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61 Cards in this Set
- Front
- Back
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Flux |
light reaching the plant measured in energy or photon units |
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Irradiance |
amount of energy that falls on a flat sensor of known area per time unit watts per meter squared Wm-2 |
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Photon irradiance |
number of incident quanta striking the leaf light or photon energy moles per square meter per second Wm-2s-1 |
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Incident sunlight |
Light that reaches the leaf Changes with angle of sun to leaf. Max when perpendicular |
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Photosynthetically active radiation |
between 400 and 700 nm Expressed as quanta (mol m-2s-2) or energy (Wm-2) |
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Reasons light gets through palisade parenchyma cells to mesophyll |
Sieve effect Light channeling Interface light scattering |
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Sieve effect |
Shading between chlorophyll molecules creating gaps where light is not absorbed and can pass through |
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Light channeling |
Some of the light is propagated through the central vacuoles and air spaces, facilitating transmission to leaf interior |
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Interface light scattering |
Water-air interfaces in mesophyll cells reflect and refract light |
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Absorptance |
the ration of the amount of radiation absorbed by a surface to the amount of radiation incident upon it (Ie how much light it gets) |
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Reflectance |
Ration of intensity of reflected radiation to that of the radiation incident upon the surface |
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Reflection |
Return of light, heat or sound after striking a surface |
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Refraction |
The change of direction of a ray of light, heat or sound in passing from one medium to another in which the wave velocity is different (IE Air to water) |
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Transmittance |
Ration of radiation transmitted through and emerging from a body to the total radiation incident on it |
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Transparent |
Having the property of transmitting rays of light through its substance |
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Sunflecks |
patches of light that pass through gaps in a leaf canopy and move across shaded leaves increase flux by 10! |
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Solar tracking
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control light absorption by moving leaves Blue light response |
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Pulvinus |
area in plant at nodes that controls leaf orientation by a change in solute potential |
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Heliotropism |
leaf movement induced by the sun |
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Diaheliotropic vs Paraheliotropic |
Dia- move to maximize light received Para- moves to minimize heating and water loss while still getting light |
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Phototropism |
growth in the direction of light source |
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Acclimation |
growth process in which newly produced leaves have set of biochemical and morphological traits suited to the environment its in Developmental plasticity. Can be moved |
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Adaption |
Genetic component. Low plasticity Die when environment changes |
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Shade leaves |
More chlorophyll in reaction center, higher ration of chl a to chl b, thinner than sun leaves |
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Sun leaves |
more rubisco and larger pool of xanthophyll cycle components |
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Light response curve |
measuring net CO2 fixation across varying levels of absorbed light |
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Light Compensation point |
CO2 uptake balances Co2 release |
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Quantum yield |
Number of photochemical products/ total number of quanta absorbed Can be expressed on either a CO2 or O2 basis |
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Non photochemical quenching |
Xanthophyll cycle with three carotenoids: violaxanthin, antheraxanthin and zeaxanthin (best for high light) |
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Photoinhibition |
Dynamic and Chronic Dynamic- quantum efficiency declines, but max photo synth rates are unchanged. can recover Chronic- damage photosystems and decrease quantum efficiency and max photo synth rates |
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Radiative heat loss |
Object emits radiation in proportion to their temperature |
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Sensible heat loss |
If the temperature of the leaf is higher than the air around the leaf, heat is transferred from leaf to air |
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Latent heat loss |
Transpiration withdraws large amounts of heat from the leaf and cools it |
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Optimal temperature |
Represents the highest photosynthetic rates in response to increasing temperature Strong genetic and environmental components |
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Greenhouse effect |
