Transcript Transport in Plants IV Water Balance of Plants cont. Phloem

Mineral Nutrition in Plants I
When one tugs at a single thing in nature,
(s)he finds it attached to the rest of the world.
John Muir
Oplopanax horridus
Devils Club
• Ethnobotany,
– Medicinal uses,
– Sacred uses,
– herbalgram.org
• Modern uses,
– Empirical studies,
 NCBI.
USDA-NRCS PLANTS Database / Britton, N.L., and A. Brown. 1913. Illustrated flora of the northern states and Canada. Vol. 2: 619.
NPR
Assimilation
•
Every organism is an open system
connected to its environment by a
continuous exchange of energy and
nutrients....
•
…in the energy flow and chemical
cycling that keep an ecosystem alive,
plants…perform the key step of
transforming inorganic compounds
into organic ones.
•
…and to synthesize organic matter,
plants also requires raw materials in
the form of CO2 H2O and a variety
of mineral present as inorganic ions
in the soil.
…prelude to Chapter 37 (old edition), Campbell and Reece.
Sessile and Dainty
…stationary,
…growth and development are a
plant’s version of locomotion,
– primary and lateral roots exploit
new space,
– axilary buds grow new stems,
yielding new leaves, that in turn
build mesophyll cells, etc.
Dainty?
- generally, no excretory organs.
Where does it go?
•
Exclusion;
–
selective permeability of the plasma
membrane (keep out),
•
–
•
secreted plant products take unwanted
substances out of solution,
vacuole
Sequestration;
–
•
active transport of unwanted substances
(kick out),
most metabolic waste products and toxic
substances are transported to the vacuole,
some to other compartments (i.e. ER),
Apoptosis and Abscission (+);
–
programmed cell death and programmed
organ death, (i.e. leaf drop).
Programmed Cell Death
Plant Nutrition and Mineral
Transport
• What elements are found in plants?
• How and where do they function?
• Phytoremediation?
• Nutrient Deficiencies?
Relative Elemental Analysis of Plants
H2O or CO2
Soil
Essential Nutrients
• Essential mineral nutrients:
– one whose absence prevents a plant
from completing its life cycle
(classic definition),
– or, one that has a clear physiological
role (current modification of classic
definition).
• Macronutrient: required in
relatively large amounts,
• Micronutrient: required in
relatively small amounts.
See 37.1
Use for reference, but we’ll organize the nutrients according to biochemical function.
Group 1. Nutrients that are part of carbon compounds.
Group 2. Nutrients that are important in energy storage or structural integrity.
Group 3. Nutrients that remain in ionic form.
Group 4. Nutrients that are involved in redox reactions.
Structural Elements, Covalently Bonded I
Group 1: Nutrients that are parts of carbon compounds...
• N: amino acids, proteins, nucleic acids, co-enzymes, etc.
• S: cysteine, methionine and proteins; lipoic acid and
coenzyme A, etc.
low S
high S
Plants assimilate these nutrients via biochemical
reactions involving oxidation and reduction.
Assimilation in leaves;
• cysteine,
• glutathione.
Mesophyll
Cell
Storage
Transport in the
xylem sap to leaves.
Some assimilation into
cysteine in the root,
Storage
Uptake;
Secondary Active
Transport
Root
Cell
Sulfur Compounds
…antioxidant.


…hormone.
Phytochelatins
• Chelate: a complex in which a metal ion is bound by a ligand,
– chelation: to remove (a heavy metal, such as lead or mercury) from
solution by means of a chelate,
Traditional Heavy Metal Pollution Treatments
• remove, and/or
• encapsulate (with concrete or asphault),
Phytoremediation,
• plants uptake, chelate and sequester metals,
• harvest plants, dry, dispose (less mass).
Accumulation in harvestable
shoot tissue.
Phytoremediation
Phytodegredation
Metal ions or
toxins
Phytoextraction
Phytostabalization
Structural Elements, Covalently Bonded II
Group 2: Nutrients important for energy storage or structure...
• P: sugar phosphates, ATP, phospholipids, also nucleic
acids, proteins,
• Si: deposited as amorphous silica in cell walls,
contributes to cell wall mechanical properties,
– “essential” for life cycle in only a few species in
hydroponic experiments,
– however, in the field, probably essential for survival of
many more plants.
• B: nucleic acid synthesis?, transport?, chlorophyll
biosynthesis?,
– and cell wall function.
