Biology Chapter 36

In addition to transporting sugar, the phloem also _____.

-transmits electrical signals -transports viral RNA throughout the plant -transports plant RNA throughout the plant -transports proteins throughout the plant

What characterizes the rates of photosynthesis and transport in a plant on a dry cloudy day?

Both the photosynthesis and transpiration rates are low.

Which of the following statements about the distribution of sap throughout a plant is true?

The mechanism that explains the movement of sugars throughout a plant is called the pressure-flow hypothesis.

A plant cell is placed in distilled water, as shown in the figure. There is a net uptake of water by osmosis, causing the cell to become turgid. Select the correct statement about this setup, after the cell is fully turgid.

The water potentials (Ψ) of the cell and its surroundings are the same.

Which of the following statements about xylem transport is true?

Water and minerals move through the root cortex into the xylem and upward through the stem and into leaves.

If a plant's stomata are closed and no transpiration is occurring, which of the following predictions is accurate?

Without transpiration, less water will be absorbed from the soil.

Which of the following is a correct statement about a difference between xylem and phloem transport?

Xylem sap moves up; phloem sap moves up or down.

Movement of phloem sap from a source to a sink

depends ultimately on the activity of proton pumps

Which tissue acts as a filter on the water absorbed by root hairs?

endodermis

True or false? Root pressure can move water a long distance up the xylem because of the higher water potential of the xylem in comparison to the water potential in the surrounding cells.

false

True or false? The rate of sugar transport in a plant depends on the rate of photosynthesis, the rate of transpiration, and the difference in turgor pressure between the source and the sink.

false (While the rate of photosynthesis and the difference in turgor pressure between the source and the sink do influence the rate of sugar transport in the phloem, the rate of transpiration does not; transpiration mainly influences the rate of water transport through the xylem.)

Which of the following would tend to increase transpiration?

higher stomatal density

A plant cell placed in a solution with a lower (more negative) water potential will _____.

lose water and plasmolyze ( Water moves from a region of higher water potential to a region of lower water potential. Loss of water pulls the plasma membrane away from the cell wall, producing plasmolysis.)

Plants must always compromise between _____ and _____.

maximizing photosynthesis ... minimizing water loss

Mycorrhizae are _____.

mutualistic associations between plant roots and fungi

Which of the following is an adaptation that enhances the uptake of water and minerals by roots?

mycorrhizae

Which term describes an area where sugars are used or stored?

sink (an area where sugars are used or stored; typically, these are the roots and fruits of a plant)

Photosynthesis ceases when leaves wilt, mainly because

stomata close, preventing CO2 from entering the leaf

The solute most abundant in phloem sap is _____.

sugar

A student is performing a chemical analysis of xylem sap. This student should not expect to find much _____.

sugar (phloem transports sugar)

Which one of the following refers to the loss of water through the stomata in a plant's leaves?

transpiration

The proton pump _____.

uses the energy stored in ATP to produce a hydrogen ion gradient across membranes

Xerophytes minimize water loss by _____.

using the CAM pathway