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biology > Lecture 27 - Plant Nutrition (part 2) > Flashcards

Lecture 27 - Plant Nutrition (part 2) Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Sugars travel from…

A

source to sinks

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2
Q

Bulk flow within xylem is…

A

unidirectional -> Roots to shoots

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3
Q

Translocation

A

is the transport of photosynthates

- is carried out by the phloem in the opposite direction -> shoots downward to stems and roots

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4
Q

Phloem sap

A

is the aqueous solution that flows through the phloem cells (sieve tubes)

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5
Q

What does phloem sap contain?

A
  • Contains mostly dissolved sugars (sucrose in most species)

* Can also contain amino acids, hormones, and minerals

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6
Q

Phloem sap moves from…

A

sources to sinks

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7
Q

Sinks

A

net consumers of sugars or will store sugar deposits

- roots, buds, stems, fruits, growing leaves and tissues

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8
Q

Sources

A

plant organ that is a net producer of sugar

- mature leaves

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9
Q

Storage organs can be both…

A

sources and sinks depending on the season

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10
Q

Storage organs in the Summer:

A

sugar stockpiling in the storage bulbs/tubers (sink)

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11
Q

Storage organs in the Spring:

A

supplies sugar for initial growth (source)

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12
Q

Sinks receive sugars from their nearest source…

A

upper leaves export to buds, lower leaves export to roots

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13
Q

Sugars must be “loaded” into sieve-tube elements before being _________

A

exported to sinks

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14
Q

Sugars must be “loaded” which can be done by what?

A
  • Can be done symplastically through plasmodesmata from mesophyll cells to sieve-tube elements
  • Other species can load sugar both symplastically and apoplastically
  • Requires active transport via proton pumping and H+/sucrose cotransporters
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15
Q

Sugars are “unloaded” at sinks via _________

A

facilitated diffusion

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16
Q

Concentration of free sugar in the sink is always _____ than the sieve-tube elements

A

lower

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17
Q

Bulk flow of phloem sap is via…

A

+ pressure (pressure flow)

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18
Q

Sugars are loaded into phloem sap by _______, which ______ the water potential of the phloem sap in that region.

This causes water to move into the _______ from nearby cells or surrounding xylem tissue

A

source cells

lowers

phloem sap

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19
Q

The increase in water pressure forces phloem sap to…

A

move through the sieve tubes

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20
Q

At sink cells, phloem is unloaded…

A

INCREASING water potential & causes water to LEAVE the phloem sap and ENTER nearby cells and xylem

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21
Q

Xylem then recycles water from…

A

sink to source

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22
Q

Sometimes a plant can have too many…

A

sinks
• Can abort buds, fruits, and seeds through selfthinning
• We use this concept to make larger apples to sell in markets

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23
Q

Plants acquire nutrients from the…

A

soil

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24
Q

Plants absorb nearly all of their water and minerals from what?

A

top layers of soil

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25
Q

What does top layers of soil contain?

A

a slew of microorganisms that can associate with plants

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26
Q

Soil texture is dependent on particle size as a result of…

A

rock weathering

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27
Q

Coarse sand:

A

0.02-2mm in diameter

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28
Q

Silt:

A

0.002-0.019mm

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29
Q

Clay particles:

A

<0.002mm

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30
Q

Soil composition forms layers called

A

horizons

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31
Q

Topsoils

A

Horizon A, consists of humus (organic matter) and soil particles

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32
Q

Plants get their nutrients from what?

A

the soil solution (between the particles)

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33
Q

Sandy soils are not good at _________, but have ________

A

water retention

good oxygen exchange

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34
Q

Clayey soils retain too much ______, lack _______

A

water

oxygen

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35
Q

Loams

A

are the most fertile topsoil, consisting of pores of 50% water, 50% air

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36
Q

Topsoil is composed of both:

A
  • Inorganic compounds

* Organic compounds

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37
Q

Inorganic compounds

A
  • Soil particles are generally negatively charged -> bind with positive cations K+, Mg2+, Ca2+
  • Don’t bind with nitrates, phosphates, sulphates (anions) -> but plants need these!
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38
Q

Organic compounds

A

Mostly humus, organic material composed by decaying leaves, feces, dead organisms, bacteria, and fungi

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39
Q

What does organic compounds prevent?

A

Prevents clay particles from sticking together

- so retains water but allows for some drainage

40
Q

Plants do not obtain ______ directly from the soil

A

nutrients

41
Q

Nutrients are dissolved into the soil solution via…

A

cation exchange

42
Q

Cation exchange

A
  • Cations are displaced from soil particles by other cations (H+)
  • Dependent on pH and adhesion sites
  • More clay and organic material in the soil, more cation exchange
43
Q

Humans can dramatically change the…

A

soil quality

44
Q

We know that fertilisation increases…

A

nutrient levels in the soil

45
Q

Increases in nutrient levels in the soil helps overcome…

A

decrease plant yields over successive years of farming by providing N, P, K

46
Q

Resulted in civilisation –>

A

we can now sit and wait for our food rather than gather surrounding resources

47
Q

Increase nutrient levels in the soil also result in…

A

soil mismanagement and nutrient overloading of ecosystems

48
Q

Describe soil mismanagement and nutrient overloading of ecosystems…

A
  • Removal of native plant species with deep roots can erode away the topsoil, leaving behind soil of poor nutrient quality
  • Lake Winnipeg nutrient enrichment leads to massive algal blooms and toxic aquatic conditions
49
Q

Where can water be very limiting in?

