Biology 2 CH 35 Water Transport (Plants)

Surface tension; Cohesion; Adhesion

1) ________ _________ in leaves generates the force that pulls water through the xylem. 2) __________ between water molecules in leaves, stems, and roots transmits that force. 3) ___________ of water to plant cell walls in leaves and stems opposes the force of gravity, which tends to pull water downward in the xylem.

load sucrose into sieve cells

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

CO2

Both water and _________ diffuse as gases through stomata.

faster rate of osmosis

Compared to a cell with few aquaporins in its membrane, a cell containing many aquaporins will _____.

low solute potentials

Compared to plants from other environments, the cells of many desert plants contain high concentrations of solutes. This helps them survive in their arid surroundings because the high solute concentrations create relatively _____, which help reduce water loss. -low solute potentials -high pressure potentials -low pressure potentials -high solute potentials

Active transport

How is sucrose from the phloem moved into the sink of a leaf?

Casparian strip; endodermis; xylem

In roots the _____ forces water and solutes to pass through the plasma membranes of _____ cells before entering the _____.

The roots and fruits

In what organs of the plant are sinks typically located?

Water enters the phloem via osmosis, which in turn creates a higher pressure within the phloem, moving sucrose into the sinks at a higher rate.

Phloem cells located in "source" regions can have relatively high pressure. How is that pressure generated?

apoplastic

The _________ pathway is a continuous route formed by cell walls, extracellular spaces, and the interior of dead xylem cells.

symplastic; plasmodesmata

The __________ pathway is made up of the cytoplasm of cells. It is also continuous because ______________ connect the cytoplasm of adjacent cells.

plasmodesmata

The channels indicated by the pointer, are _____.

cellulose microfibrils

The generation of transpirational pull in leaves depends on the interaction of water with the ____________ ____________ in mesophyll cell walls

Sucrose

The most commonly transported sugar in plants is _______.

-To minimize water loss during dry conditions, most plants must also restrict their ability to carry out photosynthesis. -Transpiration is important in cooling leaves on warm, sunny days. -Open stomata provide a low-resistance pathway for CO2 to enter and for water to exit the leaf. -In most plants, the highest rate of transpiration occurs when the rate of photosynthesis is also highest.

Transpiration provides the driving force for the movement of water from the soil to the highest leaves of plants. Transpiration is also linked to other processes in plants, including photosynthesis and the transport of mineral nutrients. Which of the following statements correctly describe(s) a relationship between transpiration and other processes in plants? Select all that apply. -To minimize water loss during dry conditions, most plants must also restrict their ability to carry out photosynthesis. -Transpiration is important in cooling leaves on warm, sunny days. -Open stomata provide a low-resistance pathway for CO2 to enter and for water to exit the leaf. -Water is pulled from the roots to the leaves by transpiration, whereas mineral nutrients diffuse from the roots to the leaves. -The large surface area exposed to air inside the leaf maximizes the plant's ability to absorb CO2 while minimizing water loss through transpiration. -In most plants, the highest rate of transpiration occurs when the rate of photosynthesis is also highest.

False

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.

True

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.

Osmosis

Water enters into the phloem from the xylem by way of ____________.

Both the photosynthesis and transpiration rates are low.

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

restricted; photosynthesis

When the stomata close to limit water loss under dry conditions, the entry of CO2 into the leaf is __________ and ____________ slows.

Sugars are first transported into companion cells and from there move into phloem.

Which of the following correctly describes how sugars move from a photosynthetic leaf cell into phloem? -Sugars are first transported into companion cells and from there move into phloem. -Sugars are transported directly from the photosynthetic leaf cell into phloem. -Sugars are first transported into xylem and from there move into phloem. -Sugars are first transported into plasmodesmata, and from there move into phloem.

They lack a nucleus and rely on companion cells to regulate their metabolic activity.

Which of the following is true regarding sieve-tube elements? -They are the primary sites where sugars are produced. -They are the primary cells in xylem that are involved in conducting water. -They contain a nucleus and many other organelles that facilitate the movement of sugars. -They lack a nucleus and rely on companion cells to regulate their metabolic activity.

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

Which of the following statements about the distribution of sap throughout a plant is true? -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. -The driving force for sugar movement is transpiration.

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

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. -Water and minerals enter the xylem by diffusion. -All water transported by the xylem is used for photosynthesis in the leaves. -The xylem cells that conduct water and minerals are alive.

mycorrhizae

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

Sink

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

Endodermis

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

Hydrogen

_____ bonds are responsible for the cohesion of water molecules.

Guard

_____ cells are the cells that regulate the opening and closing of stomata, thus playing a role in regulating transpiration.

Transpiration

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

Surface tension

_________ _________ in leaves generates the force that pulls water through the xylem.

Adhesion

__________ makes water stick to hydrophilic surfaces, such as cell walls.

Cohesion

__________ tends to keep water molecules that are away from surfaces from separating.

Adhesion

___________ results from hydrogen bonds between water and other polar molecules.

Transpiration

____________ pulls both water and mineral nutrients from the roots to the leaves. It also cools the leaves as water evaporates from cell surfaces inside the leaves.