EN
Changes in malate concentration and activity of NADP-dependent malic enzyme were observed as the effect of Botrytis cinerea infection of C₃ or CAM-performing Mesembryanthemum crystallinum plants. Biotic stress applied on C₃ plants led to increase in malate concentration during the night and in consequence it led to increase in Δ-malate (day/night fluctuations) in infected leaves on the 2nd day post infection (dpi). It corresponded with induction of additional isoform of NADP-malic enzyme (NADP-ME3). On the contrary, CAM-performing M. crystallinum plants exhibited decrease in malate concentration and decay in its diurnal fluctuations as a reaction to B. cinerea infection. This correlated with significant decrease in activities of NADP-malic enzyme isoforms on the 2nd dpi as well as no fluctuations in their activities on the 9th dpi. Presented results point out to differences between C₃ and CAM plants in the direction of changes in primary metabolism providing energy, reducing equivalents and carbon skeletons for defense responses to halt the pathogen growth.