Rapid light curves: A powerful tool to assess photosynthetic activity

• Published in: Aquatic botany Vol. 82; no. 3; pp. 222 - 237
• Main Authors: Ralph, Peter J., Gademann, Rolf
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-07-2005
• Subjects: Chlorophyll a fluorescence; Marine; PAM; Quenching analysis; RLC; Seagrass; Zostera marina; LL; PAR; LC-WIDTH; ETR; F ′ m; HL; F; F ′ o; PSII; E d; RLC; NPQ; LC-INT; E k; F m; F o; Chlorophyll a fluorescence; Seagrass; P m; F v/ F m; P s; Quenching analysis; AI; Φ PSII; rETR max; α; Q A; P– E; PAM; qN; qP
• ISSN: 0304-3770; 1879-1522
• DOI: 10.1016/j.aquabot.2005.02.006

Rapid light curves provide detailed information on the saturation characteristics of electron transport, as well as the overall photosynthetic performance of a plant. Rapid light curves were collected from samples of
Zostera marina grown under low and high-light conditions (50 and 300
μmol
photons
m
−2
s
−1) and the distinctive patterns of RLC parameters are discussed, in terms of differential sink capacity and PSII reaction centre closure. Derived cardinal points of a rapid light curve (
α,
E
k and rETR
max) describe the photosynthetic capacity of a seagrass leaf, its light adaptation state and its capacity to tolerate short-term changes in light. The shapes of the corresponding
F and
F
′
m
curves also provide information on the development of the
trans-thylakoid proton gradient and thermal energy dissipation. Low-light leaves showed limited photosynthetic capacity and reduced activity of non-photochemical quenching pathways, whereas photosynthesis of high light leaves were not limited and showed an elevated level of non-photochemical quenching, possibly associated with xanthophyll cycle activity. Light-dark kinetics are also discussed in relation to relaxation of non-photochemical quenching and its various components. A curve fitting model is recommended based on the double exponential decay function. In this paper, we explain the fundamental aspects of a RLC, describe how it reflects the response to light exposure of a leaf, how to interpret these curves, and how to quantitatively describe and compare RLCs.