Endogenous rhythms and chaos in crassulacean acid metabolism

Abstract

Endogenous free-running regular circadian oscillations of net CO2 exchange in the crassulacean-acidmetabolism (CAM) plant Kalanchoë daigremontiana Hamet et Perrier de la Bâthie under constant external conditions in continuous light have been shown to change to irregular non-predictable (chaotic) time behaviour as irradiance or temperature are raised above a critical level. A model of CAM has been constructed with pools of major metabolites of varying concentrations, flows of metabolites leading to exchange between pools, metabolite transformations determined by chemical reactions, and feedback regulations. The model is described by a system of coupled non-linear differential equations. It shows stable rhythmicity in normal dark-light cycles and in continuous light and, like the K. daigremontiana leaves in the experiments, a change to chaos as irradiance is increased. The maintenance of endogenous oscillations in the model is brought about by a hysteresis switch or beat oscillator between two stable oscillation modes. In CAM these stable modes are vacuolar malate accumulation and remobilization. The model shows that the physical nature of the beat oscillator in the leaves can be explained by the balance between active and passive transport at the tonoplast.

Temporal dynamics of stomatal conductance of plants under water deficit: can homeostasis be improved by more complex dynamics?

“…Some authors have observed chaotic dynamics in plants in different physiological processes. Lüttge and Beck (1992) showed the possible existence of chaotic dynamics in endogenous rhythms in certain CAM species. Krempaský et al (1993) indicated that varying light intensities caused changes in the patterns of photosynthetic temporal behaviors, ranging from periodic to chaotic behavior.…”

Sistemas complexos: novas formas de ver a Botânica

“…Lüttge & Beck (1992) mostraram a possível existência de dinâmica caótica no ritmo circadiano em espécies com metabolismo ácido crassuláceo (MAC). Krempasky et al (1993) mostraram que, alterando a intensidade luminosa, podem surgir padrões temporais no comportamento do sistema fotossintético variando de periódico a caótico.…”

Adaptive Estimation of Biological Rhythm in Crassulacean Acid Metabolism with Critical Manifold

“…Endogenous oscillators of living cells and organisms are based on feedback loops in complex biochemical-reaction networks. Crassulacean acid metabolism (CAM) is a specific mechanism of inorganic carbon acquisition for photosynthesis [1,2]. CAM plants take up external CO 2 during the night while the stomata are open.…”

“…The CO 2 is fixed in the plant in the form of organic acids, normally malate, via the enzyme phosphonenolpyruvate carboxylase (PEPc) and stored overnight in the vacuole [3]. The malic acid is accumulated to high concentrations of up to several hundred millimolars and stored in the cell sap vacuole [1,2]. During the daytime, malate is remobilized from the vacuole and decarboxylated again [3].…”