Chapter 35: Plant Structure,
Growth, and Development
35.1
Admit Slip
3. List 3 words you think
of when you look at the
picture/diagram
2. Write 2 ideas you have
based on the picture and
your words. If possible,
use your words as you
write your ideas.
1. Write 1 question you
have.
Plant Structure
• Plants have hierarchies of cells,
tissues, and organs
• Root system• Shoot system
• Plant Organs (leaf, stem, root)
• Differentiated cells (parenchyma,
collenchyma, sclerenchyma,
xylem, and phloem)
Root System
• Beneath the ground
– Anchors plant
– Absorbs water and minerals
– Stores sugars and starches
• Structural Characteristics
– Fibrous roots: thin root mats below
surface
– Taproots: one thick vertical root with
many lateral roots
– Root hairs: increase surface area for
absorption. May include a symbiotic
relationship with mycorrhizae (fungus
roots)
Shoot System
• Above ground
• Consists of stems and leaves
• Structural characteristics
– Terminal bud: top of the stem
where growth occurs. Growth
toward light (upward) is
accomplished by apical dominance
(terminal bud prohibits axillary bud
growth)
– Axillary bud: located in V formed
between the leaf and stem (lateral
shoot/branch)
• Leaves: main site of
photosynthesis
Modified shoots
stolons (strawberries)
tuber (potato)
rhizome (ginger)
2009
bulb (onion)
Modified leaves
tendrils (peas)
succulent leaves
spines (cacti)
2009
colored leaves (poinsetta)
Plant Tissue Types
• Leaves, stems, roots are made
up of:
– Dermal tissue: single layer of
cells that protects against water
loss and pathogens (called the
cuticle in leaves)
– Vascular tissue: transports
material between the roots and
shoots
• Xylem: transports water and
minerals
• Phloem: transports food from
leaves to the rest of the plant
– Ground tissue: “everything else”
If it is inside the vascular
tissue=pith, outside the vascular
tissue=cortex
Types of Differentiated Plant Cells
1.
2.
3.
4.
5.
Parenchyma
Collenchyma
Sclerenchyma
Xylem
Phloem
Types of Differentiated Plant Cells
1. Parenchyma: most abundant,
present throughout plant
– Perform most of the metabolism
including photosynthesis
2. Collenchyma: help support
growing parts of the plant
– Strings of celery are vascular tissue
with collenchyma surrounding it
3. Sclerenchyma: exists in parts of cell
that are no longer growing,
specialize in support
Types of Differentiated Plant Cells
4. Xylem: consist of 2 types of
water conducting cells:
tracheids and vessels (dead at
functional maturity)
– Tracheids: long, thin cells with
thick secondary cell walls (lignin).
Water moves between cells
through pits
– Vessels: (mostly in angiosperms)
pits and perforated end walls for
water movement
Types of Differentiated Plant Cells
5. Phloem Cells: conduct sugar and
other organic compounds
– Two types of cells (both alive at
functional maturity):
1.
2.
Sieve tubes: contain chains of cells
(sieve-tube elements)-highly
specialized to function in transport
Companion cells: provide for
molecular needs of sieve-tube
elements. Connected to sieve-tube
elements by plasmodesmata
Chapter 35: Plant Structure,
Growth, and Development
35.2
Meristems
• Flowering plants are classified as:
– Annuals: life cycle completed in 1 year
– Biennials: life cycle completed in 2 years
– Perennials: life cycle continues for many years
• Meristems are perpetually embryonic tissues
that are responsible for plant growth
throughout it’s life
Meristems
• Growth only occurs in meristem
tissue through cell division
– Apical meristem: located at tips
of roots and buds of shoots.
• Site of cell division.
• Growth in length=primary growth
– Lateral Meristems: growth that
thickens the shoots and roots
• Growth in ‘girth’=secondary growth
Primary growth lengthens roots and
shoots
• Root cap: protects meristem of root tip as
it moves through soil, also secretes
polysaccharide lubricant
• Has 3 zones:
1. Zone off cell division
2. Zone of elongation
3. Zone of maturation
3 zones of root tip
1. Zone off cell
division: includes
root apical
meristem. Produces
new root cells
(including cells of
root cap)
2. Zone of elongation:
cells elongate…
3. Zone of maturation:
3 systems in primary
growth complete
differentiation and
mature
• Shoot
– Apical meristem is dome of dividing cells at the tip of a
terminal bud
– Primary growth is accomplished by cell division and cell
elongation
• Epidermis
– Underside of leaf epidermis has stomata (small pores which
open and close)
• Ground tissue
– Sandwiched between the upper and lower epidermis
– Made of parenchyma cells (photosynthesis)