Exam Questions

Question 1

What is a characteristic of xerophytes?
A.	Absence of roots
B.	Absence of vascular tissue
C.	Leaves with very small surface area
D.	Large number of stomata

Answer 1

leaves with very small surface area

Question 2

Which would be an adaptation of xerophytes?
A.	Large air spaces
B.	Large numbers of stomata
C.	Hairs on the leaves
D.	Reduced roots

Answer 2

hairs on the leaves

Question 3

What causes movement of water through the xylem?
A.	Active transport in the root tissue
B.	Evaporation of water from leaves
C.	Active translocation
D.	Gravity

Answer 3

Evaporation of water from leaves

Question 4

When a farmer sprays a chemical on to crop plants, how does the chemical travel to the roots of the plants?
A. In the phloem, by active translocation
B. In the phloem, by transpiration pull
C. In the xylem, by transpiration pull
D. In the xylem, by active translocation

Answer 4

In the phloem, by active translocation

Question 5

Fertilization, pollination and seed dispersal all occur during the reproduction of a flowering plant. In what sequence do these processes occur?
A. seed dispersal pollination fertilization
B. fertilization pollination seed dispersal
C. pollination fertilization seed dispersal
D. seed dispersal fertilization pollination

Answer 5

pollination fertilization seed dispersal

Question 6

Which of the following help(s) in supporting a terrestrial woody plant?
I.	Xylem tissue
II.	Turgor pressure
III.	Phloem tissue
A.	I only
B.	I and II only
C.	II and III only
D.	I, II and III

Answer 6

I and II only

Question 7

state two other factors other than light, water and carbon dioxide concentration that affects the productivity of crop plants

Answer 7

temperature and availability of nutrients

Question 8

Explain how plant productivity can be increased by growing crops in greenhouses.

Answer 8

temperature higher inside the greenhouse than outside;
as short wave radiation can pass through the glass and re-emitted long wave cannot;
carbon dioxide levels can be enriched;
humidity levels can be kept higher so there is less transpiration;
biological control of pests works more effectively;
less wind so less transpiration / mechanical damage to crops;
possible use of artificial light;

Question 9

List 2 roles of auxins in plants

Answer 9

root formation and phototropism

Question 10

Explain the role of auxin in phototropism.

Answer 10

when a shoot is illuminated from one side;
auxin is transported laterally to the other side;
where it causes greater growth on one / dark side;
by stimulating cell elongation

Question 11

Outline the roles of auxin in plants.

Answer 11

a plant growth promotor / regulator / hormone;
act in phototropism;
causes cell elongation / bending on side away from light;
produced in shoot tips / apical dominance;
prevents lateral growth;

Question 12

Outline the effect of carbon dioxide concentration on plant productivity.

Answer 12

mass of plant dry weight / wet weight / fresh weight / harvestable biomass;
biomass per unit area of cultivated land;
relative growth rate;
net assimilation rate; 2 max

Question 13

State two adaptations of insect-pollinated flowers

Answer 13

large / colorful petals;
petals release scent;
nectaries secrete nectar;
sticky pollen grains;
sturdy filaments to hold anthers in position when brushed;

Question 14

Predict what will happen to the flowering process of a short day plant if the minimal dark period is interrupted by brief exposure to light.

Answer 14

it will not flower/bloom

Question 15

Describe the metabolic events of germination in a starchy seed.

Answer 15

absorption of water;
(embryo) increases respiration;
(embryo) secretes GA to (aleurone layer);
(stimulates) production of amylase;
digestion of starch to smaller sugars / maltose;
mobilize to tissues / transport of foods /
nutrients to embryo;

Question 16

Explain how abiotic factors affect the rate of transpiration in a terrestrial plant.
(Total 8 marks)

Answer 16

less transpiration as (atmospheric) humidity rises;
smaller concentration gradient (of water vapour);
more transpiration as temperature rises;
faster diffusion / more kinetic energy (of water molecules);
faster evaporation (due to more latent heat available);
more transpiration as wind (speed) increases;
humid air / water vapour blown away from the leaf;
increasing the concentration gradient (of water vapour);
more transpiration in the light;
due to light causing stomata to open;
wider opening with brighter light hence more transpiration;
CAM plants opposite;
narrower stomata with high carbon dioxide
concentration hence less transpiration;