Equisetum hyemale
Si obligate
Rhamnogalacturonan II
Structure is conserved in
the cell walls of all higher
plants,
11 different sugar monomers,
> 21 enzymes required for synthesis.
– boron links two
Rhamnogalacturonan II
monomers,
– contributes to cell wall
function through crosslinking with cellulose
microfibrils and other
cell wall components.
Salts, Co-factors, and Redox Reagents
Group 3,4: Nutrients that remain in ionic form...
• Salts and Co-factors:
– K, Ca, Mn, Zn, Na, Mg,
• K: co-factor for > 40 enzymes, and is the
principle cation for establishing cell
turgor and control of membrane potential,
• Ca: contributes to cell wall structure,
membrane structure, and acts in signal
transduction,
• Mg: co-factor in enzymes required for
phosphate transfers, and a component of
chlorophyll.
• Redox Reagents:
- Fe, Cu, Mo, Mn.
Dose Response Curves
saturation
toxicity
threshold
Nutrient Deficiencies
Difficult in Soils
 Chronic and acute deficiencies
of several nutrients may occur
simultaneously,
 Deficiencies (or excess) of one
element may induce
deficiencies (or excess of
another element.,
Hydroponics
Mineral deficiencies are relatively easy to
identify in controlled conditions.
 Pathogens often induce
symptoms similar to nutrient
deficiencies.
Recognizing Deficiencies
Leaf Clues;
– if an essential nutrient is
relatively mobile,
symptoms generally
appear first in older leaves,
Nutrients classified based on
their tendency to re-translocate
during deficiencies.
– deficiencies in relatively
immobile nutrients
generally appear in young
leaves.
+
K
Transport
1. K+ is transported across the root
cell plasma membrane,
2. K+ is transported from the root
symplast to the xylem,
3. K+ is transported via xylem sap to
the older leaves,
– diffuses to the apoplast and is
transported into the mesophyll
cells,
-
or, K+ diffuses into, or out of the
phloem.
5. Moves in source-sink direction.
Deficiency Characteristics
Group 1: Nutrients that are parts of carbon compounds...
• N (mobile) is most often the limiting nutrient in natural systems,
– it is a critical components in many plant cell components (especially
proteins) and deficiencies quickly limit growth,
– the most typical deficiency characteristic is chlorosis (yellow leaves),
• slowly developing deficiencies produce short, woody stemmed plants,
• anthocyanin production (red pigment).
Means for
using excess
carbohydrates.
• S (immobile) is generally available,
– deficiencies (especially proteins) quickly limit growth,
– similar general characteristics as seen in N deficiencies.
Deficiency Characteristics
Group 2: Nutrients important for energy storage or structure...
• P (mobile) can be a limiting nutrient in natural systems (esp. at high pH),
– it is a critical components in respiration and photosynthesis as well as a key
component of the phospholipids that make up membranes,
– the most typical deficiency characteristics are stunted growth and dark
green leaves,
• necrotic lesions may occur,
• anthocyanin production (red pigment).
• Si (mobile) is usually available,
– lodging (falling over) and prone to fungal infections.
• B (immobile) lots of deficiency characteristics, especially necrosis
(cell death) in expanding cells.
pH and Nutrient Availability
• The pH of the soil affects the
availability of all elements,
• Plants adapt to the soil pH,
– directly modify soil pH,
– adapt mechanisms to operate in
extreme conditions.
Width of bar corresponds to relative availability
Deficiency Characteristics
Group 3: Nutrients that remain in ionic form...
• K (mobile) deficiencies,
– mottled or marginal chlorosis, veins retain their color, necrosis at
margins, thin stems, short internodes,
• Ca (immobile) deficiencies,
– Necrosis in areas of cell division and rapid expansion (meristems),
leaf primordium, etc.
• Mg (mobile) deficiencies,
– chlorosis, beginning especially between veins,
– old leaves, or young leaves?
Deficiency Characteristics
Group 4: Nutrients that are involved in redox reactions...
• Fe (immobile) can undergo Fe2+ <--> Fe3+, are are
important in electron transfer reactions,
– chlorosis, especially between veins,
– would you expect to see it in older or younger leaves first?
• Zn (mobile) deficiencies,
– dwarfism, extreme cases display chlorosis.
• Cu (immobile) deficiencies,
– dark green leaves, necrotic spots appearing at the tips of young
leaves.
Wednesday
• Exam.
• All session.
• Closed book, closed note, no partner.
• One Essay Question.