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Growth in Animals
Determinate: Finite Size, Finite Shape, Number and Positions of Organs
May have Larval Stages, Metamorphosis, but each is determinate
Non-local regions of Cell Replication
Growth in Plants
Indeterminate: Final size, number of organs influenced by environment
Type of Organs influenced by environment
Local regions of Cell Replication
Repetitive Growth in Shoot Apex and in Radial/Lateral Meristems
Continuous Growth in Root Apex
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Growth in Plants
Local Increase in Cell Number (Cell Replication)Local Increase in Cell Size (Elongation)
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Introduction to Plant Growth
Repetitive Production of Phytomeres: a Structural Module created by a Shoot Apical Meristem (SAM)
Growth of shoots or roots in the Long or Axial Dimension is due to Shoot Apical Meristems (SAMs) and Root Apical Meristems (RAMs)
These are regions at the apex that contain Stem Cells that replicate to form Daughter Cells while maintaining the Stem Cells
As they are born and elongate, daughter cells of SAMs displace the SAMs upward and RAMs downward
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Repetitive GrowthFrom Shoot Apical Meristems
(SAMs)Nonrepetitive Growth
From Root Apical Meristems(RAMs)
SAM
RAM
Root
ShootRegion where
axillary SAM will form
Growth from Apical Meristems and LDO Primordia
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Lon
g A
xis
= A
xial
Radial/Lateral
Axes in Plants
/Adaxial/Top
/Abaxial/Bottom
/Lateral Position
Apical End/Apex
Basal End/Base
LateralDeterminateOrgan (LDO)
Axillary Position/Axil
/Medial Position
Axillary SAM
PhytomereInternode
Node
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SAM Daughter Cells form the Four Parts of the Phytomere
Node: On a stem, the point of insertion of a Lateral Determinate Organ
Lateral Determinate Organ (LDO): Leaf, Petal, etc. inserted into the Node. Some consider the LDO to be part of the Node. Axillary Shoot Apical Meristem (Axillary SAM): in the axil defined by
the distal-most position between the Internode and LDO Internode: Portion of stem between Nodes
The phytomere derives from the same group of founder cells
In eudicots, the phytomere consists of a node, its axillary SAM, and the internode above the node
In maize (a monocot), it includes the internode below the node
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VegetativePhytomere
LateralDeterminateOrgan (LDO)
Axillary VegetativeShoot ApicalMeristem (V-SAM)
Shoot
FlorescencePhytomere
8 Vegetative Phytomers in Pea
Phytomers
1
2
3
45
9
2
3
4
o1
oo
o
Inactive Axillary SAM
Active SAM
o2
3
4
o
o
BranchingShoots produced by Axillary Shoot Apical Meristems will usually be
identical to the shoot on which they are borne, that isSAMs usually produce axillary SAMs of the same Phase
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Monocot: Poaceae, Grass Family Genus: Phyllostachys, BambooPhyllostachys aurea Carrière ex A. & C. Rivière, Golden Bamboo, Fishpole BambooIntroduced; Invasive; Spreads by underground stems = rhizomes; Does not Flower
A ‘woody’ monocot, although not true wood (not made by vascular cambium)
A Case Study in Branching of Vegetative Shoots
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Phyllostachys aurea Carrière ex A. & C. Rivière, Golden Bamboo, Fishpole BambooPhyllotaxy of Leaves of Primary Shoot = Distichous (2-Ranked; Alternate)
[Do not have a term for ‘Two Adjacent Axillary SAMs per Node’]
Outgrowth of One of Two Axillary SAMs
into a Secondary Shoot
Node Two Axillary SAMs Both dormant
Outgrowth of Both Axillary SAMs into
Secondary Shoots
Internode
Phytomere
Outgrowth of One of Two Axillary SAMs
into a Tertiary Shoot
Flat surface
Flat surface
In this plant, SAMs know what order branch they are on
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Outgrowth of One of Two Axillary SAMs into a
Secondary Shoot
Node Two Axillary SAMs Both dormant
Internode
Phytomere
Phyllostachys aurea Carrière ex A. & C. Rivière, Golden Bamboo, Fishpole BambooPhyllotaxy of Leaves of Primary Shoot = Distichous (2-Ranked; Alternate)
[Higher Magnification]
I N I N I N I N
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Phyllostachys aurea Carrière ex A. & C. Rivière, Golden Bamboo, Fishpole BambooPhyllotaxy of Leaves of Primary Shoot = Distichous (2-Ranked; Alternate)
[Do not have a term for ‘Two (or Three!) Adjacent Axillary SAMs per Node’]
A third axillary SAMat this node in the
Primary Shoot!Remains dormant
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Tertiary Shoot
One axillary SAM per node in Tertiary Shoots: remains dormant.If two axillary SAMs per node, then one grows out.
