Transcript Plants and Inorganic Nutrients

Plants and Inorganic Nutrients
Animals – Heterotrophic
Plants - Autotrophic
What is plant nutrition?
Organic nutrition –
photosynthesis
Inorganic nutrition –
mineral elements from
soil
How is mineral nutrition studied under controlled
conditions?
Ideal Concentration Of Elements For The Vegetative & Reproductive
Stages Of Cucumber Plants
Plants do not need
soil to grow if they
are supplied with
specific mineral
nutrients
Hoaglands Solution
Note that the
amounts required will
be higher than found
in most soils. Why?
Elements
Vegetable State
Reproductive Stage
N
251 ppm
225 ppm
P
70 ppm
60 ppm
K
220 ppm
280 ppm
Ca
200 ppm
140 ppm
Mg
60 ppm
60 ppm
Fe
20 ppm
20 ppm
Mn
2 ppm
2 ppm
B
1 ppm
1 ppm
Cu
0.1 ppm
0.1 ppm
Mo
0.2 ppm
0.2 ppm
Zn
1.0 ppm
1.0 ppm
Hydroponics
Nutrient film technique “aeroponics”
How is mineral
nutrition studied in
the field?
Nutrient addition
experiments at
Rothhamstead
Experimental Station
Conclusions: Nutrient
availability influences
growth, species
abundance,
competition and soil
microbial populations
Park Grass Experiment started in
1856 (shown in 1941)
Variables: pH, P, K, Mg, Na, nitrate-N,
ammonium-N and Silicon
Fertilized plots have fewer species
(2-3) vs. unfertilized 50-60)
What are the essential nutrients?
Essential nutrients are needed for a plant
to complete its life cycle and/or part of
some essential plant part or molecule
17 nutrients:
Macronutrients – H, C, O, N, K, Ca, Mg,
P, S
Micronutrients – Cl, b, Fe, Mn, Zn, Cu, Ni,
Mo
Nitrogen deficiency in corn
What are the roles of the essential nutrients?
Nitrogen – 80% of
atmosphere, but not in
the form available to
plants
Pathway of absorption:
NO3-(nitrate) 
NH4+(ammonia) amino
acids (proteins, nucleic
acids, etc)
Phosphorous – often most
limiting element in natural
environment
Why?
1. uptake from soil based on
pH:
<6.8 readily taken up; 6.8 –
7.2 less readily taken up; >7.2
not available to plants
2. Organic phosphate must
first be converted to an
organic form by soil microbes
before it can be taken up by
the roots (some plants secrete
phosphatase into soil)
What are the roles of
the essential
nutrients?
Sodium – Desert plants (Atriplex
vesicaria) involved with C4 pathway
Silicon – Taken up from soil
1-2% of dry weight of corn
~16% dry weight of
Equisetum arvense (Scouring Rush)
involved with limiting fungal
infections and preventing lodging
Cobalt – legumes; required by
symbiotic N2 fixing bacteria
Selenium – accumulates in arid soils
of western US; toxic to most plants;
accumulated by certain legumes
(Astragalus example of a “Locoweed”)
What are the
beneficial nutrients?
Plant requirements for nutrients is defined in terms
of critical concentration
Critical concentration – supply of nutrient (measured in tissues) just below
concentration that gives maximum growth
Plants exhibit either morphological
or biochemical deficiency
symptoms
Nitrogen - mobile
Mobile elements –
symptoms first seen
in older leaves
Immobile elements symptoms first seen
in younger leaves
Manganese - immobile
Roots, soil and nutrient uptake
Soil has two phases:
Liquid phase – water or soil
solution, gases,
microorganisms
Solid phase – mineral particles
derived from rock, plus organic
matter
Soil solution is a very dilute
(~1mM) solution of ions
Roots take up nutrients from
soil solution that are
replenished by release from
solid phase
From:
http://www.laspilitas.com/advanced/pictures/roo
ts.jpg
Soil as a nutrient reservoir
Soil has both inorganic and organic
colloids:
Soil  clay (<0.002 mm particles),
silt (0.02-0.002), sand (0.2-0.02)
Clay forms a colloid (particles too
small to settle out, too large to go
into solution (Tyndall Effect)
Colloidal humus-organic material
that has been degraded to a
colloidal dimension
Nutrient contribution: colloidal
humus > colloidal clay (in good soil)
How do soil colloids work?
Effectiveness of colloids depend
on:
Surface area: more area, more
nutrient ions can be held
Surface charge:
Clay – kaolinite (mostly negative
charges from ionized aluminum and
silica at edge of particle)
Colloidal carbon – negative
charges because of exposed
carboxyl and hydroxyl groups
How do ions get from the soil into the plant?
Are all ions taken up by a plant equally?
Accumulation ratio – Ci (conc. inside cell)/C0 (conc. outside cell)
Ion
Co
Ci
Ci/Co
K+
0.14
160
1142
Na+
0.51
0.6
1.18
NO3-
0.13
38
292
SO4-
0.61
14
23
How do ions get across root cell membranes?
Carriers – selectivity with low transport rates
Ion channels – high transport rates (ex. K+ rates into guard cells)
Root – Microbe Interactions
Root –bacteria interactions
Root cap mucilage
www.ffp.csiro.au/research/
mycorrhiza/root.html
Cluster or proteoid roots
http://www.tau.ac.il/~ecology/virtau/3philip_nemoy/image006.jpg
Root – Microbe Interactions
Ectomycorrhizae on pine
roots
http://www.forestpests.org/nur
sery/images/fnp0-7.jpg
Endomycorrhizae
http://www.mun.ca/biology/singleton/To
pic%2012/37-14-Mycorrhizae.jpg
Benefit of mycorrhizae