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Botany: Bio 1C
Physiological Ecology
33
Biology
Undergraduate 1
10/12/2006

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Term
Phototropism
Definition
-Growth toward a light source
-Experiments done by Darwin & Darwin, Boysen-Jensen, and Frits Went
- Tip of coleoptile mmust produce a water-soluble chemical(auxin) that promotes shoot growth
-Increased concentrations of auxin lead to greater cell elongation on dark side
Term
Darwin and Darwin experiment
Definition
-Light sensed in tip of coleoptile and signal transmitted downward
-Covered stem, tip, clear, opaque
Term
Boysen Jensen experiment
Definition
-Showed that the light sensing "signal" is a water soluble chemical
-Cut off tip and placed either agar or mica between tip and stem
Term
Auxin
Definition
-Term for any chemical substance that promotes the elongation of coleoptiles
-Have multiple functions in monocots and eudicots
-Most common form is IAA(indoleacetic acid)
Term
Acid Growth Hypothesis
Definition
1. Auxin stimulates proton pumps, acidifying cell walls
2. Cell walls become more plastic and stretch more easily
3. Water moves into cell, pushing out and expanding cell wall
Term
What does Auxin Do in Plants?
Definition
-Promotes shoot elongation
-Suppresses shoot branching
-Inhibits root elongation
-Promotes root branching
-Promotes growth of Fruit
-Regulates development through interaction with other hormones
Term
Cytokinins
Definition
-Plant Hormone
-promotes lateral growth of shoots, promotes cell division and differentiation
-Works with auxin for elongation
Term
Gibberelins
Definition
-Plant Hormone
-Promote Cell Division
-Stimulate fruit development(with auxin)
-Breaks seed dormancy
Term
Abscisic Acid
Definition
-Plant Hormone
-Maintains seed dormancy
-Promotes drought resistance
-Opens potassium channels in guard cells
Term
Ethylene
Definition
-Plant Hormone
-Reaction to mechanical stress
-Promotes leaf abcission
-Apoptosis
-Fruit ripening
Term
Soil Factors
Definition
1. Texture: General structure
2. Composition: organic and inorganic
Term
How much mass of top soil is lost each year?
Definition
1700-5000 tons per square kilometer
Term
Topsoil Loss Factors
Definition
-Few grasslands/monocot soils left alone
-wind and water erosion
-single species grazers
-salination
-desertification
-sodication
Term
Plant Nutrition
Definition
-9 Macronutrients and 8 Micronutrients
-Most important Macronutrients are Potassium, Nitrogen, and Phosphorous
-Without these three visible deficiencies
Term
Most important Plant Nutrient
Definition
-Nitrogen
-Needed for proteins, nuclei acids, chlorophyll, enzymes(rubisco), etc.
Term
Rhizobium
Definition
Nitrogen fixing bacteria that live in the root nodules of legumes; mutualistic relationship
Term
Crop Rotation
Definition
Rotate nitrogen adding and nitrogen extracting crops
Term
Adaptations to Water Stress
Definition
1. Mesophytes
2. Xerophytes
3. Hydrophytes
4. Halophytes
Term
Environmental Control of Stomatal Density
Definition
During development if light intensity increase and carbon dioxide levels decrease than stomatal density will increase
Term
Stomatal Opening
Definition
-Guard Cells change turgor pressure by uptake and loss of potassium ions
-Driven by active transport of protons in membrane(creates a membrance potential)
-Accumulation of K+ lowers water potential and resutls in water gain through osmosis, so opens stoma
Term
Cues for Stomatal opening and closing
Definition
1. Bluelight receptors; stimulates the proton pumps of K+
2. Depletion of CO2 in leaf
3. Internal clock/Circadian Rhythm
4. Environmental stresses (close during day)
Term
Calvin Cycle
Definition
-Rubisco+3 CO2+RuB)
-6 3-carbon compounds
-Energy rearranged into higher energy G3P
-G3P used to build glucose
-One of six used to build and the rest used to regenerate RuBP
Term
Photorespiration and Photosynthesis
Definition
-Rubisco catalyzes two competing and opposite reactions
Term
C4 Photosynthetic Pathway
Definition
-Increases CO2 concentration about rubisco, which eliminates photorespiration
-Takes extra energy
-Only beneficial at high temperatures(unlike the C3 mechanism which favors lower temperatures)
Term
PEP Carboxylase
Definition
-The enzyme C4 plants use in the mesophyll
-Has a much higher affinity for CO2 than rubisco
Term
Advantages of C4 at higher temperatures
Definition
1. More efficient use of light energy
2. Higher Water Use efficiency
3. Higher Nitrogen Use Efficiency(reduces leaf litter nitrogen quality)

-C4 dominate in summer and hot grasslands
-Advantages negated at high CO2 concentrations
Term
CAM Photosynthesis
Definition
-Different times of the day
-Hot and Dry climates: succulents, pineapples and cacti
Term
Other Adaptations to Environmental Stress
Definition
1. Dry condition lead to suppresion of shallow roots
2. Aerial roots
3. Ethylene leads to air pockets that act as "snorkels"
4. Heat Shock Proteins for enzymes
5. Antifreeze, by high solute concentrations
Term
Plant Defenses
Definition
1. Allelopathy (biotic)
2. Physical Structures (biotic)
3. Secondary Compounds(biotic)
4. Direct competition with neighbors
Term
Herbivore defense
Definition
-First defense: Physical structures; trichomes, spines, etc.

-Second defense: Chemical Poisons; allelopathy
Term
Types of Secondary Compounds
Definition
1. Terpenes: St John's Wort
2. Phenolics: Tannins and Lignans; flavaonoids
3. Alkaloids: Psychoactive; Nitrogen containing compounds; active on nervous sytem
Term
How to compete with neighbors
Definition
1. Grow faster above ground and monopolize light resources
2. Grow faster below ground and monopolize soil resources
3. Poison: Allelopathy
Term
Allelopathic effects
Definition
-Most often inhibit seed germination or seedling growth
-May act directly on competing plants or inhibit growth via effects on soils
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