Phyllostachys aurea Carrière ex A. & C. Rivière, Golden Bamboo, Fishpole BambooPhyllotaxy of Secondary and Tertiary Shoots = Distichous (2-Ranked; Alternate)
Secondary ShootTertiary Shoot
Two axillary SAMs per node in Secondary Shoots: One remains dormant.It is not random; they are on the same side!
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Large variation in position and complexity of the shoots that bear flowers: from axillary, solitary flowers to axillary and terminal, highly
branched and complex shoots bearing many flowers
Induction of Flowering Converts Apical and Axillary AdultVeg-SAMs into one of several Reproductive SAMs
Phase Transitions
JuvV-SAM AdultV-SAM Subflor-SAM Floresc-SAM Flower-SAM
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The SAM undergoes Phase Transitions: transitions in the Identity of the SAM as evidenced by the Identity of the Phytomeres (including the
axillary SAMs) that the SAM produces
Regardless of the Phase of the SAM, it still produces phytomeres composed of a node, internode, axillary SAM and (usually) a LDO,
although their names may be phase specific
Juvenile Vegetative Shoots - can branch from axillary JuvV-SAMsAdult Vegetative Shoots - can branch from axillary AdultV-SAMsSubflorescence Shoots - can branch from axillary Subflor-SAMs
Florescence Shoots - cannot branch; axillary SAMs are Flower SAMsFlower Shoots - cannot branch; no axillary SAMs
Phase Transitions
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Juvenile-Vegetative Adult-Vegetative Subflorescence Florescence Flower Shoot Shoot (Branched Shoot) (Floral Shoot) Shoot
Lateral Juv Leaf Adult Leaf Cauline Leaf Bract S P St CDeterminate Organ(LDO)
Axillary Shoot JuvV-SAM AdultV-SAM Subflor-SAM Flower-SAM
Apical Meristem(axillary SAM)
1o Shoot Apical JuvV-SAM AdultV-SAM Subflor-SAM Floresc-SAM Flower-SAMMeristem (SAM)
Full Series of Phase Tansitionswith development of all LDOs
and some axillary SAMs
Terminal Inflorescences Only
1o
Vegetative Shoot Inflorescence
2o 2o 2o
3o 3o 3o
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Juvenile-Vegetative Adult-Vegetative Florescence Flower Shoot Shoot (Floral Shoot) Shoot
Lateral Juv Leaf Adult Leaf Bract S P St CDeterminate Organ(LDO)
Axillary Shoot JuvV-SAM AdultV-SAM Flower-SAM
Apical Meristem(axillary SAM)
1o Shoot Apical JuvV-SAM AdultV-SAM Floresc-SAM Flower-SAMMeristem (SAM)
1o
2o 2o
3o 3o
Terminal Florescences; no Subflorescence Phase
Plus Terminal Flower
S P St C
Vegetative Shoot Inflorescence
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Juvenile-Vegetative Adult-Vegetative Florescence Flower Shoot Shoot (Floral Shoot) Shoot
Lateral Juv Leaf Adult Leaf Bract S P St CDeterminate Organ(LDO)
Axillary Shoot JuvV-SAM Floresc-SAM Flower-SAM
Apical Meristem(axillary SAM)
1o Shoot Apical JuvV-SAM AdultV-SAM Floresc-SAM Flower-SAMMeristem (SAM)
