Plant science chapter 9

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

Order the steps that lead to early morning guttation, beginning with the first step at the top.

1. root xylem accumulates high concentrations of ions 2. water follows the ions into the interior of the root 3. water is pushed upward in the xylem 4. droplets of water are observed on leaves

Put in order the sequence of events as water moves through a plant. Start with water entering the plant at the top of the list.

1. water enters the roots from the soil via osmosis 2. water crosses a semipermeable membrane at the endodermis as it enters the central root system of the plant 3. water is transported up the stem and into the leaves through xylem 4. water evaporates from the leaves, leaving through the stomata

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%

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

A concentration gradient between source and sink

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

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) A high-concentration of food substances at a source

What is a diffusion gradient?

A situation where adjacent areas have different concentrations of a molecule

What is the first step in phloem-loading?

Active transport of sugars into sieve tube members (phloem)

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

________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

micronutrients

Chlorine, iron, manganese, zinc, boron, copper, molybdenum

Select all of these examples that can be signs of a nutrient deficiency in plants.

Color loss in leaves Dead spots Stunted growth

Manganese deficiency in plants

Dead spots become scattered over the leaf surface, and the effects are confined to the youngest leaves.

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.

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.

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

What structure permits guttation?

Hydathodes

What must happen for a walnut seed to swell and break through its tough outer seed coat?

Imbibition of water

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

Iron

Which of these are essential elements for plant growth?

Iron Nitrogen Sulfur Magnesium Calcium Potassium Phosphorus

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

Select all true statements about transpiration.

It is driven by evaporation. It creates tension in the xylem.

Select statements about transpiration.

It is the most important force that helps move water across long distances in plants. It pulls water upward from roots to leaves.

Nitrogen deficiency in plants

Leaves lose color, beginning with the oldest ones.

Sulfur deficiency in plants

Leaves turn pale green with dead spots, and veins become lighter than the rest of leaf

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

Macronutrients are present in larger quantities in plants.

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 up the stem and into the leaves in the xylem Movement across a membrane at the endodermis

Macronutrients

Potassium, calcium, magnesium, phosphorus, sulfur, nitrogen

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

Root pressure

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

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?

Stoma Guard cells

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

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

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

Temperature Light intensity CO2 concentration Humidity

What is Brownian movement?

The constant motion of molecules

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

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

What is diffusion?

The movement of molecules from an area of higher concentration to an area of lower concentration

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

The narrower the capillary tube is

Which of these things are happening during the imbibition of water by a wooden stake?

The wood starts to swell as it absorbs water. As cellulose molecules get wet, they develop an electrical charge, attracting more water molecules.

Which of these are true about a diffusion gradient?

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

Potassium deficiency in plants

There is yellowing of the leaves, especially at the margins. Lower leaves often have brown tips.

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

They are attracted to each other.

What are the advantages of sunken stomata for plants living in arid environments?

They can be filled with epidermal hairs that further reduce water loss. They reduce water loss.

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.

dew

Water condenses from the air onto the leaves of plants. It is typically observed on a cool morning after a humid day.

Guttation

Water is lost from leaves and expressed through the hydathodes. It is typically observed when a cool night follows a warm, humid day.

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

active

Some large molecules develop electrical charges when they get wet. Water molecules have their own electrical charges which causes them to ______ to the large particles.

adhere

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

be pulled up the stem from

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

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

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

Some desert plants have their stomata sunken into stomatal______which help reduce water loss.

crypts

Guttation is a process whereby droplets of water are expressed by the hydathodes. ______is water that has condensed from the air onto plant leaves.

dew

Cellulose develops ________ charges when wet, which attract water molecules. The water molecules are said to adhere to the charged cellulose.

electrical

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

equilibrium

Root pressure can force water droplets to exude from leaves in a process called________

guttation

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

humans

If a cool night follows a warm, humid day, some plants will experience guttation by which water droplets are produced at the tips of leaves in structures called

hydathodes

The first step in seed germination is when a lot of water moves into the seed through the process of ______________ , causing it to swell and begin growth

imbibition

Where does translocation of food substances occur in plants?

in the phloem

In order to determine the nutritional requirements of plants, scientists grow plants in a series of hydroponic solutions, each of which______

is missing one element

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

The diffusion of water molecules across a semipermeable membrane is called

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

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

polar

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

pressure

Root______is one means by which water moves through plants.

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

All plant cells have membranes that are______meaning different things move through them at different rates.

semipermeable

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

soil

When plants cannot access water to keep up with the demands of transpiration, they experience water stress. If this happens,_____will close in response to the stress.

stomata

Hydroponic cultures used for studies of mineral requirements involve plants with roots___

suspended in water

What will stomata do when plants are experiencing water stress?

they will close

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

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

True or false: Germinating seeds swelling too many times their size via the imbibition of water can generate forces powerful enough to split rock.

true

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

turgid

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 of H2O

Water and dissolved minerals are carried through the vascular tissue called

xylem

What vascular tissue carries water molecules and dissolved minerals?

xylem