TISSUESA COLLECTION OF CELLS THAT PERFORM A SPECIFIC FUNCTION

Meristems

Unlike animals, plants have permanent regions of cell division Meristems

Meristems

Apical Meristems Cell division at tips of roots and stems

Produce primary tissue

Meristems

Lateral Meristems Cell division that increases girth of roots and stems

Secondary growth

Lateral Meristems

Vascular cambium Conduction

“Plumbing”

Lateral Meristems

Vascular cambium Cambium

Thin cylinder of brick-shaped cells

Majority of growth contributes to increased girth

Lateral Meristems

Cork cambium Layer of cells outside phloem

layer of vascular cambium

Inside the outer bark

Lateral Meristems

Intercalary Meristems Grassy plants

Develop nodes along stems

Lateral Meristems

Intercalary Meristems Do not contain cork cambium

Vascular bundles

Tissues

Simple Tissues Parenchyma

Collenchyma

Sclerenchyma

Simple Tissue

Parenchyma cells Thin, pliable cell walls

The most abundant of all cell types

Space between parenchyma cells Intercellular space

Simple Tissue

Parenchyma cells that contain numerous chloroplasts Chlorenchyma tissue

Primarily photosynthesis

Parenchyma cells lacking chlorophyll Food and water storage

Soft, edible parts of fruit and vegetables

Simple Tissue

Collenchyma cells thicker and longer Primarily just below the epidermis

Flexible support for growing tissue Strands of celery

Simple Tissue

Sclerenchyma cells thickest and toughest cell walls Impregnated with lignin for support

Simple Tissue

Sclerenchyma cells form two types of tissues Form very hard tissue

Sclereids

Gritty texture of pear

Hard shell of nuts

Simple Tissue

Sclerenchyma cells form two types of tissues Longer tissue that contain a tiny cavity (lumen)

Fibers

Complex Tissue

Composed of two or more types of cells Plumbing tissues

Xylem

Phloem

DICOT

MONOCOT

Complex Tissue

Xylem Conducts water and minerals from the

roots

Transports upward

Complex Tissue

Xylem

Long tubes composed of two tissues Vessels

Large openings at each end allow for water flow

Tracheids

Conduction and support

Smaller cells

Complex Tissue

Xylem

Long tubes composed of two tissues Tracheids

Conduction and support

Smaller cells

Complex Tissue

Xylem

Openings along cell walls connect side by side cells Pits

Lateral flow in trees

Rays

Complex Tissue

Phloem Conduct water and food in both

directions

Primarily down

Complex Tissue

Phloem

Long tubes composed of two tissues Sieve tubes

Similar to xylem vessels

Perforated ends instead of large openings

Sieve plates

Complex Tissue

Phloem

Long tubes composed of two tissues Companion cells

Similar to xylem tracheids

Support sieve cell functions

Complex Tissue

Phloem

Living sieve tube cells contain callose

Injury will result in callose to plug sieve plate Callus plug

Plants seal, not heal

Xylem and Phloem

https://www.youtube.com/watch?v=LQ03xIkLLQU

Complex Tissue

Epidermis Outermost layer of cells

Skin

Complex Tissue

Epidermis

One cell thick (usually)

Multilayered examples Orchid aerial roots

Velamen roots

Complex Tissue

Epidermis Secrete fatty (waxy) substance

Cutin

Protective layer on the outside

Cuticle

Restricts water loss

Resists disease and insects

Complex Tissue

Epidermis Form tubular extensions

Root and foliar hairs

Complex Tissue

Epidermis Openings along surface

Stomata

Gas exchange

Transpiration

Complex Tissue

Epidermis Guard cells

Open and close

Complex Tissue

In woody plants, epidermis sloughed off Periderm

Outer bark

Boxy cork cells

Complex Tissue

Contain fatty substance to waterproof layer Suberin

Protects phloem tissue beneath it

Complex Tissue

Pockets of tissue protruding through periderm Lenticels

Gas exchange

Fig. 4.14

Complex Tissue

Secretory cells Exude nectar, fragrance or oil

Expel waste from cells

Xylem, Phloem, and Transpiration

https://www.youtube.com/watch?v=xGCnuXxbZGk