Transport in Plants POST TEST.

Question 1

How does having a thick waxy cuticle help xerophytes survive in dry environments?

Answer 1

1. Reduces water loss by evaporation

Question 2

How does having fewer air spaces in spongy mesophyll help xerophytes survive in dry conditions?

Answer 2

1. Reduced surface area from which water can evaporate.

Question 3

Describe how mass flow of phloem sap occurs in plants with a vascular system? INCLUDE REFRENCE TO HYDROSTATIC PRESSURE GRADIENT BETWEEN SOURCE AND SINK, AND WATER POTENTIAL.

Answer 3

1. assimilates in the sieve tube elements
2. Assimilates enter the phloem at the source this lowers water potential in the sieve tube elements
3. Water now enters sieve tube by osmosis, INCREASES HYDROSTATIC PRESSURE.
4. Assimilates then leave the sieve tube elements the the sink and this increases water potential inside sieve tube elements.
5. water leaves sieve tube by osmosis down a water potential graduate lowering hydrostatic pressure.
6. Assimilates move from high to low hydrostatic pressure down the pressure gradient.

Question 4

How can a group of students observe the position of xylem vessels in petioles of celery?

Answer 4

1. Cut a thin transverse section
2. Add stain and observe with microscope under low power.

Question 5

Give three similarity between xylem and phloem vessels?

Answer 5

1. Both made of cells joined ned to end
2. Xylem vessels and sieve tube elements both lack nuclei.
3. Both are complex tissues

Question 6

Give 3 differences between xylem and phloem?

Answer 6

Xylem has a wide lumen phloem has small lumen.

Xylem has no companion cells phloem does

Xylem has no sieve tube elements phloem does.