Hort Exam 3
Photolysis
"Splitting by Light"Breaking down of water to: 1. Release O2, 2. Productionof H+s, 3. Production of electrons. During Light-Dependent Reaction.
De-etiolation
(The greening of young seedlings when they emerge from the soil) and stem growth in plants competing for light with other plants
Environmental/growth factors
1.Light Quality 2.Light Intensity 3.Light Duration 4.CO2Concentration 5.Temperature 6.Water 7.Plant Development
C4 Events
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C4 Reactions
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Etiolation
A condition involving lack of chlorophyll, increased stem elongation, and poor or absent leaf development). It occurs in plants growing under very low light intensity or complete darkness.
Where in the leaf (or stem) does photosynthesis occur?
A majority of the photosynthetic activity is in the upper 40% of the leaf.Mostly palisade parenchyma.Most of the chlorophyll is located in this area.
Phytochrome
A pigment that has two interconvertibleforms:1. A red light absorbing form.2. A far-red light absorbing form. s a special plant pigment that responds to light duration.
Products of light energy are:
ATP (adenosine triphosphate) and NADPH (nicotinamideadenine dinucleotidephosphate)
Plant Development
As a general rule, photosynthesis activity will decline when plants reach the reproductive stage and produce flowers.
Why have plants evolved different types of CO2 acquisitions and Calvin Cycle operations?
Because of Photorespiration
Thylakoid Lumen
Biochemical reactions that transform carbon dioxide into carbohydrate.
release of O2
By-product of photosynthesis released through stomatesNot needed for the rest of photosynthesis to proceedReleased as a gas and helps photosynthesis to replenish the earth's supply of breathable air
Photosynthesis light independent reaction (Clavin cycle)
C from CO2 is used to make carbohydrates. ATP and NADPH are the energy sources. The Calvin Cycle fixes C and produces sugars One CO2in at a time. 6 turns of the cycle to make C6H12O6 RuBisCois important enzyme in the process Different types of photosynthesis are:C3C4CAM
Photosynthesis formula
CO2+ 12 H2O C6H12O6+ 6 O2+ 6 H2OLightGlucose
in order for the cycle to run it requires (light independent reactions):
CO2, ATP, and NADPH (ATP supplies energy and NADPH provides electrons)
CAM plants at night
CO2absorbed. Converted to Oxaloacetate by PEP carboxylase. Oxaloacetate converted to MalateMalateshipped to vacuole for storage
What absorbs the red and blue part of the light?
Chlorophyll and Carotenoids
Chlorophyll
Chlorophylls differ in the light that they absorb.Red(600 -700 nm)Blue(400 -500 nm)When struck by light, molecules can absorb energy and move to higher energy or "excited" states. The chlorophyll pigments have evolved to absorb light photons and thus absorb energy. Chlorophyll ais the site of conversion of the light energy into chemical energy.
Stroma Lamellae
Connection between thylakoidsin adjacent granum stacks
Thylakoid structure
Contains the green pigment chlorophyll and surrounded is by a fluid material called stroma
What purpose do ATP and NADPH serve in photosynthesis?
Convert carbon dioxide to carbohydrate. Become degraded to ADP (adenosine diphosphate) and NADP+ (oxidized form of NADPH) after their role in carbohydrate construction is completed. ADP and NADP+ then return to the light-dependent reactions for conversion back to ATP and NADPH
CAM Plants
CrassulaceanAcid Metabolismor CAM plants (Are named after the first plant species identified with this special mechanism) Are a special type of C4plant. Scientists noticed that these plants became acidic during the night and then basic during the day. CO2 acquisition and the Calvin Cycle are separated by the time of day they occur. CAM plants fix CO2 (during the cool night time periods) with the use of PEP carboxylase. The CO2is converted to malicacid and stored in the vacuole until the Calvin Cycle needs it during the day. CAM plants separate CO2fixation and the Calvin Cycle temporally and spatially (occurring now in different organelles in the cell(Chloroplast and Vacuole) Most CAM plants are succulent desert plants growing in very harsh climates
Photosynthesis part two
Do not require light and are named the Light-Independent Reactions. Occurs in the stroma
NADPH
Essentially an electron carrierSupplies electrons to ongoing chemical reactions that require them
ATP
Essentially chemical energy
Sunlight
Essentially white light. Actually composed of several colors mixed together. Spectrum or composite colors:Red, Orange, Yellow, Green, Blue, Indigo, Violet (Easy way to remember the colors and their order in a rainbow"Roy G. Biv")
C3 Plants
First chemical formed when carbon dioxide enters Calvin Cycle has three carbons (3-carbon compound (3-PGA) to produce sugars) 85% of the known plant species are C3plants. Plants with only the Calvin Cycle have less efficient photosynthesis.
