Ch 36-37 Plant Resource Acquisition and Nutrition Flashcards
What does the success of plants depend on?
Their ability to gather and conserve resources from their environment
Adaptations in plants represent compromises between what?
Maximizing the rate of photosynthesis and minimizing water loss
Water potential
Combines the effects of solute concentrations and pressure
Mpa (megapascals)
What flows from regions of (1)____ to regions of (2)___
1) Higher water potential
2) Lower water potential
What is necessary for plants to acquire water from their roots?
They must have lower water potential than the soil
Solutes have a (1)___ effect on water potential by (2)___
1) Negative
2) Binding water molecules
Positive pressure has a (1)___ effect on water potential by (2)___
1) Positive
2) Pushing water
Solutes and positive pressure have ____ effects on water movement
Opposing
Negative pressure has a (1)___ effect on water potential by (2)___
1) Negative
2) Pulling water
Apoplast
Consists of everything external to the plasma membrane
Apoplastic route into the roots
The route around living cells
Symplast
Consists of the cytosol of the living cells in a plant
Symplastic route into the roots
The route through living cells
What blocks the end of the apoblastic route?
The waxy Casparian strip
Casparian strip
Water and minerals must cross into an endodermal cell to enter the vascular cylinder
What does the Casparian strip prevent?
1) Solutes from leaking out of the xylem
2) Toxic substances from getting in
Cohesion-tension hypothesis
States that transpiration and water cohesion pull water into the plant
Transpiration
Water loss from leaves
How much of the water a plant loses leaves the plant through the stomata?
~95%
Guard cells
Control the diameter of the stomata by changing shape
Soil water potential
-0.3 Mpa
Trunk xylem water potential (lower)
-0.6 Mpa
Trunk xylem water potential (higher)
-0.8 Mpa
Leaf water potential (cell walls)
-1.0 Mpa
Leaf water potential (cell spaces)
-7.0 Mpa
Outside air water potential
-100.0Mpa
Phloem sap
An aqueous solution that is high in sucrose
Phloem sap travels from (1)___ to (2)___
1) Sugar sources
2) Sugar sinks
Sugar sources
An organ that is a net produced of sugar
Sugar sink
An organ that is a net consumer or storer of sugar
How much of a plant’s fresh mass is water?
80% to 90%
How much of plant’s dry mass is from CO2 assimilated during photosynthesis?
96%
How much of a plant’s dry mass is inorganic substances from soil?
4%
How many essential elements are required for plants?
17
How many of the essential elements required by plants are macronutrients?
9
How many of the essential elements required by plants are micronutrients?
8
Macronutrients
Essential elements required in large amount
Macronutrients of plants
1) Carbon
2) Oxygen
3) Hydrogen
4) Nitrogen
5) Phosphorus
6) Sulfur
7) Potassium
8) Calcium
9) Magnesium
Micronutrients
Essential elements required in very small amounts
Macronutrients function as what?
Cofactors
Cofactors
Nonprotein helpers in enzymatic reactions
Mycorrhizae
Mutualistic associations of fungi and plant roots
How does fungus benefit from mycorrhizae?
It receives a steady supply of sugar from the host plant
How does the plant benefit from mycorrhizae?
It receives an increased surface area for water uptake and mineral absorption
Mycorrhizal fungi secret (1)___ ___ that stimulate (2)___ ___ and (3)___
1) Growth factors
2) Root growth
3) Branching
Ectomycorhizzae
The mycelium of the fungus covers the surface of the root
What percentage of plants have ectomycorrhizae?
~10%
Arbuscular mycorrhizae
Microscopic fungal hyphae extend into the root and push into root cell
What percentage of plants have arbuscular mycorrhizae?
85%
What is most often the most important limiting nutrient for plant growth?
Nitrogen
How do plants absorb nitrogen?
As nitrate (NO3) or ammonium (NH4)
How are soils depleted of nutrients?
As plants and the nutrients they contain are harvested
What are most commercial fertilizers enriched with?
1) Nitrogen
2) Phosphorus
3) Potassium
