloem: 

  • Sieve tube elements
  • Companion cells
  • Phloem parenchyma
  • Phloem vessels

Plant tissues are grouped into 3 tissue systems: 

  • The ground tissue; variety of functions, also makes up the bulk of the plant.
  • The vascular tissue; responsible to for transportation in the plant
  • The dermal tissue; covers the plant body

 

 



 

                                                              A: Roots


                                                              B: Stems



                                                              C: Leaves



                                                    This diagram shows the distribution of each tissue.

 

  • Tissues consisting of one cell type are simple tissue
  • Tissues consisting of more than one cell type are compound tissues
  • Herbaceous plants are covered with an epidermis. In woody plants the epidermis tears and dries out eventually and a periderm (bark) is formed.



Ground Tissue: 

Parenchyma: General tissue type in plants

  • Thin-walled cells
  • Rounded to elongated
  • Can contain chloroplast
  • Intercellular spaces occur
  • Large vacuoles                                      The Cell--->

Parenchyma Function: 

  • Photosynthesis: Cells with chloroplasts are called chlorenchyma
  • Storage: Starch and oils are stored in parenchyma cells. Vacuoles of plant cells store salts and sugar
  • Secretion: e.g Resin, tannins, hormones, enzymes and nectar
  • Meristematic function: Parenchyma cells differentiate into other types of cells
  • Filling Tissues: Parenchyma cells are found filling tissue in plant organs
  • Aerenchyma: Contains large open spaces. Found in aquatic plants; floating easy and facilitates gaseous exchange 

 

Collenchyma: Found in herbaceous plants

  • Irregularly thickened walls; especially in the corners
  • Cells remain alive; when mature too
  • Mostly found in strands of ground tissue

                                                                  

Collenchyma Function: 

  • Lends Function
  • Strengthening in plant structure
  • Photosynthesize when the cells contain chloroplasts
  •                                                                  
  •                                                                     The Cell ----->




Selerenchyma: There are two types 

  • Hard and thickened walls
  • Walls are not elastic
  • No living cell contents in its mature form; in reality the cells are dead



 

Sclereids 1st type:

  • Different shapes
  • Commonly found in the shells of nuts
  • Granular structure of a pear is also because of the
  • presence of sclereids
  •                                                                             The Cell ---->
  • Fibres 1st type:
  • Elongated cells with pointed ends
  • Occur in groups in wood, inner part of bark; part of vascular tissue


Dermal Tissues:

  • Herbaceous plants are covered by an epidermis that generally consists of one layer of cells
  • Woody plants also have an epidermis, but as organs, especially the stems and roots, grow thicker, the epidermis tears and is replaced by the periderm
  • The periderm in older woody plants forms the bark


The following cover and protect the plant organs: 

  • Epidermis
  • Periderm  


The cells of the epidermis: 

  • More or less brick-shaped in cross section
  • A variety of shapes when viewed from above
  • Do not contain any chloroplasts
  • Are transparent which allows sunlight to penetrate t the photosynthesis tissues
  • The only cells that do not contain chloroplast are the guard cells
  • Guard cells are specialised cells that surround pores in the epidermis; forming the stomata surround.
  • The epidermis of exposed plant organs is covered with a waxy layer, the cuticle 
  • The cuticle prevents excess loss of water
  • Unicellular/multicellular outgrowths of the epidermis are known as trichomes 
  • Trichomes have various functions; The root hairs are trichomes that are responsible for the absorption of water  


Vascular Tissues: Responsible for transport in plants 

Xylem: Root to leaves: 

Xylem consists of 4 cells types:

  • Wood vessel cells; Responsible for transport
  • Tracheids; Responsible for transport
  • Parenchyma; Responsible for storage
  • Fibers;             Support and strength


Phloem:

Phloem consists of 4 cells types:

  • Sieve tube elements; Responsible for the transport of nutrients
  • Companion Cells;  Responsible for the transport of nutrients
  • Parenchyma; Responsible for the storage of substance
  • Phloem Fibers; Responsible for the support and strengthening


Companion Cells: 

  • Thin walled
  • Large nucleus
  • Closely associated with sieve tubes
  • Pits and plasmodesmata
  • Nucleus controls metabolic activities of both sieve tubes and companion cells


Sieve tube elements: 

  • Rounded in cross section
  • Elongated cells
  • Transverse walls perforated – sieve plate
  • Thin-slightly thickened walls
  • Pits and plasmodesmata occur
  • Closely associated with companion cells
  • No nucleus; metabolically active


Function: Sieve tube elements, Companion Cells and Phloem

  • Transport of dissolved organic food (mainly sugars) from the leaves to other plant parts
  • The sieve tubes are the main transport cells




 

 

 

Wood vessel segments: 

  • Thickened wall cell
  • No living contents
  • Elongated cells
  • Round in cross section
  • Pits for lateral transport
  • Walls impregnated with lignin
  • Transverse walls perforated
  • Hollow, continuous tubes


Tracheids: 

  • Elongated cells
  • Thickened cell walls
  • Pointed ends
  • Pits (Lateral transport)


Functions: Tracheids and Wood vessel segments

  • Upwards transport of water and dissolved mineral salts (ions) from roots to leaves
  • Wood vessels are the most important cells responsible for water transport
  • Strengthening and support in woody plants, form woods
  •  

 












Merisematic Tissue: (Similar to stem cells)

  •  Merisematic tissue in undifferentiated and unspecialised
  • Occurs in the growth regions of plants (tips of stems and roots, axillary buds)

 


 

Merisematic cells are: 

  • Small
  • Cubic
  • Densely packed with no intercellular spaces
  • The cells have a large nucleus
  • Dense cytoplasm
  • No vacuoles (There is no need)

 


The growth of plant organs and internal structures takes place by mitosis in the materialistic regions: 

  • Primary growth: Takes place a the tips of the stems and roots (apical meristem)
  • Secondary growth: Increases the girth of the stems and roots (lateral meristem –
  • cambium)


Close rings show rapid development 

Far rings shows climate wasn’t very good