Chapter 9: Water in Plants - Connect Assignment

Which of these are needed for pressure-flow to drive movement of substances in the phloem?

- A high-concentration of food substances at a source - A low-concentration of food at an area where food is being utilized, creating a sink - A concentration gradient between source (high concentration) and sink (low concentration)

Which of these statements are true of active transport?

- A transport protein is needed. Energy is expended. - A proton pump is helping to move the molecules. - Something is moved across a membrane.

Which of these environmental factors affects stomatal opening and closing and therefore transpiration rates?

- CO2 concentration - Temperature - Light intensity - Humidity

What have scientists learned about the translocation of food in plants by studying aphids?

- Dissolved sugars in phloem can move up to 100 cm per hour. - Food substances made by the plant are found only in the phloem.

What does it mean when we say water is a polar molecule?

- Each molecule is attracted to other water molecules. - It has one end with a weak positive charge and an opposite end with a weak negative charge.

Stomata are openings on a leaf that allow the uptake of carbon dioxide and the release of water vapor. Which of these are components of a stomatal apparatus?

- Guard cells - Stoma

Select all true statements about osmosis.

- It involves the movement of water molecules. - It requires a membrane.

Which of these statements is true about osmotic potential?

- It is a component of the water potential. - The pressure potential needed to offset it is called osmotic pressure. - It is a function of solute concentration.

Select all true statements about transpiration.

- It is driven by evaporation - It creates tension in the xylem OR - It is the most important force that helps move water across long distances in plants. - It pulls water upward from roots to leaves.

Which of these are true about a diffusion gradient?

- Molecules will move by diffusion from areas of high concentration to areas of lower concentration. - There are adjacent areas with higher and lower concentrations of some molecule.

Which of these are part of the pathway water takes through a plant?

- Movement from soil to roots through osmosis - Evaporation from leaf tissues and transpiration into the atmosphere - Movement across a membrane at the endodermis - Movement up the stem and into the leaves in the xylem

Which of these are essential elements for plant growth?

- Nitrogen - Calcium - Sulfur - Magnesium - Potassium - Iron - Phosphorus

Which of these statements is true about evaporative cooling in a leaf?

- Plants lose water during the process. - The evaporation of water molecules cools the plant cells. - Stomata must be open for the process to work.

Which of the following correctly describe how mangroves and saltbush plants survive in high salt areas?

- They excrete excess salt from specialized salt glands. - They accumulate large quantities of mannitol and proline to maintain the ability to get water via osmosis.

Which of these things happens at the sink end of pressure-flow translocation of dissolved sugars?

- Water enters the xylem, where it can return to the source and be recycled or transpired. - Water passively diffuses out of phloem cells. - Sugar is actively removed from phloem cells.

Water potential is calculated as Ψw=Ψs+Ψp. A cell has a solute potential (Ψs) of -0.5 MPa and a pressure potential (Ψp) of 0.2 MPa. What is the water potential of this cell?

-0.3 MPa

About how much water does a hardwood tree need to produce one pound of wood?

120 gallons

While plants get carbon, oxygen, and hydrogen from CO2 and water, there are _____ other minerals that are required for normal plant growth.

15

How much of the weight of young plant cells is made up of water?

90%

Which of these cells is turgid?

A

Which of these diagrams depicts a guard cell during photosynthesis?

A

Match the letter to the correct part of the stomatal apparatus.

A - Guard Cells B - Stomatal Opening C - Subsidiary Cell

In the pressure-flow hypothesis, what is the main factor driving the movement of dissolved organic solutes?

A concentration gradient between source and sink

What is a diffusion gradient?

A situation where adjacent areas have different concentrations of a molecule

What is it called when plants expend energy to move substances across a membrane?

Active transport

What is the first step in phloem-loading?

Active transport of sugars into sieve tube members (phloem)

Even in water that is not being stirred, there is constant motion of the molecules. This ________ movement of molecules can be observed by releasing a small droplet of dye into a water bath and observing the distribution of pigment particles over time.

Brownian

Normally, water traveling through the endodermis must cross a semipermeable membrane. However, when evaporative demand is high, water and solutes are thought to be passively pulled through the roots by what process?

Bulk Flow

Which property of water is best illustrated by this diagram?

Capillary Action

____________ strips in root endodermal cells contain suberin to limit the movement of minerals and water.

Casparian

Water moves through fine roots largely in the spaces between cells and cellulose fibers in the cell wall. When water moving through roots reaches the endodermis, what feature forces the water to diffuse across a semipermeable membrane, therefore filtering the dissolved solutes?

Casparian strips

During photosynthesis, what is happening in guard cells that brings about a change in water potential?

Cells expend energy to get potassium from epidermal cells. This lowers the water potential and increases turgor pressure.

Which of the following describes a semipermeable membrane?

Different substances pass through the membrane at different rates.

What do we call the movement of molecules from a region of higher concentration to one of lower concentration?

Diffusion

What happens at the sink end of sieve tubes during pressure-flow driven translocation of dissolved sugars?

