Chapter 26
Nutrition and
Transport in
Plants
Outline
Essential Inorganic Nutrients
Soil Formation
Soil Profiles
Soil Erosion
Water & Mineral Uptake
Transport Mechanisms
Water
Organic Nutrients
Nutrition and
Transport in Plants
2
Plant Nutrition and Soil
Nutrition and
Transport in Plants
Essential Inorganic Nutrients
About 95% of a plant’s dry weight is carbon,
hydrogen, and oxygen
Primary nutrients are carbon dioxide and water
Essential nutrients have identifiable role, and a
deficiency causes a plant to die
- Macronutrients
- Micronutrients
3
Overview of Plant Nutrition
4
Nutrient Deficiencies
5
Soil Formation
Nutrition and
Transport in Plants
Soil formation begins with weathering of rock
Organisms also play an important role
Lichens and Mosses
Humus begins to accumulate
Under ideal conditions, a centimeter of soil may
develop within 15 years
6
Nutritional Function of Soil
Nutrition and
Transport in Plants
Soil is a mixture of:
Soil particles
Decaying organic material
Living organisms
Air, and
Water
Roots take up oxygen from air spaces
Soil particles consist primarily of
Sand
Clay
Silt
7
Absorbing Minerals
8
Soil Profiles
Nutrition and
Transport in Plants
Soil profile is a vertical section from ground
surface to unaltered rock below
Parallel layers - Horizons
- A (topsoil) - Litter and humus
- B (subsoil) - Inorganic nutrients
- C (weathered rock)
Because parent material and climate differ, soil
profile varies according to particular ecosystem
9
Simplified Soil Profile
10
Soil Erosion
Nutrition and
Transport in Plants
11
Soil erosion occurs when water or wind carry soil
away to a new location
Worldwide, removes about 25 billion tons of
topsoil annually
Deforestation
Desertification
Agricultural contaminants
Nutrition and
Transport in Plants
12
Adaptation of Roots for Mineral Uptake
Important Symbiotic Relationships
Rhizobium bacteria fix atmospheric nitrogen
- Live in root nodules
Mycorrhizal association between fungi and plant
roots
- Ectomycorrhizas
- Endomycorrhizas
Water and Mineral Uptake
13
Root Nodules
14
Mycorrhizae
15
Spanish Moss
16
Nutrition and
Transport in Plants
17
Transport Mechanisms in Plants
Transported in vascular tissues
Xylem transports water
- Two types of conducting cells
 Tracheids
 Vessel
Elements
- Water flows passively from an area of higher water
potential to an area of lower water potential
Plant Transport System
18
Conducting Cells of Xylem
19
Nutrition and
Transport in Plants
20
Transport Mechanisms in Plants
Transported in vascular tissues, cont.
Phloem transports organic materials
-Conducting cells are sieve-tube members
 Have
 End
companion cells to provide proteins
walls are sieve plates
 Plasmodesmata
extend through sieve plates
Water Transport
Nutrition and
Transport in Plants
21
Water entering roots creates a positive pressure
(root pressure)
Pushes xylem sap upward
- May be responsible for guttation
- Water forced out vein endings along edges of
leaves
Guttation
22
Cohesion-Tension Model
Nutrition and
Transport in Plants
23
Cohesion-tension model of xylem transport
suggests a passive xylem transport
Water molecules tend to cling together
Polarity of water allows interaction with molecules
of vessel walls
Water column moves passively upward due to
transpiration
- Column must be continuous
- Waxy cuticle prevents water loss
Cohesion-tension Model of
Xylem Transport
24
Nutrition and
Transport in Plants
25
Opening and Closing of Stomata
Each stoma in leaf epidermis is bordered by
guard cells
Increased turgor pressure in guard cells opens
stoma
Caused by active transport of K+ into guard cells
Opening and Closing of Stomata
26
Organic Nutrient Transport
Nutrition and
Transport in Plants
27
Role of Phloem
Phloem transports sugar
Girdling of tree below the level of leaves causes
bark to swell just above the cut
Sugar accumulates in the swollen tissue
Acquiring Phloem Sap
28
Nutrition and
Transport in Plants
29
Pressure-Flow of Phloem Transport
Positive pressure drives sap in sieve tubes
Sucrose is actively transported into sieve tubes
Water follows by osmosis
Increase in volume creates flow that moves water
and sucrose to a sink
Pressure-flow Model of Phloem Transport 30
Review
Essential Inorganic Nutrients
Soil Formation
Soil Profiles
Soil Erosion
Water & Mineral Uptake
Transport Mechanisms
Water
Organic Nutrients
Nutrition and
Transport in Plants
31
Ending Slide Chapter 26
Nutrition and
Transport in
Plants