Detection of Chlorophyll fluorescence at crop canopies level: Remote Sensing of Photosynthesis Part I : Background, central and alternative photosynthetic electron transport pathways and active fluorescence measurement Oded Liran Department of Precision Agriculture 1
Photosynthesis is the main driver of the global carbon cycle Earthhow.com 2
Specialized organelles within the leaf mesophyll trap light energy and transform it into chemical energy (Drusch, M, 2017) 3
The light dependent reactions of the photosynthetic apparatus are a series of transmembrane and soluble protein complexes located within the thylakoid membranes in the chloroplast 4 pung5.wikispaces.com
Photosystem II & I are multi pigment-protein complexes that convert physical to chemical energy and drive the electron transport chain (Wei-Zong H, 1992) (WikiVisually.com) 5
Photosynthetic pigments capture light energy from different regions of the electromagnetic spectrum 6
Energy transferred to chlorophylls excite electron to a higher energy level which can then relaxed back in various different transition states Photochemistry (..to primary acceptor) (Sciencedump.com) Interaction with Oxygen ( to ROS) 7
Light harvesting complexes funnel down absorbed light by energetic transfer towards the reaction centers of PSII and PSI Quantum Coherence (Anna JM, 2013) Forster Resonance Energy Transfer (Knox RS, 2002) DOI: 10.5772/67887 8
Excitation which results in electron transfer to the primary acceptor of PSII, can continue in a non-cyclic pathway towards the FNR Ferredoxin:NADP + Reductase (H 2 O -> NADPH pathway) 9
NADPH and ATP created in the light dependent reactions of photosynthesis are used in the Calvin-Benson-Bassham cycle in order to produce sugars- the building blocks of life (Wikipedia) 9
Alternative electron transport pathways modulate energy distribution between the two Photosystems Active at the beginning of a light period to account for ATP needed to activate CBB cycle (Joliot 2002) Used as a part of a photoprotection Mechanism in order to avoid oxidative stress to the chloroplast (Yamori W, 2015) Yamori W, 2016 11
Alternative electron transport pathways modulate energy distribution between the two Photosystems (H 2 O -> H 2 O cycle) Mehler reaction is elevated under water stress condition (Asada, 2000) (Skillman JB, 2011) 12
The photosynthetic light reactions are limited by the activity of the Calvin-Benson-Bassham cycle carbon fixation step (Teiz and Zeiger, 3 rd edition) 11 13
The photosynthetic apparatus obtains time dependent lines of defense in order to protect itself from reaching an oxidative stress otherwise known as Non-Photochemical Quenching Seconds to minutes: qe = Energy Dependent Non photochemical quenching (xanthophyll cycle) Minutes to hours: qt = Light Harvesting Complex state transition towards PSI Hours to days: qi = reversible photoinhibition (closure of damaged Photosystem II units) PQ (Dent RM, 2001) 12 14
The photosynthetic apparatus reaches a sustained photoprotection conditions especially in the winter CBB cycle activity is slowed down The Photosynthetic apparatus is found on sustained NPQ conditions (Porcar-Castell, 2011) Most of the energy of light is dissipated on the antenna (Nilkens M, 2010) 15
Active measurement of chlorophyll fluorescence requires a special flourometer that manipulates the photosynthetic apparatus performance in a unique way In making a strong beam of the sun s light pass through the green fluid, I was surprised to observe that its color was a brilliant red, complementary to the green When illuminating Chlorophyll extract from plants : - Sir David Brewster, 1834 When illuminating a leaf About 90% of the light is emitted back to the viewer How much will be emitted back to the viewer? 14
Upon switching on the light, a fast fluorescence induction is recorded followed by a slower relaxation (fluorescence quenching) (Kautsky and Hirsch, 1931) 15
Fluorescence induction and CO 2 assimilation takes on opposite behavior within a light period Both of the wheat samples were illuminated for ~10 minutes in strong light, however, (1) and (2) were let to relax in the dark for 20 and 60 minutes respectively Fluorescence CO 2 assimilation (McAlister & Myers, 1940) 16
Application of a photosynthetic electron transport chain inhibitor results in a continuous excitation of fluorescence On 1963, Duysens and Sweers experienced a constant fluorescence profile after application of Diuron: Di-Chlorophenyl dimethyl Urea (Flors C, 2006) 17
