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LIFE 103 > Soil and Plant Nutrition > Flashcards

Soil and Plant Nutrition Flashcards

1
Q

Layers of soil

A

horizons

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2
Q

Upper layers of soil

A

topsoil

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3
Q

Soil particles in order of smaller to largest

A

clay
silt
sand

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4
Q

what does topsoil consist of?

A

mineral particles, living organisms, and decaying organic material, humus

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5
Q

humus

A

decaying organic material

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6
Q

Loams

A

soils that support highly productive plant growth - composed of roughly equal parts sand, silt, and clay

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7
Q

Inorganic components

A

cations (K+, Ca2+, Mg2+ adhere to negatively charged soil particles; this prevents them from leaching out of soil as water flows through

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8
Q

cation exchange

A

cations are displaced from soil particles by other cations

Displaced cations enter the soil solution and can be taken up by plant roots

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9
Q

Negatively charged ions

A

do not bind with soil particles and can be lost rom the soil by leaching from percolating groundwater

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10
Q

Agriculture impacts on soil

A

depletes nutrients
increases erosion
taxes water resources
soil compaction

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11
Q

Where is usable fresh water from

A

surface water (lakes and streams) or ground water (aquifers)

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12
Q

depleting of aquifers can result in

A

subsidence

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13
Q

subsidence

A

the settling or sinking of land

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14
Q

irrigation can lead to salinization

A

the concentration of salts in soil as water evaporates

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15
Q

Advantages of drip irrigation

A

requires less water and reduces salinization

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16
Q

Fertilization

A

replaces mineral nutrients that have been lost from the soil

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17
Q

Commercial fertilizers are enriched in

A

nitrogen, phosphorus, and potassium

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18
Q

organic fertilizers composed of

A

manure, fishmeal, or compost

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19
Q

Large monoculture farms with high fertilizers have _____ dominated soil food webs

A

bacteria

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20
Q

Natural systems and organic farms have ____ based soil food webs

A

fungal

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21
Q

Erosion

A

Topsoil from thousands of acres of farmland is lost to water and wind erosion each year in the US
Erosion of soil causes loss of nutrients

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22
Q

Erosion can be reduced by

A

planting trees as windbreaks
terracing hillside crops
cultivating in a contour pattern
practicing no-till agriculture

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23
Q

essential element

A

if a chemical element is required for a plant to complete its life cycle

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24
Q

Macronutrients

A

9 of the essential elements,

plants require them in relatively large amounts

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25
What are the macronutrients
carbon, oxygen, hydrogen, nitrogen, phosphorus, sulfur, potassium, calcium, and magnesium
26
Micronutrients
remaining seven, plants need them in very small amounts
27
what are the micronutrients
chlorine, iron, manganese, boron, zinc, copper, and molybdenum
28
Rhizosphere
the layer of soil bound to the plant's roots | The rhizosphere has high microbial activity because of sugars, amino acids, and organic acids secreted by roots
29
Rhizobacteria
free-living Function in the rhizosphere can enter roots
30
What roles do rhizobacteria play
produce hormones that stimulate plant growth produce antibiotics that protect roots from disease absorb toxic metals make nutrients more available to roots
31
What can increase crop yields
Inoculation of seeds with Rhizobacteria
32
_____ can be an important limiting nutrient for plant growth
nitrogen
33
nitrogen cycle
transforms nitrogen and nitrogen-containing compounds
34
Most soil nitrogen comes from
actions of soil bacteria
35
Plants absorb nitrogen as
either NO3- or NH4+
36
Bacteria break down organic compounds or use _____ to produce _____ which is converted to ______
N2 NH3 NH4+
37
Nitrification
carried out by bacteria that convert NH3 into NO3-
38
Nitrogen fixation
the conversion of nitrogen from N2 to NH3
39
Symbiotic relationships with nitrogen-fixing bacteria
provide some plant species with a built-in source of fixed nitrogen
40
Key symbioses occur between
nitrogen-fixing bacteria and plants, including those in the legume family (peas, beans, and other similar plants)
41
Along a legume's roots are swellings called
nodules
42
nodules
composed of plant cells "infected" by nitrogen-fixing Rhizobium bacteria
43
Inside the root nodule, Rhizobium bacteria assume a form called
bacteroids
44
bacteroids
are contained within vesicles formed by the root cell
45
Bacteria of a root nodule obtain sugar from
the plant and supply the plant with fixed nitrogen
46
where do carnivorous plants grow
acidic soils that lack nitrogen
47
How is prey digested in carnivorous plants
digested with enzymes secret from specialized glands
48
Pitcher plants
have pitcher-shaped leaves with cavity filled with digestive fluid
49
Venus flytrap
when hairs are touched, the two halves of the leaf snap together
50
Sundews
Glandular trichomes secrete both sticky mucilage and digestive enzymes
51
Waterwheel
Uses trigger hairs and snaps to capture and digest small aquatic animals
52
Snap-trap mechanism
was acquired by a common ancestor of the Venus flytrap and the aquatic waterwheel
53
Parasitic Plants
may be photosynthetic or non-photosynthetic | At least 3,000 types of plants
54
Dodder
nonphotosynthetic wraps around its host Relies on host for its nutritional needs
55
Indian pipe
non photosynthetic | hooks into host trees through mycorrhizae
56
Calvin cycle
fixes CO2 into sugar Ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco) catalyzes the first step Can bind CO2 or O2 I
57
If CO2 binds
a 3-C sugar is made, that can be used to make glucose and sucrose
58
If O2 binds
photorespiration occurs | neither nutrient nor energy storage
59
C3 photosynthesis
occurs in mesophyll cells
60
C4 photosynthesis
uses an extra pathway to shuttle carbon deep within the leaf This reduces photorespiration by limiting the Calvin cycle to cells surrounding the vascular tissue where O2 levels are low
61
In C3 plants, as CO2 increases
the Calvin cycle becomes more efficient should lead to increased photosynthesis and plant growth plants have less nitrogen and minerals per unit mass - ratio of carbon to nitrogen increases results in lower nutritional value for herbivores
62
As CO2 levels increase, relatively less nitrogen and other macronutrients are found in leaves
Herbivores need to eat more biomass to obtain adequate nutrients, particularly protein Protein deficiencies in human diets could result from decreased nitrogen in crops
63
Phytoremediation
use of plants to concentrate or breakdown pollutants
64
Phytodegradation
contaminant is taken up from soil and broken down
65
Phytovolatiliation
contaminant is taken up from soil and released through stomata
66
Phytoaccumulation
contaminant is taken up from soil and concentrated in shoots | These are later harvested
67
Trichloroethylene
May be removed from the soil by poplar trees Degraded into CO2 and chlorine A fraction moves rapidly through the xylem ad is released through stomata
68
Trinitrotoluene
May be removed from soil and degraded by poplar and bean plants But at high concentrations, it is toxic to these plants
69
Use of Phytoremediation
Phytoremediation is a promising technique | costs are 50-80% lower than cleanup methods involving mechanical removal of contaminated soil

LIFE 103 (28 decks)

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