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Text Reference: Biology Source 11
Also refer to the cross-section diagrams of the root from your notes.
 Recall: plants produce their own food by the process of photosynthesis:
sunlight
6CO2 + 6H2O
C6H12O6 + 6O2
 Plants require water for photosynthesis and require minerals for growth and for
cellular functions.
Water and minerals must be absorbed from the soil and must travel throughout the plant
this movement is accomplished by combined mechanisms at work in the roots, the
stem, and the leaves.
(I) In the Roots
Water and mineral transport is carried out by the
process of water and mineral uptake begins in the
Absorb minerals from the soil by the process of
in vascular plants. The
of plants.
.
1. Why is it advantageous for the plant to have root hairs as extensions of the
roots?
2. Where does the energy needed for the absorption of minerals come from?
3. What prevents the minerals from diffusing back out into the soil at this point?
Now there is a concentration of minerals inside the root that creates
that is
to the soil, thereby creating a concentration gradient
for
to diffuse into the root by
. As long as the
root hairs continue to absorb minerals by active transport, water will continue to flow into
the root without the input of energy. The accumulation of water and dissolved minerals
in the root creates pressure called
which will
.
(II) In the Stem
A second property of water that enables it to move through the xylem, against the force
of gravity, is
. water molecules tend to “stick” to each other
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because of the
molecules.
bonds that exist between
water
4. How does the diameter of the xylem contribute to the plant’s ability to “pull” water
from the ground to its tallest leaves?
5. To what can the strength of a column of water be compared?
(III) in the Leaves
The third mechanism that contributes to the movement of water and dissolved minerals
up the stem of the plant comes from the leaves. This “pulling” action is referred to as
leaf pull or
. As water molecules enter the leaf, most are lost as
a result of
. When one molecule leaves the leaf, the next
molecule is “pulled up” behind it. This process continues in an unbroken cohesive chain
all the way from the leaf to the roots. Therefore, the rate of xylem sap movement is
dependent on the rate of
.
6. Define the term transpiration.
Evaporation of liquid from the surface of the leaf requires
which is obtained from the
,
.
7. To summarize the flow of water from the roots to the leaves of vascular plants,
complete the following diagram.
2