Spatiotemporal variation in metabolism in a plant circadian rhythm: The biological clock as an assembly of coupled individual oscillators

Date

2001

Authors

Rascher, Uwe
Hutt, Marc Thorstern
Siebke, Katharina
Osmond, C. Barry
Beck, Friedrich
Luttge, Ulrich

Journal Title

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Volume Title

Publisher

National Academy of Sciences (USA)

Abstract

The complex dynamic properties of biological timing in organisms remain a central enigma in biology despite the increasingly precise genetic characterization of oscillating units and their components. Although attempts to obtain the time constants from oscillations of gene activity and biochemical units have led to substantial progress, we are still far from a full molecular understanding of endogenous rhythmicity and the physiological manifestations of biological clocks. Applications of nonlinear dynamics have revolutionized thinking in physics and in biomedical and life sciences research, and spatiotemporal considerations are now advancing our understanding of development and rhythmicity. Here we show that the well known circadian rhythm of a metabolic cycle in a higher plant, namely the crassulacean acid metabolism mode of photosynthesis, is expressed as dynamic patterns of independently initiated variations in photosynthetic efficiency (ΦPSII)over a single leaf. Noninvasive highly sensitive chlorophyll fluorescence imaging reveals randomly initiated patches of varying ΦPSII that are propagated within minutes to hours in wave fronts, forming dynamically expanding and contracting clusters and clearly dephased regions of ΦPSII. Thus, this biological clock is a spatiotemporal product of many weakly coupled individual oscillators, defined by the metabolic constraints of crassulacean acid metabolism. The oscillators operate independently in space and time as a consequence of the dynamics of metabolic pools and limitations of CO2 diffusion between tightly packed cells.

Description

Keywords

Keywords: acid; carbon dioxide; chlorophyll; crassulacean acid; unclassified drug; article; biological rhythm; carbon dioxide transport; circadian rhythm; controlled study; diffusion; fluorescence; gas exchange; metabolism; nonhuman; oscillator; photosynthesis; pla

Citation

Source

PNAS - Proceedings of the National Academy of Sciences of the United States of America

Type

Journal article

Book Title

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DOI

10.1073/pnas.191169598

Restricted until

2037-12-31