Question 1

Which of the following best explains why land plants evolved specialized transport tissues?

Accepted Answer

Land plants needed to move water and minerals between roots and shoots due to their exposure to different environments.

Question 2

Which process describes the passive movement of molecules down their concentration gradient across a membrane, without the expenditure of metabolic energy?

Accepted Answer

Passive transport

Question 3

What is the primary function of the proton pump in the plasma membrane of plant cells?

Accepted Answer

To hydrolyze ATP and pump hydrogen ions ($$\mathrm{H^+}) $$out of the cell, creating a proton gradient and membrane potential.

Question 4

Which equation correctly represents water potential ($$\Psi) in $$plant cells?

Accepted Answer

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

Question 5

A plant cell is placed in a solution with a lower solute concentration than its cytoplasm. What will happen to the cell?

Accepted Answer

Water will enter the cell by osmosis, causing it to become turgid.

Question 6

Which route allows substances to move through the cytoplasm of adjacent plant cells via plasmodesmata?

Accepted Answer

Symplastic route

Question 7

What is the role of the endodermis in plant roots?

Accepted Answer

It acts as a selective checkpoint for the passage of minerals from the cortex to the vascular tissue.

Question 8

Which physical property of water is most important for the ascent of xylem sap in plants?

Accepted Answer

Cohesion and adhesion

Question 9

Transpiration in plants is best described as:

Accepted Answer

The loss of water vapor from leaves and other aerial parts of the plant.

Question 10

Root pressure in plants is generated by:

Accepted Answer

The accumulation of minerals in the stele, lowering water potential and forcing fluid up the xylem.

Question 11

Which phenomenon is caused by root pressure pushing xylem sap into the shoot system, resulting in the exudation of liquid water from leaves?

Accepted Answer

Guttation

Question 12

The transpiration-to-photosynthesis ratio for many plant species is approximately:

Accepted Answer

$$600:1$$

Question 13

Which of the following best describes the mechanism by which potassium ions ($$\mathrm{K^+}) $$regulate stomatal opening?

Accepted Answer

Potassium ions are actively transported into guard cells, lowering water potential and causing water to enter, making the cells turgid and opening the stoma.

Question 14

Phloem sap primarily contains which solute in most plants?

Accepted Answer

Sucrose

Question 15

Which statement best describes the direction of phloem transport in plants?

Accepted Answer

It is variable, generally moving from a sugar source to a sugar sink.

Question 16

In the process of phloem loading, how is sucrose actively transported into sieve-tube members?

Accepted Answer

Proton pumps create an $$\mathrm{H^+}$$ gradient, and sucrose is cotransported with $$\mathrm{H^+}$$ back into the cell.

Question 17

Why does sugar diffuse from the phloem into sink tissues at the end of the sieve tube?

Accepted Answer

The concentration of free sugar in the sink is lower than in the phloem.

Question 18

Which of the following is a multi-step process involving both active and passive transport in plant cells?

Accepted Answer

Phloem loading, where proton pumps actively create a gradient and sucrose is passively cotransported with $$\mathrm{H^+}.$$

Question 19

A plant species has a transpiration-to-photosynthesis ratio of $$300:1. $$What does this indicate about its water use efficiency compared to a species with a ratio of $$600:1$$?

Accepted Answer

It loses less water per gram of $$\mathrm{CO_2$}$$ assimilated, indicating higher water use efficiency.

Transport in Plants: Mechanisms and Pathways

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