transport in plants

Question 1

What color change does phloem tissue show in Benedict’s test?

Answer 1

Phloem tissue shows more of a color change when the non-reducing version of Benedict’s test is used due to the sucrose contained within it being a non-reducing sugar.

Question 2

What are FAD and NAD?

Answer 2

FAD and NAD are coenzymes that transfer hydrogen atoms in beta oxidation.

Question 3

How do root hairs absorb water?

Answer 3

Root hairs absorb water by osmosis as there is a lower water potential inside root hair cells than in the soil.

Question 4

What can small scattered populations lead to?

Answer 4

Small scattered populations can speed up extinction of a species due to difficulty finding a mate, inbreeding, and low genetic diversity.

Question 5

What evidence supports that translocation is an active process?

Answer 5

The rate of transpiration increases with temperature and sugars can be transported both up and down the plant.

Question 6

What indicates that sugars are translocated from source to sink?

Answer 6

An increase in sugar content of leaves is followed by a similar change in the sieve tube contents in the stem.

Question 7

How does mass flow of phloem contents occur?

Answer 7

Assimilates enter the sieve tube elements at the source, lowering water potential, causing water to enter by osmosis and increasing hydrostatic pressure.

Question 8

Where is cambium found?

Answer 8

Cambium is found between phloem and xylem.

Question 9

Why do trees further from the river have greater leaf hair density?

Answer 9

Trees further from the river have greater leaf hair density to reduce water loss by transpiration.

Question 10

How can xylem vessels be viewed in plants?

Answer 10

Put leaf stalks in dye, cut them transversely into thin slices, add a stain, and observe with a microscope.

Question 11

What is a hydrophyte?

Answer 11

A hydrophyte has less lignin and thinner xylem walls than deciduous woodland plants.

Question 12

What is a xerophyte?

Answer 12

A xerophyte has more lignin and thicker xylem walls than deciduous woodland plants.

Question 13

What are the similarities between xylem and phloem?

Answer 13

Both are made up of cells joined end to end, lack nuclei, and are complex tissues made up of more than one cell type.

Question 14

What are the differences between xylem and phloem?

Answer 14

Xylem is lignified, has a wide lumen, no end walls, no companion cells, and has vessels, while phloem contains cellulose, has a small lumen, has sieve plates, companion cells, and sieve tube elements.

Question 15

What is meristematic tissue?

Answer 15

Meristematic tissue is the type of tissue that undergoes cell division.

Question 16

What is not found in a mature xylem vessel?

Answer 16

A nucleus, cytoplasm, and end walls would not be found in a mature xylem vessel.

Question 17

What are the characteristics of xylem cell walls?

Answer 17

Xylem cell walls are thicker than normal plant cell walls, are lignified, and have bordered pits.

Question 18

What does phloem tissue contain?

Answer 18

Phloem tissue contains sieve tube elements, companion cells, and parenchyma.

Question 19

Why do plants need a transport system?

Answer 19

Large plants have a low surface area to volume ratio, making diffusion too slow to supply their requirements.

Question 20

What is cohesion tension theory?

Answer 20

Water moves up the plant as evaporation creates tension in xylem, pulling water molecules in a chain due to cohesion.

Question 21

What is transpiration?

Answer 21

Transpiration is the loss of water vapor from aerial parts of the plant, such as leaves, via the stomata.

Question 22

What is the transpiration stream?

Answer 22

The transpiration stream is the movement of water up xylem vessels from the roots to the leaves.

Question 23

How can water be lost from the plant?

Answer 23

Water can be lost through the leaf epidermis and the waxy cuticle.

Question 24

Where is meristematic tissue found?

Answer 24

Meristematic tissue is found just behind the tips of the roots and shoots, and in the cambium, pericycle, and vascular bundle.

Question 25

How is water loss replaced in transpiration?

Answer 25

Water loss from the leaf is replaced via the apoplast, symplast, and vacuolar pathways.

Question 26

How can cut flowers survive longer?

Answer 26

Cut flowers survive longer if the ends of the stem are removed immediately before being put in water to remove bubbles blocking the xylem.

Question 27

What do potometers measure?

Answer 27

Potometers measure water uptake.

Question 28

How do you set up a potometer?

Answer 28

Cut a healthy shoot underwater, ensure the apparatus is full of water, insert the shoot, and record the position of the air bubble.

Question 29

What adaptations do xerophytes have?

Answer 29

Xerophytes have hairy leaves, sunken stomata, rolled leaves, high solute concentration, thicker waxy cuticle, small leaves, fewer stomata, and stomata that close during the day.

Question 30

What is a source and a sink in phloem?

Answer 30

A source is where assimilates are loaded into phloem, and a sink is where they are unloaded.

Question 31

What happens when a complete ring of bark is removed from a tree?

Answer 31

The phloem in that area is removed, causing swelling above the cut due to sugars being unable to pass the cut.

Question 32

Why is water loss unavoidable during the day?

Answer 32

Stomata are open for gaseous exchange, allowing water vapor to leave down the water vapor potential gradient.

Question 33

What adaptations of leaves reduce evaporation?

Answer 33

Fewer stomata, stomata closing during the day, and most stomata on the lower surface reduce evaporation.

Question 34

What is the role of xylem?

Answer 34

The role of xylem is to transport water and mineral ions up the plant and support the plant stem.

Question 35

What is lignin's role in xylem?

