Deck 18: Plant Nutrition, Transport and Adaptation to Stress

Question 1

To photosynthesise, land plants require

A) light, oxygen and water.
B) minerals, light and oxygen.
C) light, carbon dioxide and water.
D) light, minerals and carbon dioxide.
E) carbon dioxide, minerals and water.

Answer 1

light, carbon dioxide and water.

Question 2

What is 'the dilemma of land plants'?

A) Obtaining enough water to grow.
B) Water loss due to respiration.
C) Lack of nutrients.
D) In order to obtain carbon dioxide, plants risk losing water.
E) Water balance.

Answer 2

In order to obtain carbon dioxide, plants risk losing water.

Question 3

Eucalypt seedlings grown on calcareous, alkaline soils tend to be

A) elongated and spindly due to an oversupply of nitrogen.
B) stunted, due to a lack of all micronutrients.
C) stunted due to an overabundance of iron.
D) yellow, due to a lack of all micronutrients.
E) yellow, due to iron deficiency.

Answer 3

yellow, due to iron deficiency.

Question 4

Mineral nutrients in the form of ions have a general function and may also have specific functions. Which of the following statements is correct?

A) Mineral nutrients have no effect on water balance.
B) Trace elements such as Cu and Fe are rarely involved in redox reactions.
C) Mg is a component of chlorophyll.
D) Ca is essential for the maintenance of mitochondrial redox.
E) Cytochromes, involved in electron transport reactions, contain Zn but not Fe.

Question 5

Australian soils are widely

A) deficient in phosphorus and copper.
B) high in phosphorus.
C) high in the trace element molybdenum (Mo).
D) deficient only in phosphorus.
E) deficient in phosphorus and oxygen.

Question 6

The symbiotic association between plants and mycorrhizal fungi increases plant growth rates by

A) stimulating the growth of proteoid roots.
B) forming cluster roots which release exudates to solubilise phosphorous for uptake.
C) facilitating the conversion of gaseous nitrogen to organic nitrogenous compounds in root nodules.
D) enhancing the uptake of minerals from the soil.
E) increasing the rate of nutrient transport from roots to shoots.

Question 7

The apoplast in plants

A) is the intracellular volume.
B) is a pore in the plasmodesmata.
C) contains the vacuole.
D) is the volume of the vacuole in the cell.
E) is the volume of the cell outside the plasma membrane.

Question 8

Transport of non-gaseous substances in plants

A) involves hydrostatic pressure differences over long distances.
B) must be apoplastic to utilise plasmodermata.
C) does not occur across the tonoplast.
D) is by diffusion in the phloem of tall plants.
E) is rarely an active process.

Question 9

Typically for plants

A) water moves up a water potential gradient.
B) cytoplasmic solutes reduce the free energy of water.
C) the free energy of water molecules is less in soil than in cell cytoplasm.
D) the osmotic potential is lower in the xylem compared with that in leaf cells.
E) transpiration increases the water potential in xylem cells.

Question 10

If the osmotic potential of a plant cell is -1.4 MPa, and the pressure potential is 0.6 MPa, then the water potential of the cell is

A) -2.0 MPa.
B) +0.8 MPa.
C) -0.8 MPa.
D) 0 MPa.
E) 2.0 MPa.

Question 11

When a plant cell loses water and decreases in volume, the

A) pressure potential and the osmotic potential both decrease.
B) pressure potential decreases but the osmotic potential increases.
C) water potential does not change.
D) water potential increases but the pressure potential decreases.
E) solute concentration decreases and osmotic potential increases.

Question 12

A loss of turgor is NOT associated with

A) restricted photosynthesis.
B) increased pressure potential.
C) leaf wilting.
D) increased turgor pressure.
E) stomatal closure.

Question 13

Halophytes (salt-tolerant plants)

A) are resistant to damage caused by wilting.
B) typically accumulate sufficient solutes to generate a cell water potential less than -6 MPa.
C) concentrate solutes in cell vacuoles to decrease cell water potential and prevent wilting.
D) accumulate water to generate a high osmotic pressure.
E) can accumulate organic solutes but not inorganic ions.

Question 14

Osmotic adjustment in plants is a response to dry conditions and saline soils. This response involves plants

A) actively moving water around to change turgor.
B) actively increasing water uptake rates from the soil.
C) increasing the amount of solutes in their vacuoles.
D) wilting in order to decrease cell water potential.
E) increasing the amount of water in their vacuoles.

