MB Ch32

Can you trace the path that water follows as it moves through a plant?

1) Into the roots 2) Up the xylem 3) In a film on the surface of a leaf 4) In the air spaces inside the leaves 5) Out the leaf pores

Worldwide, about __________% of all fresh water is used for crop irrigation.

75 With a growing world population, the need for irrigation may be even greater in the future.

_____ describes the tendency of water molecules to stick to the fibers of plant cell walls.

Adhesion

_____ is responsible for the movement of sugars from leaves to taproots; _____ is responsible for the movements of sugar from taproots to leaves.

Bulk flow ... bulk flow In both situations the mechanism of movement is the same.

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

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.

_____ describes the tendency of water molecules to stick to each other.

Cohesion

Both epiphytes and parasitic plants grow in association with another plant. What is the difference between these two groups?

Epiphytic plants simply live attached to their hosts, whereas parasitic plants obtain minerals and/or nutrients from their hosts. Epiphytic plants attach to their host plants, usually to obtain better lighting, but do not directly harm the host plant. Parasitic plants obtain nutrients from their host plant, which can cause some harm.

What happens to the xylem system during drought, when water is scarce?

Falling moisture levels in the leaf cause the guard cells to change shape, closing the stomata. This reduces water loss from the plant.

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

Guard Guard cells regulate the opening and closing of stomata.

_____ bonds are responsible for the cohesion of water molecules.

Hydrogen Hydrogen bonds among water molecules are responsible for the tendency of those molecules to stick together.

You conduct an experiment to learn more about how water moves within the plant body. You take a common houseplant and cut the stem off about one inch above the soil surface. Water begins collecting at the cut--in the stem stump--as if some force is pushing the water up through the roots and remaining stem. How could you best explain this observation?

Minerals, unable to move up to the leaves, are accumulating in the root, which causes water to rush in due to osmosis. Water enters the roots to dilute the solutes (osmosis). This excess water produces pressure that pushes water up against gravity. This pressure is called root pressure.

A developer decides to plant pine trees in a barren hill adjacent to his property. Unfortunately, the trees are not doing very well; in fact, many are starting to die, even though there are ample nutrients and water in the area. What is the likely culprit of the deaths in this tree plantation?

Mycorrhizal fungi are not present in the soil. If the fungus is not free-living in the soil, or the soil is not inoculated at the time of planting, the trees may not do well. Roots can be transformed into mycorrhizae only if they are exposed to the appropriate species of fungus. For example, if seeds are collected in one environment and planted in foreign soil, the plants may show signs of malnutrition resulting from the absence of the plants' natural mycorrhizal partners.

_____ transport(s) sugars from leaves to, for example, taproots.

Phloem Phloem is responsible for the transport of sugars.

Root pressure is positive pressure that helps to push water up out of the roots and into the aboveground plant. How is it formed?

Root cells bring mineral nutrients into the root using active transport. This sets up a concentration gradient that draws water into the root by osmosis.

How do root hairs aid in water uptake in roots?

Root hairs increase the surface area of a root, thus increasing the root's absorptive capacity. As extensions of the root epidermal cells, root hairs greatly increase the uptake surface area of a root.

What is a reason that stomata would close during the day?

Stomata close when the plant is suffering a water deficiency. When the plant is suffering a water deficiency, guard cells will close the stomata to prevent further water loss.

Imagine that you spray a large, actively growing tree with a sealant that instantly seals off all of the stomata. What would happen in the xylem system?

The flow of xylem sap would stop, except for some minimal upward movement that might be generated by root pressure.

_____ describes the process by which water is lost from plants by evaporation.

Transpiration

_____ provide(s) the major force for the movement of water and solutes from roots to leaves.

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.

Xylem tissues create a system of very thin pipes that connect plant roots and leaves. Which option best describes the nature and function of xylem tissue?

Xylem is dead tissue. The pipes convey xylem sap from the roots to the leaves. Active transport is not important in moving xylem sap.

Which of the following is a difference between transport by xylem and transport by phloem?

Xylem sap moves up, and phloem sap moves up or down. The direction of movement in xylem is from roots to leaves. Phloem sap is transported throughout the plant and moves from source to sink.

In an apple tree that is producing sugars, sugar might flow from __________ to ___________.

a leaf; a developing apple A leaf is a sugar source, and a developing fruit is a sugar sink.

The diagram below shows a cross-section of a plant's root. Can you identify the different paths through which water can flow within the root?

a) A path through the cytoplasm of root cells b) A path though cell walls c) Waxy barrier d) Xylem e) Root hair

Can you correctly place the labels in this concept map that summarizes symbiotic relationships in plants?

a) mycorrhizae b) epiphytes c) parasitic plants d) plant roots e) nitrogen-fixing bacteria

The figure below shows nutrient uptake in a tree. Use this figure to help you fill in the table. a)Requirement:____ How plant obtains: Enters through roots; exits through leaf pores via transpiration. Function: Maintains cell turger b)R____ HPO: Exits through leaf pores; some enters through leaves and roots. F: Product of photosynthesis; required for cellular respiration. c)R_____ HPO: Enters through roots. F: Required for photosynthesis. d)R_____ HPO: Enters through roots. F: Component of xylem sap; used in various molecules such as enzymes. e)R____ HPO: Strikes leaves and other photosynthetic organs. F: Required for photosynthesis

a) water b) oxygen c) carbon dioxide d) minerals e) sunlight

At a sugar sink, sugar is removed from phloem by _____.

active transport Active transport moves sugar from phloem into a sugar sink.

