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The Effect of Irradiance on Carboxylating/Decarboxylating Enzymes and Fumarase Activities in Mesembryanthemum crystallinum L. Exposed to Salinity Stress
Author(s) -
Miszalski Z.,
Niewiadomska E.,
Slesak I.,
Lüttge U.,
Kluge M.,
Ratajczak R.
Publication year - 2001
Publication title -
plant biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.871
H-Index - 87
eISSN - 1438-8677
pISSN - 1435-8603
DOI - 10.1055/s-2001-11743
Subject(s) - mesembryanthemum crystallinum , crassulacean acid metabolism , fumarase , malate dehydrogenase , malic enzyme , biology , phosphoenolpyruvate carboxylase , enzyme , salinity , malic acid , biochemistry , light intensity , botany , dehydrogenase , photosynthesis , ecology , physics , optics , citric acid
In Mesembryanthemum crystallinum plants, treated for 9 days with 0.4 M NaCl at low light intensities (80 ‐ 90 or 95 ‐ 100 μE m ‐2 s ‐1 ; λ = 400 ‐ 700 nm), no day/night malate level differences (Δmalate) were detected. At high light (385 ‐ 400 μE m ‐2 s ‐1 ) strong stimulation of PEPC activity, accompanied by a Δmalate of 11.3 mM, demonstrated the presence of CAM metabolism. This indicates that, to evolve day/night differences in malate concentration, high light is required. Salt treatment at low light induces and increases the activity of NAD‐ and NADP‐malic enzymes by as much as 3.7‐ and 3.9‐fold, while at high light these values reach 6.4‐ and 17.7‐fold, respectively. The induction of activity of both malic enzymes and PEPC (phospo enol pyruvate carboxylase) take place before Δmalate is detectable. An increase in SOD (superoxide dismutase) was observed in plants cultivated at high light in both control and salt‐treated plants. However, in salt‐treated plants this effect was more pronounced. Carboxylating and decarboxylating enzymes seem to be induced by a combination of different signals, i.e., salt and light intensity. Plants performing CAM, after the decrease of activity of both the decarboxylating enzymes at the beginning of the light period, showed an increase in these enzymes in darkness when the malate pool reaches higher levels. In CAM plants the activity of fumarase (Krebs cycle) is much lower than that in C 3 plants. The role of mitochondria in CAM plants is discussed.