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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
Q

What are the macronutrients

A

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

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26
Q

Micronutrients

A

remaining seven, plants need them in very small amounts

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27
Q

what are the micronutrients

A

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

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28
Q

Rhizosphere

A

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
Q

Rhizobacteria

A

free-living
Function in the rhizosphere
can enter roots

30
Q

What roles do rhizobacteria play

A

produce hormones that stimulate plant growth
produce antibiotics that protect roots from disease
absorb toxic metals
make nutrients more available to roots

31
Q

What can increase crop yields

A

Inoculation of seeds with Rhizobacteria

32
Q

_____ can be an important limiting nutrient for plant growth

A

nitrogen

33
Q

nitrogen cycle

A

transforms nitrogen and nitrogen-containing compounds

34
Q

Most soil nitrogen comes from

A

actions of soil bacteria

35
Q

Plants absorb nitrogen as

A

either NO3- or NH4+

36
Q

Bacteria break down organic compounds or use _____ to produce _____ which is converted to ______

A

N2
NH3
NH4+

37
Q

Nitrification

A

carried out by bacteria that convert NH3 into NO3-

38
Q

Nitrogen fixation

A

the conversion of nitrogen from N2 to NH3

39
Q

Symbiotic relationships with nitrogen-fixing bacteria

A

provide some plant species with a built-in source of fixed nitrogen

40
Q

Key symbioses occur between

A

nitrogen-fixing bacteria and plants, including those in the legume family (peas, beans, and other similar plants)

41
Q

Along a legume’s roots are swellings called

A

nodules

42
Q

nodules

A

composed of plant cells “infected” by nitrogen-fixing Rhizobium bacteria

43
Q

Inside the root nodule, Rhizobium bacteria assume a form called

A

bacteroids

44
Q

bacteroids

A

are contained within vesicles formed by the root cell

45
Q

Bacteria of a root nodule obtain sugar from

A

the plant and supply the plant with fixed nitrogen

46
Q

where do carnivorous plants grow

A

acidic soils that lack nitrogen

47
Q

How is prey digested in carnivorous plants

A

digested with enzymes secret from specialized glands

48
Q

Pitcher plants

A

have pitcher-shaped leaves with cavity filled with digestive fluid

49
Q

Venus flytrap

A

when hairs are touched, the two halves of the leaf snap together

50
Q

Sundews

A

Glandular trichomes secrete both sticky mucilage and digestive enzymes

51
Q

Waterwheel

A

Uses trigger hairs and snaps to capture and digest small aquatic animals

52
Q

Snap-trap mechanism

A

was acquired by a common ancestor of the Venus flytrap and the aquatic waterwheel

53
Q

Parasitic Plants

A

may be photosynthetic or non-photosynthetic

At least 3,000 types of plants

54
Q

Dodder

A

nonphotosynthetic
wraps around its host
Relies on host for its nutritional needs

55
Q

Indian pipe

A

non photosynthetic

hooks into host trees through mycorrhizae

56
Q

Calvin cycle

A

fixes CO2 into sugar
Ribulose 1,5-bisphosphate carboxylase/oxygenase (rubisco) catalyzes the first step
Can bind CO2 or O2
I

57
Q

If CO2 binds

A

a 3-C sugar is made, that can be used to make glucose and sucrose

58
Q

If O2 binds

A

photorespiration occurs

neither nutrient nor energy storage

59
Q

C3 photosynthesis

A

occurs in mesophyll cells

60
Q

C4 photosynthesis

A

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
Q

In C3 plants, as CO2 increases

A

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
Q

As CO2 levels increase, relatively less nitrogen and other macronutrients are found in leaves

A

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
Q

Phytoremediation

A

use of plants to concentrate or breakdown pollutants

64
Q

Phytodegradation

A

contaminant is taken up from soil and broken down

65
Q

Phytovolatiliation

A

contaminant is taken up from soil and released through stomata

66
Q

Phytoaccumulation

A

contaminant is taken up from soil and concentrated in shoots

These are later harvested

67
Q

Trichloroethylene

A

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
Q

Trinitrotoluene

A

May be removed from soil and degraded by poplar and bean plants
But at high concentrations, it is toxic to these plants

69
Q

Use of Phytoremediation

A

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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