1. Plant Structures Roots, Stems, and Leaves
Chapter 23

2. 23-3 Stems Stem Structure Essential part of transport system
Produce leaves, branches, and flowers
Hold leaves up
Transport substance between roots and leaves
Essential part of transport system
Function in storage and photosynthesis

3. 23-3 Stems Xylem and phloem – major tubule systems
Transport water and nutrients
Composed of three tissue layers
Contain nodes – attachment for leaves
Internodes – regions between the nodes
Buds – undeveloped tissue

4. 23-3 Stems
Stem Types
Monocot – vascular bundles are scattered throughout
Distinct epidermis
Dicot – vascular tissue arranged in a cylinder
Pith – parenchyma cells inside the ring

5. 23-3 Stems
Stem Growth
Primary growth – new cells produced at the root tips and shoots
Increases the length
Secondary growth – increase in stem width
Vascular cambium – produces tissue and increases thickness
Cork cambium – produces outer covering of stems

6. 23-3 Stems Formation of Vascular Cambium
Xylem and phloem bundles present intially
Secondary growth initiates production of a thin layer
The vascular cambium divides
Produces new xylem and phloem

7. 23-3 Stems Formation of wood Wood – layers of exlem
Produced year after year
Results from the older xylem not conducting water – heartwood
Becomes darker with age
Sapwood – surrounds heartwood