Application of a photosynthetic electron transport chain inhibitor results in a continuous excitation of fluorescence DCMU (Bonasera KF, 2006) We can use the OPENED/CLOSED PSII principle to our advantage! 18
Short and strong pulsed light reports on the PSII state on top of continuous light experiments How much short? Qb 600 µsec 200 µsec ~10,000 µe Energy Qa Pheo P680 * 200 µsec 200 nsec 20 nsec 1 µsec 0.05 µe 3 psec 20 nsec 1 2 H 2 O 2H e O2 (Schreiber U, 1986) 19
Summary of the First part of the Lecture: 1. The global Carbon cycle affect the greenhouse effect, ocean acidification and the global eco-physiology of all life on earth. 2. The Plants (unicellular and multicellular) are the main driver for the carbon cycle, as they are responsible for Gross Primary Production, that is the utilization of light energy in chemical reactions that produce sugars. 3. The photosynthetic apparatus uses the absorbed light energy in various biosynthetic pathways the main of which is sugar biosynthesis. 4. We can use the photosynthetic apparatus properties to our advantage and to study the activity state of the Photosystem II. Thank you for your attention 22
References: 1. https://earthhow.com/carbon-cycle/ 2. Drusch, Matthias, et al. "The FLuorescence EXplorer Mission Concept ESA s Earth Explorer 8." IEEE Transactions on Geoscience and Remote Sensing 55.3 (2017): 1273-1284. 3. pung5.wikispaces.com 4. http://mendel.berkeley.edu/~wzh/chapter3/text.html 5. https://wikivisually.com/lang-de/wiki/photosystem_i 6. Guidi, L., Tattini, M., & Landi, M. (2017). How Does Chloroplast Protect Chlorophyll Against Excessive Light?. In Chlorophyll. InTech. 7. Anna, J. M., Scholes, G. D., & van Grondelle, R. (2013). A little coherence in photosynthetic light harvesting. BioScience, 64(1), 14-25. 8. Knox, R. S., & Van Amerongen, H. (2002). Refractive index dependence of the Förster resonance excitation transfer rate. The journal of physical chemistry B, 106(20), 5289-5293. 9. http://www.sciencedump.com 10. http://www.life.illinois.edu/govindjee/z-scheme.html 11. Yamori, W., Makino, A., & Shikanai, T. (2016). A physiological role of cyclic electron transport around photosystem I in sustaining photosynthesis under fluctuating light in rice. Scientific reports, 6, 20147. 12. Asada, K. (2000). The water water cycle as alternative photon and electron sinks. Philosophical Transactions of the Royal Society of London B: Biological Sciences, 355(1402), 1419-1431. 13. Skillman, J. B., Griffin, K. L., Earll, S., & Kusama, M. (2011). Photosynthetic Productivity: Can Plants do Better?. In Thermodynamics-Systems in Equilibrium and Non-Equilibrium. InTech. 14. Taiz, L., & Zeiger, E. (2002). Plant Physiology, Sinauer Associates. 21
References: 15. Dent, R. M., Han, M., & Niyogi, K. K. (2001). Functional genomics of plant photosynthesis in the fast lane using Chlamydomonas reinhardtii. Trends in plant science, 6(8), 364-371. 16. Porcar Castell, A. (2011). A high resolution portrait of the annual dynamics of photochemical and non photochemical quenching in needles of Pinus sylvestris. Physiologia Plantarum, 143(2), 139-153. 17. Nilkens, M., Kress, E., Lambrev, P., Miloslavina, Y., Müller, M., Holzwarth, A. R., & Jahns, P. (2010). Identification of a slowly inducible zeaxanthin-dependent component of non-photochemical quenching of chlorophyll fluorescence generated under steady-state conditions in Arabidopsis. Biochimica et Biophysica Acta (BBA)-Bioenergetics, 1797(4), 466-475. 18. Kautsky, H., & Hirsch, A. (1931). Neue versuche zur kohlensäureassimilation. Naturwissenschaften, 19(48), 964-964. 19. McAlister, E. D., & Myers, J. (1940). Time course of photosynthesis and fluorescence. Science, 92(2385), 241-243. 20. Flors, C., Fryer, M. J., Waring, J., Reeder, B., Bechtold, U., Mullineaux, P. M.,... & Baker, N. R. (2006). Imaging the production of singlet oxygen in vivo using a new fluorescent sensor, Singlet Oxygen Sensor Green. Journal of experimental botany, 57(8), 1725-1734. 21. Bonasera, J. M., Meng, X., Beer, S. V., Owens, T., & Kim, W. S. (2004, July). Interaction of DspE/A, a pathogenicity/avirulence protein of Erwinia amylovora, with pre-ferredoxin from apple and its relationship to photosynthetic efficiency. In X International Workshop on Fire Blight 704 (pp. 473-478). 22