Plants

Question 1

What are the three different types of plant tissue and what are their purposes?

Answer 1

Dermal tissue - protection
Vascular tissue (xylem and phloem) - long-distance transport of materials
Ground tissue - specialized cells for functions such as storage, photosynthesis, and support

Question 2

What is the difference between C3 and C4 plants? What are some of the advantages of C3 over C4 and vice versa and briefly explain why.

Answer 2

C3 plants incorporate CO2 straight into Calvin cycle, C4 plants store CO2 in mesophyll cells (converted to C4 acids) before being exported to bundle sheath cells where the CO2 is incorporated into the Calvin cycle

When a plants somata are open, water evaporates so in hot dry weather plants have to close their somata which prevents CO2 from entering the plant and O2 leaving the plant, resulting in photorespiration which reduces photosynthetic rate.
C4 plants avoid this problem by undergoing the Calvin Cycle in separate cell (bundle sheath cells) and using a different enzyme, therefore are optimal at higher temps where stomata remains closed for long stretches.
But C4 uses more ATP then C3, so at low temperatures C3 photosynthesis is more efficient than C4

Question 3

What is primary and secondary growth? What plant structures are responsible for each type of growth?

Answer 3

Primary growth of shoot – vertical direction – elongation of shoots and roots. Controlled by apical meristems
Secondary growth – horizontal direction, resulting in thickness in woody plants. Controlled by lateral meristem.

Question 4

How do guard cells regulate the opening and closing of stomata? Draw a diagram.

Answer 4

Guard cells regulate opening and closing of stomata by reversible uptake or loss of K+ creating osmotic gradient which results in water entering or leaving the cell.
When water enter, the cells swell and open the stomata, whereas when water leaves, the stomas closes

Question 5

Briefly explain the different mechanisms that allow sap to move up the xylem.

Answer 5

Transpiration, loss of water due to evaporation at stomata which creates negative pressure and a lifting force for the sap. Cohesion, intermolecular forces between water molecules, and adhesion forces between water molecular and xylem walls also help the sap to overcome gravity and water goes up. Water and minerals through roots.

Question 6

1. What is the primary function of the light reactions of photosynthesis?
   a) to produce energy-rich glucose from carbon dioxide and water
   b) to produce ATP and NADPH
   c) to produce NADPH used in respiration
   d) to convert light energy to the chemical energy of GTP
   e) to use ATP to make glucose

Answer 6

b) to produce ATP and NADPH

Question 7

What would a A- + B- mutant produce

a) Se, Pe, St, Ca
b) Se, Se, St, St
c) Ca, Ca, Ca, Ca
d) St, St, St, Ca
e) Ca, St, St, Ca

Answer 7

c) Ca, Ca, Ca, Ca

Question 8

Which of the following is true about secondary growth in plants?

a) Flowers may have secondary growth
b) Secondary growth is a common feature of eudicot leaves
c) Secondary growth is produced by both the vascular cambium and the cork cambium
d) Primary growth and secondary growth alternate in the life cycle of a plant
e) Plants with secondary growth are typically the smallest ones in an ecosystem

Answer 8

c) Secondary growth is produced by both the vascular cambium and the cork cambium

Question 9

What is the main force by which most of the water within xylem vessels moves toward the top of a tree?

a) active transport of ions into the stele
b) atmospheric pressure on roots
c) evaporation of water through stoma
d) the force of root pressure
e) osmosis in the root

Answer 9

c) evaporation of water through stoma

Question 10

Which of these conclusions is supported by the research of both Went and Charles and Frances Darwin on shoot responses to light?

a) When shoots are exposed to light, a chemical substance migrates toward the light
b) Agar contains a chemical substance that mimics a plant hormone
c) A chemical substance involved in shoot bending is produced in shoot tips
d) Once shoot tips have been cut, normal growth cannot be induced
e) Light stimulates the synthesis of a plant hormone that responds to light

Answer 10

c) A chemical substance involved in shoot bending is produced in shoot tips

Question 11

Describe the ABC model and plant whorls

Answer 11

3 types of genes, type A expressed in first two whorls, C in the last two whorls and B expressed in 2 and 3 whorls. A and c can not overlap.
Sepal, petal, staments, carpels

Question 12

What did Charles and Francis Darwin’s experiment reveal about the sensing of light by plants? Describe the experiment and its results and explain and justify the conclusions that can be drawn from them.

