37 Chapter Flashcards
Basic physical properties of soil:
Texture
Composition
Different-sized particles of soil arise ultimately from the weathering of rock.
True
Soil particle sizes:
Coarse sand (biggest)
Silt
Microscopic clay particles (smallest)
Humus
The remains of dead organisms and other organic matter.
Topsoil
A mixture of particles derived from rock, living organisms, and humus.
Soil horizons
Soil layers
Soil solution
The water and dissolved minerals in the pores between soil particles.
Loams
Are composed of roughly equal amounts of sand, silt, and clay. Is the topsoil that is most fertile.
Loamy souls have enough small silt and clay particles to provide ample surface area for the adhesion and retention of minerals and water. Meanwhile, the large spaces between sand particles enable efficient diffusion of oxygen to the roots.
True
Inorganic material
Minerals
Leaching
The percolation of water through the soil.
Most soil particles are negatively charged.
True
Cation exchange
A process in which cations are displaced from soil particles by other cations, particularly H+
The more clay and organic matter in the soil, …
the higher the cation exchange capacity
The major organic component of topsoil is _______
humus
Fertilization makes soil a renewable resource.
True
Sustainable agriculture
Long-term productive farming methods that are environmentally safe.
Irrigation is a huge drain on freshwater resources.
True
Aquifers
Underground water reserves
Land subsidence
A gradual settling or sudden sinking of Earth’s surface.
Salinization
The addition of salts to the soil that make it too salty for cultivating plants.
-Product of irrigation
Drip irrigation
The slow release of water to soil and plants from perforated plastic tubing placed directly at the root zone.
Fertilization
The addition of mineral nutrients to the soil.
Fertilizers are usually enriched in…
Nitrogen, phosphorus, and potassium
Examples of organic fertilizers
Manure, fishmeal, and compost
Before plants can use organic material it must be decomposed into the inorganic nutrients that roots can absorb.
True
Soil pH is an important factor that influences mineral availability by its…
Effect on cation exchange and the chemical form of minerals.
Most plants prefer slightly acidic soil because the high H+ concentration can displace positively charged minerals from soil particles, making them more available for absorption.
True
No-till agriculture
Plowing technique used to reduce erosion.
Soil remediation
The detoxification of contaminated soils
Phytoremediation
A nondestructive biotechnology that harnesses the ability of some plants to extract soil pollutants and concentrate them in portions of the plant that can be easily removed for safe disposal.
Essential element
A chemical element that is required for the plant to complete its life cycle and produce another generation.
Hydroponic culture
A technique used to determine which chemical elements are essential, in which plants are growing in mineral solutions instead of soil.
Macronutrients
Plants require these 9 essential elements in relatively large amounts.
Micronutrients
Plants need these essential elements in only tiny quantities.
Micronutrients function in plants mainly as cofactors.
True
9 macronutrients
Carbon
Oxygen
Hydrogen
Nitrogen
Potassium
Calcium
Magnesium
Phosphorus
Sulfur
Major function of carbon
Major component of plant’s organic compounds
Major function of oxygen
Major component of plant’s organic compounds
Major function of hydrogen
Major component of plant’s organic compounds
Major function of nitrogen
Component of nucleic acids, proteins, and chlorophyll
Major function of Potassium
Cofactor of many enzymes; major solute functioning in water balance; operation of stamata
Major function of calcium
Important component of middle lamella and cell walls; maintains membrane function; signal transduction
Major function of magnesium
Component of chlorophyll; cofactor of many enzymes
Major function of phosphorus
Component of nucleic acids, phospholipids, ATP
Major function of sulfur
Component of proteins
8 micronutrients
Chlorine
Iron
Manganese
Boron
Zinc
Copper
Nickel
Molybdenum
Chlorosis
Yellowing of leaves
Smart plants
Signal when a nutrient deficiency is imminent before damage has occurred.
-Genetically modified
Rhizobacteria
Bacteria that live in the rhizosphere
Rhizosphere
The soil closely surrounding the plant’s roots
Endophytes
Are nonpathogenic bacteria (or fungi) that live between cells within the plant itself but do not form deep, intimate associations with the cells or alter their morphology.
Both endophytic bacteria and rhizobacteria depend on nutrients such as sugars, amino acids, and organic acids secreted by plant cells.
True
Nitrogen cycle
Describes transformations of nitrogen and nitrogenous compounds in nature.
The forms of nitrogen a plant can use
Ammonium ions (NH4+)
Nitrate ions (NO3-)
Ammonification
The process of converting organic forms of nitrogen into ammonium
Nitrogen-fixing bacteria
Convert gaseous nitrogen (N2) to NH3, which then picks up another H+ in the soil solution, forming NH4+
Nitrification
A two-step process, which consists of the oxidation of ammonia (NH3) to nitrite (NO2-), followed by oxidation of NO2- to NO3-.
-Nitrifying bacteria mediate each step.
After the roots absorb NO3-, a plant enzyme reduces it back to NH4+, which other enzymes incorporate into amino acids and other organic compounds.
True
Denitrifying bacteria
Convert NO3- to N2
Nitrogen fixation
A process which converts N2 to NH3
All nitrogen-fixing organisms are _______
Bacteria
The process of nitrogen fixation requires _______ ATP molecules for every _____ NH3 molecules
16, 2
Nodules
Swellings along the root composed of plant cells “infected” by Rhizobium (“root living”) bacteria
Bacteroids
A form of the bacterium Rhizobium contained within the vesicles formed by the root cells of a root nodule.
Nitrogen fixation requires an anaerobic environment.
True
Leghemoglobin
An iron-containing protein that binds reversibly to oxygen.
Crop rotation
The practice of growing different crops in succession on the same land chiefly to preserve the productive capacity of the soil.
Two main types of micorrhizae
Ectomycorrhizae
Arbuscular mycorrhizae
Ectomycorrhizae
Association of a fungus with a plant root system in which the fungus surrounds the roots but does not cause invagination of the host plant cell’s plasma membrane.
Ectomycorrhizae forms…
A dense sheath, or mantle of mycelia (mass of branching hyphae)
Fungal hyphae greatly increases…
The surface area for water and mineral absorption
Arbuscular mycorrhizae
Association of a fungus with a plant root system in which the fungus causes the invagination of the hot plant cell’s plasma membranes.
The process of invagination is analogous to poking a finger gently into a balloon without popping it.
True
Arbuscules
Important sites of nutrient transfer between the fungus and the plant.
-Formed by the branching of fungal hyphae after invagination
Epiphyte
A plant that grows on another plant.
Parasitic plants
Absorb water minerals, and sometimes products of photosynthesis from their living hosts.
Carnivorous plants
Are photosynthetic but supplement their mineral diet by capturing insects and other small animals.