Question 17

Compare the adaptations of xerophytes and hydrophytes

Answer 17

xerophytes are adapted to reduced availability of water / deserts;
hydrophytes are adapted to living in / on water (reject high rainfall);
named example of each;
xerophytes have small leaves / no leaves / spines and hydrophytes have large
(floating) leaves / finely divided (submerged) leaves (accept suitable drawing);
xerophytes have reduced stomata and hydrophytes have no stomata on submerged
leaves / stomata on upper surface only of floating leaves;
xerophytes have a thick waxy cuticle and hydrophytes have little or no cuticle;
xerophytes have extensive / deep root systems and hydrophytes have reduced /
absent roots;
xerophytes have hairs (to reflect sunlight), hydrophytes do not;
hydrophytes have tissues with airspaces, xerophytes do not;
xerophytes can be CAM / C4, hydrophytes can not;
xerophytes have water storage tissues, hydrophytes do not;
[8]

Question 18

Describe how water is transported in a plant.

Answer 18

transported in xylem (vessels);
passive / no energy used by plants;
evaporation / transpiration causes low pressure / suction / pull;
transpiration stream / continuous column of water from roots to leaves;
water molecules are cohesive (so transmit the pull) / hydrogen bonding;
root pressure can move water up the plant;
apoplastic pathway is through cell walls

Question 19

Distinguish between xerophytes and hydrophytes, giving one structural adaptation for each type of plant.

Answer 19

xerophytes:
adapted to arid / dry climates / deserts;
hydrophytes:
adapted to grow submerged in water / floating on water;
Reject “grows in wet areas “ or “needs lots of water”.

Question 20

Explain how manipulation of day length is used in the production of flowers.

Answer 20

some flowering plants are short-day plants;
others are long-day plants;
important variable is length of darkness / photoperiod;
some plants grown in greenhouses with controlled light conditions;
short-day plants kept in the dark during daylight hours;
long-day plants artificially lit during the night;
using an appropriate wavelength / far-red light / 730 nm;
possible to expose only for brief periods to keep costs down
but long enough to interrupt the dark period;
involves interaction of phytochromes with metabolic reactions;
controlled by the plant’s biological clock;

Question 21

Explain how the abiotic factors of light, wind and humidity affect the rate of transpiration

Answer 21

light: [2 max]
causes stomatal opening in morning, increasing transpiration;
increasing light increases transpiration;
because stomatal opening increases;
no light causes stomatal closure, reducing transpiration;
wind: [3 max]
removes water / vapour from around leaf;
increases water vapour / humidity gradient so increases transpiration;
increases transpiration / lack of wind can reduce transpiration;
no increase in transpiration if humidity is 100 %;
humidity : [3 max]
high humidity reduces water vapour gradient so lowers transpiration;
high humidity lowers transpiration rate;
lowering humidity can increase transpiration rate (to a point);
at very low humidity stomata may shut down;

Question 22

Explain the process of water uptake and transport by a plant.

Answer 22

roots have a large / increased surface area (in relation to their rohme);
root hairs increase the surface area;
water is absorbed by osmosis;
solute concentration inside the root is higher than in the soil / outside;
due to active transport of ion into the root;
apoplastic and symplastic transport across root;
apoplastic route is through the cell walls (and intercellular spaces);
symplastic route is through the cytoplasm (and plasmodesmata);
carried up stem by xylem (vessel elements/tracheids);
water has to pass through cytoplasm of endodermis /
Casparian strip blocks water;
water movement in xylem due to pulling force /
transpiration pull from leaves;
cohesion between water molecules;

Question 23

Explain how roots absorb water and then transport it to the xylem, noting any special adaptations that help these processes to occur.
(Total 9 marks)

Answer 23

roots have a large/increased surface area (in relation to their volume);
branching/lateral roots (increases the surface area);
root hairs increase the surface area;
cortex cell walls (increase the surface area);
water is absorbed by osmosis;
solute concentration inside the root is higher than in the soil / outside;
due to active transport of ions into the root;
apoplastic and symplastic transport across the root;
apoplastic route is through the cell walls (and intercellular spaces);
symplastic route is through the cytoplasm (and plasmodesmata);
water has to pass through cytoplasm of endodermis / Casparian strip blocks walls;
water movement in xylem due to pulling force / transpiration pull;
cohesion between water molecules;