Deriving C4 Photosynthesis Parameters by Fitting Intensive A/Ci Curves
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Rapid Light Bcurve Application Note 3 22 12 Test 2.Cdr
App Note #0412 Rapid Light Curves, a solution for variable light environments, an overview: Resulting ETR values Fluorometer RLC trace in the RLC showing the results of increasing light intensity Typical trace of a Rapid Light Curve. The quantum yield of PSII, or Y(II), ETRMAX, " ,and IK values are reported with details for each step on one screen. A separate screen shows both the raw light trace and the resulting Rapid Light Curve. Rapid light curves have been heavily used by researchers to study aquatic plants, and for under canopy research on land, where it is common for the light irradiation level to constantly change. Most traditional chlorophyll fluorescence parameters and methods run into difficulty when light level changes rapidly. While the measurement of quantum yield of PSII, or Y(II), and ETR, only takes a second or two, They are defined as a measurements taken during steady state photosynthesis, a process which takes between fifteen and twenty minutes at non-changing light levels for land plants (Genty 1989, 1990) (Maxwell and Johnson 2000). Aquatic plants are subject wave action, changes in water column depth, tides, currents, clouds and turbidity changes, where as under canopy land plant leaves are exposed to variable shading from other plants and wind. Traditional Y(II), ETR, and standard light response curves run into problems with these samples and over estimate photosynthetic activity (Macintyre 1997). Of course, Fv/Fm may be used to measure the health of PSII with many of these situations; however, the need to study and measure the reaction of plants under changing ambient condi tions, and the need to study light saturation characteristics, have driven research to methods such as Rapid Light Curves. -
Photophosphorylation in Intact Algae: Effects of Inhibitors, Intensity of Light, Electron Acceptor and Donors
Plant & CellPhysiol. 14: 1081-1097 (1973) Photophosphorylation in intact algae: Effects of inhibitors, intensity of light, electron acceptor and donors Glenn W. Bedell II and Govindjee Downloaded from Department of Botany, University of Illinois, Urbana, Illinois 61801 U. S. A. (Received May 1, 1973) http://pcp.oxfordjournals.org The luciferin-luciferase method was used to determine ATP extracted from dark- maintained and light-exposed samples of the green alga Chlorella pyrenoidosa and of the blue-green alga Anacystis nidulans. A few measurements on Synechococcus lividus (a blue- green thermophile, clone 65°C) are also reported. 1. The light-minus-dark ATP levels (JATP) from aerobic cells of Chlorella and Anacystis were negative; however, JATP from Synechococcus was positive. Large positive JATP was obtained in regularly grown (RG: moderate light) Chlorella treated with oligomycin; dark levels were reduced, light levels remained essentially unaffected. In high-light exposed (HLE) Chlorella, oligomycin reduced both light and dark ATP levels, but positive A ATP was still obtained. However, in Anacystis, which has a different organization of thylakoid membrane, oligomycin severely reduced both the light and at University of Illinois Urbana-Champaign on July 7, 2010 the dark ATP levels and the JATP remained negative. 2. The oligomycin (12 fit*) treated Chlorella and the untreated Anacystis and Syne- chococcus show the presence of cyclic photophosphorylation under conditions in which the non-cyclic electron flow from photosystem II to photosystem I is blocked by 10 f*M 3-(3,4-dichlorophenyl)-l,l-dimethylurea (DCMU), or not allowed to operate by the absence of CO2. Cyclic photophosphorylation ranged from 10-30% of the maximum JATP in RG, to 40-50% in HLE Chlorella. -
Light-Dependent Growth Kinetics and Mathematical Modeling Of
Light-Dependent Growth Kinetics and Mathematical Modeling of Synechocystis sp. PCC 6803 by Levi Straka A Dissertation Presented in Partial Fulfillment of the Requirements for the Degree Doctor of Philosophy Approved March 2017 by the Graduate Supervisory Committee: Bruce Rittmann, Chair Peter Fox César Torres ARIZONA STATE UNIVERSITY May 2017 ABSTRACT One solution to mitigating global climate change is using cyanobacteria or single- celled algae (collectively microalgae) to replace petroleum-based fuels and products, thereby reducing the net release of carbon dioxide. This work develops and evaluates a mechanistic kinetic model for light-dependent microalgal growth. Light interacts with microalgae in a variety of positive and negative ways that are captured by the model: light intensity (LI) attenuates through a microalgal culture, light absorption provides the energy and electron flows that drive photosynthesis, microalgae pool absorbed light energy, microalgae acclimate to different LI conditions, too-high LI causes damage to the cells’ photosystems, and sharp increases in light cause severe photoinhibition that inhibits growth. The model accounts for all these phenomena by using a set of state variables that represent the pooled light energy, photoacclimation, PSII photo-damage, PSII repair inhibition and PSI photodamage. Sets of experiments were conducted with the cyanobacterium Synechocystis sp. PCC 6803 during step-changes in light intensity and flashing light. The model was able to represent and explain all phenomena observed in the experiments. This included the spike and depression in growth rate following an increasing light step, the temporary depression in growth rate following a decreasing light step, the shape of the steady-state growth-irradiance curve, and the “blending” of light and dark periods under rapid flashes of light. -
Variable Chlorophyll Fluorescence – Overview (2013)
Variable Chlorophyll Fluorescence – Overview (2013) Chlorophyll absorbs light most effectively in the red and blue parts of the visible spectrum. Chlorophyll fluorescence is light that is re-emitted at a longer wavelength after being absorbed by chlorophyll molecules at a shorter wavelengths. Variable chlorophyll fluorescence is only observed in chlorophyll “a” in photosystem II. By measuring the intensity and nature of variable chlorophyll fluorescence, and using protocols that have been developed, plant physiology can be investigated (Baker 2004). The variable nature of chlorophyll fluorescence allows research into the light reaction of plants, plant photo-protection mechanisms, heat dissipation, correlation with photosynthesis carbon assimilation, and measurement of most types of plant stress at usable levels (Baker 2004). As stated earlier, the sole origin of variable chlorophyll fluorescence is chlorophyll “a” in photosystem II (Zhu 2005). Light energy entering photosystem II can be converted to chemical energy by photochemistry. It can also be re-emitted as chlorophyll fluorescence or it can be re-emitted as heat. These three processes are in competition, so that when photochemistry output is high, chlorophyll fluorescence and heat are lower. Conversely, if fluorescence is maximized, then the other two paths are minimized. While photosystem I does emit chlorophyll fluorescence as well, it is at a much lower level and it is not variable. For that reason, chlorophyll fluorescence of photosystem II is of much greater interest. (Schreiber 2004) Photosynthesis is comprised of a light reaction and a dark reaction. The light reaction converts light energy into chemical energy that can be used in the dark reaction. The dark reaction uses the energy molecules NADPH and ATP, created by the light reaction, to produce simple sugars in conjunction with the assimilation of CO2 from the air.