Transcript Friday, Jan. 26

Monday, Jan. 9
AIM: How do plants grow?
DO NOW: What are the differences between
monocots and dicots?
HW: Read Ch. 35, pp. 729-738.
Study notes and diagrams.
Multiple Choice packet, Ch. 35
• Life span of a plant vs. an animal
• Indeterminate growth – meristematic
tissue
Annuals –one year (i.e., germinate, flower,
produce seeds, die) (wildflowers, food
crops like cereal grains and legumes)
Biennial – life span of 2 years (beets,
carrots)
Perennials – life span of many years (trees,
shrubs, some grasses like Buffalo grass)
411
• Some Buffalo grass
has been growing for
10,000 years from
seeds that sprouted
at the end of the last
Ice Age.
Meristematic Tissue
• Capable of perpetual
embryonic growth
• Apical meristem 
primary growth in tips
of youngest parts of
plant (i.e., 10 xylem &
10 phloem)
• Lateral meristem 
secondary growth
(girth) (eg. 20 xylem
and 20 phloem in
woody plants)
Roots: Primary Growth
Primary growth in roots
3 zones of cells in root
meristem:
1. Zone of cell
division
2. Zone of elongation
3. Zone of
maturation
Primary Structure of a Root
Primary Structure of Roots
1. Epidermis –  root hairs
2. Cortex – main part of root – stores starch in
plastids
3. Endodermis -- tightly packed cells
surrounding vascular cylinder
 Each cell wrapped in suberin which leads to
water-impermeable barrier called casparian
strip
 NB: CASPARIAN STRIP FOUND ONLY IN
ROOTS.
4. Stele – AKA vascular cylinder
Dicot Root
Suberin & Casparian strip
Stems
• Consist mainly of vascular bundles
Dicot vs. Monocot Stems
Dicot Stem
• Vascular
bundles
arranged in a
ring
• Phloem external
to xylem
• Vascular
cambium
between xylem
& phloem
Monocot Stem
• Vascular bundles
scattered throughout
the ground tissue
• Do not confuse monocot and dicot roots
with monocot and dicot stems.
Growth of Stems
• Primary growth (apical dominance)
• Secondary growth (girth)
(Secondary growth occurs in all
gymnosperms, but takes place only in
angiosperms that are dicots.)
2 Lateral Meristems that lead to
lateral growth
1. Vascular cambium – give rise to
secondary xylem and phloem
 Wood = accumulation of secondary xylem
2. Cork cambium – gives rise to periderm
(bark)
Secondary Structure of Stems &
Roots
• Cells on inside of vascular cambium
differentiate into secondary xylem which
increases girth of tree
• Cells on outside differentiate into
secondary phloem
Annual Growth Rings
• Produced by cambium dormancy, early
wood production, and late wood
production each year
• Sapwood – recent
xylem that remains
active in transporting
water
• Heartwood – older
xylem in center of stem
that functions only in
support
What happened here?