BY 124- Ch 37 Gibbons

Why do plants need minerals from the soil?

• Nitrogen, phosphorus, potassium, and other minerals are essential for plant growth

• They play important roles in both cell structure and cell function

Water, air, and soil minerals all contribute to plant growth

• 80–90% of a plant’s fresh mass is water

• 96% of a plant’s dry mass is from CO2 assimilated into carbohydrates during photosynthesis

• 4% of a plant’s dry mass is inorganic substances

  from soil

Essential Elements

• Definition: Chemical elements that are required for reproduction and completion of life cycle

• There are 17 essential elements for plants

• Researchers use hydroponic culture to determine which chemical elements are essential

Nine essential macronutrients

• Nine of the essential elements are macronutrients (plants require them in relatively large amounts)

• carbon, oxygen, hydrogen, nitrogen, phosphorus, sulfur, potassium, calcium, and magnesium

• Nitrogen contributes the most to plant growth and crop yields

Eight essential micronutrients

• Eight essential elements for plants are micronutrients (required only in very small amounts)

• chlorine, iron, boron, manganese, zinc, copper, nickel, and molybdenum

• Micronutrients function as cofactors, nonprotein helpers in enzymatic reactions

Where does the majority of the dry mass of a plant come from?

A. Nutrients, like nitrogen, from the soil

B. Water from the soil

C. CO2 from the air

D. There’s no way to know.

C. CO2 from the air

Mineral deficiency

• Depend on the nutrient’s function and mobility

  within the plant

• The most common deficiencies are those of

  nitrogen, potassium, and phosphorus

Global Climate Change and Food Quality effect on plants

• Climate change (increased CO2 and rising temps)

  is predicted to cause (or is causing):

  • Increase in Global food production but only in certain parts of the world

  • Decline in the nutritional quality of wild and crop plants, possibly due to insufficient uptake of nutrients by plants

  • Decline in pollinators, maybe from declining quality of their food source

The difference between macronutrients and micronutrients is that _____.

A. the molecules of macronutrients are larger than those of micronutrients

B. macronutrients are essential for physiological function of plants, while micronutrients amplify plant growth if they are available

C. macronutrients are needed for growth, while micronutrients are needed only for reproduction

D. macronutrients are required by plants in larger quantities than are micronutrients

D. macronutrients are required by plants in larger quantities than are micronutrients

Symbiosis with both species benefitting from close interactions

Mutualisms

Plants-Bacteria Mutualism

• Plants have mutualistic relationships with soil bacteria

• Dead plants provide energy needed by soil-dwelling microorganisms

• Secretions from living roots support a wide variety of microbes in the near-root environment

Fungus-Bacterium Mutualism

• Lichen- mutualistic association between a fungus and a photosynthetic partner

• The cyanobacterium provides food (through photosynthesis); the fungus provides anchorage, protection, minerals, and water

Animal-Bacterium Mutualism

• Puffer fish form a mutualism with a bacterium that produces a nerve toxin called tetrodotoxin

• The fish gains a chemical defense, the bacteria live in a

  high nutrient, low competition environment

Animal-Fungus Mutualism

• Leaf-cutter ants harvest leaves which they feed to

  fungal gardens in their nests

• The ants are able to eat part of the fungus

Plant/Algae–Bacterium Mutualism

• Aquatic fern Azolla forms mutualisms with nitrogen-fixing

  cyanobacteria

• The cyanobacterium provides the fern with nitrogen, while

  the fern provides it with food (sugars)

Plant-Fungus Mutualism

• Most plant species have mutualisms with mycorrhizal fungi

• The fungus absorbs food (sugars); the fungus expands the

  absorptive surface of the plant roots for uptake of water and minerals

Plant–Animal Mutualism

• Acacia plants provide carbohydrate–rich nectar to ants; ants protect them from predators and competitors

Rhizobacteria

• Rhizobacteria- mutualistic bacteria that live in close association with plant roots

• Plants provide food (sugars); rhizobacteria help the plant in many ways

  • producing antibiotics that protect roots from disease

  • absorbing toxic metals or increasing nutrient availability

  • converting nitrogen gas into forms usable by the plant

  • producing chemicals that stimulate plant growth

Bacteria in the Nitrogen cycle

• Nitrogen is required in large amounts by plants, and is abundant in the atmosphere as N2

• Nitrogen deficiency usually the most limiting nutrient to plant growth

• Plants can only absorb nitrogen as NO3– or NH4+

• Some soil nitrogen derives from inorganic sources, but most comes from the activity of soil bacteria