Trapping of long-wavelength radiation in the atmosphere. Influenced by different particles in air: water vapor, CO2, methane, ect |
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Types of resistance CO2 faces in a leaf |
Boundary layer Stomatal- most important and only significant resistance Intercellular airspace Liquid phase resistance- enters the cell |
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CO2 compensation point |
Increasing intercellular Co2 to the concentration at which photosynthesis and respiration are balanced. |
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C3 vs C4 plants: Efficieny with CO2, high light and heat |
C3- more Co2 is better. Does good in high light. not great in heat C4- More CO2 doesn't help anything. less efficient with high light, does very good in heat |
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CAM Idling |
allows plants to survive long periods of drought. Keep stoma closed and only use CO2 from mitochondia |
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Free Air CO2 Enrichment (FACE) |
way to study plant phys and ecology with increased CO2 concentrations
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Stomatal Opening (What cells? What Controls it?) |
Guard Cells Blue light controls opening of stomata. Abscisic acid (from stress) will keep stoma closed Guard cells swell with blue light |
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How does blue light cause stomatal opening (basic)? |
Blue light stimulates the uptake of ions and creates a difference is solute potential, so the guard cells have more solutes. Water flows in and makes the cells turgid |
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Three pathways to supply osmotically active solutes to guard cells |
-Uptake of K- and Cl- coupled with the synthesis of malate within the guard cells -Production of sucrose in guard cell cytoplasm from precursors from starch hydrolysis in guard cell chloroplast -Production of sucrose from precursors made in photosynthetic carbon fixation |
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Blue-light photoreceptors |
1. Cryptochromes- inhibit stem elongation and flowering 2. Phototropins-function mainly in phototropism 3. Zeaxanthin- Blue-light response of stomatal movement and photo protection. No blue light response if absent. |
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Callose |
Long term sealing method when phloem is damaged B1,3-glucan Shuts down sieve pores. Can be broken down if phloem is repaired |
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P-Proteins |
Short term sealing of phloem Many shapes based on species and maturity Plug up sieve plate pores to seal them off. Not a permanent fix |
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Companion Cell Types |
Ordinary Transfer Intermediary |
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Ordinary companion cell |
Chloroplasts with well developed thylakoids Cell wall with smooth inner surface Symplastic or apoplastic short distance travel in source leaves |
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Transfer Companion Cells |
Finger-like wall ingrowths from ER Solute transfer transmembrane Plasmodesmata connect to sieve element Transport sugar from apoplast to symplast of sieve element and companion cell in Source |
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Intermediary Cells |
take up solutes via cytoplasmic connections Numerous plasmodesmata attaching them to bundle sheath cells Numerous vacuoles and poorly developed thylakoids, lack starch grains Symplastic transport of sugars from mesophyll cells to sieve elements |
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Sources |
exporting organs, such as mature leaves Capable of producing photosynthate in excess of their own needs Also storage organs like tubers |
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Sinks |
Non-photosynthetic organs and organs that don't photosynthesize enough Roots, tubers, developing fruits, immature leaves |
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Non-reducing sugars |
Non reactive sugars Sucrose, raffinose (sucrose +n galactose), etc and sugar alcohols like mannitol or sorbitol |
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Other solutes found in phloem |
Nitrogen, amino acids, mRNAs, pathogenic RNAs, plant hormones, nucleotide phosphates, magnesium, phosphate and chloride, p-proteins and other water soluble proteins, non-reducing sugars |
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Pressure-flow model |
ONLY FOR ANGIOSPERMS Flow of solution driven by osmotically generated pressure gradient between a source and a sink |
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Phloem loading |
movement of photosynthate into sieve elements |
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Phloem unloading |
movement of photosynthates from sieve elements to sink cells |
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Four major processes of Respiration |
Glycolysis, oxidative pentose phosphate pathway, citric acid cycle and oxidative phosphorylation |
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Substrate level Phosphorylation |
Takes an inorganic phosphate from the 'substrate' and adds it to the ADP to make ATP |
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Gluconeogenesis |
Synthesis of sugars from organic acids. 'Reverse' of glycolysis. Oil is stored in seeds and returned to sugar for germination |
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Cytoplasmic Male Sterility |
A naturally occurring rearrangement of genes in the mitochondria that makes male flower parts sterile Useful for crossing plants. Reduces work for farmers |
