Chapter 38

What pressure would be required on the plunger to cause water to flow from left to right? 0.1 MPa 10 MPa 1 MPa 2 MPa

0.1 MPa *A decrease in pressure will cause water to flow from left to right.

What characterizes the rates of photosynthesis and transport in a plant on a dry cloudy day? The photosynthesis rate is low and stomata are open. Both the photosynthesis and transpiration rates are low. The photosynthesis rate is high and phloem transport rates are low. Both the photosynthesis and transpiration rates are high.

Both the photosynthesis and transpiration rates are low. *On a cloudy day with low soil moisture, the photosynthesis rate is low and stomata are closed, so the transpiration rate is low.

In roots the ________ forces water and solutes to pass through the plasma membranes of ________ cells before entering the ________. Casparian strip ... endodermis ... phloem xylem ... endodermis ... Casparian strip Casparian strip ... endodermis ... xylem Casparian strip ... ectoderm ... xylem transpiration ... endodermis ... xylem

Casparian strip ... endodermis ... xylem *The Casparian strip is a waterproof barrier that forces water and solutes to pass through the plasma membranes of endodermis cells.

Which tissue acts as a filter on the water absorbed by root hairs? Cortex Vascular tissue Epidermis Endodermis

Endodermis *Endodermal cells filter solutes from water and allow them to pass through to the vascular tissue.

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. The driving force for sugar movement is transpiration. Companion cells form the conducting tissue for sap. The main component of phloem sap is glucose.

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

Why does overwatering a plant kill it? Water neutralizes the pH of the soil. The roots are deprived of oxygen. Water supports the growth of root parasites. Water lowers the water potential of the roots. Water does not have all the necessary minerals a plant needs to grow.

The roots are deprived of oxygen.

Which of the following statements about xylem transport is true? All water transported by the xylem is used for photosynthesis in the leaves. Water and minerals enter the xylem by diffusion. Water and minerals move through the root cortex into the xylem and upward through the stem and into leaves. The xylem cells that conduct water and minerals are alive.

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

Which structure or compartment is part of the symplast? the interior of a sieve tube the cell wall of a root hair the cell wall of a mesophyll cell the interior of a vessel element an extracellular air space

the interior of a sieve tube

This is an animation of the movement of water and ions through the root ________. via the mycorrhizal route via a combination of the movement through plasmodesmata and across cell membranes from cell to cell, across cell membranes and cell walls via the symplastic route via the apoplastic route

via the apoplastic root *The animation illustrates water and ions moving along a cell wall continuum.

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 *Root pressure can move water a short distance up the xylem because of the lower water potential of the xylem in comparison the water potential in surrounding cells.

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 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.

________ cells are the cells that regulate the opening and closing of stomata, thus playing a role in regulating transpiration. Companion Tracheid Casparian strip Sieve-tube member Guard

Guard

Movement of phloem sap from a source to a sink ________. depends on tension, or negative pressure potential results mainly from diffusion of sugars into companion cells depends on active transport of water into sieve-tube elements at the source depends upon active transport of sugars into the sieve-tube elements occurs through the apoplast of sieve-tube elements

depends upon active transport of sugars into the sieve-tube elements at the source

Which of the following would tend to increase transpiration? higher stomatal density spiny leaves a rainstorm a thicker cuticle sunken stomata

higher stomatal density

Most of the water taken up by a plant is ________. used as a solvent used as a hydrogen source in photosynthesis converted to carbon dioxide lost during transpiration used to keep cells turgid

lost during transpiration

Water potential is generally most negative in which of the following parts of a plant? cells of the root cortex xylem vessels in roots mesophyll cells of the leaf xylem vessels in leaves root hairs

mesophyll cells of the leaf

Which of these are symbiotic associations? symplast root hairs mycorrhizae Casparian strips apoplasts

mycorrhizae *Mycorrhizae are mutualistic associations of roots and fungi.

________ bonds are responsible for the cohesion of water molecules. Hydrogen Polar covalent Nonpolar covalent Ionic Peptide

Hydrogen

Which term describes an area where sugars are used or stored? Source Leaves Sink Stomata

Sink *Typically, these are the roots an fruits of a plant.

Which of the following supports the finding that sugar translocation in phloem is an active (energy-requiring) process? Movement of water occurs from xylem to phloem and back again. ATPases are abundant in the plasma membranes of the mesophyll cells. Strong pH differences exist between the cytoplasm of the companion cell and the mesophyll cell. Sucrose occurs in higher concentrations in companion cells than in the mesophyll cells where it is produced.

Sucrose occurs in higher concentrations in companion cells than in the mesophyll cells where it is produced.

________ provide(s) the major force for the movement of water and solutes from roots to leaves. Root pressure Translocation Transpiration Bulk flow Transfer cells

Transpiration *Transpiration, the evaporation of water from leaves, exerts a pull that bears the primary responsibility for the movement of water and solutes from roots to leaves.

The channels indicated by the pointer are ________. tight junctions plasmodesmata desmosomes mycorrhizae gap junctions

plasmodesmata *Water and ions can pass from cell to cell via these channels. Recall that plasmodesmata are a type of cell junction.

Which of the following features of plat cells allows for apoplastic movement of water? plasmodesmata large central vacuole porous cell walls endodermal cells

porous cell walls

What would enhance water uptake by a plant cell? the loss of solutes from the cell decreasing the Ψ of the surrounding solution increasing the Ψ of the cytoplasm positive pressure on the surrounding solution increasing the pressure exerted by the cell wall

positive pressure on the surrounding solution

Which of the following structural features of plants would not be expected to reduce transpiration? sunken stomata thick cuticle on leaves and stems abundant epidermal hairs on leaves and stems reduced leaf size stomata on upper and lower surfaces of the leaves

stomata on upper and lower surfaces of the leaves