Nitrogen cycle

natural processes that transform nitrogen and nitrogen-containing compounds

Nitrification

• Soil NO3– is formed in a two-step process called nitrification

• Nitrifying bacteria oxidize ammonia (NH3) to nitrate to NO3–

• Plant enzymes convert NO3– to ammonium (NH4+), which is incorporated into organic compounds

How do plants acquire N in a usable form? (NH4+)

• Nitrogen-fixing bacteria convert N2 into NH3 (ammonia); NH3 picks up an H+ in the soil solution and forms NH4+

• Ammonifying bacteria break down dead organic

  compounds and release NH4+

Bacteria and Nitrogen Fixation

• Nitrogen is abundant in the atmosphere but unavailable to plants because of the triple bond between atoms in N2

• Nitrogen fixation by bacteria (like Rhizobium) make atmospheric Nitrogen available to plants

• The rhizobia form nodules on the roots of legumes in a mutualistic relationship.

Nitrogen Fixation and Agriculture

• Crop rotation takes advantage of the agricultural benefits of symbiotic nitrogen fixation

• When legumes (with Rhizobia) are rotated with non-legumes (like corn), you can recover fixed nitrogen that was depleted by a nitrogen depleting crop.

Fungi and Plant Nutrition

• Mycorrhizae are mutualistic associations of fungi and roots

• The host plant provides the fungus with sugar

• The fungus increases the surface area for water and mineral uptake by the host plant by promoting root branching

Mycorrhizae and Plant Evolution

• Early land plant fossils show associations with mutualistic fungi (from about 400 to 500 million years ago, which would be a very harsh environment)

• Early plants lacked the ability to extract essential nutrients from the soil, while fungi were unable to produce carbohydrates

• The mycorrhizal association between early land plants and fungi allowed both to exploit the terrestrial environment

The most limiting nutrient for plants is usually

A. Nitrogen

B. Carbon

C. Phosphorous

D. Potassium

E. Sodium

A. Nitrogen

Agricultural and Ecological Importance of Mycorrhizae

• Farmers inoculate seeds to promote mycorrhizal mutualisms with their crops

• Garlic mustard (invasive exotic plant) disrupts interactions between native plants and their mycorrhizal fungi, by inhibiting growth of mycorrhizae

Legumes (such as soybeans) commonly obtain their nitrogen through a mutualistic association with _____.

A. nitrifying bacteria, which oxidize ammonium to nitrite

B. ammonifying bacteria, which convert organic nitrogen to ammonium

C. denitrifying bacteria, which convert organic nitrite to ammonium

D. nitrifying bacteria, which extract nitrogen from decomposing animals

E. nitrogen-fixing bacteria, which convert gaseous nitrogen to ammonium

F. Mycorrhizae, which increase the mass of their roots

E. nitrogen-fixing bacteria, which convert gaseous nitrogen to ammonium

Other Nutritional Adaptations in Plants:

• Some plants have nutritional adaptations that use other organisms in nonmutualistic ways

• Epiphytes, parasitic plants, and carnivorous plants

Epiphyte

• An epiphyte grows on another plant and obtains water and minerals from rain

• Epiphytes do not tap into hosts for sustenance

• Examples include staghorn ferns, bromeliads, and many orchids

Parasitic plants

• Parasitic plants absorb water, minerals, and sugars from their living host plant

• Some species photosynthesize, but others rely entirely on the host plant for sustenance

• Some species parasitize the mycorrhizal hyphae of other plants

Carnivorous Plants

• Carnivorous plants have adaptations for trapping insects and other small animals

• They are photosynthetic, but obtain nitrogen by killing and digesting mostly insects

True or False: Parasitic plants and carnivorous plants are non-photosynthetic

A. True

B. False

B. False

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

• sugars; because they can't make enough in photosynthesis

• nitrogen; to make protein

• nitrogen; to make sugar

• phosphorus; to make protein

• water; because they live in dry soil

nitrogen; to make protein

Which of the following nutrient-deficiency symptoms is correctly matched with the deficient nutrient?

• poor growth; nitrogen

• wilting; boron

• general chlorosis in young leaves; carbon

• mottling of older leaves, with drying of leaf edges; calcium

• reduced internode length; zinc

reduced internode length; zinc

A cattle farmer is forced to use antibiotics to treat an outbreak of bacterial infections in his herd of cattle. The antibiotic is excreted by the cattle in their urine and feces and ends up in an irrigation ditch that provides water for a nearby soybean (a legume) farmer. The soybean farmer begins to notice that his soybean crop is not growing as well as usual.