The water pressure that pushes water and sugar from sugar source to sugar sink is referred to as _____.

bulk flow Bulk flow is the force responsible for the translocation that occurs in phloem.

Guard cells __________.

can regulate the rate of transpiration Guard cells control the rate of transpiration by causing the stomata to be open or closed.

Which of the following substances does the plant obtain from the air?

carbon Carbon is obtained in the form of atmospheric CO2.

Nitrogen-fixing bacteria in the soil __________.

convert atmospheric nitrogen to ammonia Nitrogen fixation is the conversion of N2 (atmospheric nitrogen) to NH3.

A(n) ____ is a chemical element that a plant must obtain from the environment in order to grow and reproduce.

essential element

What is the main source of energy that moves water upward in the trunk of a tree?

evaporation of water by the sun As water evaporates and moves out of the leaf through the stomata, more water is drawn up by transpirational pull.

In this modern age of science, which of the following shows the most promise in producing crops with a higher yield?

genetic engineering of crop plants Genetic engineering allows us to incorporate genes for specific traits that improve the efficiency of the crop plant.

A __________ is a sugar source.

green leaf Leaves produce sugar. Leaves are the primary sugar sources in most mature plants. A storage organ, such as a tuber or a bulb, may be a source or sink, depending on the season.

A(n) _____ is a nutrient mixture that is composed of naturally-occurring or manufactured mineral compounds.

inorganic fertilizer

The sundew plant has to digest insects because __________.

it obtains nitrogen from their bodies that it cannot get from the soil The sundew lives in soil that is poor in nitrogen and other nutrients; thus, it is adapted to obtain its nitrogen from the digestion of insects.

A(n) ____ is an element, such as carbon or calcium, that a plant must obtain in relatively large quantities.

macronutrient

When you add "plant food" to your potted geraniums, you are actually providing the plant with _____.

minerals Of the essential nutrients required by plants, most are minerals.

Which of these are symbiotic associations?

mycorrhizae Mycorrhizae are mutualistic associations of roots and fungi.

Mutually beneficial associations between roots and soil fungi are called _____.

mycorrhizae Mycorrhizae are mutually beneficial associations between soil fungi and roots.

Fertilizers are usually enriched in __________.

nitrogen, phosphorus, and potassium Farm and garden soils are most likely to be deficient in these macronutrients.

By trapping insects, carnivorous plants obtain __________, which they need __________.

nitrogen; to make protein The manufacture of protein requires nitrogen.

In general, stomata are __________ during the day and __________ at night.

open; closed In general, stomata are open during the day and closed at night. This prevents the plant from needlessly losing water when it is too dark for photosynthesis.

A(n) ____ is a nutrient mixture that is composed of chemically complex carbon-containing matter, such as compost.

organic fertilizer

Water moves into phloem by _____.

osmosis Water moves down its concentration gradient into phloem by osmosis.

Which of these processes is responsible for leaves being considered sugar sources?

photosynthesis Leaves produce sugar via photosynthesis.

The channels indicated by the pointer, are _____.

plasmodesmata Water and ions can pass from cell to cell via these channels. Also, recall that plasmodesmata are a type of cell junction.

Which of the following is NOT an essential plant micronutrient?

potassium Potassium is one of the essential macronutrients needed by plants.

Sugar moves from leaves into the _____ of _____ by _____.

sieve-tube members ... phloem ... active transport

In a sugar sink, such as a taproot, sugar is converted into _____.

starch Plants store carbohydrates in the form of starch.

The solute most abundant in phloem sap is _____.

sugar Phloem transports sugar from a sugar source to a sugar sink.

A student is performing a chemical analysis of xylem sap. This student should not expect to find much _____.

sugar Phloem, not xylem, transports sugar.

Guard cells actively open and close the stomata of leaves. What delicate internal balance do these guard cells control with their actions?

the balance between water uptake and gas exchange Guard cells control the internal water balance and oxygen/carbon dioxide balance within the plant.

When food is labeled 'organic' it means that _____.

the farmer grows food and processes it according to strict guidelines established and regulated by the USDA Organic farming relies on the principles of ecology rather than on synthetic chemicals or pesticides, and these guidelines are enforced by the USDA.

Stomata open during the day in response to __________.

the uptake of K+ by guard cells The uptake of K+ makes guard cells turgid, causing the stomata between the cells to open.

One of the major problems encountered when growing genetically modified (GM) crops is __________.

their extraordinary demand for nitrogen This has to be supplied in the form of commercial fertilizers, and these are expensive to produce.

Water vapor moves out of leaves through open stomata. This process is known as _____.

transpiration

An undergraduate student had a terrarium on her windowsill containing various houseplants. She wondered why the glass was often fogged with water droplets. A friend who had taken a biology class, tried to explain that it was because of _____.

transpiration By definition, transpiration is the evaporation of water from a plant.

This is an animation of the movement of water and ions through the root _____.

via the apoplastic (extracellular) route The animation illustrates water and ions moving along a cell wall continuum.

The rate of transpiration is expected to be greatest on a _____ day.

warm and dry The rate of transpiration will be greatest on a day that is sunny, warm, dry, and windy because those are the environmental factors that increase the evaporation of water.