1o
2o 2o
3o 3o
Terminal and Axillary Florescences;no Subflorescence Phase
Plus Terminal Flower
S P St C
Vegetative Shoot Inflorescence
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Juvenile-Vegetative Adult-Vegetative Flower Shoot Shoot Shoot S P St C
Lateral Juv Leaf Adult Leaf S P St C
Determinate Organ(LDO)
Axillary Shoot JuvV-SAM Flower-SAM
Apical Meristem(axillary SAM)
1o Shoot Apical JuvV-SAM AdultV-SAM Meristem (SAM)
1o
2o 2o
3o 3o
Solitary, Axillary Flowers
Plus Gradual Change in AdultV LDO
Vegetative Shoot Inflorescence
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Fig. 9.8A L&D
Primary Inflorescence/ Reproductive ShootAxillary SAMs are Subflor-SAMs
Tertiary Inflorescence
Primary Florescence/ Floral Shoot (No Branching)Axillary SAMs are Flower-SAMs
Vegetative and Reproductive Structures and PhytomeresThe Florescence is the apical, unbranched, part of an Inflorescence
VegetativeShoot
FlorescencePhytomer
Subflorescence Phytomere
Flower containing 4 phytomers
Warning: There are other nomenclatures for reproductive structuresIn Taxonomy, ‘Inflorescence’ usually includes Inflorescence, Florescence, and Flowers;
for example, ‘Inflorescences axillary, solitary flowers’
Lateral RosetteInflorescence
Arabidopsis
Subflorescence(Branched, Branchable)
22An Alternative Nomenclature for Arabidopsis
Types of Phytomeres:1 = Basal [Vegetative] Rosette (same use as GG)2 = Basal part of Flowering [Inflorescence] Stalk [the Subflorescence as used by GG]3 = Florescence (same use as GG) Types of Branches containing ….Type 3 on Primary Shoot = Primary Florescence
(Florescence on 1o shoot as used by GG)Type 3 Collectively = Coflorescence (no GG term)Type 2 and Type 1 = Paraclade (Higher-order Inflorescences as used by GG)Types 1+2+3 Collectively = Inflorescence
1
2
3
3
3
primary
primary
rosettesecondaryparaclade
2
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1o
1o2o
2o3o
Arabidopsis violatesseveral rules
2o
3o
Vegetative Shoot Inflorescence Juvenile-Vegetative Adult-Vegetative Subflorescence Florescence Flower Shoot Shoot (Branched Shoot) (Floral Shoot) Shoot
Lateral Juv Leaf Adult Leaf Cauline Leaf None S P St CDeterminate Organ(LDO)
Axillary Shoot Subflor-SAM None Subflor-SAM Flower-SAM
Apical Meristem Accessory Accessory (SAM) Subflor-SAM Subflor-SAM
1o Shoot Apical JuvV-SAM AdultV-SAM Subflor-SAM Floresc-SAM
Meristem (SAM)
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Juvenile-Vegetative Adult-Vegetative Flower Shoot Shoot Shoot S P St C
Lateral Juv Leaf Adult Leaf Bract S P St CDeterminate Organ(LDO)
Axillary Shoot JuvV-SAM Floresc-SAM
Apical Meristem(axillary SAM)
1o Shoot Apical JuvV-SAM AdultV-SAMMeristem (SAM)
1o
2o
3o 3o
Axillary, not terminal, Florescences;no Subflorescence Phase
Plus Gradual Change in AdultV LDO2o
Vegetative Shoot Inflorescence