Download Concept 35.4 Secondary growth adds girth to stems and roots in

Concept 35.4 Secondary growth adds girth to
stems and roots in woody plants
Involves lateral meristems
◦ Vascular cambium: produces secondary xylem
(wood)
◦ Cork cambium: produces tough covering that
replaces epidermis
 Bark = all tissues outside vascular cambium

What does a
plant need?
Solute transport
across plant cell
plasma membranes
Osmosis

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**Water potential (ψ): H2O moves from high ψ  low
ψ potential, solute conc. & pressure
◦ Pure water: ψ = 0 MPa
◦ Plant cells: ψ = 1 MPa
Water potential equation: ψ = ψS + ψP
◦ Solute potential (ψS) – osmotic potential
◦ Pressure potential (ψP) – physical pressure on
solution; turgor pressure
Bulk flow: move H2O in plant from regions of high 
low pressure
** Review AP Lab 1
Flaccid: limp (wilting)
 Plasmolyze: shrink, pull away from cell wall (kills
most plant cells) due to H2O loss
 Turgid: firm (healthy plant)

Turgid Plant Cell
Plasmolysis
Vascular Tissues: conduct molecules
Xylem
Phloem
Nonliving functional
Living functional
Xylem sap = H2O &
minerals
Phloem sap = sucrose,
minerals, amino acids,
hormones
Source to sink
(sugar made) to (sugar
consumed/stored)
Apoplast = continuum of cell walls/extracellular spaces
Symplast = continuum of cytosol
Absorption of H2O and minerals
Root hairs: increase surface area of absorption
at root tips
 Mycorrhizae: symbiotic relationship between
fungus + roots
◦ Increase H2O/mineral absorption

The white mycelium of the fungus
ensheathes these roots of a pine tree.
Transport of H2O and minerals from
root hairs xylem