Question 1

Which of the following best describes the role of the Casparian strip in the endodermis of plant roots?

Accepted Answer

It blocks the apoplastic route, forcing water and minerals to cross a selectively permeable plasma membrane before entering the vascular cylinder.

Question 2

A plant is experiencing drought stress. Which adaptation would most likely help reduce water loss?

Accepted Answer

Developing a thicker cuticle and sunken stomata lined with hairs.

Question 3

Which pathway allows water and minerals to move through the cytoplasm of root cells, passing from cell to cell via plasmodesmata?

Accepted Answer

Symplastic route

Question 4

According to the cohesion-tension hypothesis, what is the primary force that pulls water upward through the xylem?

Accepted Answer

Transpirational pull resulting from water evaporation at the leaf surface

Question 5

Which of the following equations correctly represents water potential ($$\Psi) in $$plant cells?

Accepted Answer

$$\Psi = \Psi_s + \Psi_p$$

Question 6

Why does bulk flow in the xylem not require energy from the plant?

Accepted Answer

Because it is driven by evaporation and pressure potential differences, not by active transport.

Question 7

Which of the following best explains why xylem sap can continue to flow even if cavitation occurs?

Accepted Answer

Water can detour through pits between adjacent xylem cells or use new outer layers of secondary xylem.

Question 8

Which of the following is a correct statement about phloem transport in angiosperms?

Accepted Answer

Phloem sap moves by bulk flow driven by positive pressure (pressure flow).

Question 9

A storage root acts as a sugar sink in summer and a sugar source in winter. What does this indicate about the direction of phloem transport?

Accepted Answer

The direction of phloem transport can reverse depending on the plant's needs.

Question 10

Which process is primarily responsible for the opening of stomata in the morning?

Accepted Answer

Uptake of potassium ions ($$K^+) by $$guard cells, increasing turgor pressure

Question 11

Which adaptation is characteristic of CAM plants that helps them survive in arid environments?

Accepted Answer

Opening stomata at night for gas exchange

Question 12

Which of the following best describes the difference between bulk flow and diffusion in plant transport?

Accepted Answer

Bulk flow moves the entire solution through hollow dead cells, while diffusion moves individual molecules across membranes of living cells.

Question 13

A plant's leaf water potential ($$\Psi) is $$measured at $$-1.0$$ MPa, while the soil water potential is $$-0.3$$ MPa. In which direction will water move?

Accepted Answer

From the soil to the leaf

Question 14

Which of the following is NOT a function of guard cells?

Accepted Answer

Transporting sugars from source to sink

Question 15

Which route does water take if it moves through cell walls and extracellular spaces without crossing any membranes until it reaches the endodermis?

Accepted Answer

Apoplastic route

Question 16

Which of the following best explains why vessel elements and tracheids have thick secondary walls?

Accepted Answer

To prevent collapse under the negative pressure generated by transpirational pull

Question 17

Which of the following is a correct sequence for the movement of water from soil into the xylem?

Accepted Answer

Soil → root hair → cortex → endodermis → xylem

Question 18

Which of the following is a real-world consequence of cavitation in xylem vessels?

Accepted Answer

Reduced water transport leading to wilting during drought

Question 19

Which process is responsible for loading sucrose into sieve-tube elements during phloem transport?

Accepted Answer

Active transport involving proton pumping and cotransport with $$H^+$$ ions

Question 20

Which of the following best describes the function of companion cells in phloem loading?

Accepted Answer

They enhance solute movement between the apoplast and symplast.

Transport of Water, Minerals, and Sugars in Plants

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