Unit 1
Chapter 5
Mineral Nutrition
1
Essential nutrients
• Essential elements:
- an intrinsic component in the structure or
metabolism of a plant,
- its absence causes severe abnormalities in plant
growth, development, or reproduction.
There are a total of 17 essential mineral elements:
Macronutrients:
N, P, K, Ca, Mg, Sulfur, Carbon, Hydrogen,
Oxygen
Micronutrient
Cl, Fe, Boron, Mn, Zn, Cu, Ni, Mo
2
Figure 12.1
Solution culture
(hydroponics)
Solution must be
replenished
regularly or the
growth of plants
will be stopped.
Aeration to keep
plants from anoxia
Container painted
black or wrapped to
keep out light so the
growth of algae will
be reduced.
Figure 5.2 Various types of solution culture systems
Solution culture
Hydroponics
4
Plant and Inorganic Nutrients
• The acquisition of inorganic nutrients
(minerals) is part of the plant nutrition.
• Plant nutrition can be viewed as two parts:
organic nutrition, which is mainly dealing
with photosynthesis; and inorganic
nutrition.
• Organic nutrition (photosynthesis) and
inorganic nutrition are highly
interdependent.
Essential nutrient elements
There are 17 essential elements in plants.
Absence of any one of the element could prevent
plants from completing its normal life cycle or some
essential plant constituent or metabolite will not be
manufactured.
According to the relative concentrations found in
tissue (or the relative concentrations required in
nutrient solution), these 17 elements are classified as
macronutrients and micronutrients (trace elements).
Macronutrients are more than 10 mmole per kilogram
of dry weight, micronutrient are less than 10 mmole
per kilogram of dry weight.
Chapter Outline
• Mineral nutrition study
methods
• Essential and
benefical elements
• Macronutrients and
micronutrients
• The metabolic roles of
the 17 essential
mineral elements
• The concept of critical
and deficient
concentration
• Deficiency symptoms
• Micronutrient toxicity
Because in solution culture the replenishment of
nutrient solution is a disadvantage, other methods
were developed.
In these methods, plants were grown in nonnutritive
medium (perlite or vermiculite) and fresh nutrient
solution was applied from the top (slop culture) or
slowly dripping from a reservoir (drip culture).
perlite
vermiculite
Figure 12.2
Nutrient film technique
(subirrigation)
Table 12.4
Beneficial elements
Sodium, Silicon, Cobalt, and Selenium are required
for some plants. Because they are not required for all
plants, they are called beneficial elements instead of
essential elements.
Beneficial elements - Sodium
Sodium is required for plants that have C4
photosynthetic pathway (ex. bladder salt bush). For
these, when sodium is deficient, they will exhibit
symptoms like
- reduced growth
- chlorosis (yellowing
due to loss of chlorophyll)
- necrosis (dead tissue)
of the leaves
Beneficial elements – Silicon
Silicon is particularly beneficial for grasses. It
accumulates in the cell walls to prevent lodging (stems
bent over by heavy winds or rain). It also has roles in
fending off fungal infections.
Beneficial elements - Cobalt
Cobalt is required for nitrogen fixing bacteria. So it
was found to be a requirement for legumes. However,
if fixed nitrogen is provided to legumes the need of
cobalt cannot be demonstrated.
Beneficial elements - Selenium
Selenium are probably not required for plants.
Although selenium is toxic to most plants and animals,
Astragalus spp. are known to accumulate selenium.
Eating Astragalus spp. causes alkali poisoning or
blind-staggers in grazing animals. They are called
“loco weeds”.
Nutrient roles and deficiency
symptoms
It is difficult to categorize the nutrient element
according to their functions because one
nutrient element could have several different
functions.
Figure 5.5 Influence of soil pH on the availability of nutrient elements in organic soils
• Soil pH has a large influence on the availability of
mineral nutrients to plants
16
• The soil is a complex substrate –
physically, chemically, and biologically.
The size of soil particles and the cation
exchange capacity of the soil determines
the extent to which a soil provides a
reservoir for water and nutrients
• A soil with higher cation exchange
capacity generally has a larger reserve of
mineral nutrients
Because the ability of exchange cations of
colloidal surfaces, the colloidal fraction of
soil is the principal nutrient reservoir for the
soil.
Protons (hydrogen ion)
can replace most of
the cations easily.
Therefore, plant roots
also secrete protons to
make cations available
for absorption. Acid
rain will wash out the
cations of soil
solutions and colloidal
surfaces by the same
mechanism of cation
exchange.
Ion uptake by roots
• The most popular
organ for study of
ion uptake is
excised roots.
• So called “low-salt
roots” are grown
under conditions
(see fig. 13.11 for
the legend) that
encourage depletion
of nutrient elements.
