Introduction to Plant Development

Keep a green tree in your heart and perhaps the singing bird will come.

...Chinese proverb

Plant Biology and Related Fields

Plant BiologyPlant Biology

AgricultureAgriculture

PharmaceuticalsPharmaceuticals

Basic BiologyBasic Biology

GeneticsGenetics

MolecularCellular Biology

MolecularCellular Biology BiotechnologyBiotechnology

EcologyEcology

EvolutionSystematics

EvolutionSystematics

Already

• What are the major organ systems that make up the plant body?

– what are the major functions of these organs?

• What are the three major tissues that make up plant organs?

– which cell types comprise these tissues? – what are some functions of these cells?

• What cellular structures or cellular processes are unique to plants (or at least highly unusual compared with animals)?

Today and Monday

• How do plant organs, tissues and cells develop?

– Examine Plant Growth,

• the irreversible increase in size that (in plants) almost always results from both cell division and cell enlargement,

– Examine Plant Cell Differentiation,

• the process by which a cell acquires metabolic, structural and functional properties distinct from those of its progenitor,

• Development,

– the sum total of events that contribute to the progressive elaboration of the body of an organism.

Developmental Programs

• Indeterminate growth/development,

– capacity for g/d over an extended period of time,

• vegetative growth and flowering,

– g/d is not genetically limited and can* continue as long as environmental conditions and resources permit.

• Determinate growth/development

– g/d is genetically limited.

Plants display great phenotypic plasticity due to a life-style of indeterminate growth and development.

*plants have genetically limited life spans.

(Toti)potency

…the potential of a single cell to become a progenitor for an entire organism (organ, tissue, or cell type),

– growth and development are genetically and epigenetically controlled in all organisms,

• epigenetics: DNA methylation, chromatin remodeling, etc.

- in contrast with most animals, plants retain the capacity to initiate developmental programs throughout their lives,

- nucleated plant cells are (all) totipotent.

Stem Cells

totipotent

Blastocyst

pluripotent

animal development

multipotent

initials initials

derivatives initials

derivatives

plant development

…all nucleated plant cells are totipotent.

initials

Zygote ---> Several Div.

Apical-Basal Axial Development

Arabidopsis Zygote (4h)

EmbryogenesisSee fig. 23.5

Meristems...

…persistent populations of small isodiametric cells with embryonic characteristics.

Apical Meristems

• cells that remain in the meristem are termed initials,

• cells that are displaced from the meristem and later differentiate, are called derivatives.

Shoot Apical Meristem

(SAM)

Root Apical Meristem

(RAM)

initials initials

derivatives initials

derivatives

plant development

…all nucleated plant cells are totipotent.

initials

Totipotency

Primary Meristems

• Derive from apical meristems and produce primary growth (apical-basal),

– Protoderm: dermal meristem,

– Procambium: vascular meristem,

– Ground meristem.

Plant Cell Division

Plasmodesmata

Apoplast / Symplast

Symplast

The interconnected protoplasts and their

plasmodesmata.

Apoplast

The cell wall continuum of a plant.

“Outside of the symplast.”

Plant Structure

SAMShoot Apical Meristem

Distal: away from the point of reference,Proximal: situated near the point of reference (the main body),Central/Peripheral: “girth”, also termed lateral,Adaxial/Abaxial: ad (toward), ab (away).

Tunica / Corpus

Tunica / Corpus

Tunica

Corpus

SAMShoot Apical Meristem

Primary Meristems

Study this one, and look at lab examples.

Leaf Development

• Tunica cells differentiate into a leaf founder cell,

– divide more rapidly and form the leaf primordium, a meristem with determinate growth,

• Sub-organ domains develop, i.e. upper leaf, lower leaf, mesophyll, vasculature, etc.

• L1 (epidermis), L2 (ground tissue) and L3 (vasculature).

Phyllotaxy

• The number and order in which leaf primordia form is genetically determined and is generally

characteristic of species.

Leaf Anatomy

Study this slide.Review in lab.Ask questions?

stomata

stomata

Developmental Plasticity I

Sun Leaf

Shade Leaf

Thermopsismontana

Developmental Plasticity II

Mucilage

Sloughing off

Primary Root Morphology

Fig. 36.17

Root Morphology

The Root Cap

To reduce friction from growth in soil

The root cap secretes mucilage

The root cap sloughs cells

The Zone of Mitosis(Meristematic)

Makes new cells by Mitosis

Meristematic Cells Divide by Mitosis

The Zone of Elongation

Cells Grow in Size

Vacuole Appears and Grows

Mature Organelles are Produced

RAMRoot Apical Meristem

See Fig. 36.17

RAMRoot Apical Meristem

…produces new cells proximally and distally.

More Root Morphology

Casparian Strip:

…suberin (fatty) band around the endodermis.

Endodermis:

...innermost layer of the cortex.

Stele:

…central cylinder within roots and stems of dicots.

Primary Root Morphology

Lateral roots form primary meristems in mature regions of roots,

• form new roots (organs).

Pericycle

…outermost layer of the stele in roots, the source of nascent meristematic cells that gives rise to lateral roots,

…root primordia form,

…protoderm, ground meristem and procambium form,

…root cap forms, pushes through the cortex,

…vasculature forms between stele and differentiating derivatives of the root primordium.

Meristemsknow them

Monday: lateral meristems (2o growth).

Patterns of Development

ZygoteZygote EmbryoEmbryoCotyledonsHypocotyl

Root

CotyledonsHypocotyl

Root

SAMSAM

RAMRAM

apical/basal, axial

embryogenesis

primarygrowth

SAMSAM Cell Differentiation

Cell Differentiation

Leaf Primordia

Leaf Primordia

Stem Tissues

Stem Tissues

1o Growth1o Growth

primarygrowth

RAMRAM RootTissues

RootTissues

? ? ?

Structure/Function

?

?

1o Growth1o Growth

2o Growth2o Growth

2o Growth2o Growth

Monday

• Read the rest of the chapter,

• Stump the me with questions?