plant nutrient use Flashcards
soil plant soil cycle?
- movement of nutrients to roots
- uptake by roots
- nutrient use
- nutrient loss
what are nutrients?
chemical elements essential for living organisms
what do nutrients constrain?
productivity of terrestrial biosphere
- part of below ground resources that control GPP,NPP, decomp
what does experimental addition of nutrients show?
almost always shows an increase in ecosystem prod - nutrients are generally limiting
what are macronutrients
maacronutrients – needed in large quantity – N-P-K-S (sometimes Mg and Ca
what are micronutrients
Micronutrients – needed in small quantity – Cu, Cl, Fe, B, Mn, Zn
what are beneficial nutrients?
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
macronutrient functions?
N- amino acids, proteins
P- ATP, nucleic acids
K - enzyme activity, protein formation, stomata
S - amino acids
Ca - cell walls, membrane funct.
Mg - cholrophyll
micronutrient functions?
Fe- chlorophyll synth
Cl - photosynth reactions
B- sugar metabolism
what does inadequate supply of any nutrient do?
negatively affect plant metabolism + growth
look at graph
how is nutrient cycling through plants
balance btwn nut. supply and plant requirements
differential rates of absorp?
nut. most limiting are preferentially absorbed
abundant nut. absorbed more slow - unabsorp lost from ecosystem
multiple nut. colimitation? look at example
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)
how is nutrient cycling done in terrestrial
-highly localized
- nut. absorbed return to soil below
e.g. >90% N &P absorbed is from recycled nutrients
how much of plants are roots? what do roots do?
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
how do nutrients get to roots (3)
diffusion (most important)
mass flow
root interception (not important)
describe diffusion
NEt movement of molecules/ions along concentration gradients
major mechanisms that supplies potentially limiting nutrients (N,P,K) to plants
describe mass flow
movement of dissolved nutrients to root surface in flowing soil water
describe root interception
as roots elongate into new soil they intercept nut. in unoccupied soil
response ratio?
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
driving forces of diffusion?
nutrient uptake - lowers conc. near root
mineralization - increases conc in bulk soil
diffusion rates influenced by?
nutrient (ion type), soil texture and density, moisture content, CEC, AEC
what does diffusion rate influence?
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)
how does mass flow work? when is it insuffcient vs important?
- 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
why is root interception unimportant?
nut cost of building roots»_space;> amount of nut. intercepted in soil
what delivers highest % macro nut.? ex?
diffusion, seen by comparison of natural ecosystem vs agricultural where in both cases diffusion delivers the most
what controls rate of uptake
nutrient supply in soil
root length
root uptake activity
what is nutrient supply the major factor for?
accounting for differences among ecosystems in nutrient uptake
even plants in fertile soil respond to nutrient addition
when do plant traits influence uptake
triats = root length + uptake activity
when supply rate» nutrient requirements
why is root length important of uptake
-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
what are mycorrhizae? how do they help nutrient intake?
mutualism btwn fungi and roots in nearly all higher plants
- increase root SA
- plants provide carbs to fungi
describe Ectomycorrhizae
temperate woodly plants
sheath of hyphae around root
enhance H2O, N, and P absorp,
prolong root life
describe Arbuscular mycorrhizae
herbs, grasses, early succession forests
penetrate root cells
phosphorus uptake
ex of mycorrhizae inoculation
fir seedlings work better with than without
Root uptake activity?
active transport of ions against a conc. gradient
- large component of root respiration (30-50% of carbon budget of root)
Nutrient use efficiency? maximized by?
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
look at NUE graph
ok
biomass N:ratio of litter fall vs N in litterfall
trade offs in NUE ex?
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
avenues of nutrient loss from plants?
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
what is senescence
major avenue of nut. loss