Answer 12

That plants can sense light, but only the tip
If they removed or completely covered the tip, no response. But if covered in transparent cap or base in opaque shield it could still sense.
Eventually led to discovery of plant hormones.

Question 13

Outline with a diagram the basic steps of cell elongation to auxin.

Answer 13

According to a model called the acid growth hypothesis
Proton pumps play a major role in the growth response of cells to auxin
The term auxin - Used for any chemical substance that promotes cell elongation in tissues
Rarely expand equally in all directions
The direction of cell elongation is controlled by the orientation of cellulose microfibrils within the cell wall
But the springs are attached so cant expand fully, need to be detached by enzyme

Question 14

Explain what will happen if the tip of a plant is removed and reattached with an impermeable barrier and then exposed to light from one side of the plant.

Answer 14

No response as the hormone cant pass through it

Question 15

For Light reactions and dark reactions:
Located where?
System Inputs
System Outputs

Answer 15

Light reactions Dark reactions
Thylakoid membrane Stoma
H2O, Light, NADH ADP ATP and NADH and CO2
ATP and NADH Sugar

Question 16

What would be the biological consequences of mutating the inward potassium channels.

Answer 16

Molecular – if pump K channels inside, water will move in due to osmosis
Cellular – will not reach shape that it needs to be so will be flaccid so stomata will be closed
Organism – stomata will be closed so no gases exchange so lack of CO2 will slow down photosynthesis and O2 accumulation will cause photorespiration
Stop xylem flow as no H2O evaporation – no nutrients and overheat

Question 17

What would happen if we mutate the outward potassium channels.

Answer 17

Two guard cells full of K, so full of water and will always be open
This will result in continuous water evaporation, plant dehydration

Question 18

A long-day plant will flower if…

a. the duration of continuous light exceeds a critical length
b. the duration of continuous light is less than a critical length
c. the duration of continuous darkness exceeds a critical length
d. the duration of continuous darkness is less than a critical length
e. it is kept in continuous heat

Answer 18

d. the duration of continuous darkness is less than a critical length

Question 19

The Agrobacterium Ti plasmid

1. Contains phytohormone synthesis genes
2. Contains opine biosynthesis genes
3. Contains the T-DNA that is transferred to the plant genome
4. Can be used to transfer foreign genes into plants
5. All of the above

Answer 19

5. All of the above

Question 20

Which of these equations best summarizes photosynthesis?

a) H2O → 2 H+ + 1/2 O2 + 2e-
b) C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + Energy
c) 6 CO2 + 6 O2 → C6H12O6 + 6 H2O
d) 6 CO2 + 6 H2O → C6H12O6 + 6 O2
e) C6H12O6 + 6 O2 → 6 CO2 + 12 H2O

Answer 20

d) 6 CO2 + 6 H2O → C6H12O6 + 6 O2

Question 21

Where does the Calvin cycle occur?

Answer 21

Stoma

Question 22

The light reactions of photosynthesis use _____ and produce _____.

a) NADPH … NADP+
b) carbon dioxide … oxygen
c) water … NADPH
d) NADPH … oxygen
e) carbon dioxide … sugar

Answer 22

c) water … NADPH

Question 23

What is the biological significance of the light-independent reactions of photosynthesis?

a) They make oxygen.
b) They convert ATP to sugar.
c) They convert carbon dioxide to sugar.
d) They generate ATP and NADPH.

Answer 23

c) They convert carbon dioxide to sugar.

Question 24

Which of the following statements best describes the relationship between the light-dependent and light-independent reactions of photosynthesis?

a) The light-dependent reactions produce ATP and NADPH, which are then used by the light-independent reactions.
b) The light-dependent reactions pass electrons through an electron transport chain to the light-independent reactions.
c) The light-dependent reactions produce carbon dioxide, which is then used by the light-independent reactions.
d) The light-independent reactions release energy, and the light-dependent reactions require energy.

Answer 24

a) The light-dependent reactions produce ATP and NADPH, which are then used by the light-independent reactions.

Question 25

What is the basic role of CO2 in photosynthesis?

a) CO2 is taken in by plants as a form of inverse respiration, in which carbon dioxide is “breathed in” and oxygen is “breathed out.”
b) CO2 is a source of electrons in the formation of organic molecules.
c) CO2 is fixed or incorporated into organic molecules.