Dissolved sugars are actively removed, leading to passive exiting of water at the sink through osmosis.

Explain the "active" in active transport.

Energy is required to move things across a membrane.

Molecules that have become evenly distributed throughout a space (through random motion), are said to be in what state?

Equilibrium

What prevents leaves from overheating in the sun on a hot day?

Evaporative cooling

True or false: Water moves from the soil into the plant only if the water potential of the soil is less than the root.

False

If diffusion is driven by Brownian movement of molecules, which state of matter should have the fastest rate of diffusion?

Gas

Diffusion happens at different speeds in different states of matter. Put the states of matter in order from fastest diffusion speed at the top to the slowest at the bottom.

Gas Liquid Solid

Stomata allow plants to take up CO2 into their leaves and as a result, release water vapor into the atmosphere. The _______________ cells control when the stomata are open and when they are closed.

Guard

Which of these organisms is able to recycle water through its circulatory system, thus using water most efficiently?

Humans

Which element is not one of the nine macronutrients required by plants?

Iron

Which of the following statements about diffusion is true?

Larger molecules diffuse more slowly than smaller molecules.

Which of the following statements correctly states a difference between macronutrients and micronutrients?

Macronutrients are present in larger quantities in plants.

The diffusion of water molecules across a semipermeable membrane is called __________.

Osmosis

In the diagram, fluid is rising in the neck of the tube as water moves across the membrane, down a concentration gradient. Which component of the water potential is driving the water across the membrane?

Osmotic potential

What part of the plant has the aphid in the photograph pierced with its mouthparts?

Phloem

Where does translocation of food substances occur in plants?

Phloem

Because water molecules are _________ they are attracted to other molecules with weak electric charges.

Polar

When some plants are pruned in the spring, water will exude from the cut ends. What causes this?

Root pressure

Mangroves like to live where _______________ concentrations are very high. They survive by accumulating large quantities of organic solutes, which are so concentrated that the plants can still get water into their cells via osmosis.

Salt

In addition to the carbon and oxygen plants get from CO2 and the hydrogen they get from H2O, there are several other minerals necessary for normal plant growth. Where do those come from?

Soil

The minerals needed for plant growth are typically dissolved in water and taken up by plant roots from the

Soil

What is Brownian movement?

The constant motion of molecules

What is diffusion?

The movement of particles from an area of high concentration to an area of low concentration.

During capillary action, the water will rise higher in which situation?

The narrower the capillary tube is

Water is cohesive. Which statement correctly describes this feature of water molecules?

They are attracted to each other.

What is the name of the process in which water vapor is lost from the internal leaf atmosphere?

Transpiration

When stomata open and close in response to temperature, humidity, or light intensity, what process will change along with it?

Transpiration Rate

The most abundant and important substance in any plant cell is _________________, without which enzymes wouldn't function, there would be no chemical activities, including photosynthesis, and herbaceous plants would lose their rigidity.

Water

What type of gradient enables transport from roots to shoots in the xylem?

Water Potential

In contrast to osmosis, which requires no energy to move things across membranes, some substances require _________________ transport to to be moved into or out of a cell.

active

Evaporation of water in a leaf creates negative pressure in the xylem. This causes water to ______ the roots.

be pulled up the stem from

Typically water traveling through roots is forced through a membrane at the endodermis. However, when large quantities of water are moving through a plant on a hot day, water might travel by _________ flow, where little osmosis is taking place.

bulk

Because polar water molecules attract each other, water is said to be

cohesive

When molecules are distributed evenly through random movement, they are in a state of ____________

equilibrium

The elements that are most abundant in plants are called _______,whereas the rest of the elements present in lower quantities are called _______.

macronutrients; micronutrients

Once sugars have been loaded into phloem by active transport, water moves into the cells due to ________________, pushing the sugars through the phloem down a concentration gradient.

osmosis

Plasmolysis would occur when a cell is ______.

placed in a very concentrated solution.

If a cell loses water, the cell membrane pulls away from the wall in a process called

plasmolysis

In the water potential formula (Ψw=Ψs+Ψp), the term Ψp is referred to as _______________potential

pressure

All plant cells have membranes that are ________, meaning different things move through them at different rates.

semipermeable

Guard cells are like two sausage-shaped balloons that are joined at each end. The part of the cell wall nearest the opening is ________ than the rest of this wall, allowing each stoma to be opened and closed by means of changes in guard cell turgor pressure.

thicker

Water helps to move dissolved sugars during a process called ___________ carried out by the phloem.

translocation

Water is pulled through the xylem by the process of

transpiration

Water transport in xylem is driven by evaporation from leaves, a process called

transpiration

A cell that is swollen with water is said to be _______.

turgid

The pressure that builds as water enters plant cells, called _______________ pressure, is what makes plant cells rigid. If that pressure is lost, plants wilt.

turgor

Turgor pressure requires cell ______ the expansion of cells as they take up water.

walls to constrain

Water and dissolved minerals are carried through the vascular tissue called

xylem