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terrestrial > plant nutrient use > Flashcards

plant nutrient use Flashcards

1
Q

soil plant soil cycle?

A
  1. movement of nutrients to roots
  2. uptake by roots
  3. nutrient use
  4. nutrient loss
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2
Q

what are nutrients?

A

chemical elements essential for living organisms

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3
Q

what do nutrients constrain?

A

productivity of terrestrial biosphere
- part of below ground resources that control GPP,NPP, decomp

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4
Q

what does experimental addition of nutrients show?

A

almost always shows an increase in ecosystem prod - nutrients are generally limiting

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5
Q

what are macronutrients

A

maacronutrients – needed in large quantity – N-P-K-S (sometimes Mg and Ca

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6
Q

what are micronutrients

A

Micronutrients – needed in small quantity – Cu, Cl, Fe, B, Mn, Zn

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7
Q

what are beneficial nutrients?

A

equired by certain plants or under certain conditions – Co (N-fixing
symbionts), Si (diatoms)
All are dependent on soil conditions
Some require nutrients to be made available

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8
Q

macronutrient functions?

A

N- amino acids, proteins
P- ATP, nucleic acids
K - enzyme activity, protein formation, stomata
S - amino acids
Ca - cell walls, membrane funct.
Mg - cholrophyll

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9
Q

micronutrient functions?

A

Fe- chlorophyll synth
Cl - photosynth reactions
B- sugar metabolism

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10
Q

what does inadequate supply of any nutrient do?

A

negatively affect plant metabolism + growth
look at graph

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11
Q

how is nutrient cycling through plants

A

balance btwn nut. supply and plant requirements

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12
Q

differential rates of absorp?

A

nut. most limiting are preferentially absorbed
abundant nut. absorbed more slow - unabsorp lost from ecosystem

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13
Q

multiple nut. colimitation? look at example

A

supply of most limiting nut. determines cycling rates of others
- plants respond to additions of multiple nutrients differently than addition of single nutrients
- the usage of one nutrient (e.g. N to build proteins) may require the presence of another (e.g. P to produce ATP)

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14
Q

how is nutrient cycling done in terrestrial

A

-highly localized
- nut. absorbed return to soil below
e.g. >90% N &P absorbed is from recycled nutrients

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15
Q

how much of plants are roots? what do roots do?

A

roots constitute <1% of below ground volume
roots can only absorb dissolved nutrients that contact live root cells
nutrients must move from bulk soil to root surface

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16
Q

how do nutrients get to roots (3)

A

diffusion (most important)
mass flow
root interception (not important)

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17
Q

describe diffusion

A

NEt movement of molecules/ions along concentration gradients
major mechanisms that supplies potentially limiting nutrients (N,P,K) to plants

18
Q

describe mass flow

A

movement of dissolved nutrients to root surface in flowing soil water

19
Q

describe root interception

A

as roots elongate into new soil they intercept nut. in unoccupied soil

20
Q

response ratio?

A

Response ratio – how well something will growth in treatment compared to control
Different compounds are interactive in their affect, thus only reducing one limitation will
have a maximum. Thus reducing two limiations , nitrogen and phosphorous

21
Q

driving forces of diffusion?

A

nutrient uptake - lowers conc. near root
mineralization - increases conc in bulk soil

22
Q

diffusion rates influenced by?

A

nutrient (ion type), soil texture and density, moisture content, CEC, AEC

23
Q

what does diffusion rate influence?

A

diffusion shell:
zone of nutrient depletion around each root
- larger for more mobile ions (nitrate)
-higher root densities needed to exploit soil for less mobile ions (phos, ammonium)

24
Q

how does mass flow work? when is it insuffcient vs important?

A
  • moves transpirational water to root surface
  • sat. flow = gravity
    insuff. for growth limiting/macro nut.
  • important for supplying abundant nut. or nut. needed in small quantities
  • helps replenish diffusion cells
25
Q

why is root interception unimportant?

A

nut cost of building roots&raquo_space;> amount of nut. intercepted in soil

26
Q

what delivers highest % macro nut.? ex?

A

diffusion, seen by comparison of natural ecosystem vs agricultural where in both cases diffusion delivers the most

27
Q

what controls rate of uptake

A

nutrient supply in soil
root length
root uptake activity

28
Q

what is nutrient supply the major factor for?

A

accounting for differences among ecosystems in nutrient uptake
even plants in fertile soil respond to nutrient addition

29
Q

when do plant traits influence uptake

A

triats = root length + uptake activity
when supply rate» nutrient requirements

30
Q

why is root length important of uptake

A

-increase in uptake SA
- important for belowground comp
- elongation important when there are unexploited zones in soil (e.g. after disturbance)
- mycorrhizal associations increase SA for absoprtion

31
Q

what are mycorrhizae? how do they help nutrient intake?

A

mutualism btwn fungi and roots in nearly all higher plants
- increase root SA
- plants provide carbs to fungi

32
Q

describe Ectomycorrhizae

A

temperate woodly plants
sheath of hyphae around root
enhance H2O, N, and P absorp,
prolong root life

33
Q

describe Arbuscular mycorrhizae

A

herbs, grasses, early succession forests
penetrate root cells
phosphorus uptake

34
Q

ex of mycorrhizae inoculation

A

fir seedlings work better with than without

35
Q

Root uptake activity?

A

active transport of ions against a conc. gradient
- large component of root respiration (30-50% of carbon budget of root)

36
Q

Nutrient use efficiency? maximized by?

A

NUE= g biomass (gN)^-1 yr^-1 x yr
amount of biomass produced per mass of nitrogen
maximized by high nut. prod. and long residence time of nut. in plants

37
Q

look at NUE graph

A

ok
biomass N:ratio of litter fall vs N in litterfall

38
Q

trade offs in NUE ex?

A

looking at P in forests hawaii
p poor soils = long residence times, high P use efficienly, low litter P conc, low decomp and slow P regeneration

39
Q

avenues of nutrient loss from plants?

A

usually interal ecosystem transfers
- tissues senescence or death
-leaching
-herbivory
- disturbance
losses from plants go to soil - available for uptake by microbes and plants; lost from ecosystem

40
Q

what is senescence

A

major avenue of nut. loss

terrestrial (28 decks)

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