1

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

2

Growth in Plants

Local Increase in Cell Number (Cell Replication)Local Increase in Cell Size (Elongation)

3

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

4

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

5

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

7

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

10

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

13

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

23

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)

24

25

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