Transcript Root Apical Meristem

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
Genetics
Agriculture
Ecology
Plant Biology
Basic Biology
Evolution
Systematics
Pharmaceuticals
Molecular
Cellular Biology
Biotechnology
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,
• Determinate
growth/development
– g/d is genetically limited.
• vegetative growth and
flowering,
– g/d is not genetically limited and
can* continue as long as
environmental conditions and
resources permit.
*plants have genetically limited life spans.
Plants display great
phenotypic plasticity due to
a life-style of indeterminate
growth and development.
(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.
Apical-Basal Axial Development
Arabidopsis Zygote (4h)
Embryogenesis
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)
animal development
Zygote ---> Several Div.
Blastocyst
pluripotent
totipotent
multipotent
plant development
initials
initials
derivatives
initials
initials
derivatives
…all nucleated plant cells are totipotent.
Stem Cells
Primary Meristems
• Derive from apical meristems and produce
primary growth (apical-basal),
– Protoderm: dermal meristem,
– Procambium: vascular meristem,
– Ground meristem.
Plant Cell Division
Plasmodesmata
SAM
Shoot 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
QuickTime™ and a TIFF (LZW) decompressor are needed to see this picture.
Tunica / Corpus
Tunica
Corpus
SAM
Shoot 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.
Fig 35.25
Leaf Anatomy
stomata
stomata
Developmental Plasticity I
Sun Leaf
Thermopsis
montana
Shade Leaf
Developmental
Plasticity II
Primary Root Morphology
Mucilage
Sloughing
off
Root Morphology
The Zone of Elongation
Cells Grow in Size
Vacuole Appears and Grows
Mature Organelles are Produced
The Zone of Mitosis
Makes new cells by Mitosis
Meristematic Cells Divide by Mitosis
The Root Cap
To reduce friction from growth in soil
The root cap secretes mucilage
The root cap sloughs cells
See Fig. 35.22
RAM
Root Apical Meristem
RAM
Root Apical Meristem
…produces new cells
proximally and distally.
More Root Morphology
Endodermis:
...innermost layer of
the cortex.
Casparian Strip:
…suberin (fatty)
band around the
endodermis.
Stele:
…central cylinder
within roots and
stems of dicots.
Lateral roots form primary
meristems in mature regions of
roots,
• form new roots (organs).
Primary Root Morphology
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.
Meristems
know them
Monday: lateral meristems (2o growth).
apical/basal, axial
Patterns of
Development
SAM
embryogenesis
Zygote
Embryo
RAM
primary
growth
SAM
? ? ?
primary
growth
Cotyledons
Hypocotyl
Root
Leaf
Primordia
Cell
Differentiation
Stem
Tissues
?
1o Growth
2o Growth
Structure/Function
RAM
Root
Tissues
1o Growth
?
2o Growth
Monday
• Read pp. 811 - 827,
• Stump the Chump (me)?