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|Title:||Studies of crassulacean acid metabolism in Mesembryanthemum crystallinum and Kalanchoe daigremontiana.|
|Authors:||Paul, Matthew J.|
|Presented at:||University of Leicester|
|Abstract:||Studies of crassulacean acid metabolism in Mesembryanthemum crystallinum and Kalanchoe daigremontiana Matthew J. Paul Studies of crassulacean acid metabolism (CAM), were undertaken in Kalanchoe daigremontiana and in the inducible CAM plant Mesembryanthemum crystallinum. Irrigation of M. crystallinum plants with 400 mM NaCl initiated CAM activity; CAM was deinduced by saturating the cultivation soil with water. Diel fluctuations and amounts of malic acid in M. crystallinum correlated with levels of endogenous inorganic phosphate (Pi). However, growth of M. crystallinum plants at varying concentrations of exogenous Pi resulted in an inverse relationship between these components. Indeed, diel fluctuations of malic acid in C3 M. crystallinum grown at 0 Pi were CAM-like. Cellular compartmentation of Pi and multi-functional roles of Pi and malic acid may explain these phenomena. The response of carbohydrate levels in M. crystallinum to photon fluence rate revealed that in conditions of restricted assimilate supply the CAM form partitioned carbohydrate preferentially as starch. Investigations of the control of this partitioning implicated differences in the properties of cytosolic fructose 1, 6 bisphosphatase between C3 and CAM M. crystallinum. Growth of M. crystallinum at varying exogenous Pi concentrations demonstrated less perturbation of starch accumulation at high Pi in the CAM form. The involvement of fructose 1, 6 bisphosphatase and Pi in carbohydrate partitioning is discussed. Dry matter data, carbohydrate levels and saturation of carbohydrate accumulation and malic acid decarboxylation at 250 umol m-2 s-1 in CAM M. crystallinum indicated low productivity. Preferential partitioning of carbohydrate into starch, the adoption of CAM and growth in a saline environment may contribute to this. CAM induction in M. crystallinum was accompanied by the accumulation of pinitol. Preparations of protoplasts, vacuoles and chloroplasts showed pinitol to be chloroplastic at a probable concentration of about 230 mM and cytosolic at about 100 mM. No pinitol was detected in vacuoles. Pinitol, a putative compatible solute, may contribute to osmotic adjustment particularly in chloroplasts in response to the cellular accumulation of NaC1. There was no indication of a causal link between pinitol and CAM.|
|Rights:||Copyright © the author. All rights reserved.|
|Appears in Collections:||Theses, Dept. of Biology|
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