Welcome to Mineral Nutrition

• 16 Overview and principles

• 17 Potassium + Q and A on Zoom
• 18 Nitrogen – Sonja Dunbar
• 19 Phosphate
• 20 Micronutrients

• Julia Davies jmd32@cam.ac.uk

• Sonja Dunbar sdd29@cam.ac.uk

1
 Today
• Importance of mineral nutrition
• Soil – the basics
• Nutrient requirements
• Uptake and distribution
• Root system architecture

2
 Today
• Importance of mineral nutrition
• Soil – the basics
• Nutrient requirements;uptake and
distribution
• Root system architecture

3
Nutrition determines diversity
• Ability to access nutrients from
soil/water determines species
presence
Ericaceae on low N acid
heathland soils
• Ability to form symbioses to access
nutrients
• Rhizobia/mycorrhizae 4
Plant mineral nutrition is essential
to human health
• Entry point for minerals into food webs
• Human health depends on plant mineral
uptake
• Cereal diets, Fe and Zn deficiency
• 80% world population Fe-deficient
• Miscarriage, stillbirth, foetal abnormality

5
 Problems are not restricted to
“developing” economies
• Selenium 60-75 μg per day
• Male fertility, immune function, thyroid
and possibly cancer prevention
• UK average 39 μg per day
• UK soils Se-poor; bread has low content
• Biofortification through fertiliser
• Se uptake competes with S uptake
6
 Plant nutrition is big business
• Agriculture (human and animal feed;
brewing/malting/oils), horticulture
• UK cut flower industry £1.45 billion cf
music £2 billion

7
 Sustainable crop production
relies on understanding mineral
nutrition
• NPK fertiliser manufacture releases
greenhouse gases
• <50% N recovered, <10% P recovered,
<40% K
• Pollution hazard

8
P use typifies the problem

9
 P reserves running out
• >31 M tonnes manufactured
phosphates used worldwide every year
• >150 M tonnes rock phosphate (RP)
• 0.2% global energy consumption
• None left in EU; 75% RP in Morocco
• World reserves due to run out by end of
this century
10
 Plants for bioremediation
• Exploitation of plants for remediation of
polluted land but really slow and can only tolerate so much

• Arsenic, Caesium, Cadmium, Lead

11
 Today
• Importance of mineral nutrition
• Soil – the basics
• Nutrient requirements;uptake and
distribution
• Root system architecture

12
 Soil – the basics
• Importance of mineral nutrition
• Nutrient composition and distribution
• Root system architecture
• Transport processes in plants

13
 Soil horizons
• Available minerals will depend
on bedrock, weathering and
vegetation history
• Vegetation determines humic
(organic) component agriculture deprives soil
of humic content by removing all vegetation

14
 Cation exchange capacity
determines availability
• Soil particles are negatively charged –
bind cations (e.g., K+)
• Cations can be exchanged with soil
water
• Particle size distribution, humic content
and pH will affect CEC
cation exchange capacity of soil

15
 Soil composition determines
CEC
• Clay better than sand (bigger particles)

CEC (meq/100g)

Organic matter 130-500

Sand 1-4
Clay 4-60
16
 Soil mineral composition
varies
Composition of soil solution in agricultural soils

17
phosphorous notably low
Soil availability determines yield

K in barley shoots
18
 Today
• Importance of mineral nutrition
• Soil – the basics
• Nutrient requirements;uptake and
distribution
• Root system architecture

19
 Plants require a range of
minerals to complete life cycle
Macronutrients Micronutrients
1000-15000 mg/kg DW
Element Concentration in
Element Concentration in plant
plant dry matter dry matter
(mg kg-1) (mg kg-1)
Nitrogen 15000 Chlorine 100

Potassium 10000 Iron 100

Manganese 50
Calcium 5000
Zinc 20
Magnesium 2000
Boron 20
Phosphorus 2000
Copper 6
Sulphur 1000
Nickel 0.1

Silicon 1000 Molybdenum 0.1 20

Each nutrient has specific roles
Elements Functions
N, S Assimilated into organic
compounds
P, B why boron
Energy storage and
structural integrity