Z-Scheme of photosynthesis
From 2 molecules of H2O, one molecule of O2is formed, 4 H+, and 4 electrons. Hydrogen ions are pumped out of the lumen into the stromato produce 3 ATPs. 4 electrons are used to reduce 2 NADP+to 2 NADPH's. This is called the Light Reaction of Photosynthesis.
Photosynthesis light dependent reaction
H2O split to produce H+, electrons, and O2. Light photons excite electrons to higher levels"Z" Scheme. As they return to ground states, the energy released photophosphorilates ADP to ATP and creates NADPH from NADP+. These energy rich intermediates are used to synthesize C6H12O6 in the Calvin Cycle.
C4 Plants
Have bothmesophylland bundle sheath chloroplasts. More efficient photosynthesis. Low to zero rates of photorespiration. First product from carbon dioxide in C4plants has four carbons
Light Saturation Point
Increases in light intensity but will not increase photosynthesis activity.
Photorespiration
Inefficient loss of C from Calvin Cycle when enzyme combines with O2instead of CO2. Only under certain climactic conditions
Internal factors affecting the rate of respiration
Injury, Levels of available food, Age or kind of tissues concerned, Levels of intermediates utilized in the respiration process, Increasing levels of O2 and CO2 increase and decrease, respectively, the rates of respiration. O2 is used up during respiration, so when it is limiting, respiration decreases. (Technique used in refrigeration and produce storage in modified atmospheres can slow post-harvest respiration)
Photorespiration ( ???? What else to add)
Is the release of CO2 and the consumption of O2 which occurs in the light under specific climactic conditions.
photomorphogenesis
Light also affects plant growth and development
How does light energy power this process?
Light energy is converted to chemical energyWater is broken down to release: Oxygen, Electrons, Protons
CAM plants during the day
Malate shipped from vacuole to chloroplasts. Malate broken down:CO2 Used to make sugar (normal photosynthesis) Pyruvate Used to make starch in chloroplast
Oxidative phosphorylation
Mitochondriahave a double membrane. Electron transport systemis physically located in the inner membrane. Oxidative phosphorylation refers to the combination of the oxidation/reduction reactions of electron transport. These reactions enable a cell to use the energy in NADH and FADH to convert ADP plus Piinto ATP.
light duration
Most photomorphogenicresponses are regulated by the phytochromepigment system.
does a plant use all the colors of white light?
No, Photosynthesis process uses onlythe red and blue part of sunlight. Leaf absorbs the red and blue. Other colors are reflected back
Electron Transport System??????
Occurs on the inner membrane of the mitochondrion. Site of the greatest amount of energy production. Converts NADH and FADH to ATP. Water is made.(Uses H+)
Water
Only a small amount (<0.1%) of water is used directly during photosynthesis.
Adaptive forms of photosyntheses
Plants are classified as to how the Calvin Cycle operates and what is the Carbon accepting molecule. C3 Plants, C4Plants, CAM Plants
Action Spectrum
Plotting the activity of photosynthesis over the different wavelengths of light produce
Light Intensity
Refers to brightness, or level of light. The sun is the source of energy for photosynthesis and other plant processes. This band of radiation is referred to as:Visible Light or Photosynthetic Active Radiation(PAR). Green color of plantsChlorophyll absorbs light in BLUE/VIOLETwavelengths (400-510 nm) and REDwavelengths (610-700 nm).Plants transmit and reflect the wavelengths between 510 and 610 nm. Will affect photosynthesis rates.But, the effect of light intensity variesbetween different plants species
Light quality
Refers to the wavelengths or energy value of the light striking the plant. Blue light has lower wavelengths and higher frequencies. 1.8 times more energy than REDlightMore "energetic" potential than photons of REDlightTheoretically, BLUElight would result in a higher photosynthetic rate.
