Transcript SWES 316 - University of Arizona

Plant Nutrition
SWES 316
Section H
What Do Plants Need to Grow?
• Van Helmont early 1600s
– Grew a tree in 200# of soil for 5 years, gave it
only water. After 5 yrs, he accounted for all
but 2 oz of soil. Conclusion: water is the only
essential nutrient for plants.
• Boyle mid 1600s
– Plants contain “salts, spirits, earth, and oil”,
which he thought were derived from water.
Agreed with van Helmont.
What Do Plants Need to Grow?
• John Woodward 1700
– Grew spearmint in water from different
sources (e.g. fresh, sewage).
– Concluded that “earth”, not water, was the
principal nutrient of vegetation.
• Jethro Tull 1700
– Believed that roots “eat” soil.
• Justus von Liebig early 1800s
– C in plants comes from atmosphere, H and
O come from water, other elements from
soil.
What are Plants Made of?
Plant Composition
Dry Matter
Dry Matter
10.0%
"Mineral Elements"
5.0%
Water
90.0%
Water
Dry Matter
C, H, O
95.0%
C, H, O
"Mineral Elements"
Elements Found in Plants
• At least 50 chemical elements have been
found in plants. However, most are not
needed for plant growth.
• There are 17 chemical elements that are
apparently required for all plants, and some
more that are required for some plants.
• Plants are about 90% water and only 10%
solids. Of the solids, only about 5-10%
actually comes from the soil.
Essential Nutrient Elements
• An element is essential if it functions in some
way in plant metabolism.
• Specifically, essential elements are those for
which:
– 1) it is impossible for the plant to complete its life
cycle without that element,
– 2) a deficiency can only be solved by supplying
that element, and
– 3) the element is directly involved in the nutrition
of the plant (and not in solving an environmental
circumstance).
Essential Elements
• The above definition includes 17 elements
required by all plants:
"Macronutrients": C, H, O, N, P, K, S, Ca, Mg
"Micronutrients": Fe, Mn, Zn, Cu, Mo, B, Cl, Ni
Additional: Na, Si, V, Co
Essential Elements
• Organized by position in the periodic
table:
– Nonmetals:
• C, H, O, N, P, Cl, S, B
– Alkali and alkaline earth metals:
• K, Mg, Ca
– Transition metals:
• Mn, Fe, Ni, Cu, Zn, Mo
Representative Element
Concentrations in Plants
Element
C
N
K
P
Ca
Mg
Fe
Zn
Mo
Concentration (ppm)
450000
15000
10000
2000
5000
2000
100
20
0.1
Nutrient Uptake (kg/ha/yr)
N
P
K
Ca
Mg
Zn
Broccoli
165
10
210
Celery
195
50
435
New
Hamp.
Hardwood
116
12
67
62
10
Alfalfa
397
30
400
212
35
California
Chaparral
131
7
46
74
14
0.3
Nutrient Functions in Plants
• C, H, O Main structural components of
plants
• N Amino acids, nucleic acids, proteins,
chlorophyll
• P phospholipids, energy transfer (ATP)
• K osmotic regulation
• S proteins
Nutrient Functions in Plants
• Ca
• Mg
• Fe, Mn,
Cu, Zn
• B
• Cl
• Mo
strengthens cell walls
chlorophyll
enzyme activation, electron
transport
cell division
osmotic regulation
nitrate reductase enzyme
Nutrient Functions in Plants
• Co
• V
• Na
• Si
• Ni
essential for N fixation
oxidation reduction reactions
essential for halophytes, osmotic
regulation
required for some grasses,
strengthens cell walls
essential for legumes, urease
enzyme
How do nutrients
get into plants?
Root Morphology
Slower
nutrient
uptake
Zone of most
rapid nutrient
uptake
Cross-section of maturation zone
Nutrient Uptake
• Apoplasmic Transport
– transport in the root “free space”. Is a “dead-end”
except in the youngest part of the root.
• Symplasmic Transport - involves uptake
across the plasma membrane:
– Passive transport
– Active transport
The Plant Cell
Nutrient Uptake
• Movement through the root to the xylem
– Apoplasmic vs. Symplasmic
– Apoplasmic in the youngest part of the root
– Symplasmic in young and old parts of root
• Uptake into the Symplasm
– Nutrients must cross plasma membrane
– Active vs. Passive
– Active: energy input needed
– Passive: no energy input needed
Nutrient Uptake
Cell Structure
The Plant Cell
Plasma Membrane
• Function: to control the passage of water and
solutes into and out of the cell
• Structure:
– Phospholipid bilayer--hydrophilic outside,
hydrophobic inside. When intact is impermeable
to water and solutes
– Embedded proteins: “channels” and “carriers” for
passage of water and solutes. Under metabolic
control.
The Plasma Membrane
Nutrient Uptake
• Definition: passage of nutrient ions or
molecules across the plasma membrane.
Nutrients thus taken up are then transported
to the xylem for redistribution to sinks
throughout the plant
• Active transport (uptake): requires direct
input of energy (ATP)
• Passive transport (uptake): does not require
energy
Apoplasmic vs. Symplasmic
• Most nutrients can be transported
apoplasmically and symplasmically, and
therefore can be taken up along the root
axis.
• However, in many plant species, Ca is
not transported symplasmically.
– Therefore, only the youngest part of the
root system takes up Ca.
– This explains why some plants are
especially susceptible to Ca deficiency.
Remobilization
• Remobilization is the movement of nutrients
from one part of the plant to another. Some
nutrients are mobile and some are immobile
within plants.
• Remobilization from mature leaves to areas
of new growth is essential to the life of the
plant under conditions of limited nutrient
availability (e.g wildland soils, poorly fertilized
agricultural soils).
• Nutrient mobility affects where nutrient
deficiencies are manifested.
Nitrogen and Corn
Ca Deficiency
Nutrient Mobility
• Mobility of a nutrient is often related to
the function(s) of that nutrient in plants.
• Mobile nutrients: N, P, K, Mg, Cl
• Immobile: Ca, S, B, Fe, Mn, Cu, Mo, Zn
Nutrient Deficiencies
• Nutrient deficiency symptoms are often
related to the function of that nutrient in
plants.
• An "educated guess" regarding what nutrient
is responsible for a particular deficiency can
be made by considering the following:
– position of deficiency on plant (old, young)
– pattern of deficiency
– color of deficiency
Magnesium
Deficiency Symptom
Corn
Older leaves
Interveinal chlorosis
Calcium
Deficiency Symptom
Tomato
Fruit
“Blossom end rot”
Nitrogen
Deficiency Symptom
Cabbage
Older leaves
Chlorosis
Iron
Deficiency Symptom
Cotton
Younger leaves
Interveinal chlorosis
Potassium
Deficiency Symptom
Alfalfa
Older leaves
Spotting, necrosis
Salt, sodium toxicity
Deficiency Symptom?
Grapes
All leaves
Marginal burning,
necrosis