Roots
• Plants develop extensive root systems to obtain
nutrients
• Roots have a relatively simple structure
• Roots continually deplete the nutrients from the
immediate soil around them, and roots grow
continuously.
• Different areas of the root absorb different ions:
– in barley, Ca absorption is restricted to the apical
region; K, nitrate, and ammonium can be absorbed at
all locations of the root surface.
– In corn, elongation zone has the maximum rate of K
and nitrate absorption.
21
Figure 5.7 Fibrous root systems of wheat (a monocot)
22
Figure 5.8 Taproot system of two adequately watered dicots
23
Root-microbe interactions
Bacteria
mucilages (mucigels)
proteoid roots
Mycorrhiza
ectomycorrhizae
endomycorrhizae
VAM (vasicular-arbuscular
mycorrhiza)
Figure 5.9 Diagrammatic longitudinal section of the apical region of the root
25
Ectomycorrhizae
-this family of
mycorrhizae is
restricted to temperate
trees and shrubs such
as pines and beech.
-they are short, highly
branched, and
ensheathed by a
tightly interwoven
mantle of fungal
hyphae.
-it also penetrates the
intercellular of
apoplastic spaces of
the root cortex,
forming a intercellular
network
Because bacteria can
enhance nutrient
uptake of roots, the
Golgi apparatus of root
cells (root cap cells,
young epidermis cells,
and root hairs) secrete
polysaccharide-based
mucilages to attract
bacteria.
Mucilages
Bacteria
Colloidal soil particles
Endomycorrhizae
-it is found in some species
of virtually every
angiosperm family and most
gymnosperms.
-it is developed extensively
within cortical cells of the
host roots.
-VAM (vesicular-arbuscular
mycorrhiza) is the most
common type of
endomycorrhiza.
-VAM forms arbuscule with
host cells without
penetrating protoplasm of its
host. Arbuscules increase
contact surface area by two
or three times.
Maize seedlings that
is not colonized by
myccorrhiza.
Figure 13.15
Nutrient depletion zone defines
the limits of the soil from which
the root is able to readily extract
nutrient elements.
Mycorrhiza can extend the
nutrient depletion zone for a
plant.
Figure 13.16
Figure 13.12
Apparent free space (AFS)
Cations in
AFS is lost
Simple diffusion
is occuring in
AFS
=
Ca2+ is being
exchanged by Mg2+
Ions lost in the AFS is a two-step process
• Because cell wall component (galacturonic
acid residues of pectic acid), which is the
main constituent of AFS, is negatively
charged, cations will not be readily lost
once they have been absorbed. However,
it can be exchanged.
Apparent free space (AFS) is the cell wall and intercellular
spaces of the epidermis and cortex of the roots (regions of
the root that can be entered without crossing a membrane;
apoplast space of the root epidermal and cortical cells).
AFS occupied about 10%~25% of root volume.
AFS includes space accessible to free diffusion and ions
restrained electrostatically due to charges that line the
space.
Figure 5.11
Root epidermis
Endodermis + suberized Vascular tissues: vessel
(rhizodermis), cortical cells
Casparian band
elements, parenchyma cells
Ion
Symplast
Apoplast
Symplast
Apoplast
Fig. 13.3
Facilitated diffusion
Facilitated diffusion
The solutes are
transported by transport
proteins (channels and
carriers). The direction
of transport is still
determined by the
concentration gradient.
Active transport
- leads to accumulation of
solute
- requires energy
- unidirectional
- pumps
Selectively uptake of ion
Although [K+] is
higher inside than
outside, due to the
[cation] of the cell
wall space is higher
than cytosol, so
K+ will still move
into the cell until the
membrane potentials
on the both sides
reaches equilibrium.
antiport
symport
Uncharged
solute (ex.
sugars)
ATPase-proton pumps
are the major factor in
the membrane potential
of most plant cells
plasma
membrane-type protonpumping ATPase (Ptype ATPase)
tonoplast-type
proton-pumping ATPase
(V-type ATPase
The other function of Casparian band
Because the ion concentration of stelar
apoplast is much higher than in the
surrounding coretx, the other function of
Casparian band could be to prevent loss of
ions from the stele by diffusion.
Inhibitors of ion transport such as
cycloheximide suggests that ion release into
the vessels is a different kind of process than
ion uptake by the roots.
The uptake of ions is not uniform along the
length of the root.
What takes up in the tip remains in the root.
Growth falls
off sharply in
this range
At this range additional
increments in nutrient
content will have no
beneficial effect on
growth.
The concentration of that nutrient, measured in the
tissue, just below the level that gives maximum growth.