Question 15

The movement of water through plants is

A) maintained during the day by the positive water potential of the air.
B) along a gradient where the water potential is lower in the roots and higher in the leaves.
C) possible because xylem sap is more dilute than root cell vacuoles.
D) along a water potential gradient maintained in the xylem by negative hydrostatic pressure.
E) by active transport in the phloem.

Question 16

Xylem cells in flowering plants

A) conduct assimilates from leaves to roots.
B) include vessels and tracheids.
C) are connected via sieve plates.
D) is the symplastic pathway for solute transport.
E) conduct sugars from roots to shoots.

Question 17

Water rises to the top of tall trees in the

A) phloem via mass transport.
B) xylem due to cavitation.
C) xylem due to the cohesion of water molecules.
D) xylem due to root pressure.
E) xylem under positive hydrostatic pressure.

Question 18

In plants, an increase in stomatal guard cell turgor is caused by

A) the uptake of water via osmosis from surrounding cells.
B) the active transport of hydrogen ions into the cells.
C) the active transport of K⁺ and Cl^- ions out of the cell.
D) the diffusion of K⁺ ions out of the cell.
E) an increase in guard cell water potential.

Question 19

In plants, ion movements in and out of stomatal guard cells are driven by

A) electrons from the hydrolysis of water.
B) photons captured from light via Photosystem II.
C) proton pumping via membrane-bound ATPase.
D) osmotic gradients due to the presence of assimilates.
E) malate transport by PEP carboxylase.

Question 20

In plants, the substances known as assimilates are

A) the end products of photosynthesis.
B) transported from the roots to allow growth.
C) moved around the tree via xylem vessels.
D) root hormones.
E) amino acids.

Question 21

A plant is grown in the presence of carbon-14-labelled carbon dioxide. In an autoradiograph, you would NOT expect to find carbon-14-labelled assimilates in the

A) roots.
B) young, expanding leaves.
C) fully expanded leaves.
D) shoot tips.
E) stomata.

Question 22

In relation to the movement of assimilates in plants

A) sources are always sites of photosynthesis.
B) sinks may import assimilates from storage reserves or from sites of photosynthesis.
C) sinks tend to be supplied equally by neighbouring and distant sources.
D) a structure cannot switch between being a source or a sink.
E) sources are always roots.

Question 23

Plants have many strategies for coping with drought conditions including

A) being able to maintain cell turgor even at very low water potentials.
B) avoiding a dormant phase in the life cycle.
C) usually being able to withstand total dehydration.
D) maximising water loss and minimising CO₂ assimilation.
E) having a small root system to survive low water potential.

Question 24

Arid plants that can minimise water loss and maximise the assimilation of CO₂ would typically

A) be able to have their stoma partially open during the day to conserve water without greatly reducing photosynthesis.
B) have their stoma open at midday, even in the hottest months of the year.
C) have leaves unresponsive to root signals relating to soil dryness.
D) not limit water loss at the expense of carbon gain.
E) not open their stoma during the day, but continue photosynthesis.

Question 25

Evolutionary modifications to the basic type of photosynthesis have enabled some plants to improve their water use efficiency. Which of the following statements is correct?

A) C₃ plants are able to photosynthesise effectively with very low levels of CO₂.
B) Facultative CAM plants can switch from C₃ to CAM photosynthesis as water becomes limiting.
C) CAM plants have very high levels of water use efficiency and high rates of photosynthesis.
D) C₄ plants are rarely found in arid environments.
E) CAM plants use less water in the photosynthetic ATP production than do C₃ plants.

Question 26

The water potential of a seedling was estimated to be -0.3 MPa. It was planted in saline soil with a water potential of -1.5 MPa. What would the seedling need to do in order to absorb water?

A) Decrease its root cell water potential.
B) Increase its root cell water potential.
C) Actively secrete salts into the soil.
D) Actively take up salts at the leaves.
E) increase transpiration so there is increased evaporation, leading to increased water uptake.

Question 27

Under waterlogged conditions

A) root growth is likely to increase due to increased water availability.
B) lack of O₂ is likely to result in decreased root growth.
C) anaerobic organisms are less likely to be producing toxic substances.
D) increased plant xylem to transport water rapidly from the roots.
E) root cells are more permeable to water and ions.

Question 28

Which of the following statements about the effects of temperature on plant cells is correct?

