BIO 366: CHAPTER 6 PLANT ADAPTATIONS
32 Cards in this Set
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Primary Producer
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Only autotrophs can transform carbon in the form of CO2 into organic molecules and living tissue.
- Chemoautotrophs
- Photoautotrophs
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Chemoautotrophs
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Convert Carbon dioxide into organic matter via the oxidation or inorganic molecules (hydrogen gas or sulfide)
- Dominant primary producers in oxygen deficient environments
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Photoautotrophs
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Dominant form of primary producers use the Sun's energy to drive the process of converting CO2 into simple organic compounds
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Light Reactions of Photosynthesis
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Begins with initial photochemical reaction where chlorophyll molecules within the chloroplasts absorb light energy. The photon absorption raises the energy level of the chlorophyll molecule, exciting electrons and causing them to return to ground state, releasing energy in the process.
T…
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Dark Reaction of Photosynthesis
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ATP fuels the dark reactions of photosynthesis but they are not directly dependent on the sunlight's energy.
A 5 carbon molecule (RuBP) combines with CO2 to form two, 3 carbon molecules (3-PGA). The 3-PGA combines with Rubisco and creates a high energy sugar molecule G3P.
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Calvin-Benson Cycle (C3)
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This photosynthetic pathway involves the initial fixation of CO2 into a 3 carbon PGA.
One Major Drawback: The enzyme Rubisco (which drives carboxylation) can also catalyze the reaction between O2 and RuBP which can result in the release of CO2. This reduces the efficiency of this proce…
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Cellular Respiration
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(Aerobic Respiration)
Involves oxidation of carbohydrates to generate energy in the form of ATP (ie. chemical breakdown of the sugars or other carbohydrates). This process takes places exclusively in the mitochondria of the cell.
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Fermentation
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(Anaerobic Respiration)
Enables some cells to convert glucose into lactic acid and ATP
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Net Photosynthesis
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Net Photosynthesis = Photosynthesis - Respiration
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Availability of PAR (Light energy)
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The availability of PAR on a leaf directly influences the rate of photosynthesis
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Light Compensation Point (LCP)
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As the amount of light declines, the rate of carbon uptake in photosynthesis will eventually decline to a level where it equals the rate of carbon loss in respiration - At this point Net Photosynthesis equals zero - At light levels below compensation point, rate of carbon loss exceeds the…
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Light Saturation Point
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The value of PAR, above which no further increase in photosynthesis occurs.
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Photoinhibition
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In some plants that prefer shady environments, photosynthetic rates decline as light levels exceed saturation
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Mesophyll Cells
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Where the process of photosythesis occurs. CO2 enters the leaf via stomata (tiny openings on the surface of the leaf) through a process called diffusion.
- As long as photosynthesis occurs, the gradient for CO2 remains
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Transpiration
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Loss of water vapor out of the stomata
- How rapid the movement of water is depends on the concentration gradient in the outside atmosphere
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Turgor Pressure
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The force exerted outward on a cell wall by the water contained in the cell. When a plant is fully hydrated their processes will occur at max rate.
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Water Use Efficiency
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If water is scarce, the plant must balance the opening and closing of the stomata, taking up enough CO2 while minimizing the amount of water lost.
- The ratio of carbon fixed per unit of water lost is called the water use efficiency
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Carbon Uptake for Aquatic Plants
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CO2 diffuses directly from the waters on the leaf across the cell membrane. Aquatic plants do not have stomata.
- Some plants can use the aquatic bicarbonate CO2 source but they must first convert it using enzyme Carbonic anhydrase
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Trade-off for Plants that live in more shade
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Plants who live in environments with less direct sunlight often have a larger leaves, with lower respiration rates, a lower light compensation point, and a lower maximum rate of photosynthesis
- These plants also tend to spend more of their carbon energy on producing more leaves rather t…
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Trade-offs for plants that have more direct sunlight
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Leaves at the top of a canopy receive higher levels of solar radiation and experience higher temperatures. Upper leaves are smaller, thicker and more lobed to allow for heat exchange
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Shade-Intolerant Plant Species
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Adapted to high light environments
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The Link Between Water Demand and Temperature
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- As temperature rises the saturation of vapor pressure will rise and thus increase the gradient of the inside to outside of a leaf.
- The amount of water required by a plant is to offset the amount lost to the environment (transpiration).
- Leaf curling allows the plant to reduce water…
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C4 Photosynthetic Pathway
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These plants have two types of photosynthetic cells
- Mesophyll + Bundle sheath cells
In C4 plants, CO2 reacts with enzyme PEP to produce OAA (initial product) OAA is then transformed into into the 4 carbon molecules: Malic + aspartic acid. These molecules are then transported to the …
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PEP Carboxylase
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Enzyme that catalyzes the initial step in the pathway of C4 photosynthetic plants. It produces OAA (oxaloacetate)
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Advantages of the C4 Pathway
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- PEP does not react with oxygen like RuBP (thus increasing its efficiency in relation to C3)
- Conversion of malic and aspartic acids into CO2 in the bundle sheath cells helps to concentrate the CO2 increasing the efficiency of the reaction of CO2 and RuBP (via Rubsico)
- Higher max ra…
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Characteristic of a C4 plant
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- Higher water use efficiency (for a stomatal opening the plant fixes more CO2)
- C4 has a higher energy expenditure because of the need to produce PEP enzyme.
- Tropical & subtropical regions
- Warmer and drier conditions
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CAM Photosynthetic Pathway
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Similar to the C4 pathway in that CO2 initially reacts with PEP and is transformed into 4 carbon compounds and then back to CO2 which then becomes glucose
- Both processes occur in the mesophyll cells at different times
- At night, stomata open and plants takes in CO2 + converts it to m…
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Advantages/Disadvantages of CAM Pathway
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Common process for desert plants)
+ Opening stomata only at night allows CO2 uptake when temp is lowest and humidity is highest
+ Increases water-use efficiency
- Very slow and inefficient in the fixation of CO2
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Effects of a decrease in water available in the soil
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- Increasing the allocation of carbon to the production of the roots while decreasing the production of the leaves (This also reduces the amount of water lost through the surface area of the leaves)
- Smaller and thicker leaves, thicker cell walls
- Some have small hairs, waxy/resin cov…
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Adaptations for Extreme Cold
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- Frost hardening due to genetics develops in the fall seasons by synthesizing sugars and amino acids that are distributed to cold-sensitive cells functioning as an anti-freeze, lowering the temp at which freezing occurs
- Once spring starts, the tolerance leave quickly and another frost…
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Macronutrients
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Nutrients essential for growth, survival and reproduction that are need in large amounts
(Carbon, Hydrogen, Oxygen form majority of plant tissues and are obtained from CO2 + H2O in environment)
(Nitrogen, Phosphorus, Potassium, Calcium, Mg, Sulfur)
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Micronutrients
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Trace elements that are needed in lower amount but are still EQUALLY important to the survival of the plant
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BIO 366: TEST 2