ISSN:
1432-2048
Keywords:
Circadian rhythm
;
Crassulacean acid metabolism
;
Kalanchoe
;
Model simulations
;
Phase setting
;
Tonoplast
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Leaves of Kalanchoë daigremontiana Hamet et Perr. at a photon flux density (PFD) above 220 μmol·m−2s−1 (400–700 nm) or at leaf temperatures above 27.0 °C showed a rapid loss of rhythmicity, and a more or less pronounced damping-out of the endogenous circadian rhythm of CO2 exchange under continuous illumination. This rhythm was reinitiated after reduction of the PFD by 90–120 μmol·m−2·s−1 or reduction of leaf temperature by 3.5–11.0 °C under otherwise unchanged external conditions. The reduction in the magnitude of the external control parameter of the Crassulacean acid metabolism (CAM) rhythm (i.e. PFD or leaf temperature) set the phase of the new rhythm. The maxima of CO2 uptake occurred about 5, 28, 51, 75 h after the reduction. Simulations with a CAM model under comparable conditions showed a similar behaviour. The influence of temperature on the endogenous CAM rhythm observed in K. daigremontiana in vivo could be simulated by incorporating into the model temperature-dependent switch modes for passive efflux of malate from the vacuole to the cytoplasm. Thus, the model indicates that tonoplast function plays an important role in regulation of the endogenous CAM rhythm in K. daigremontiana.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00197593
