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Temperature Effects on Crassulacean Acid Metabolism: EPR Spectroscopic Studies on the Thermotropic Phase Behaviour of the Tonoplast Membranes of Kalanchoë daigremontiana
Author(s) -
Kluge M.,
Kliemchen A.,
Galla H.J.
Publication year - 1991
Publication title -
botanica acta
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.871
H-Index - 87
eISSN - 1438-8677
pISSN - 0932-8629
DOI - 10.1111/j.1438-8677.1991.tb00241.x
Subject(s) - crassulacean acid metabolism , kalanchoe , thermotropic crystal , vacuole , electron paramagnetic resonance , malic acid , membrane , chemistry , biophysics , phase (matter) , materials science , biochemistry , biology , botany , nuclear magnetic resonance , organic chemistry , photosynthesis , cytoplasm , liquid crystalline , physics , citric acid
The thermotropic phase behaviour of tonoplast material isolated from leaf mesophyll protoplasts of the obligatory CAM plant Kalanchoë daigremontiana was investigated by electron power magnetic resonance (EPR) spectroscopy using a spin label technique. The data clearly show that at temperatures below 9 °C the tonoplast membrane is in a rigid state. Above 9 °C, an increasing fluidization of the tonoplast occurs. Two distinct temperature ranges were observed: a cooperative melting process between 9 and 14 °C being followed by a second broad melting process starting at 18 °C, with continuously increasing membrane fluidity up to 51 °C, which was the highest temperature tested. These results are important for a better understanding of the mechanism of the temperature modulation of CAM. The data support the hypothesis that temperature affects CAM via the permeability of the tonoplast membrane, which determines the rates of the passive malic acid efflux from the vacuole and thus the capability of the plant to accumulate malic acid in the vacuoles overnight at a given temperature.