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 Growth From Shoot Apical Meristems (SAMs) Nonrepetitive Growth From Root Apical Meristems (RAMs) SAM RAM Root Shoot Region where axillary SAM will form Growth from Apical Meristems and LDO Primordia

5 Long Axis = Axial Radial/Lateral Axes in Plants /Adaxial/ Top /Abaxial/ Bottom / Lateral Position Apical End/ Apex Basal End/ Base Lateral Determinate Organ (LDO) Axillary Position/ Axil /Medial Position Axillary SAM Phytomere Internode Node

6 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 Vegetative Phytomere Lateral Determinate Organ (LDO) Axillary Vegetative Shoot Apical Meristem (V-SAM) Shoot Florescence Phytomere

8 Vegetative Phytomers in Pea Phytomers

o 1 o o o Inactive Axillary SAM Active SAM o o o Branching Shoots produced by Axillary Shoot Apical Meristems will usually be identical to the shoot on which they are borne, that is SAMs usually produce axillary SAMs of the same Phase

10 Monocot: Poaceae, Grass Family Genus: Phyllostachys, Bamboo Phyllostachys aurea Carrière ex A. & C. Rivière, Golden Bamboo, Fishpole Bamboo Introduced; 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

11 Phyllostachys aurea Carrière ex A. & C. Rivière, Golden Bamboo, Fishpole Bamboo Phyllotaxy 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 In this plant, SAMs know what order branch they are on

12 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 Bamboo Phyllotaxy of Leaves of Primary Shoot = Distichous (2-Ranked; Alternate) [Higher Magnification] I N I N

13 Phyllostachys aurea Carrière ex A. & C. Rivière, Golden Bamboo, Fishpole Bamboo Phyllotaxy 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 SAM at this node in the Primary Shoot! Remains dormant

14 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 Bamboo Phyllotaxy of Secondary and Tertiary Shoots = Distichous (2-Ranked; Alternate) Secondary Shoot Tertiary Shoot Two axillary SAMs per node in Secondary Shoots: One remains dormant. It is not random; they are on the same side!

15 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

16 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-SAMs Adult Vegetative Shoots - can branch from axillary AdultV-SAMs Subflorescence Shoots - can branch from axillary Subflor-SAMs Florescence Shoots - cannot branch; axillary SAMs are Flower SAMs Flower Shoots - cannot branch; no axillary SAMs Phase Transitions

17 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 C Determinate Organ (LDO) Axillary Shoot JuvV-SAM AdultV-SAM Subflor-SAM Flower-SAM Apical Meristem (axillary SAM) 1 o Shoot Apical JuvV-SAM AdultV-SAM Subflor-SAM Floresc-SAM Flower-SAM Meristem (SAM) Full Series of Phase Tansitions with development of all LDOs and some axillary SAMs Terminal Inflorescences Only 1o1o Vegetative Shoot Inflorescence 2o2o 2o2o 2o2o 3o3o 3o3o 3o3o

18 Juvenile-Vegetative Adult-Vegetative Florescence Flower Shoot Shoot (Floral Shoot) Shoot Lateral Juv Leaf Adult Leaf Bract S P St C Determinate Organ (LDO) Axillary Shoot JuvV-SAM AdultV-SAM Flower-SAM Apical Meristem (axillary SAM) 1 o Shoot Apical JuvV-SAM AdultV-SAM Floresc-SAM Flower-SAM Meristem (SAM) 1o1o 2o2o 2o2o 3o3o 3o3o Terminal Florescences; no Subflorescence Phase Plus Terminal Flower S P St C Vegetative Shoot Inflorescence

19 Juvenile-Vegetative Adult-Vegetative Florescence Flower Shoot Shoot (Floral Shoot) Shoot Lateral Juv Leaf Adult Leaf Bract S P St C Determinate Organ (LDO) Axillary Shoot JuvV-SAM Floresc-SAM Flower-SAM Apical Meristem (axillary SAM) 1 o Shoot Apical JuvV-SAM AdultV-SAM Floresc-SAM Flower-SAM Meristem (SAM) 1o1o 2o2o 2o2o 3o3o 3o3o Terminal and Axillary Florescences; no Subflorescence Phase Plus Terminal Flower S P St C Vegetative Shoot Inflorescence

20 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) 1 o Shoot Apical JuvV-SAM AdultV-SAM Meristem (SAM) 1o1o 2o2o 2o2o 3o3o 3o3o Solitary, Axillary Flowers Plus Gradual Change in AdultV LDO Vegetative Shoot Inflorescence

21 Fig. 9.8A L&D Primary Inflorescence/ Reproductive Shoot Axillary SAMs are Subflor-SAMs Tertiary Inflorescence Primary Florescence/ Floral Shoot (No Branching) Axillary SAMs are Flower-SAMs Vegetative and Reproductive Structures and Phytomeres The Florescence is the apical, unbranched, part of an Inflorescence Vegetative Shoot Florescence Phytomer Subflorescence Phytomere Flower containing 4 phytomers Warning: There are other nomenclatures for reproductive structures In Taxonomy, ‘Inflorescence’ usually includes Inflorescence, Florescence, and Flowers; for example, ‘Inflorescences axillary, solitary flowers’ Lateral Rosette Inflorescence Arabidopsis Subflorescence (Branched, Branchable)

22 An 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 1 o 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 Collectively = Inflorescence primary rosette secondary paraclade 2

23 1o1o 1o1o 2o2o 2o2o 3o3o Arabidopsis violates several rules 2o2o 3o3o 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 C Determinate Organ (LDO) Axillary Shoot Subflor-SAM None Subflor-SAM Flower-SAM Apical Meristem Accessory Accessory (SAM) Subflor-SAM Subflor-SAM 1 o 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 C Determinate Organ (LDO) Axillary Shoot JuvV-SAM Floresc-SAM Apical Meristem (axillary SAM) 1 o Shoot Apical JuvV-SAM AdultV-SAM Meristem (SAM) 1o1o 2o2o 3o3o 3o3o Axillary, not terminal, Florescences; no Subflorescence Phase Plus Gradual Change in AdultV LDO 2o2o Vegetative Shoot Inflorescence