K, Ca, Mg, Remain as ions. Osmotic

Cl, Mn relations, signalling,
enzyme cofactors
Fe, Zn, Redox reactions
Cu, Ni, Mo
21
There is a dose-response relationship
for each nutrient

ideal amount

22
The Goldilocks problem
Too little Too much

Cork spot
calcium both results in necrosis

deficiency

23
Boron toxicity in barley leaf
 Mineral accumulation is species-specific

K concentrations in 250 plant species

Feeds into breeding programmes, eg Selenium

24
 Mineral uptake varies between
species and reflects habitat

avenella adapted to poor phosphate soil

Avenella
flexuosa…wavy
Urtica dioica…
hair grass
common nettle
adapted to acidic
ruderal 25
nutrient poor soil
 Three routes to the xylem from the
soil
coupled transcellular pathway is through specific
efflux and influx proteins in and out of cells?

Symplastic
Apoplastic

26
endodermal cells can have
suberised cell walls -- allowing
only symplastic.

27
selective uptake zone
reliant on symplastic
path

high uptake zone

28
 LATS and HATS enable
uptake and distribution
Plasma membrane
In channel
antiport symport
H+ S
ATP H+

H+ S
out
Channels –passive low affinity transport systems
H+-coupled – low and high affinity
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 dependent on soil avaiability and distribution

Transport protein complement changes

to enable uptake and distribution
Uptake rates
Phosphate Sulphate Chloride
Shoots
starved

replete

Roots

30
 Transpiration drives movement to leaves
Mobilisation from leaf
by phloem

Nutrients are redistributed from

leaves to seeds
31
 Mineral distribution is heterogeneous

Scanning electron
microscopy
of barley

cross section of barley leaf - most strongly stored in epidermis (perhaps important in defence)

X-ray microanalysis
K+ content

Why and how? 32

Cellular composition changes
with nutrient supply

Cytosol

Vacuole

Barley root cell 33

Aim of the game; adequate zone

34
 Storage occurs at maximal growth
Nitrogen

maximal growth at 450mm,

there is still uptake and accumulation is triggerred.

NO3- accumulation triggered - vacuole 35

Hyperaccumulators of heavy metals
may aid bioremediation strategies

Alyssum bertolonii
(Nickel)
Iberis intermedia
(Thallium)
36
Hyperaccumulators tolerate toxic levels

Species Element Concentration in plant

(mg kg-1 dry matter)

Hyperaccumulator Normal
plant

Thlaspi caerulescens Cd 3,000 1

Thlaspi calaminare Zn 10,000 4

Alyssum bertolonii Ni 13,400 2

Macadamia neurophylla Mn 55,000 400

37
Differential transport leads to specific
distributions in hyperaccumulators

How and why? 38

 Today
• Importance of mineral nutrition
• Soil – the basics
• Nutrient requirements;uptake and
distribution
• Root system architecture

39
Roots comprise an extensive uptake network
crops especially have wide networks.

Plant Total root length Root density

(km m-2) (cm cm3)
Winter wheat 36.6 12.2
Winter oilseed rape 24.8 9.7
Spring barley 12.6 6.8
Potato 4.4 2.0
Soybeans 2.5 1.0

40
Nutrient deprivation stimulates assimilate
investment in roots
N treatment Dry weight Root:shoot
(mM) Shoot Root ratio
0.05 0.8 0.45 0.56
0.5 3.5 1.39 0.40
5.0 9.2 1.82 0.20
when nutrient availability is low root growth is triggered.

41
 Root system architecture
adapts to nutrient supply

Localised Uniform
supply supply

Number of 14 40
laterals 332 27

11 18

50 mM Pi New roots adapted?42

Root hairs can assist in nutrient uptake

43
 Summary
Understanding nutrition is central to sustainable crop
production

Aim is to keep levels of each nutrient in adequate

zone

Nutrient distribution is heterogeneous at organ,

tissue and cell level; mediated by a range of
transporters

Root system architecture and transport adapt to

maintain adequate nutrition 44
 Textbooks
Relevant Chapters in:

• L. Taiz and E. Zeiger Plant Physiology, DA 261

• F.B. Salisbury and C.W. Ross Plant Physiology DA 244
• P.S. Nobel Physicochemical and Environmental Plant
Physiology DA 258
• H. Marschner Mineral Nutrition of Plants, 2nd Edition,
DF 68

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