Answer 25

c) CO2 is fixed or incorporated into organic molecules.

Question 26

Select the correct statement about the Calvin cycle.

a) The Calvin cycle takes place primarily in the dark.
b) The Calvin cycle has three phases: carbon fixation, reduction, and regeneration of RuBP.
c) The basic function of the Calvin cycle is the conversion of solar energy to chemical energy.

Answer 26

b) The Calvin cycle has three phases: carbon fixation, reduction, and regeneration of RuBP.

Question 27

Which of the following statements about the vascular cambium is true?

a) It is a layer of undifferentiated cells that develops into secondary xylem and phloem.
b) It develops into cork cells on the outside of the cortex.
c) It is a type of apical meristem.
d) It is located between the primary xylem and cortex

Answer 27

a) It is a layer of undifferentiated cells that develops into secondary xylem and phloem.

Question 28

Which tissue acts as a filter on the water absorbed by root hairs?

a) Vascular tissue
b) Epidermis
c) Endodermis
d) Cortex

Answer 28

c) Endodermis

Question 29

Which of the following statements about the distribution of sap throughout a plant is true?

a) The main component of phloem sap is glucose.
b) Companion cells form the conducting tissue for sap.
c) The mechanism that explains the movement of sugars throughout a plant is called the pressure-flow hypothesis.
d) The driving force for sugar movement is transpiration.

Answer 29

c) The mechanism that explains the movement of sugars throughout a plant is called the pressure-flow hypothesis.

Question 30

Which term describes an area where sugars are used or stored?

a) Sink
b) Source
c) Stomata
d) Leaves

Answer 30

a) Sink

Question 31

Which of the following statements about xylem transport is true?

a) All water transported by the xylem is used for photosynthesis in the leaves.
b) Water and minerals enter the xylem by diffusion.
c) Water and minerals move through the root cortex into the xylem and upward through the stem and into leaves.
d) The xylem cells that conduct water and minerals are alive.

Answer 31

c) Water and minerals move through the root cortex into the xylem and upward through the stem and into leaves.

Question 32

What characterizes the rates of photosynthesis and transport in a plant on a dry cloudy day?

a) The photosynthesis rate is high and phloem transport rates are low.
b) Both the photosynthesis and transpiration rates are high.
c) The photosynthesis rate is low and stomata are open.
d) Both the photosynthesis and transpiration rates are low.

Answer 32

d) Both the photosynthesis and transpiration rates are low.

Question 33

In roots the _____ forces water and solutes to pass through the plasma membranes of _____ cells before entering the _____.

a) transpiration … endodermis … xylem
b) Casparian strip … endodermis … phloem
c) Casparian strip … ectoderm … xylem
d) Casparian strip … endodermis … xylem
e) xylem … endodermis … Casparian strip

Answer 33

d) Casparian strip … endodermis … xylem

Question 34

_____ provide(s) the major force for the movement of water and solutes from roots to leaves.

a) Root pressure
b) Translocation
c) Transfer cells
d) Transpiration
e) Bulk flow

Answer 34

d) Transpiration

Question 35

_____ bonds are responsible for the cohesion of water molecules.

a) Ionic
b) Hydrogen
c) Nonpolar covalent
d) Polar covalent
e) Peptide

Answer 35

b) Hydrogen

Question 36

_____ cells are the cells that regulate the opening and closing of stomata, thus playing a role in regulating transpiration.

a) Casparian strip
b) Sieve-tube member
c) Companion
d) Guard
e) Tracheid

Answer 36

d) Guard

Question 37

For a short-day plant, the _____ is critical in determining if flowering will occur.

a) minimum number of hour of light
b) minimum number of hours of darkness
c) None of these is correct, since short-day plants are also known as day-neutral plants.
d) maximum number of hours of light
e) maximum number of hours of darkness

Answer 37

b) minimum number of hours of darkness

Question 38

For a long-day plant, the _____ is critical in determining if flowering will occur.

a) minimum number of hours of darkness
b) maximum number of hours of light
c) maximum number of hours of darkness
d) None of these is correct, since short-day plants are also known as day-neutral plants.
e) minimum number of hours of light

Answer 38

c) maximum number of hours of darkness

Question 39

Which of these would inhibit flowering in a short-day plant with a critical night length of 12 hours?