Some symptoms could tell us more
about this particular nutrient
Chlorosis (yellowing)
deficiency of this nutrient element
causes plant unable to synthesize chlorophyll
Symptoms first appear at older tissue
this nutrient element is probably mobile
Symptoms first appear at younger tissue
this nutrient element is probably
immobile
Mineral deficiencies
• If an essential element is mobile,
deficiency symptoms tend to appear first in
older leaves.
• Deficiency of an immobile essential
element becomes evident first in younger
leaves.
Si, Ni, Mn ??
Nutrients
N: component in amino acids, DNA
Deficiency: chlorosis
in old leaves.
S: component in amino acids, vitamins. Deficiency: chlorosis
in mature and young leaves. Veins and petioles show a very
distinct reddish color.
Nitrogen
3(NO ,
4+
NH )
-N
Phosphorus deficiency symptoms
intense green coloration of the leaves
malformed leaves and necrotic spots
(anthocyanin accumulation)
rapid senescence and death of the older
leaves
shortened and slender stems
reduced yield of fruits and seeds
Excess
abundant growth of the roots
Nutrition
• Group 2: energy
storage or structural
integrity
P: components in DNA,
RNA, phospholipids,
ATP, etc
Deficiency: stunted
growth, dark green
coloration containing
necrotic spots; slight
purple coloration
Phosphorus(PO4
-P
3-)
Potassium deficiency symptoms
mottling or chlorosis of older leaves
necrotic lesions at leaf margins
stems are shortened and weakened
 easily lodged
increased susceptibility to rootrotting fungi
Potassium,
+
K
Nutrition
• Group 3: nutrients in
ionic form
Potassium: marginal
chlorosis; necrosis, shown
first in old or mature leave.
A more advanced
deficiency status show
necrosis in the interveinal
spaces between the main
veins along with interveinal
chlorosis. This group of
symptoms is very
characteristic of K
deficiency symptoms.
Silicon: components of
cell wall
Deficiency: lodging and
fungal infection
Boron: function unclear
(cell wall component)
Deficiency: necrosis of
young leaves and
terminal buds
Nutrition deficiencies
Calcium: necrosis around the base
of the leaves. The very low
mobility of calcium is a major
factor determining the expression
of calcium deficiency symptoms in
plants.
Classic symptoms: blossom-end rot
of tomato (burning of the end part
of tomato fruits), tip burn of
lettuce, blackheart of celery and
death of the growing regions in
many plants. All these symptoms
show soft dead necrotic tissue at
rapidly growing areas, which is
generally related to poor
translocation of calcium to the
tissue rather than a low external
supply of calcium.
Calcium deficiency symptoms
symptoms appears at meristematic
region
young leaves deformed and necrotic
death of the meristem
roots discolored and slippery
2+
Calcium(Ca )
2+
-Ca
Group 3
Leaf chlorosis and
necrosis
Small necrotic
spots, chlorosis in
young or old leaves
Chlorosis in old leaves
Magnesium deficiency
symptoms
usually happens in strongly acid,
sandy soils
chlorosis in the interveinal region
symptoms first appears at older
leaves
Magnesium
2+
(Mg )
Sulfur (SO4
2-)
Sulfur deficiency symptoms
generalized chlorosis of the leaf because
reduced protein synthesis
symptoms first appear at younger leaves
Iron
3+
(Fe ,
2+
Fe )
-Fe
Iron deficiency symptoms
loss of chlorophyll and degeneration
of chloroplast structure
chlorosis in the interveinal region of
younger leaves  chlorosis progress to
the vein  leaves turn white
Boron deficiency symptoms
marked structural abnormalities
inhibition of cell division and root
elongation (stubby, bushy roots)
necrosis of meristem
Boron (BO3
3-)
Copper deficiency symptoms
stunted growth
distortion of young leaves
summer dieback of citrus trees
Copper
2+
(Cu )
Zinc deficiency symptoms
shortened internode
smaller leaves
Zinc
2+
(Zn )
Maganese
2+
(Mn )
Manganese deficiency
symptoms
grey speck of cereal grains
greenish grey, oval-shaped
spots on the basal regions of young
leaves
interveinal chlorosis, discoloration
and defromities in legume seeds
Molybdenum (MoO4
2-)
Molybdenum deficiency
symptoms
whip-tail (twisted and deformed
young leaves)
interveinal chlorosis
necrosis along the veins of older
leaves
Chlorine
(Cl )
Chlorine deficiency
symptoms
reduced growth
wilting of the leaf tips
general chlorosis
Nickel
2+
(Ni )
Nickel deficiency symptoms
low germination rate
depressed seedling vigor
chlorosis
necrotic lesions in the leaves