Light-Dependent Growth Kinetics and Mathematical Modeling Of
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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. -
Deriving C4 Photosynthesis Parameters by Fitting Intensive A/Ci Curves
bioRxiv preprint doi: https://doi.org/10.1101/153072; this version posted October 13, 2018. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license. 1 Deriving C4 photosynthesis parameters by fitting intensive A/Ci curves 2 Haoran Zhou1, Erol Akçay1 and Brent R. Helliker1 3 4 1 Department of Biology, University of Pennsylvania, Philadelphia, PA 19104, USA 5 6 Correspondence: Haoran Zhou 7 Address: 433 S University Ave. 8 314 Leidy Labs 9 Philadelphia, PA 19104 10 Phone: 1-215-808-7042 11 Email: [email protected] 12 Brent R. Helliker: [email protected] 13 Erol Akçay: [email protected] 14 Running head: Deriving C4 photosynthesis parameters 1 bioRxiv preprint doi: https://doi.org/10.1101/153072; this version posted October 13, 2018. The copyright holder for this preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity. It is made available under aCC-BY 4.0 International license. 15 ABSTRACT 16 Measurements of photosynthetic assimilation rate as a function of intercellular CO2 (A/Ci 17 curves) are widely used to estimate photosynthetic parameters for C3 species, yet few 18 parameters have been reported for C4 plants, because of a lack of estimation methods. Here, 19 we extend the framework of widely-used estimation methods for C3 plants to build 20 estimation tools by exclusively fitting intensive A/Ci curves (6-8 more sampling points) for 21 C4 using three versions of photosynthesis models with different assumptions about carbonic 22 anhydrase processes and ATP distribution. -
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.