Fluorescence Quick Introduction and Overall Awareness
- RS STORE ENTERPRISE
- Dec 2, 2024
- 3 min read
Original video: https://youtu.be/ctuUCCQ8hxk
Delivered on: 3 September 2024
An introductory session on chlorophyll fluorescence and the fluorescence system on LiCOR LI-6800. This session offers a comprehensive introduction to chlorophyll fluorescence, emphasising its importance in studying plant physiology. Participants will learn how the LI-6800 fluorescence system works and get a brief introduction on analysing fluorescence data, providing insights into plant health, stress responses, and photosynthetic efficiency.
Video Timestamps:
00:11 Brief introduction on fluorescence
00:23 Analogy of fluorescence
03:27 PAR definition
06:00 Five fates of excited chlorophyll molecule
15:00 The concept of open/close reaction center
17:08 Mode of action of herbicide - Interfere the reaction center
17:55 The typical range of the light capture efficiency
18:55 Introduction to the fluorescence system of LI-6800
22:52 How fluorescence signal is measured?
33:53 Fluorescence parameters
38:48 Fluorescence labels and descriptions
44:00 Test your understanding
50:34 How ATP is manufactured
55:40 Which one is shade plant? Determine using data fluorescence
1:05:32 Demonstration on dark adapting a leaf
Location:
Department of Crop Science, UPM
XPMM+8R Seri Kembangan, Selangor
2.9833022017431574, 101.73468532055584
Note can be downloaded here:
Decoding Plant Health: An Introduction to Chlorophyll Fluorescence
Welcome to a deep dive into the invisible mechanics of plant physiology! Today, we are exploring the fascinating world of photosynthesis through the lens of a Fluorescence Training program conducted by Nazmin Yaapar at Universiti Putra Malaysia (UPM). Embodying the motto "Agriculture. Innovation. Life," UPM's research continues to advance agricultural science for the people.
Whether you are a researcher, a student, or simply an agriculture enthusiast, understanding how plants process light is crucial to understanding plant health.
The Fate of Sunlight
When sunlight touches a leaf, the energy is either reflected, transmitted through the leaf, or absorbed by the plant. The light that is successfully absorbed excites the chlorophyll pigment from its ground state to a highly energetic state.
Once excited, the plant must safely manage this energy. In a fully functioning photosynthetic system, the energy has three primary fates:
Photochemistry: The energy is successfully used to drive linear electron transport and carbon fixation.
Heat Dissipation: Excess energy is safely dissipated as heat, a process governed by non-photochemical quenching to prevent damage to the plant.
Fluorescence: A small percentage of the absorbed light is re-emitted as chlorophyll fluorescence.
Because these three processes compete for the same excited energy, measuring the amount of fluorescence emitted gives us direct, real-time insight into the efficiency of a plant's photochemistry and heat dissipation mechanisms.
Open vs. Closed Reaction Centres
To understand fluorescence, we must look at the plant's Photosystem II (PSII) reaction centres:
Open Reaction Centres: When a reaction centre is "open" and ready to accept electrons, photochemistry is operating at maximum capacity (1), and fluorescence drops to a minimum (0).
Closed Reaction Centres: When a reaction centre is "closed"—either because it is currently processing a photon or blocked by a PSII inhibitor—photochemistry drops to zero, and the fluorescence signal spikes to its maximum (1).
Key Fluorescence Parameters
By using specialised tools like a Multiphase Flash Fluorometer—which utilises blue (475 nm), red (625 nm), and far-red (735 nm) LEDs—scientists can trigger and measure specific fluorescence states.
Here are the most vital parameters used to evaluate plant efficiency:
Parameter | Description | Mathematical Formula |
Maximum Quantum Yield (Fv/Fm) | Represents the maximum efficiency of PSII under dark-adapted conditions, indicating potential chemical energy conversion when all reaction centres are open. | (Fm - Fo) / Fm |
Effective Quantum Yield (ΦPSII) | Measures the relative effective quantum yield of photochemical energy conversion at a steady, light-adapted state. | (Fm' - Fs) / Fm' |
Non-Photochemical Quenching (NPQ) | Estimates the attenuation of light energy dissipated as heat. This acts as a protective mechanism for the plant against excess light energy. | (Fm - Fm') / Fm' |
Photochemical Quenching (qP) | Estimates the exact fraction of open reaction centres during light adaptation. | (Fm' - Fs) / (Fm' - Fo') |
Electron Transport Rate (ETR) | An estimation of the actual electron transport rate flowing through PSII. | ΦPSII × PPFD × f × α |
Why This Matters
Chlorophyll fluorescence provides a non-destructive window directly into the internal workings of a leaf. By analysing metrics like Fv/Fm and NPQ, agriculturists can detect early signs of plant stress, optimise lighting for crop yields, and better understand how crops interact with their environment. As UPM's training highlights, knowledge is the foundation of agricultural innovation, allowing us to better serve both the plants we grow and the people who rely on them.
Attribution 4.0 International — CC BY 4.0 - Creative Commons
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