Answer 35

Lignin strengthens the cell wall to prevent xylem vessels from collapsing and waterproofs the cell.

Question 36

What do bordered pits allow in xylem?

Answer 36

Bordered pits allow water to move between vessels and supply water to other cells in tissues.

Question 37

What is needed to record results of a potometer?

Answer 37

You need a scale and a timer.

Question 38

How to ensure a potometer is set up correctly?

Answer 38

Ensure the shoot is healthy, cut underwater, check for air bubbles, and ensure the apparatus is airtight.

Question 39

What can cause the rate of transpiration to decrease?

Answer 39

The rate may decrease if the plant is unhealthy, stomata are closed, or there is less air movement.

Question 40

What does a potometer estimate?

Answer 40

The potometer estimates the rate of transpiration but does not account for all water uptake.

Question 41

How does water move up the xylem?

Answer 41

Water moves up the xylem from roots to leaves due to root pressure and evaporation creating low hydrostatic pressure.

Question 42

What happens when steam comes out of a cut stem's xylem vessel?

Answer 42

Steam can come out because xylem has no cross walls and is hollow, allowing for continuous flow.

Question 43

How are sieve tubes adapted for mass flow?

Answer 43

Sieve tubes are elongated, joined end to end, have perforated end plates, and minimal cytoplasm to prevent impediment of flow.

Question 44

How are assimilates loaded into phloem?

Answer 44

Assimilates are actively loaded into phloem by active transport of hydrogen ions and facilitated diffusion.

Question 45

What does xylem consist of?

Answer 45

Xylem consists of vessels and participates in the transpiration stream.

Question 46

What does phloem consist of?

Answer 46

Phloem consists of sieve tube elements and companion cells and is involved in translocation.

Question 47

How do roots absorb minerals?

Answer 47

Roots absorb minerals from the soil by active transport, aided by root hairs and many mitochondria.

Question 48

How does temperature affect translocation?

Answer 48

Translocation is affected by temperature as it influences ATP production and the movement of sugars and water.

Question 49

What leads to a greater rate of transpiration?

Answer 49

More leaves lead to a greater rate of transpiration due to increased stomata and surface area.

Question 50

What happens if a shoot has no leaves in a potometer?

Answer 50

Some bubble movement will still occur as not all water uptake is due to transpiration.

Question 51

Why should leaves not be wet when setting up a potometer?

Answer 51

Getting leaves wet reduces the water vapor potential gradient, affecting the accuracy of the potometer.

Question 52

How does increased temperature affect transpiration?

Answer 52

Increased temperature will increase transpiration, so room temperature should be controlled unless it is the factor being investigated.

Question 53

Where do branches grow from on a cut surface?

Answer 53

Branches grow from just under the bark where cambium is found, producing new cells for growth.

Question 54

What are lenticels?

Answer 54

Lenticels are areas of loosely packed cells in bark that allow oxygen to reach tissues for aerobic respiration.

Question 55

What evidence supports translocation in phloem?

Answer 55

Labelled carbon can be observed in phloem soon after being supplied, and the rate of flow of sugars is higher than diffusion.

Question 56

What can be seen in companion cells under an electron microscope?

Answer 56

Companion cells contain many large mitochondria, plasmodesmata, ribosomes, extensive RER, and proteins in the membrane.

Question 57

What is translocation?

Answer 57

Translocation is the mass flow of assimilates from source to sink.

Question 58

What is a characteristic of xerophytic leaves?

Answer 58

Xerophytic leaves tend to have a smaller surface area to reduce transpiration.

Question 59

Why can't plants that lack vascular tissue grow large?

Answer 59

They cannot grow large as they lack support from vascular tissues and rely solely on diffusion.

Question 60

What is a consequence of water loss from plants?

Answer 60

Water is lost from plants during transpiration, which is unavoidable.

Question 61

What is translocation in plants?

Answer 61

Translocation is the mass flow of assimilates (i.e: sucrose and amino acids) from source to sink.

Question 62

How do xerophytic leaves adapt to reduce transpiration?

Answer 62

Xerophytic leaves tend to have a smaller surface area as this means less transpiration.

Question 63

Why can't plants without vascular tissue grow large?

Answer 63

Plants that lack vascular tissue cannot grow large as they have no support from vascular tissues such as the xylem and can only use diffusion to supply their needs.

Question 64

What is the limitation of diffusion in non-vascular plants?

Answer 64

Diffusion is too slow to enable substances to move large distances, so there is a short diffusion pathway and a large surface area to volume ratio.

Question 65

How is water lost from plants without vascular tissue?

Answer 65

Water is lost from plants without vascular tissue by evaporation via transpiration.

Question 66

What pathways do water take in plants?

Answer 66

Water moves by the symplast and apoplast pathways, through and along cell walls by capillary action and adhesion (apoplast pathway).

Question 67

What happens to the water potential of leaf cells during water loss?

Answer 67

Water loss reduces the water potential of leaf cells, and water moves from higher water potential to lower water potential (down water potential gradient) by osmosis (symplast pathway) through plasmodesmata.

Question 68

What non-vascular tissues are found in plant leaves?

Answer 68

Non-vascular tissue found in plant leaves includes palisade mesophyll, spongy mesophyll, guard cells, and upper and lower epidermal cells.

Question 69

How do needle-shaped leaves compare to nearly round leaves?

Answer 69

Needle-shaped leaves have a larger surface area to volume ratio than nearly round leaves.