FORM 5

CHAPTER 4 TRANSPORT IN PLANTS

FORMATIVE PRACTICE 4.1
1. Do all plants need a transport system? Explain.

 No. Small plants like moss and algae have large surface areas to absorb water
directly from its surroundings.

2. A tree is attacked by a type of bacteria which damages its xylem vessels. Predict the
effects to the tree.

 The plant will die as the xylem cannot transport water. This causes the plants to
not be able to carry out photosynthesis.

3. Transport of organic compounds such as sucrose by active transport along the sieve
tubes needs a lot of energy. How does this process happen even though the sieve tubes
have very few mitochondria?

 Sieve tubes have companion cells that are rich in mitochondria. The
mitochondria in companion cells will generate energy (ATP) to be used by sieve
tubes.

FORMATIVE PRACTICE 4.2

1. State the factors involved in the water and mineral salts pathway from soil to leaves.

 Root pressure, capillary action (adhesion and cohesion forces) and

transpirational pull.

2. Give the definition of guttation and state its importance.

 Guttation is a secretion of water droplets through a special structure at the end

of leaf veins without involving the stomata caused by a high root pressure.
Guttation maintains an effective root pressure. Hence, more water and mineral
salts is absorbed by the root.
3. What is the difference between guttation and transpiration?

 Guttation happens at night and early morning whereas transpiration happens on

hot and windy days.
 Guttation happens in herbaceous plants whereas transpiration happens in all
plants.
 Guttation releases water droplets whereas transpiration released water vapour.
 Guttation happens through a special structure at the end of the leaf veins
whereas transpiration happens through stomata.
 Guttation happens when root pressure is high whereas transpiration is
controlled by the stomatal opening and closing.
 4. On a hot and windy condition, water absorption by the roots and water transport in the
xylem becomes faster. Do you agree with the statement? Justify.

 Agree. The conditions stated causes an increase in evaporation of water through

transpiration, thus leading to an increase in transpiration pull.

FORMATIVE PRACTICE 4.3

1. State the definition of translocation.

 The process of transporting organic substances such as sucrose, amino acids and
hormones in the phloem from the leaves to other parts of the plant such as the
roots and stem.

2. What is the role of translocation in plants?

 Translocation helps in transporting photosynthetic products from the leaves to

other parts of the plant that need them for growth and respiration such as roots,
fruits, tip of shoots or developing flowers. Other than that, translocation also
transports excess photosynthetic products to other parts of the plants such as
rhizomes, tubers and bulbs.

3. How does translocation occur from the leaves to the roots? Explain.

 Sucrose is actively transported into the sieve tube. The transport of sucrose into
the sieve tube through the companion cell from the leaf reduces the water
potential in the sieve tube. This causes water to diffuse from the xylem into the
sieve tube via osmosis. The water diffusion increases the hydrostatic pressure in
the sieve tube. The increase in the hydrostatic pressure causes the phloem sap to
be pushed along the sieve tubes to other organs of the plant. The phloem sap
(sucrose) is transported from the sieve tubes to others parts such as stems,
roots, shoots, fruits and tubers by active transport. The high water potential in
the phloem causes the water to diffuse in order for it to return into the xylem by
osmosis. Transpiration pulls water along the xylem vessel against the direction
of gravitational pulls.

4. Compare sucrose concentration in a leaf cell and sieve tube. What is the effect of the
difference?

 The concentration of sucrose in leaf cells is higher than in sieve tubes. The
hydrostatic pressure in the sieve tubes increases, causes the phloem sap (sucrose)
to move into the sieve tube actively.

5. How does translocation affect a plant’s yield?

 An efficient translocation from the leaf to the storage organs such as fruit will
increase the size of fruit or the tuber.
FORMATIVE PRACTICE 4.4
1. What does phytoremediation mean?

 Phytoremediation is one of the treatment methods which uses plants for the
purpose or degradation, extraction or elimination of pollute substances from soil
and water.

2. Name two uses of phytoremediation in daily life.

 (a) To treat waste water by eliminating heavy metals and trap nutrients and
microorganisms.
 (b) To remove heavy metals from contaminated soil.

SUMMATIVE PRACTICE 4
1. (a) Are xylem vessels living or dead structures? Give a reason for your answer.

 Xylem tissues are dead cells at maturity as they are hollow and do not have
cytoplasm.

(b) What is the main function of the xylem vessel? State three structural adaptations of
the xylem vessels and their functions.

 To transport water and mineral salts that are absorbed by the roots, to the stems
and leaves.
 Adaptations:
 The tissue is hollow to allow water transport.
 The walls have lignin to provide support and prevent them from collapsing.
 Arranged longitudinally from end to end to allow water flow.

(c) How are the adaptations in the roots of plants similar to the adaptations of the small
intestines in humans for nutrient absorption? Explain.

 The high number of root hairs increases the surface area for water absorption.
This is similar to the high number of villi in small intestine that increases the
surface area for nutrient absorption from digested food.

(d) Systemic pesticides could be absorbed and carried throughout the whole plant. Does
spraying pesticides systematically onto leaves kill insects such as aphids that primarily
feed on the shoots of plants? Explain.

 Systemic pesticides seep into plants. When insect pests consume and digest the
plant, the chemicals in the pesticide kills it.
2. Photosynthesis product such as sucrose is transported by the phloem through translocation
from the leaves to other parts of the plants such as the seeds, fruit, roots and tubers.
(a) Describe the pathway of sucrose molecules as it is transported from the leaves to
other part of the plant such as the fruit.

 Sucrose is transported through companion cells from the leaves to the sieve
tubes. This reduces the water potential in the sieve tube. Water diffuses into the
sieve tube by osmosis and increases the hydrostatic pressure in the sieve tube.
The phloem sap is transported from the sieve tubes to other parts such as fruits
and tubers.

(b) Plan an experiment using aphid to prove that the translocation of sucrose and amino
acids occur in the phloem.

 1. Expose a balsam plant under sunlight for one hour.

 2. Introduce an aphid to the young stem of the plant.
 3. Observe the aphid with a magnifying glass.
 4. Using a knife, separate the body of the aphid from the stylet once the stylets is
embedded into the phloem.
 5. Place a microscope slide at the edge of the stylet to collect the secreted liquid.
 6. Observe the liquid under a light microscope.

3. Photograph 1 shows the aftermath of the nuclear plant explosion in Chernobyl, Russia, in
1986.

(a) One of the methods used to treat the soil after the explosion is by removing
pollutants through plants. What is the method called?

 Phytoremediation

(b) Suggest one type of plant that can be used for the method mentioned in 3(a).

 Sunflowers
 (c) Mr. Sani is a modern farmer who farms near to an industrial area. Mr. Sani digs a
trench to provide irrigation water for his plants. He also plants common water hyacinths
in the trench. Justify Mr. Sani’s actions.

 Industrial wastes may seep into the irrigation water. The water hyacinth can help
to remove the contaminants from the water. Hence, the pumped water used to
water the vegetables is free from the contaminants.

21st CENTURY MIND

4. Photograph 2 shows Lake A, an artificial lake that is located near a market. More than 3000
fish from various species were released into this lake to propagate fishing activities. When the
fish were matured enough to be caught, the lake was found to contain high amounts of lead.
Imagine you work as a chemical engineer for the city council of that area, suggest one method to
solve this problem. Plan an experiment to test the effectiveness of your method.

 The phytoremediation method can be used by planting the water spinach plant
as the phytoremediation agent. This plant will absorb the lead from the lake
water. Experiment 4.5 on page 91 can be conducted.