What might be the cause of this change in the growth of the soybeans?

• None of the listed responses is correct.

• The antibiotic is toxic to the soybean plants and stunts their growth.

• Bacteria in the water that contained the urine and feces affects soybean growth.

• The antibiotic got into the soil and killed many of the bacteria that provide usable phosphorous to the soybeans.

• The antibiotic got into the soil and killed many of the bacteria that provide usable nitrogen to the soybeans.

The antibiotic got into the soil and killed many of the bacteria that provide usable nitrogen to the soybeans.

Which of the following statements is correct regarding mycorrhizae?

• Arbuscular mycorrhizae form a dense sheath over the surface of a plant’s roots.

• Arbuscular mycorrhizae are less common than ectomycorrhizae.

• Ectomycorrhizae penetrate the cell walls of a plant’s root cells.

• Ectomycorrhizae form a dense sheath over the surface of a plant’s roots.

• Ectomycorrhizae are the most common type of mycorrhizae.

Ectomycorrhizae form a dense sheath over the surface of a plant’s roots.

Soil can easily become deficient in ________, because these ions are negatively charged and do not stick to negatively charged soil particles.

• magnesium

• potassium

• nitrate

• calcium

• ammonium

nitrate

Which of the following statements correctly describes the relationship between plants and the mutualistic bacteria associated with them?

• Endophytes and rhizobacteria both depend on plants for various nutrients.

• Endophytes live between cells within a plant.

• Endophytes and rhizobacteria both can enhance plant growth.

• All of the listed responses are correct.

• Rhizobacteria live in the rhizosphere, the soil surrounding a plant’s roots.

All of the listed responses are correct.

Crop rotation benefits agriculture by __________.

• restoring the concentration of fixed nitrogen in the soil

• using up all the fixed nitrogen in the soil

• None of the listed responses is correct.

• replenishing the concentration of magnesium in the soil

• replenishing the concentration of phosphorous in the soil

restoring the concentration of fixed nitrogen in the soil

Nitrogen fixation is __________.

• using nitrogen to build molecules such as proteins and nucleic acids

• converting nitrogen in the air to a form usable by plants

• performed by fungus inhabiting root nodules

• recycling nitrogen from organic matter in the soil

• absorbing N₂ from the soil

converting nitrogen in the air to a form usable by plants

Fertilizers are usually enriched in __________.

• iron, manganese, and zinc

• calcium and boron

• all essential nutrients

• nitrogen, phosphorus, and potassium

• molybdenum, copper, and magnesium

nitrogen, phosphorus, and potassium

Which of the following statements correctly describes macronutrients?

• Examples of macronutrients are iron, zinc, and copper.

• Plants require macronutrients in relatively small amounts.

• Plants require macronutrients in relatively large amounts.

• Macronutrients function in plants mainly as cofactors.

• The macronutrient nitrogen contributes the least to crop growth and yield.

Plants require macronutrients in relatively large amounts.

All of the following statements regarding soil pH are correct except ________.

• Soil pH below 5 allows toxic aluminum ions to be absorbed by plants.

• Plants prefer basic soil pH.

• Soil pH should be matched to a crop’s mineral needs.

• Soil pH influences mineral availability.

• Plants prefer slightly acidic soil pH.

Plants prefer basic soil pH.

Which of the following processes occurs in the nodules of legume roots?

• pH regulation

• cation exchange

• nitrogen fixation

• All of the listed responses are correct.

• carbon fixation

nitrogen fixation

Which is true regarding mineral deficiency symptoms in plants?

• Deficiency symptoms of immobile nutrients will show up first in older organs.

• Deficiency symptoms of freely moving nutrients will show up first in younger organs.

• Symptoms of mineral deficiency always show up in older leaves first.

• Growing tissues would show signs of mineral deficiency of mobile nutrients after older tissues.

• Symptoms always show up in younger leaves first.

Growing tissues would show signs of mineral deficiency of mobile nutrients after older tissues.

Which of the following nutrient-deficiency symptoms is correctly matched with the deficient mineral?

• chlorosis at the tips of older leaves; nitrogen

• chlorosis between veins; carbon

• reduced internode length; iron

• None of the listed pairs is matched correctly.

• very slow development; magnesium

• poor growth; calcium

chlorosis at the tips of older leaves; nitrogen

“Smart plants” are genetically engineered plants that can _________.

• fix gaseous nitrogen into nitrogen usable by a plant

• eat insects and small animals to supplement their diets

• None of the listed responses is correct.

