PLANT STRUCTURE
Flowering
plants
Conebearing
plants
Ferns and
their relatives
Flowers; Seeds
Enclosed in Fruit
Mosses and
their relatives
Seeds
Chapter 23
BIO 392
Water-Conducting
(Vascular) Tissue
Green algae
ancestor
Remember…
• Organisms are
made up of:
– Organ Systems
– Organs
– Tissues
– Cells
•
•
•
•
Plants are made up of:
Organ Systems
Organs: Roots, Stems, Leaves
Tissues: Dermal, Vascular,
Ground, Meristematic
• Cells: epidermal cells,
tracheids, vessel elements,
sieve tube elements,
companion cells,
parenchyma, collenchyma,
sclerenchyma,
Concept Map
Section 23-1
Plant Tissues
include
Dermal
tissue
Meristematic
tissue
includes
Epidermal
cells
includes
Xylem
includes
Tracheids
Vascular
tissue
Vessel
elements
Ground
tissue
includes
Phloem
Parenchyma
cells
includes
Sieve tube
elements
Companion
cells
Collenchyma
cells
Schlerenchyma
cells
PLANT TISSUE SYSTEMS (4)
A) MERISTEMATIC Source of new growth
for the entire life of the plant
• Primary Growth  plants grow taller and
deeper
– Only in tips of roots & shoots
– Apical meristem  “the bud”
• Secondary Growth  plants grow wider
– Lateral Meristem tissue
– (Also known as: vascular or cork cambium)
PLANT TISSUES cont.
B) DERMAL TISSUE  The outer covering of the
plant, “the skin”
– May have waxy covering to prevent water loss
C) VASCULAR TISSUE transports fluids &
nutrients throughout the plant,
“the bloodstream”
– Xylem  transports water
– Phloem  transports food (sugars made)
D) GROUND TISSUE  everything else
3 Plant Organs
• Roots
• Stems
• Leaves
ROOTS
FUNCTION
1. Absorbs water & dissolved nutrients from soil
2. Anchors plant & prevents erosion
TYPES:
1. Taproots  long & thick,
2. Fibrous roots  thin & branching
ROOTS cont.
STRUCTURE (by tissue)
& TRANSPORT
1. Outer epidermal layer
a. covered by tiny root hairs – more S.A.
b. contain active transport proteins in their cell
membranes to pump minerals from soil into
plant.
c. water follows by osmosis
ROOT STRUCTURE cont.
2. Large layer of Ground tissue
a. spongy cortex
b. endodermis encloses vascular tissue
i. cells are surrounded by Casparian strips
- waterproof barriers that force water
to go through cells, not around.
- Keep flow one way (osmosis)
3. Central Vascular cylinder
a. water moves into the xylem
b. because it cannot go backward, the only place
to go is up the stem
i. “Root Pressure”
STEMS
FUNCTION
1. Support; hold leaves up in the sunlight
2. Transport substances between roots & leaves
TRANSPORT
1. Capillary Action
a. water moves by cohesion from roots
b. 1 way
2. Nutrients are transported through stem
a. in phloem
b. in 2 directions
LEAVES
FUNCTION
1. Site of Photosynthesis
STRUCTURE
1. epidermis is covered by cuticle
a. reduce evaporation
2. Mesophyll – specialized ground tissue
a. lots of chloroplasts
b. where photosynthesis occurs
3. Veins of xylem & phloem branch
LEAVES cont.
SPECIAL STRUCTURES
1. Stomata  exterior openings on underside
of leaf. Site of gas exchange (pores)
a. O2 out
b. CO2 in
c. water vapor out
2. Guard cells  surround
and control stomata
openings
LEAVES cont.
TRANSPORT
1. Water escapes through stomata
a. process of transpiration (evaporation)
b. as water exits, more is drawn up
through stem from roots
2. Stomata open and close to prevent
excessive water loss.
Shoots and Roots
Stem