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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. |
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A plant cell placed in a solution with a lower (more negative) water potential will _____. |
lose water and plasmolyze |
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The proton pump _____. |
uses the energy stored in ATP to produce a hydrogen ion gradient across membranes. |
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Mycorrhizae are _____. |
mutualistic associations between plant roots and fungi |
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Plants must always compromise between _____ and _____. |
maximizing photosynthesis … minimizing water loss |
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Select the accurate statement about water potential. |
Water in a turgid cell has positive pressure potential. |
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Which one of the following refers to the loss of water through the stomata in a plant’s leaves? |
transpiration |
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Select the correct mechanism of stomatal opening and closing. |
The radial orientation of cellulose microfibrils in the cell walls of guard cells causes them to bow outward and open the stomatal pore when turgid. |
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The solute most abundant in phloem sap is _____. |
sugar |
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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 |
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A student is performing a chemical analysis of xylem sap. This student should not expect to find much _____. |
sugar |
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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. |
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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. |
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Photosynthesis ceases when leaves wilt, mainly because |
stomata close, preventing CO2 from entering the leaf |
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Which structure or compartment is part of the symplast? |
the interior of the sieve tube |
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Root hairs are most important to a plant because they |
increase the surface area for absorption. |
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What is the role of proton pumps in root hair cells? |
acquire minerals from the soil |
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In plant roots, the Casparian strip is correctly described by which of the following? |
It ensures that all water and dissolved substances must pass through a cell membrane before entering the stele. |
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Which of the following is not an important component of the long-distance transport process in plants? |
the root parenchyma |
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A water molecule could move all the way through a plant from soil to root to leaf to air and pass through a living cell only once. This living cell would be a part of which structure? |
the endodermis |
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True or False. The apoplast is the cytoplasmic continuum linked by plasmodesmata. The symplast is the continuum of cell walls and extracellular spaces. |
False |
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What is the main force by which most of the water within xylem vessels moves toward the top of a tree? |
evaporation of water through stoma |
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Water rises in plants primarily by the cohesion-tension model. Which of the following is not true about this model? |
The "tension" of this model represents the excitability of the xylem cells. |
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Xylem vessels, found in angiosperms, have a much greater internal diameter than tracheids, the only xylem conducting cells found in gymnosperms. The tallest living trees, redwoods, are gymnosperms. Which of the following is an advantage of tracheids over vessels for long-distance transport to great heights? |
Adhesive forces are proportionally greater in narrower cylinders than in wider cylinders, and cohesive forces are greater in narrow tubes than in wide tubes of the same height. |
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True or False. Water can cross the cortex via the symplast or apoplast, but minerals moving via the apoplast must finally cross the selective membranes of endodermal cells. |
True |
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True or False. Transpiration raises water potential in the leaf by producing a positive pressure potential. This higher water potential draws water from the xylem. |
False |
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All of the following normally enter the plant through the roots except |
carbon dioxide |
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True or False. When guard cells take up K+, they bow outward, widening the stomatal pore. Stomates close when K+ is actively transported out of the guard cells. |
True |
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The opening of stomata is thought to involve |
an increase in the osmotic concentration of the guard cells. |
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Phloem transport of sucrose can be described as going from "source to sink." Which of the following would not normally function as a sink? |
mature leaf |
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Which tissue acts as a filter on the water absorbed by root hairs? |
endodermis |
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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 |
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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. |
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Which term describes an area where sugars are used or stored? |
sink |
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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. |
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What characterizes the rates of photosynthesis and transport in a plant on a dry cloudy day? |
Both the photosynthesis and transpiration rates are low. |
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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 |
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Phloem transport is described as being from source to sink. Which of the following would most accurately complete this statement about phloem transport as applied to most plants in the late spring? Phloem transports __________ from the __________ source to the __________ sink. |
sugars; leaf; apical meristem |
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According to the pressure flow hypothesis of phloem transport, |
solute moves from a high concentration in the "source" to a lower concentration in the "sink." |
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A plant cell with a Ψs of -0.65 MPa maintains a constant volume when bathed in a solution that has a Ψs of -0.30 MPa and is in an open container. The cell has a |
Ψp of +0.35 MPa |
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Which structure or compartment is not part of the apoplast? |
the lumen of a sieve tube |
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The opening of stomata is thought to involve |
an increase in the solute concentration of the guard cells. |
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All of the following are adaptations that help reduce water loss from a plant except |
transpiration |
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