a) 12 hours of light followed by 12 hours of dark
b) 12 hours of light, 6 hours of dark, a flash of red light, a flash of far-red light, a flash of red light, a flash of far-red light, 6 hours of dark
c) 12 hours of light, 6 hours of dark, a flash of red light, a flash of far-red light, 6 hours of dark
d) All of these regimens would inhibit flowering in a short-day plant with a critical night length of 12 hours.
e) 12 hours of light, 6 hours of dark, a flash of red light, 6 hours of dark

Answer 39

e) 12 hours of light, 6 hours of dark, a flash of red light, 6 hours of dark

Question 40

Which of these would stimulate flowering in a long-day plant with a critical night length of 12 hours?

a) 12 hours of light, 6 hours of dark, a flash of red light, 6 hours of dark
b) 12 hours of light, 6 hours of dark, a flash of red light, a flash of far-red light, 6 hours of dark
c) 8 hours of light and 16 hours of dark
d) 12 hours of light, 6 hours of dark, a flash of red light, a flash of far-red light, a flash of red light, a flash of far-red light, 6 hours of dark
e) 12 hours of light followed by 12 hours of dark

Answer 40

a) 12 hours of light, 6 hours of dark, a flash of red light, 6 hours of dark

Question 41

What is the physical basis of the phototropic response?

a) Cell shortening.
b) Cell transport.
c) Cell elongation.
d) Photosynthesis.

Answer 41

c) Cell elongation.

Question 42

Which of the following statements about hormones is true?

a) Hormones are produced only in plants.
b) Hormones are small inorganic molecules.
c) Hormones are produced at the sites where they are needed.
d) Hormones can function at very low concentrations.

Answer 42

d) Hormones can function at very low concentrations.

Question 43

How does auxin produce phototropism?

a) Auxin accumulates in cells on the side of the plant opposite the source of light and stimulates their elongation.
b) Auxin accumulates in cells on the side of the plant facing the source of light and causes them to shorten.
c) Auxin accumulates in cells on the side of the plant opposite the source of light and causes them to shorten.
d) Auxin accumulates in cells on the side of the plant facing the source of light and stimulates their elongation.

Answer 43

a) Auxin accumulates in cells on the side of the plant opposite the source of light and stimulates their elongation.

Question 44

How do plant and animal hormones differ?

a) Unlike animal hormones, plant hormones act only locally.
b) Unlike animal hormones, plant hormones do not bind to a specific receptor and trigger responses in target cells and tissues.
c) In plants more so than in animals, it is the balance between existing hormones, rather than hormones acting in isolation, that controls growth and development.

Answer 44

c) In plants more so than in animals, it is the balance between existing hormones, rather than hormones acting in isolation, that controls growth and development

Question 45

What are the two classes of photoreceptors

Answer 45

blue light photoreceptor - hypocotyle elongation, stomal opening and phototropism
phytochrome - responses involved light such as seed germination, control of flowering etc

Question 46

Is flowering controlled by day or night length?

Answer 46

Night length

Question 47

What are the consequences of a flash of red light during the night for a short-day plant during the winter? How can it be reversed?

Answer 47

the plant will flower earlier than usual and providing a flash of far red light during the night can reverse it

Question 48

Why is Agrobacterium used to transfer genes?

Answer 48

agrobacterium already naturally transfers part of its genome into the plant to infect it through the usual of Ti plasmid, so easy

Question 49

What are some limitations of Agrobacterium?

Answer 49

not effective on monocot plants

Question 50

Explain how mechanical stimuli affects plant growth. What is the pathway involved?

Answer 50

process is called thigmorphogensis. wind/touch etc results in induction of ACC synthase gene whcih results in a short burst of ethylene as a result of the ethylene biosynthetic pathway. As a result, primary growth is stopped and secondary growth is induced for a short time. For trees, this results in shorter and thicker trees which is benefical as they can withstand wind better

Question 51

C3 plants

Answer 51

standard plant
close stomata if hot and dry
photorespiration 
efficient if water is abundant 
rubisco

Question 52

C4 plants

Answer 52

spatial seperation
mesophyll cells to fix carbons
calvin cycle in bundle sheath cells
PEP carboxylase
less atp efficient
higher tems

Question 53

CAM

Answer 53

Temporal seperation
stomata open at night allow for fixation
stomata closed in day
carbon fixation and calvin cycle same cell
efficient at high temps