• signal, only after damage to the plant has occurred, when a nutrient deficiency is imminent

• increase the surface area for absorption by a plant’s roots

• signal, before any damage to the plant has occurred, when a nutrient deficiency is imminent

signal, before any damage to the plant has occurred, when a nutrient deficiency is imminent

Cation exchange is the process in which _________.

• humus develops from dead organisms

• mineral nutrients are added to the soil

• anions enter the soil solution by being displaced by other anions

• cations enter the soil solution by being displaced by other cations, particularly H⁺

• soil is carried away from different areas by wind and rain

cations enter the soil solution by being displaced by other cations, particularly H⁺

Many people add various types of fertilizers to their plants to facilitate growth. What does fertilizer contain that facilitates plant growth?

• Fertilizer contains amino acids, which facilitate plant growth.

• Fertilizer contains organic carbon, which plants can use for growth.

• All of the listed responses are correct.

• Fertilizer contains minerals that are essential for healthy plant growth.

• Fertilizer contains water, which plants need for growth.

Fertilizer contains minerals that are essential for healthy plant growth.

The biological process that produces 96% of the dry mass of a plant is called __________.

• photosynthesis

• cation exchange

• oxidation

• transpiration

• respiration

photosynthesis

The relationship between mycorrhizae and plants benefits both organisms because _________.

• the host plant depletes the fungus of sugar, and the fungus reduces the surface area of the plant’s roots for nutrient absorption

• the host plant provides the fungus with a steady supply of minerals, and the fungus has no effect on the plant

• the host fungus provides the plant with a steady supply of sugar, and the plant increases the surface area of the fungus for nutrient absorption

• All of the listed responses are correct.

• the host plant provides the fungus with a steady supply of sugar, and the fungus increases the surface area of the plant’s roots for nutrient absorption

the host plant provides the fungus with a steady supply of sugar, and the fungus increases the surface area of the plant’s roots for nutrient absorption

If a plant's leaves are yellowing, it may be that the plant is deficient in the elements needed to make chlorophyll, one of which is __________.

• copper

• phosphorus

• molybdenum

• magnesium

• sulfur

magnesium

If a plant is deficient in __________, it will not be able to make DNA.

• iron

• phosphorus

• magnesium

• sulfur

• manganese

phosphorus

Legumes (members of the pea family) have roots with swellings called nodules that __________.

• increase the surface area for water uptake

• produce antibiotics that protect the plant from soil bacteria

• contain nitrogen-fixing bacteria

• provide a steady supply of sugar to the host plant

• form fungal hyphae

contain nitrogen-fixing bacteria

The most abundant gas in our atmosphere cannot be used by plants directly in its atmospheric form and is, therefore, captured by certain bacteria that live symbiotically in their roots.

What is this gas?

• Oxygen

• Hydrogen

• Nitrogen

• Iron

• Carbon dioxide

Nitrogen

The topsoil and other soil layers are referred to as _________.

• cations

• soil horizons

• loams

• humus

• None of the listed responses is correct.

soil horizons

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

• Water

• Nitrogen

• Carbon

• All of the listed responses are correct.

• Magnesium

Carbon

At low soil pH levels (5 or less), what can happen?

• Absorption of calcium is enhanced, but iron is unavailable.

• Absorption of negatively charged ions is enhanced, causing the plants to grow faster.

• Toxic aluminum ions become more available, stunting the plant's growth.

• Cation exchange will be enhanced, causing the plants to grow faster.

• Plant roots are eaten away by the acidic soil.

Toxic aluminum ions become more available, stunting the plant's growth.

Epiphytes are a type of plant that ________.

• increases the surface area for nutrient absorption by other plants

• fixes gaseous nitrogen into usable nitrogen in the soil

• grows on other plants without using the host plants for nutrients

• grows on other plants and absorbs nutrients from its hosts

• captures insects and small animals to supplement its diet

grows on other plants without using the host plants for nutrients

What is the goal of phytoremediation?

• To replace lost minerals in soil.

• To clean contaminated sites by using plants that have the ability to extract and store soil pollutants.

• To test whether an element is essential to a certain species of plant.

• To grow crops such as alfalfa and wheat that provide good ground cover.

• To increase resistance to aluminum toxicity

To clean contaminated sites by using plants that have the ability to extract and store soil pollutants.

Mycorrhizae develop __________.

• when nutrients are required by plants in relatively large amounts

• when soil is too compact and lacks sufficient air spaces

• to control the evaporation of water from leaves

• when nutrients are required by plants in relatively small amounts

• between roots and beneficial fungi

between roots and beneficial fungi