Plant Transport Part 1
Need for Transport Systems
 Take
in substances from environment
 Get rid of waste
 (cell respiration)
Transport Systems in Different
Organisms
Single-celled organism

Transport occurs
quickly



No point in the cell
is very far from the
surface; diffusion
from anywhere in
the cell can occur
quickly with cell
membrane
Gasses diffuse
easily from any
point within cell
Large surface area
to volume ratio
Large, multicellular organism
 Diffusion NOT sufficient b/c:

Centre of organism may be a long
way to the surface


It would take too long for substances
to diffuse all the way
Surface area to volume ration of
cell is large
Large, multicellular organism

Diffusion NOT sufficient b/c:

Centre of organism may be a long
way to the surface


It would take too long for substances to
diffuse all the way
Surface area to volume ratio of cell is
large
 Solutions
to transport
problems:


Transport Systems
Increase surface area
of parts of body
involved in exchange
with the environment





Ex. Thin, flat leaves
Ex. Highly folded gas
exchange surface
Ex. Cristae in
mitochondria
Ex. Grana (granum)
Ex. Alveoli
Transport
in
Plants
Large organisms with branching shape


(helps keep surface area to volume ratio
large)
Small energy needs compared to animals



Role and structure of Leaves




Respiration does not take place as quickly
Rely on diffusion to supply cells with O2
and remove CO2
Thin
large surface area inside in contact with
air spaces
Diffusion is sufficient to supply mesophyll
cells with CO2 for photosynthesis and
remove O2
Plant transport systems Do NOT transport
gas

2 transport systems
Two Transport Systems in Plants

Xylem


Transports water and
inorganic ions from
roots to other parts of
plant
Phloem

Transports substances
made in plant
(sucrose and amino
acids) to all parts of
the plant
Important:!
• Do NOT transfer GAS
• SLOW transfer (not
rapid)
• NO pump involved
(like heart)
Transport in Phloem


Translocation movement of ORGANIC substances in
phloem tissue
Main substances moved (in solution):

ASSIMILATES (substances that have been made by plants)


Amino acids
Sucrose
Xylem: Water movement

Driving force moving water:
TRANSPIRATION


Loss of water vapour from a plant
Occurs mostly in leaves






Contain many cells in contact with air
spaces in the mesophyll layers
Liquid water in cells changes to water
vapour
Water vapour then DIFFUSES into the air
spaces
Water vapour then diffuses out of the leaf
through the STOMATA (down water potential
gradient) into the air surrounding the leaf
Guard cells control opening and closing of
stomata (change shape depending on
conditions)
Photosynthesis requires OPEN stomata


CO2 comes in and water vapour leaves
Water loss is inevitable
Factors
Affecting
Transpiration
 High
Temp
 High Humidity
 High Wind Speed
 High Light
intensity
• Plant cells very similar to animal cells PLUS extra structures
• Usually large than plant cells
• Plant cell size varies
• Cell wall of plants very different than cell membrane
• Cell walls: thick, strong, freely permeable
• Cell membrane: thin, partially permeable
• Vacuoles are NOT confined to only plant cells
• Plant cells have LARGE, PERMENENT CENTRAL vacuole
• Animal cells have SMALL, TEMPORARY PHAGOCYTIC vacuoles
• Plasmodesmata (singular:
Plasmodesma)
• Fine strands of cytoplasm that connect
neighboring plant cells
• Pass through pore-like structures in cell
walls
• Movement through pores is thought to
be controlled by the structure of the
pores
• Cells
• Basic unit of life; specific function
• Tissues
• Specialized groups of similar cells
with common function
• Organs
• Specialized groups of tissues
working together to perform a
specific task
• System
• Group of specialized organs that
work together to perform a
common task
• Xylem Cells
• Phloem Cells
• Histology: study of tissue
• Collection of cells and
any intercellular
secretion produced by
these cells that are
specialized to perform
particular functions
• Maybe same type of cell
• Ex: parenchyma in plants
• Ex. Squamous epithelium
in animals
• Maybe mixed type
• Xylem and phloem in
plants\cartilage, bone,
blood, and connective
tissue in animals
• Dermal Tissue
•
•
•
•
Protective outer covering of plant
Young plantssingle layer of cells
Older plantscan be many layers thick
In roots, dermal tissue includes root hairs
• Vascular Tissue
• Supports plant body
• Transports water and nutrients throughout plant
• Two types: xylem and phloem
• Ground Tissue
•
•
•
•
•
Neither dermal nor vascular
Produces and stores sugars
Contributes to physical support of plant
Edible parts of potato, asparagus, squash are made of ground tissue
Can Consist of three types of cells:
• PARENCHYMA cells (thin cell wall and large central vacuole)
•
In leaves, parenchyma cells contain many chloroplasts
• COLLENCHYMA cells have strong flexible cell wall; help support plant organs
•
Strings in celery is made of long chains of collenchyma cells
• SCLERENCHYMA cells have EXTREMELY thick cell wall
• Makes strong ground tissue such as seed coats
• Sclerenchyma fibers are used to make rope; shell of walnut
• Part of body of organism
which forms a structural and
functional unit
• Composed of more than 1
tissue
• Examples of plant organs:
• Leaves
• Stems
• Roots
• Examples of animal organs:
•
•
•
•
Brain
Heart liver
Eye
kidney
• Collection of organs
with particular
function
• Examples in plants:
• Vascular System
(xylem and phloem)
• Examples in
animals:
• Excretory system
• Reproductive system
• Cardiovascular
system
• Digestive system
• Monocots
• Dicots
• Dermal Tissue
• Epidermis
• Vascular Tissue
• Pericycle
• Xylem
• Phloem
• Ground Tissue
• Cortex
• Endodermis
• Epidermis: surface of the stem made of a number
of layers often with a waxy cuticle to reduce
waterloss.
• Cortex Tissue: Forming a cylinder of tissue around
the outer edge of the stem. Often contains cells
with secondary thickening in the cell walls which
provides additional support.
• Vascular bundle: contains xylem, phloem and
cambium tissue.
• Xylem: a longitudinal set of tubes that conduct
water from the roots upward through the stem to
the leaves.
• Phloem (sieve elements) transports sap through the
plant tissue in a number of possible directions.
• Vascular cambium is a type of lateral meristem
that forms a vertical cylinder in the stem. The
cambium produces the secondary xylem and
phloem through cell division in the vertical plane.
• In the centre of the stem can be found the pith tissue
composed of thin walled cells called parenchyma. In
some plants this section can degenerate to leave a
hollow stem.
LEAF Tissues:
• (a) Phloem transports the products
of photosynthesis (sugars, amino
acids).
• (b) Xylem transports water and
minerals into the leaf tissue from
the stem and roots.
• (c) Epidermis produces a waxy
cuticle for the conservation of
water.
• (d) Palisade layer which is the
main photosynthetic region.
• (e) Spongy layer creates the
spaces and surfaces for the
movement of water and gases.
• (f) Lower epidermis contains the
stomatal pores which allow gas
exchange with the leaf.
• The xylem and phloem tissues
combine in the vascular tissue to
provide support to the leaf.
• You will usually have to do a plan diagram of an organ (ex. A leaf)
• Organ contains many different types of cells arranged in a particular
pattern characteristic of the organ, with cells of a similar type
• This is a distinctive “tissue”
• Drawing that shows where different TISSUES are located
• Shows OUTLINE of the various TISSUES in an organs
• Does NOT show individual cells