Skip to main content
Ch. 35 - Water and Sugar Transport in Plants
Chapter 34, Problem 7

A mutant plant lacking the ability to pump protons out of leaf companion cells will be unable to do which of the following? a. initiate transpiration b. load sucrose into sieve-tube elements c. carry out photosynthesis d. transport water through the xylem

Verified Solution

Video duration:
1m
This video solution was recommended by our tutors as helpful for the problem above.
Was this helpful?

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Proton Pumping

Proton pumping is a process where protons (H+ ions) are actively transported out of cells, creating a proton gradient across the cell membrane. This gradient is essential for various cellular processes, including nutrient transport. In plants, proton pumps in companion cells help load sugars like sucrose into the phloem for transport.
Recommended video:
Guided course
08:38
Ion Channels and Pumps

Sieve-Tube Elements

Sieve-tube elements are specialized cells in the phloem of plants that facilitate the transport of sugars and other organic nutrients. They are connected end-to-end, forming long tubes. The loading of sucrose into these elements is crucial for efficient nutrient distribution, and it relies on the proton gradient established by proton pumps.
Recommended video:
Guided course
03:36
Elements of Life

Transpiration

Transpiration is the process by which water vapor is released from plant leaves into the atmosphere. It creates a negative pressure that helps draw water up from the roots through the xylem. While transpiration is vital for water transport, it is not directly dependent on the proton pumping mechanism in companion cells, which primarily affects phloem loading.
Recommended video:
Guided course
08:29
Water Potential in Soil and Air
Related Practice
Textbook Question

Consider the following statements regarding the transport of phloem sap. Select True or False for each statement. T/F This is a passive process that is driven by the evaporation of water from leaves. T/F Sugars tend to move from sources to sinks. T/F Phloem sap moves through sieve-tube elements under positive pressure. T/F Sieve-tube elements and vessel elements are commonly involved in the transport of phloem sap.

407
views
Textbook Question

The cells of a certain plant species can accumulate solutes to create very low solute potentials. Which of these statements is correct? a. The plant's transpiration rates will tend to be extremely low. b. The plant can compete for water effectively and live in c. relatively dry soils. d. The plant will grow most effectively in soils that are saturated with water year-round. e. The plant's leaves will wilt easily.

284
views
Textbook Question

Draw a plant cell in pure water. Add dots to indicate solutes inside the cell. Now add more dots to indicate an increase in solute potential inside the cell. Add an arrow showing the net direction of water movement in response. Add arrows showing the direction of wall pressure and turgor pressure in response to water movement. Repeat the same exercise, but this time, add solutes to the solution outside the cell at a concentration that is greater than inside the cell.

448
views
Textbook Question

Your friend claims that phloem always carries sugars down a plant. What, if anything, is wrong with that statement?

402
views
Textbook Question

Consider a tree that is 50 m tall and is transpiring roughly 90 liters of water each day. Approximately how many calories will the tree use to transpire this quantity of water?

365
views
Textbook Question

Salt is used to melt snow and keep roads clear during the winter in many cities. Land adjacent to de-iced roads often ends up with a high concentration of salt in the soil. Explain why plants growing near salted roads may appear wilted in the spring.

458
views