Photosynthesis part one
Require light and chlorophyll and are called the Light-Dependent Reactions. Occurs in the thylakoid
reaction center photosystem 2
Specialized Chlorophyll (P680) Produces ATP And Releases oxygen through photolysis
reaction center photosystem 1
Specialized chlorophyll (P700) Received electrons from photosystem II through plastoquinoneand plastocyanin(electron transport chain).Transfers light energy received from light harvesting chlorophylls, or directly from light, to electrons derived from PSII. Generates NADPH
Granum (Grana)
Stacks of thylakoids.
Where does photosynthesis take place?
Takes place in green tissues only. Because of its requirement for a green pigment called cholorophyll
Glycolysis
Takes place in the cytoplasm. Pyruvic acid is produced from glucose in a series of enzyme-catalyzed reactions
environmental factors affecting the rate of respiration
Temperature (Increase temperature causes increase in respiration rate. Respiration doubles for each 10°C rise in temperature between 5°and 36°C) Water Levels of O2 and CO2.
how Oxidative phosphorylation works
The H+ions enter the space between the two membranes setting up a proton gradient. Pressure is relieved as protons escape through the ATP synthase to form ATP1 NADH can produce 3 ATPs1 FADH2can produce 2 ATPs.
Light independent reactions
The next phase of photosynthesis is really incorrectlycalled the Dark Reaction.It just means that light is not used in the process or pathway. if light were removed from the plant this process would stop too. 1950s M. Calvin (Calvin Cycle)
Photosynthesis
The process in which light energy from the sun is converted to chemical energy and in turn is used to construct carbohydrates for the plant to use as food and fuel
Both reaction centers PS1 and PS2
The reactions that begin with PSII and end with PSI are referred to as the "Light Dependent-Reactions".(Reactions fueled by light intensity.) Store energy that came from LIGHT. (ATP and NADPH)
Carbon Dioxide
Third most abundant gas in the atmosphere.350 ppm. Absorbed from the air through the stomata
Chloroplast structure
Thylakoid Structure, Thylakoid Lumen, Granum(Grana), and Stroma Lamellae
Chloroplast has two "assembly sites"
Thylakoids and Stroma
Wave Length Independent
Type of light scattering due to a combination of airborne particles:DustWater DropletsIce Crystals in CloudsAll wavelengths are scattered equally.Typically clouds are white, unless they contain dust particles that absorb more light than is scattered.Scattering due to clouds substantially reduces light intensities at the earth's surface.
Wave Length Dependent
Type of light scattering due to an interaction of light waves with individual molecules of the atmosphere.The basis for the blue color of the sky.Blue light is more likely to be scattered because it has a shorter wavelength.As a result much of the blue light reaches the earth through an indirect route
Productionof H+s
Used by the plant to produce "energy carrying compounds"
Productionof electrons
Used by the plant to produce "energy carrying compounds"
Light Compensation Point
When photosynthesis and respiration are equalthere is a net gas exchange of zero. (equal CO2and O2exchange)
Carotenoids
Yellow and orange pigments also found in the thylakoidsof chloroplasts. Considered to be accessory or helper pigments in the light-dependent reactions. Can also intercept and pass on light energy to chlorophyll
Respiration
breaks down carbohydratesto produce energy(ATP) while using oxygenand giving off carbon dioxide
Photoperiodism
is the photomorphogenicresponse to seasonal variations in the amount of daylight.Many plants respond to the number of hours of light received during a day.Also known as Photoperiod
Unit of measure for intensity of photosynthetic light
micromoles per square meter per second (molm-2s-1)PPF (Photosynthetic Photon Flux)
Angle of Incidence
or Sun's Altitude influenced by Tilt of Earth, Position on Globe, Time of day, Photosynthesis Rates, Light Intensity and Reflection
Site of conversion of light energy into chemical energy is?
reaction center
heliotropic movements
some plants can compensate for the reduced light intensity and increased reflection at low solar angles, in which leaf angles are adjusted so that the sun's rays are normal, or perpendicular, to the leaf during most of the day
