[Effect of malonate on the structural and functional changes of wheat Triticum aestivum L. root cells]

A study was made of respiration, output of K+ and ultrastructure of wheat root cells treated for 6 h with malonic acid (MA) (15 mM), an inhibitor of succinate dehydrogenase. After a 1 h treatment, on the background of a decrease in respiration, and output of K+ an increased number of lumens of smooth endoplasmic reticulum was observed. These changes may be the result of lipid biosynthesis. Within first hours of treatment with MA, the mitochondrial matrix was becoming more brightened, and after 3 h all organelles became transparent. Moreover, mitochondria increased in size and almost lacked cristae. After 4 h mitochondria assumed their normal sizes due, presumably, to a competitive action of malonate. After 5 h the matrix was brightened again, mitochondria augmented in size, several organelles acquired torus shapes, and their outer area was eventually increased. We found contacts of endoplasmic reticulum lumens with mitochondria, which may suggest the synthesis of an enzyme, able to transform to malonate. After a 6 h exposure of MA, we observed the increase of respiration, re-entry of K+ and normal ultrastructure of mitochondria. Based on our experiments, we conclude that adaptation of root cells may be a result of external NADPH-dehydrogenase activity and MA detoxification.