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31.E: Soil and Plant Nutrition (Exercises)

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  • 31.1: Nutritional Requirements of Plants

    Plants are unique organisms that can absorb nutrients and water through their root system, as well as carbon dioxide from the atmosphere. Soil quality and climate are the major determinants of plant distribution and growth. The combination of soil nutrients, water, and carbon dioxide, along with sunlight, allows plants to grow.

    Review Questions

    For an element to be regarded as essential, all of the following criteria must be met, except:

    1. No other element can perform the function.
    2. The element is directly involved in plant nutrition.
    3. The element is inorganic.
    4. The plant cannot complete its lifecycle without the element.


    The nutrient that is part of carbohydrates, proteins, and nucleic acids, and that forms biomolecules, is ________.

    1. nitrogen
    2. carbon
    3. magnesium
    4. iron


    Most ________ are necessary for enzyme function.

    1. micronutrients
    2. macronutrients
    3. biomolecules
    4. essential nutrients


    What is the main water source for land plants?

    1. rain
    2. soil
    3. biomolecules
    4. essential nutrients


    Free Response

    What type of plant problems result from nitrogen and calcium deficiencies?

    Deficiencies in these nutrients could result in stunted growth, slow growth, and chlorosis.

    What did the van Helmont experiment show?

    van Helmont showed that plants do not consume soil, which is correct. He also thought that plant growth and increased weight resulted from the intake of water, a conclusion that has since been disproven.

    List two essential macronutrients and two essential nutrients.

    Answers may vary. Essential macronutrients include carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur. Essential micronutrients include iron, manganese, boron, molybdenum, copper, zinc, chlorine, nickel, cobalt, sodium, and silicon.

    31.2: The Soil

    Soil is the outer loose layer that covers the surface of Earth. Soil quality is a major determinant, along with climate, of plant distribution and growth. Soil quality depends not only on the chemical composition of the soil, but also the topography (regional surface features) and the presence of living organisms. In agriculture, the history of the soil, such as the cultivating practices and previous crops, modify the characteristics and fertility of that soil.

    Review Questions

    Which factors affect soil quality?

    1. chemical composition
    2. history of the soil
    3. presence of living organisms and topography
    4. all of the above


    Soil particles that are 0.1 to 2 mm in diameter are called ________.

    1. sand
    2. silt
    3. clay
    4. loam


    A soil consists of layers called ________ that taken together are called a ________.

    1. soil profiles : horizon
    2. horizons : soil profile
    3. horizons : humus
    4. humus : soil profile


    What is the term used to describe the solid rock that lies beneath the soil?

    1. sand
    2. bedrock
    3. clay
    4. loam


    Describe the main differences between a mineral soil and an organic soil.

    A mineral soil forms from the weathering of rocks; it is inorganic material. An organic soil is formed from sedimentation; it mostly consists of humus.

    Name and briefly explain the factors that affect soil formation.

    Parent material, climate, topography, biological factors, and time affect soil formation. Parent material is the material in which soils form. Climate describes how temperature, moisture, and wind cause different patterns of weathering, influencing the characteristics of the soil. Topography affects the characteristics and fertility of a soil. Biological factors include the presence of living organisms that greatly affect soil formation. Processes such as freezing and thawing may produce cracks in rocks; plant roots can penetrate these crevices and produce more fragmentation. Time affects soil because soil develops over long periods.

    Describe how topography influences the characteristics and fertility of a soil.

    Topography affects water runoff, which strips away parent material and affects plant growth. Steeps soils are more prone to erosion and may be thinner than soils that are on level surfaces.

    31.3: Nutritional Adaptations of Plants

    Plants obtain food in two different ways. Autotrophic plants can make their own food from inorganic raw materials, such as carbon dioxide and water, through photosynthesis in the presence of sunlight. Green plants are included in this group. Some plants, however, are heterotrophic: they are totally parasitic and lacking in chlorophyll. These plants, referred to as holo-parasitic plants, are unable to synthesize organic carbon and draw all of their nutrients from the host plant.

    Review Questions

    Which process produces an inorganic compound that plants can easily use?

    1. photosynthesis
    2. nitrogen fixation
    3. mycorrhization
    4. Calvin cycle


    Through mycorrhization, a plant obtains important nutrients such as ________.

    1. phosphorus, zinc, and copper
    2. phosphorus, zinc, and calcium
    3. nickel, calcium, and zinc
    4. all of the above


    What term describes a plant that requires nutrition from a living host plant?

    1. parasite
    2. saprophyte
    3. epiphyte
    4. insectivorous


    What is the term for the symbiotic association between fungi and cyanobacteria?

    1. lichen
    2. mycorrhizae
    3. epiphyte
    4. nitrogen-fixing nodule


    Free Response

    Why is biological nitrogen fixation an environmentally friendly way of fertilizing plants?

    Because it is natural and does not require use of a nonrenewable resource, such as natural gas.

    What is the main difference, from an energy point of view, between photosynthesis and biological nitrogen fixation?

    Photosynthesis harvests and stores energy, whereas biological nitrogen fixation requires energy.

    Why is a root nodule a nutritional adaptation of a plant?

    A nodule results from the symbiosis between a plant and bacterium. Within nodules, the process of nitrogen fixation allows the plant to obtain nitrogen from the air.

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