Plant Structure
Transport
http://www.howe.k12.ok.us/~jimaskew/
3) Vascular Tissues - transport water and food
through the plant.
a. Phloem: straw-like tubes conducting food
downward in a plant.
b. Xylem: straw-like tubes conducting water and
minerals upward in a plant.
A. Roots
1) Function
- Roots support and
anchor the plant (Similar
to Rhizoids)
- Roots absorb water and
minerals from the soil
- Roots store glucose
(starch)
–
Root cell growth pattern:
Division, elongation, and
differentiation
Roots anchor plants and absorb mineral nutrients from soil.
• Roots provide many
functions.
– support the plant
– absorb, transport, and store
nutrients
– root hairs help absorption
b. Structure: Roots are made up of many
tissues
• Dermal Tissue-covers the outside of a plant.
– protects the plant –the root cap
– Absorbs water from the soil-the root hairs
• Ground Tissue-found inside-provides support
-stores materials in roots
• Vascular Tissue-contains xylem and phloem
– Xylem transports water
– -Phloem transports food and minerals
Types of roots
- Taproot
- Fibrous
- Aboveground(epiphytes)
Fibrous root systems have fine branches. They are usually
extensive and shallow.
Taproot systems have one main root.
Fibrous
root
Ex. Grasses
Taproot
Ex.carrots
Epiphytes
Plants that are not rooted in soil but instead grow directly
on the bodies of other plants. Most are found in tropical
rainforest biomes and they are NOT parasitic.
Spanish Moss
Orchid
B. Stems
1) Function
- stems support the plant
- stems hold the leaves toward the
sunlight
- inside the stem water and nutrients travel
to other plant parts
- stems of some plants store glucose in the
form of starch
Types of Tissues in Stems
•
•
•
•
Dermal Tissue- Outer bark of woody stems
Ground Tissue
Vascular tissue- xylem and phloem
Meristematic Tissue-contain both apical and
lateral meristematic tissue for growth
Annual
Rings
.
The width of tree rings help
determine the amount and
conditions of growth.
1/30/07 L
Tree rings help determine the
age of a tree
13
C. Leaf
1) Function
- leaves capture light
from the sun
- leaves make glucose
through photosynthesis
- leaves take-in CO2
release oxygen O2
2) Structure
- top layer is made of a waxy cuticle (prevents
H2O loss) and epidermis(dermal layer)
-middle layer is the mesophyll (ground tissue)
contains most of the chloroplasts
-bottom layer exchanges gases through the
stomata
Stomata
Stomata
visual concept: Guard cells
Image of a Stomata
Guard Cells
Plant Adaptations
Aquatic plants
To take in sufficient oxygen,
aquatic plants, have tissues
with large air-filled spaces
through which oxygen can
diffuse. Stomata located on
top of leaf!
Desert plants
Have extensive roots,
reduced leaves, and thick
stems that can store water.
Leaves are modified to
reduce evaporative water
loss and, often, to deter
herbivores.
Transport in Plants
• KEY CONCEPT
The vascular system allows for the
transport of water, minerals, and sugars.
Water and dissolved minerals move through
xylem.
UVWX
Up / vascular tissue/water travels / in xylem
Water travels from roots to the top of trees.
3 main ways
Transport of Water
• animation of water transport
• -1- Absorption
• -2- Capillary action(cohesion-tension
theory)
• -3- Transpiration
Capillary Action
The cohesion-tension theory explains water movement
– Plants passively transport water through the
xylem.
– Cohesion is the tendency of water molecules to
bond with each other.
– Adhesion is the tendency of water molecules to
bond with other substances.
Transpiration is the loss of water
vapor through leaves.
– water vapor exits leaf stomata
– helps pull water to the top branches
– Factors that affect transpiration:
– Temperature
– -Wind
– -Humidity
Phloem carries sugars from photosynthesis
throughout the plant.
• Phloem contains specialized cells.
– sieve tube elements have holes at
ends
– companion cells help sieve tube
elements
– unlike xylem, phloem tissue is alive
• PH-F-Food
The Pressure-flow model explains sugar movement
2
phloem
xylem
sugars
1.Sugars move from their source,
such as photosynthesizing leaves,
into the phloem.
water
2.Water moves from the xylem into the
phloem by osmosis, due to the higher
concentration of the sugars in the phloem.
The water flow helps move sugars through
the phloem
3. The sugars move into the sink, such as
root or fruit, where the are stored.