Download Transport in Plants - Holy Trinity Academy

Lesson 8: Transport In Multicellular
Organisms
Key Points:
1. Understand how transport within cells is similar
and involved in transport in a multicellular
Organism.
2. Understand how nutrients (water, sugar and
minerals) are transported in vascular plants.
3. Learn the structure of vascular plants.
4. Learn what forces are involved in this transport.
General Characteristics of Vascular Plants
The resources a land plant needs to survive are spatially
separated: The soil provides water and minerals, but there is no
light underground for photosynthesis.
The body of a vascular plant is differentiated into a subterranean
root system that absorbs water and minerals and an aerial shoot
system of stems and leaves that make food.
Adaptations of Vascular Plants
 An important terrestrial adaptation of vascular plants
is lignin, a hard material embedded in the cell walls
of plant cells that functions in support.
Adaptations of Vascular Plants
 Turgor Pressure
(pressure of water in
vacuoles) contributes
to the support of small
plants but it is the
skeleton of lignified
walls that holds up a
tree or any other large
vascular plant.
Roots
 Roots anchor the plant in the soil, absorb minerals and
water, conduct water and nutrients, and store food.
Stems
 The main purpose of stems is to support the plant and transport
nutrients from the roots to the leaves. The stem must have a
great deal of turgor pressure in its cells and sufficient lignin in
the cell walls.
Leaves
 Leaves are the main photosynthetic organs of most plants, although green
stems also perform photosynthesis. Leaves have veins, which transport
nutrients to the cells of the leaf. These can be arranged in a number of ways.
Leaves vary extensively in form, but they generally consist of a flattened
blade and a stalk, the petiole, which joins the leaf to a node of the stem.
Transport in Plants
Transport in Plants
These Notes refer to the transport in Plants diagram.
1. Roots absorb water and dissolved minerals from the soil.
2. Roots exchange gases with the air spaces of soil taking in O2 and
discharging CO2. This gas exchange supports the cellular respiration
of root cells.
3. Water and minerals are transported upward as xylem sap within
xylem, from the roots into the shoot system.
4. Transpiration, the evaporation of water from leaves (mostly through
stomata), creates a force within leaves that pulls xylem sap upward.
5. Leaves also exchange gases through stomata taking in CO2 that
provides carbon for photosynthesis and expelling O2.
6. Sugar is produced by photosynthesis in the leaves.
7. Sugar is transported within the phloem in a solution called phloem
sap to roots and other non-photosynthetic parts of the plant.
Transport in Plants
 Two tissues are responsible for transporting material in plants.
The Phloem and the Xylem. Each transports different material in
different ways.
Xylem
 The xylem transports water up the plant. This tissue is located in the
center of the stem/trunk. Transport is accomplished by a process
involving Osmosis, adhesion and cohesion of water molecules. As
water evaporates from the leaves, the remaining solution in the xylem
becomes more concentrated, this pulls more water up the stem to help
balance the concentration. This same process allows the roots to take
up water as well.
Phloem
 The phloem transports the sugars synthesized in photosynthesis down
the plant to tissues not capable of photosynthesis (stem and roots).
This is accomplished mainly by gravity. The process is slow however
because the phloem sap is quite viscous and adheres to the inside of
the very small phloem tubes, so some osmosis and diffusion is still
required.
Questions For Review
1.
2.
3.
4.
5.
What processes/properties are used in both intracellular
transport and transport in multicellular organisms? How are they
used?
If you were tapping a maple tree to harvest sap for syrup, which
transporting tissue would you tap? Why? Where is it located?
In the leaf why are so many cells packed together near the
surface of the leaf? How are they continually supplied with
water?
Would a plant be able to transport water to its leaves more
easily for less easily on a humid day?
You have a plant that does not look very full (few stringy
branches). What would you do to give it a more full appearance
(have more short branches full of leaves)?