Lecture 11 - Development, tissues and cell types

Development definition

series of events that progressively form an organism’s body

Three overlapping stages of development

1. growth

2. morphogenesis

3. differentiation

Growth

irreversible increase in size, cell division and expansion

Morphogenesis

shape/form

Differentiation

process of specialization

Scientific approaches for studying development

1. observing

2. physical manipulation

3. mutations

4. molecular tools and markers

Fate map

Determines which cells develop into other cells

Uses of molecular tools

• cloning and determining gene function

• detect gene expression in tissues/cells

• transgenic reporter lines to visualize gene expression during development

vegetative organs

root, stem, leaves

reproductive organs

flower and fruit

3 tissue types of every organ

• ground

• vascular

• dermal

Dermal tissue types

epidermal

Ground tissue types

• parenchyma

• collenchyma

• sclerenchyma

Vascular tissue types

• xylem

• phloem

Xylem types

• tracheids

• vessel elements

Phloem types

• sieve tube elements

• companion cells

Dermal tissue function

1. substance movement in/out plant

2. protection

3. anchor

Epidermis

outermost layer, composed of parenchyma

primary growth

Periderm

Multi-layer of parenchyma cells, replaces epidermis

secondary growth

Epidermis cell type examples

• stomata

• trichomes

• root hair

periderm cell types

• cork

• parenchyma

ground tissue cell types

• parenchyma

• collenchyma

• sclerenchyma

parenchyma

found throughout the plant, performs photosynthesis

collenchyma

structural support in herbaceous plants

found under stem epi. and along leaf veins

cells alive at maturity and only functions while alive

strong and flexible cell walls, support larger plants

‘celery strings’

sclerenchyma

hard structural support in trees

may be alive or dead and still functional

ground tissue parenchyma

between dermal and vascular tissue

main component of ground tissue, conducts photosynthesis in leaves

thin cell walls, large central vacuoles

photosynthesis and food storage

sclerenchyma - fibers

long, thin cells found in strands/bundles that function in support

vascular tissue

sclerenchyma - sclereids

short, branched cells with variable shape

ground tissue

Vascular tissue - function

transport system for water, materials and nutrients

includes xylem and phloem

Xylem functions

transport water/minerals from roots to shoots

mechanical support

Tracheids - xylem

long, dead cells w/ tapered ends

Xylem - Vessel members (angiosperms)

Dead cylindrical cells stacked

Xylem development

Mature xylem are dead with thick cell walls, lacking organelles and nuclei

Phloem functions

Transports metabolites and signals

Phloem - sieve tube element

end-to-end conductive cells

lack most organelles and nucleus

Phloem - companion cells

Specialized parenchyma that carries out metabolism of sieve tube cells

Phloem development

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