A

arid regions or areas with longer days (equatorial)

50
Q

Irrigation allows for water to be…

A

diverted to the soils

51
Q

Water has lots of dissolved nutrients, so can increase…

A

soil nutrient levels to a point

52
Q

Too much irrigation can leave behind…

A

salts due to evaporation, which can decrease the plant’s ability to absorb water

53
Q

Soil pH can affect the plant’s ability for…

A

cation exchange

54
Q

Most plants prefer…

A

slightly acidic soil

55
Q

pH 8 ->

A

plants absorb calcium, but not iron

56
Q

pH 5 or lower ->

A

toxic minerals such as aluminum become more soluble and are absorbed by the roots

57
Q

Water and wind erosion can remove…

A

layers of topsoil

• Removal of native grass species no longer anchor the soil

58
Q

Wind & wind erosion can counteract that with…

A

wind breaks, terrace hillside crops, contour patterns of crop cultivation

59
Q

Phytoremediation

A

is a non-destructive biotechnology that uses the special ability of some plant species to remove contaminants/pollution from soil

60
Q

Dr. Renault and Dr. Markham have studied the effect of using…

A

dogwoods and cattail species to revegetate gold mine tailing sites and areas of high salinity and toxic substances

61
Q

Plants need…

A

essential elements to grow

62
Q

Essential elements

A

are needed to complete a plant’s life cycle and reproduce

63
Q

Macronutrients

A

9 essential elements needed in relative larger amounts

• C, O, H, N, P, S, K, Ca, Mg

64
Q

Micronutrients

A

need only in minute quantities

• Cl, Fe, Mn, B, Zn, Cu, Ni, Mb (and sometimes Na)

65
Q

Plants lacking enough essential elements show signs of what?

A

nutrient deficiency

66
Q

What does nutrient deficiency affect?

A

Affect the plant’s function, development, and life cycle

67
Q

Chlorosis

A

Mg deficiency, causes chlorophyll to break down and turn leaves yellow (though it could also be caused by iron deficiency since Fe is used as a cofactor in chlorophyll synthesis)

68
Q

If nutrients move freely, symptoms of nutrient deficiency appear in the…

A

older tissues/organs first

69
Q

Mg is a mobile element ->

A

gets shunted to younger leaves if not enough is obtained

70
Q

Immobile elements shortages show up in the…

A

younger tissues

• Ie. Iron is immobile and causes young leaves to turn yellow

71
Q

Plants nutrition depends on what?

A

interactions

72
Q

Plants can enhance nutrient acquisition through what?

A

associations and interactions with bacteria and fungi

73
Q

Rhizobacteria

A
  • Live associated with plant roots or in the rhizosphere (soil surrounding plant roots)
  • Depend on the nutrients secreted from plant roots
  • Provide a variety of benefits
  • Can be free-living in the rhizosphere or endophytic in plant roots, producing nodule
74
Q

What are the variety of benefits that Rhizobacteria provides?

A
  • antibiotics to prevent root disease
  • absorb toxic materials so plants do not absorb them
  • Nitrogen fixation
75
Q

Nitrogen fixation

A

converting atmosphere N2 gas to ammonium/nitrate (NH3)

76
Q

All nitrogen-fixing organisms are what?

A

bacteria

77
Q

If nitrogen fixation is associated with plants…

A

form nodules on the roots (Rhizobium spp., in soybean, other legumes)

78
Q

What is nitrogen fixation driven by?

A

the enzyme nitrogenase

79
Q

nitrogenase

A

energy intensive which is why N-fixing bacteria need plant associations

80
Q

Ammonification

A

organic nitrogen (from decaying matter) is converted to NH3 or NH4+

81
Q

Nitrifying

A

Oxidises ammonium to nitrite and nitrite to nitrate

82
Q

Denitrifying

A

Nitrates are reduced back to nitrogen gas

83
Q

Farmers can utilise plants that associate with N-fixing bacteria in their crop rotations to help what?

A

to help return nitrogen back into the soil for the next year’s crops

84
Q

Plants can also associate with…

A

mycorrhizal fungi -> evolutionary adaptation to moving onto land

85
Q

Ectomycorrhizal fungi

A
  • Form a dense sheath of mycelia around the plant roots, roots do not form root hairs
  • Hyphae can also grow into the root cortex and inhabit the apoplast
  • 10% of plant species associate with this kind of mycorrhizal fungi (pine, oak, birch, eucalyptus)
86
Q

Arbuscular mycorrhizal fungi

A
  • Also called ENDOmycorrhizal fungi

* EMBEDDED within the plant root, forming arbuscules

87
Q

Crop yields can often depend on what?

A

the association with mycorrhizae

88
Q

Planting seeds from one area to another can result in…

A

plants of poor health since they lack their natural mycorrhizal associations

89
Q

Plants can acquire nutrients from animals…

A
  • Dead salmon decompose, releasing nitrogen into terrestrial ecosystems surrounding streams
  • Carnivorous plants
90
Q

Carnivorous plants

A

Photosynthesise but acquire nutrients (microelements and nitrogen) from digesting insects and small animals

91
Q

Plants can acquire nutrients from other plants…

A
  • Epiphytes

* Parasitic plants

92
Q

Plants can acquire nutrients from what?

A

animals & other plants

93
Q

Epiphytes

A
  • Plant grows on another plant

* They produce their own food and acquire their own nutrients (do not tap into the plant it is living on)

94
Q

Parasitic plants

A
  • Absorb water, nutrients, and sometimes photosynthates from the host plant
  • Roots function as haustoria
95
Q

Carnivorous plants examples

A

Sundews, butterworts, Venus fly traps

96
Q

Epiphytes examples

A
  • Staghorn ferns
  • Air plants
  • Orchids
  • Bromeliads
97
Q

Parasitic plants examples

A
  • Ex. Dwarf mistletoe only steals water and minerals

* Ex. Monotropa uniflora absorbs nutrients from the mycorrhizae associated with other plants

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