A) Extracellular ice formation may cause cell dehydration.
B) Plant cells are more likely to freeze than their extracellular fluid.
C) Very low temperatures have no effect on membrane fluidity.
D) Damage to plants at temperature extremes is due to decreased uptake of water.
E) High temperatures have no effect on enzyme shape and function.

Question 29

Plants such as mangroves and rice have adaptations for survival in low-oxygen soils, including

A) decreasing rates of anaerobic fermentation in the roots.
B) increasing the rate of photosynthesis and so increasing water uptake.
C) decreasing rates of growth, nutrient uptake and water use.
D) production of air canals on the soil surface.
E) production of lateral canals in the roots.

Question 30

Proteoid roots

A) are an adaptation to obtain oxygen in waterlogged soils.
B) store proteins.
C) are a symbiotic association between plant roots and fungi.
D) are an adaptation to nutrient-poor soils.
E) store carbohydrates.

Question 31

Stomatal opening and closing is affected by

A) sunlight.
B) CO₂ concentration.
C) atmospheric water.
D) abscisic acid concentration.
E) All of the answers are correct.

Question 32

Phloem sap is a concentrated solution consisting mainly of sucrose. This is because sucrose

A) is a non-reducing sugar and so does not modify other compounds such as proteins during transport.
B) is easily converted to other sugars such as raffinose and mannitol which are metabolically active.
C) maintains the high negative pressure required for transport of assimilates.
D) is able to diffuse through the cell membrane and enter cells for energy.
E) is readily taken up by the roots.

Question 33

Most plants have adapted to infertile conditions. Modifications to obtain essential nutrients include

A) increased root hairs.
B) uptake systems for insoluble phosphates.
C) internal recycling of nutrients.
D) nitrogen fixation by symbiotes.
E) All of these answers are correct.

Question 34

When a cell loses water and decreases in volume

A) pressure potential and osmotic potential both decrease and water potential increases.
B) pressure potential and water potential both decrease and osmotic potential increases.
C) pressure potential and osmotic potential both increase and water potential also increases.
D) pressure potential and osmotic potential both decrease and water potential also decreases.
E) pressure potential and osmotic potential both increase and water potential decreases.

Question 35

Osmotic adjustment

A) is a response of plants to lack of water where solute in the cell increases and the osmotic potential decreases.
B) is the capacity of a cell to retain water.
C) is the accumulation of cell vacuoles containing salt in halophytes.
D) only occurs in response to dry soil.
E) All of the answers are correct.

Question 36

The raw materials for the growth of a plant come from the translocation of assimilates through the plant by

A) transport in phloem from leaf to root.
B) transport in phloem from root to leaf.
C) transport in xylem from leaf to root.
D) transport in xylem from root to leaf.
E) the direction of transport is dependent on the time of day and the ability of the plant to undergo photosynthesis.

Question 37

A scientist wants to capture and analyse some of the water that is being lost by transpiration via evaporation. She wants to capture the most amount of water in the quickest time from an actively transpiring plant in the sun. Which organs should she use to capture this water, and why?

A) Mature leaves, as these have the highest rates of transpiration.
B) Juvenile leaves, as these have the highest rates of transpiration.
C) The bottom most leaves, as these will have the highest amount of exudates due to guttation.
D) The green sections of the stem, as this has the lowest surface area to volume ratio.
E) Flag leaf one and two, as these are most rapidly expanding leaves.

Question 38

After being loaded into the phloem, dissolved nutrients in the xylem sap may be intercepted and directed towards which tissues?

A) Roots and/or tubers
B) Leaves and fruits
C) Developing flowers
D) Stem tissue
E) Meristematic cambium

Question 39

During hot spells, why could drier conditions in the future lead to massive tree death?

A) Leaf-drop due to water stress
B) Phloem collapse due to decreased turgor
C) More frequent embolisms and difficultly in recovering from them
D) Xylem collapse due to decreased turgor
E) All of the answers are correct

Question 40

Which of the following elements are ALL micronutrients?

A) Molybdenum, potassium, boron, copper
B) Nickel, chlorine, magnesium, manganese
C) Calcium, iron, zinc, sulphur
D) Phosphorous, potassium, magnesium, calcium
E) Copper, manganese, zinc, iron

Question 41

Which of the following are NOT adaptations of Australian plants to nutrient poor soils?

A) Root clusters
B) Organic acid exudates
C) Symbioses between roots and microorganisms
D) Root mucilage sheath
E) Full functionality at relatively low nutrient levels